FLUID, ELECTROLYTE, AND ACID-BASE BALANCES Show The physiological functions and alterations of body fluid and acid-base balance are presented in this chapter. The term body fluid is used to denote both water and electrolytes, whereas the term body water refers to water alone. Homeostasis, or equilibrium of the internal environment, refers to the state of balance of body fluid. PHYSIOLOGY OF FLUIDAND ACID-BASE BALANCE The body normally maintains a balance between the amount of fluid taken in and the amount excreted. Health promotion requires a maintenance of body fluid and acid-base balance. Fluid Compartments The body’s fluid is contained within three compartments: cells, blood vessels, and the tissue space (space between the cells and blood vessels). To understand this concept, visualize cars on a freeway. The cars represent cells; the lanes represent the blood vessels, and the space between the cars in the lanes represents the tissue space. The freeway itself is the body. Just as traffic is ongoing and continuous, fluids move constantly from one compartment to another to accommodate the cell’s metabolic needs (Figure 37-1). Specific terms are used in describing compartmentalized body fluid. The prefixes (see the accompanying display) used with the root words for the compartments that contain the body fluid give meaning to the following terms: • Intracellular fluid: within the cell • Intra vascular fluid: within blood vessels • Interstitial fluid: between cells; fluid that surrounds cells There are two types of body fluid: intracellular (ICF) and extracellular (ECF). Because intravascular and interstitial fluid are outside the cells, these fluids are extracellular. Key terms used in explaining the movement of molecules in body fluids are: • Solute: Substance dissolved in a solution • Solvent: Liquid that contains a substance in solution • Permeability: Capability of a substance, molecule, or ion to diffuse through a membrane (covering of tissue over a surface, organ, or separating spaces) • Semipermeable: Selectively permeable (All membranes in the body allow some solutes to pass through the membrane without restriction but will prevent the passage of other solutes.) Cells have permeable membranes that allow fluid and solutes to pass into and out of the cell. Permeability allows the cell to acquire the nutrients it needs from extracellular fluid to carry on metabolism and to eliminate metabolic waste products. Blood vessels have permeable membranes that bathe and feed the cells. The intravascular fluid of arterioles carries oxygen and nutrients to the cells. The venules take in the waste products from the cells’ metabolic activity. Cells and capillaries form a meshlike structure that creates a tissue space between cells and the vascular system to allow cellular access to the vascular system. Interstitial space promotes access of the cells to the arterioles and venules. Body Water Distribution Water is the largest single constituent of the body, representing 45% to 75% of the body’s total weight. About twothirds of the body fluid is intracellular. The remaining one-third is extracellular, with one-fourth of this fluid being intravascular and three-fourths being interstitial fluid. Bones are made up of nearly one-third water, while the muscles and brain cells contain 70% water. Body fat is essentially free of water; therefore, the ratio of water to body weight is greater in leaner people than in obese people. Water is present in all body tissues and cells, and serves two main functions: to act as a solvent for the essential nutrients, so that they can be used by the body; and to transport nutrients and oxygen from the blood to the cells and to remove waste material and other substance from the cells back to the blood so they can be excreted by the body. Water is also needed by the body to: • Give shape and form to the cells • Regulate body temperature • Act as a lubricant in joints • Cushion body organs • Maintain peak physical performance Water loss has a negative effect on the body’s ability to function, because every 2% to 5% of water loss results in a 30% decrease in work performance (Kloss, 1995; Kleiner, 1999). Electrolytes An electrolyte is a compound that, when dissolved in water or another solvent, forms or dissociates into ions (electrically charged particles) (Figure 37-2). The electrolytes provide inorganic chemicals for cellular reactions and control mechanisms. Electrolytes have special physiological functions in the body that promote neuromuscular irritability, maintain body fluid osmolarity, regulate acid-base balance, and distribute body fluids between the fluid compartments. Electrolytes are measured in terms of their electrical combining power, the quantities of cations and anions in a solution, expressed as milliequivalents per liter (mEq/L). Because electrolytes produce either positively charged ions (cations) or negatively charged ions (anions), they are critical regulators in the distribution of body fluid. The main electrolytes in body fluid are: sodium (Na+), potassium (K+), calcium (Ca2+), and magnesium (Mg2+). Table 37-1 discusses the distribution of electrolytes in body fluid, their regulatory functions, and dietary sources. As shown in Table 37-1, the extracellular fluid contains the largest quantities of sodium, chloride, and bicarbonate ions, but only small quantities of potassium, calcium, magnesium, phosphate, sulfate, and organic acid ions. The intracellular fluid contains only small quantities of sodium and chloride ions and almost no calcium ions. Large quantities of potassium and phosphate ions with moderate quantities of magnesium and sulfate ions are contained within intracellular fluid (see the accompanying display).
Movement of Body Fluids The physiological forces that affect the movement of body fluids through cell walls and capillaries can be perceived as a mass-transportation system that carries traffic between the compartments. These forces transport molecules of water, foods, gases, wastes, and ions to maintain a physiological balance between extracellular and intracellular fluid volumes. These transport processes account for fluid shifts between the compartments (Table 37-2).
Figure 37-3 The process of diffusion. A. A small lump of sugar is placed in a beaker of water, its molecules dissolve and begin to diffuse outward. B., C. The sugar molecules continue to diffuse through the water from an area of greater concentration to an area of lesser concentration. D. Over a long period of time, the sugar molecules are evenly distributed throughout the water, reaching a state of equilibrium. Example of diffusion in the human body: Oxygen diffuses from an alveolus in a lung, where it is in greater concentration, across the capillary membrane, into a red blood cell, where it is in lesser concentration.
Regulators of Fluid Balance The body has many regulators that maintain fluid balance, including fluid and food intake, skin, lungs, gastrointestinal tract, and kidneys. When all organs are functioning normally, the body is able to maintain homeostasis. Fluid and Food Intake and Loss There are three natural sources by which water enters the body: oral liquids; water in foods; and water formed by oxidation of foods. A normal diet provides the electrolytes required by the body (see the accompanying display for the typical daily amount of body fluid intake for an adult). Body fluid is replenished by the ingestion of liquids and food products such as meats and vegetables, which contain 65% to 97% water. The third source of body fluid is the metabolism of foods, which yields water of oxidation. The kidneys excrete the largest quantity of fluid; other avenues for water loss are the lungs, skin, and gastrointestinal tract. Skin An estimated water loss of 300 to 400 ml per day occurs by diffusion through the skin of an adult. Because the person is not aware of this water loss, it is called insensible loss. Water is also lost through the skin by perspiration; however, the total amount of water lost by perspiration can vary from 1.5 to 3.5 L per hour, depending on environmental factors and body temperature. Lungs An estimated insensible water loss of 300 to 400 ml per day occurs in an adult through expired air, which is saturated with water vapor. This amount may vary with the rate and depth of respirations. Gastrointestinal Tract Although a large amount of fluid—about 8,000 ml per day in the adult—is secreted into the gastrointestinal tract, almost all of this fluid is reabsorbed by the body. In adults, about 200 ml of water is lost per day in feces. Severe diarrhea can cause a fluid and electrolyte deficit because the gastrointestinal fluids contain a large amount of electrolytes. Kidneys The kidneys play a major role in maintaining fluid balance by excreting 1,200 to 1,500 ml/day in the adult. The excretion of water by healthy kidneys is proportional to the fluid ingested and the amount of waste or solutes excreted. When an extracellular fluid volume deficit occurs, hormones play a key role in restoring the extracellular fluid volume. The release of the following hormones into circulation causes the kidneys to conserve water: • Antidiuretic hormone (ADH) from the posterior pituitary gland acts on the distal tubules of the kidneys to reabsorb water. • Aldosterone (produced in the adrenal cortex) causes the reabsorption of sodium from the renal tubules. The increased reabsorption of sodium causes water retention in the extracellular fluid, increasing its volume. • Renin, which is released from the juxtaglomerular cells of the kidneys, promotes vasoconstriction and the release of aldosterone. The interaction of these hormones with regard to renal functions serves as the body’s compensatory mechanism to maintain homeostasis. Sodium is the main electrolyte that promotes the retention of water. An intravascular water deficit causes the renal tubules to reabsorb more sodium into circulation. Because water molecules go with the sodium ions, the intravascular water deficit is corrected by this action of the renal tubules. FACTORS AFFECTING FLUID AND ELECTROLYTE BALANCE The balance of fluids and electrolytes in the body is dependent on many factors and will vary depending on such elements as age and lifestyle. Age Body water distribution is relative to body size. The smaller the body, the larger the fluid content: • Adult, 60% water • Child, 60% to 77% water • Infant, 77% water • Embryo, 97% water In the elderly, body water diminishes because of tissue loss; the percentage of total body weight that is fluid may be reduced to 45% to 50% in persons over age 65. Caution must be used when administering diuretics, especially thiazide diuretics, to the elderly to prevent diuretic-induced electrolyte disturbances. Lifestyle Loss of body fluids can result from stress, exercise, or a warm or humid environment. Stress leads to increased blood volume and decreased urine production, with a subsequent intensification of antidiuretic hormone levels. Sweating and exercise cause the body to lose water and sodium, thus necessitating electrolyte replacement and intensifying the thirst response. Warm climates can exert a similar effect. An individual’s diet will also determine fluid and electrolyte levels. Adequate intake of fluids, carbohydrates, potassium, calcium, sodium, fats, and protein is essential in helping the body maintain homeostatis and function properly. Dehydration is one of the most common yet most serious fluid imbalances that can occur from poor monitoring of diet. One nursing goal is to ensure that all clients understand the role water plays in health and to see that clients understand how to maintain adequate hydration status. DISTURBANCES IN ELECTROLYTE BALANCE The clinical management of clients experiencing disturbances in sodium, potassium, calcium, magnesium, and phosphate is presented using the functional health pattern model. See Table 37-3 for the causes, clinical manifestations, and nursing interventions for these electrolyte disturbances. Because chloride has several characteristics similar to other ions, a brief discussion of chloride imbalance is also presented. Acid-base imbalances caused by a disturbance in the level of either carbonic acid or bicarbonate are also presented using the functional health pattern model.
Electrolyte Disturbances In health, normal homeostatic mechanisms function to maintain electrolyte and acid-base balance. In illness, one or more of the regulating mechanisms may be affected, or the imbalance may become too great for the body to correct without treatment. Refer to Chapter 28, Table 28-7, for the normal laboratory values of electrolytes. Sodium Sodium is the primary determinant of extracellular fluid concentration because of its high concentration and inability to cross the cell membrane easily. As discussed in Table 37-3, alterations in sodium concentration can produce profound central nervous system effects on cognition and sensory perception and on the circulating blood volume. When the kidneys reabsorb sodium ions, chloride and water are reabsorbed with the sodium to maintain the body’s fluid volume.
Hyponatremia Hyponatremiais a deficit in the extracellular level of sodium. With hyponatremia, there is either a sodium deficit or a water excess; a hypo-osmolar state exists because the ratio of water to sodium is too high. The water moves out of the vascular space into the interstitial space and then into the intracellular space, causing edema. The low extracellular serum sodium causes water to enter the cells in the brain, thereby producing cerebral edema as manifested by the cognitive and sensory changes listed in Table 37-3. Hypernatremia Hypernatremia is an excess in the extracellular level of sodium. With an excess of sodium or a loss of water, a hyperosmolar state exists because the ratio of sodium to water is too high. This ratio causes an increase in the extracellular osmotic pressure, which pulls fluid out of the cells into the extracellular space. The symptoms of this increase depend on the cause and the location of the edema (see Table 37-3). Potassium The normal range of extracellular potassium is narrow (3.5–5.0 mEq/L). The slightest decrease or increase can cause serious or life-threatening effects on physiological functions. A reciprocal relationship exists between sodium and potassium; large sodium intake results in an increased loss of potassium, and vice versa. When potassium is lost from the cells, sodium enters the cells. Intracellular potassium deficit may coexist with an excess of extracellular potassium. There are two main categories of diuretics that can cause hypokalemia: 1. Potassium-wasting diuretics excrete potassium and other electrolytes, such as sodium and chloride. 2. Potassium-sparing diuretics retain potassium but excrete sodium and chloride. Hypokalemia Hypokalemia is a decrease in the extracellular level of potassium. Gastrointestinal-tract disturbances and the use of diuretics can place the client at risk for hypokalemia and an acid-base imbalance (metabolic alkalosis). Potassium-wasting diuretics can cause NURSING ALERT Hypokalemia Hypokalemia can cause a cardiac arrest when: 1. The potassium level is less than 2.5 mEq/L. 2. The client is taking digitalis (a drug that strengthens the contraction of the myocardium and slows down the rate of the heart). Hypokalemia enhances the action of the drug, causing toxicity. Hyperkalemia Hyperkalemia is an increase in the extracellular level of potassium. There are major drug groups that may cause hyperkalemia: • Potassium-sparing diuretics • Central nervous system agents • Oral and intravenous replacement potassium salts Hyperkalemia can also inhibit the action of digitalis. Calcium Most of the body’s calcium (99%) is deposited in bone as phosphate and carbonate. The remaining 1% is in the blood plasma (serum). Normally, 50% of the serum calcium is ionized (physiologically active), with the remaining 50% bound to protein. Free, ionized calcium is needed for cell membrane permeability. The calcium that is bound to plasma protein cannot pass through the capillary wall and therefore cannot leave the intravascular compartment. A stable blood level of calcium is maintained by a negative-feedback system controlled by vitamin D, parathyroid hormone, calcitonin (thyrocalcitonin), and the serum concentrations of calcium and phosphate ions. A decreased blood level stimulates the parathyroid gland to secrete parathyroid hormone, which in turn mobilizes the release of calcium from the bone, increases the renal reabsorption, and increases intestinal absorption in the presence of vitamin D. Likewise, calcitonin, secreted by the thyroid gland, reduces the blood calcium concentration. Calcium ions are never completely absorbed from the gastrointestinal tract. Dietary calcium absorption and utilization require an adequate amount of protein and vitamin D. Besides being needed by the body for bone and tooth formation, calcium is an important ion in the blood-clotting mechanism and for maintaining the integrity of the neuromuscular system. Hypocalcemia Hypocalcemia is a decrease in the extracellular level of calcium. The rapid administration of citrated blood, alkalosis, and elevated levels of serum albumin increase the activity of calcium binders, thereby decreasing the amount of free calcium. Hypercalcemia Hypercalcemia is an increase in the extracellular level of calcium. The clinical symptoms result from a decrease in neuromuscular activity, reabsorption of calcium from bone, and the kidney’s response to a high serum calcium concentration. Magnesium Magnesium plays an important role as a coenzyme in the metabolism of carbohydrates and proteins and as a mediator in neuromuscular activity. Magnesium has the unique characteristic of being the only cation that has a higher concentration in cerebrospinal fluid than in extracellular fluid. Hypomagnesemia Hypomagnesemia is a decrease in the extracellular level of magnesium and usually occurs with hypokalemia and hypocalcemia. It is probably the most undiagnosed electrolyte deficit because it is asymptomatic until the serum level approaches 1.0 mEq/L; the normal range is 4.5–5.5 mEq/L (Kee & Paulanka, 2000). Drugs that may cause hypomagnesemia include: digitalis, potassium-wasting diuretics, cortisone, aminoglycosides, and amphotericin B; the chronic use of laxatives may also cause the condition. Clinical manifestations are related to the neuromuscular, neurologic, or cardiovascular system (see Table 37-3). NURSING ALERT Potassium Chloride Never administer more than 10 mEq of intravenous potassium chloride (KCl) per hour; the normal dose of intravenous KCl is 20–40 mEq/L to infuse over an 8-hour period. NURS I N G T I P Serum Calcium Approximately 50% of the serum calcium level is bound to protein. Correlate the serum calcium level with the serum albumin level when evaluating the laboratory results. Any change in serum protein will result in a change in the total serum calcium. NURSING ALERT Hypercalcemic Crisis A rapid increase in the extracellular level of calcium (above 8 to 9 mEq/L) can trigger a hypercalcemic crisis. To prevent a hypercalcemic crisis, provide adequate hydration and administer diuretics or phosphate or both as prescribed by the health care practitioner. Hypermagnesemia Hypermagnesemia refers to an increase in the extracellular level of magnesium. It rarely occurs from excessive dietary ingestion; however, overuse of magnesiumcontaining drugs (antacids, laxatives, and intravenous magnesium sulfate) can cause hypermagnesemia. The clinical manifestations of hypermagnesemia are nonspecific (refer to Table 37-3). Phosphate Phosphate is the main intracellular anion; it appears as phosphorus in the serum. Phosphorus is similar to calcium in that vitamin D is needed for its reabsorption from the renal tubules. Hypophosphatemia Hypophosphatemia is a decreased extracellular level of phosphorus. An increase in parathyroid hormone causes decreased renal reabsorption and increased excretion of phosphates. The aim of nursing care is to protect the client from injury and to correct the deficit (see Table 37-3). Hyperphosphatemia Hyperphosphatemia is an increased extracellular level of phosphorus. Excessive administration (oral or intravenous) of phosphate-containing substances can cause hyperphosphatemia. Other causes of hyperphosphatemia are hypoparathyroidism, renal insufficiency, and laxatives containing phosphate. Chloride As previously stated, chloride and water move in the same direction as sodium ions, influencing the osmolality of extracellular fluid. Although chloride losses usually follow sodium losses, the proportion will differ because a loss of chloride can be compensated for by an increase in bicarbonate. Therefore, signs and symptoms of a chloride imbalance will be similar to those of a metabolic acid-base imbalance, discussed later in this chapter. A deficit of either chloride or potassium will lead to a deficiency of the other electrolyte. Hypochloremia Hypochloremia is a decrease in the extracellular level of chloride. Gastrointestinal tract losses may cause a decrease in chloride because of the acid content of gastric juices, mainly hydrogen chloride. Because the bicarbonate ion compensates for the loss of chloride, the client is at risk for developing metabolic alkalosis. The signs and symptoms of hypochloremia are muscle twitching and slow, shallow breathing. With a severe loss of chloride and extracellular fluid volume, there may be a drop in blood pressure. Hyperchloremia Hyperchloremia is an increase in the extracellular level of chloride. It usually occurs with dehydration, hypernatremia, and metabolic acidosis. The signs and symptoms of hyperchloremia are muscle weakness, deep, rapid breathing, and lethargy progressing to unconsciousness if untreated. ACID-BASED BALANCE Acid-base balancerefers to the homeostasis of the hydrogen ion concentration in extracellular fluid. The slightest variation in the hydrogen ion concentration causes marked alterations in the rate of cellular chemical reactions. The pH symbol is used to indicate the hydrogen ion concentration of body fluids; 7.35 to 7.45 is the normal pH range of extracellular fluid. Hydrogen ions (H+), which carry a positive charge, are protons. Depending on the number of hydrogen ions present, a solution can be either acidic, neutral, or alkaline. As the number of hydrogen ions increases, the fluid becomes acidic. Acidity of a solution increases as the pH value decreases. An acid is a substance that donates hydrogen ions. For example, hydrochloric acid (HCl) ionizes in water (a solution) to form hydrogen ions and chloride ions. HCl, which is found in gastric juices, has a strong tendency to form ions, discharging hydrogen ions into the solution; carbonic and acetic acids are considered weak acids because in a solution they provide a low concentration of hydrogen ions. As the number of hydrogen ions decreases, the fluid becomes alkaline. Alkalinity of a solution increases as the pH value increases. A base is a substance that accepts hydrogen ions (proton acceptor). A neutral solution has a pH of 7. In such a solution there are equal numbers of hydrogen ions (H+) and hydroxyl ions (OH–), which can combine to form water (H2O). When the number of hydrogen ions is increased, the solution becomes acidic (pH value below 7); a decrease in the number of hydrogen ions causes the solution to become alkaline (pH value above 7). When the number of free hydrogen ions in a solution increases to the point that the pH value becomes less than 7.35, the body is in a state of acidosis. The opposite occurs with alkalosis, in which a pH value higher than 7.45 results from a low hydrogen ion concentration. Regulators of Acid-Base Balance The body has three main control systems that regulate acid-base balance to counter acidosis or alkalosis: the buffer systems; respiration; and renal control of hydrogen ion concentration. These systems vary in their reaction time in regulating and restoring balance to the hydrogen ion concentration of a solution. Buffer Systems All body fluids are supplied with an acid-base buffer system (a solution containing two or more chemical compounds that prevents marked changes in hydrogen ion concentration when either an acid or a base is added to a solution). The buffer system reacts within a fraction of a second to prevent excessive changes in the hydrogen ion concentration. There are several chemical buffer systems of body fluids, which are activated under different conditions; however, the bicarbonate-carbonic acid system (carbonate system) is the body’s primary buffer system. The carbonate system consists of a mixture of carbonic acid (H2CO3) and sodium bicarbonate (NaHCO3). The pH of the extracellular fluid can be returned to normal limits by this system because carbonic acid is a weak acid, which ionizes to a limited extent, and bicarbonate is a weak base, which yields the hydroxyl ion. Bicarbonate helps to stabilize pH by combining reversibly with hydrogen ions. Most of the body’s bicarbonate is produced in red blood cells, where the enzyme carbonic anhydrase accelerates the conversion of carbon dioxide to carbonic acid. The production of bicarbonate is illustrated in the following reversible equation: CO2 + H2O H2CO3 H+ + HCO3 When the hydrogen ion concentration increases in the extracellular space, the reaction shifts toward the left; a decreased concentration of hydrogen ion drives the reaction to the right. Respiratory Regulation of Acid-Base Balance The respiratory buffering system helps to maintain acidbase balance by controlling the content of carbon dioxide in extracellular fluid. The rate of metabolism determines the formation of carbon dioxide. Carbon dioxide is continually being formed in the body by different intracellular metabolic processes. The carbon in foods is oxidized by oxygen to form carbon dioxide. It takes the respiratory regulatory mechanism several minutes to respond to changes in the carbon dioxide concentration of extracellular fluid. With the increase of carbon dioxide in extracellular fluids, respirations are increased in rate and depth so that more carbon dioxide is exhaled. As the respiratory system removes carbon dioxide, there is less carbon dioxide in the blood to combine with water to form carbonic acid. Likewise, if the blood level of carbon dioxide is low, respirations are depressed to maintain a normal ratio between carbonic acid and basic bicarbonate. Renal Control of Hydrogen Ion Concentration The kidneys control extracellular fluid pH by eliminating either hydrogen ions or bicarbonate ions from body fluids. If the bicarbonate concentration in the extracellular fluid is greater than normal, the kidneys excrete more bicarbonate ions, making the urine more alkaline. Conversely, if more hydrogen ions are excreted in the urine, the urine becomes more acidic. The renal mechanism for regulating acid-base balance cannot readjust the pH within seconds, as can the extracellular fluid buffer system, nor within minutes as can the respiratory compensatory mechanism, but it can function over a period of several hours or days to correct an acid-base imbalance. FACTORS AFFECTING FLUID AND ELECTROLYTE BALANCE The balance of fluids and electrolytes in the body is dependent on many factors and will vary depending on such elements as age and lifestyle. Age Body water distribution is relative to body size. The smaller the body, the larger the fluid content: • Adult, 60% water • Child, 60% to 77% water • Infant, 77% water • Embryo, 97% water In the elderly, body water diminishes because of tissue loss; the percentage of total body weight that is fluid may be reduced to 45% to 50% in persons over age 65. Caution must be used when administering diuretics, especially thiazide diuretics, to the elderly to prevent diuretic-induced electrolyte disturbances. Lifestyle Loss of body fluids can result from stress, exercise, or a warm or humid environment. Stress leads to increased blood volume and decreased urine production, with a subsequent intensification of antidiuretic hormone levels. Sweating and exercise cause the body to lose water and sodium, thus necessitating electrolyte replacement and intensifying the thirst response. Warm climates can exert a similar effect. An individual’s diet will also determine fluid and electrolyte levels. Adequate intake of fluids, carbohydrates, potassium, calcium, sodium, fats, and protein is essential in helping the body maintain homeostatis and function properly. Dehydration is one of the most common yet most serious fluid imbalances that can occur from poor monitoring of diet. One nursing goal is to ensure that all clients understand the role water plays in health and to see that clients understand how to maintain adequate hydration status. Acid-Base Disturbances The common types of acid-base imbalances are respiratory acidosis and alkalosis and metabolic acidosis and alkalosis.
Laboratory Data The biochemical indicators of acid-base imbalance are assessed by measurement of arterial blood gases (ABGs). Arterial blood gases measure the levels of oxygen and carbon dioxide in arterial blood. The levels of blood pH, bicarbonate ion, sodium, potassium, and chloride are also important in the assessment of acid-base imbalance. In the determination of whether the acid-base imbalance is caused by a respiratory or a metabolic alteration, the key indicators are bicarbonate and carbonic acid levels (Figure 37-6). With respiratory acidosis and alkalosis, the bicarbonate level is normal and carbonic acid is either increased (acidosis) or decreased (alkalosis). With metabolic acidosis and alkalosis, the carbonic acid is normal and the bicarbonate level is either decreased (acidosis) or increased (alkalosis).
Respiratory Acidosis (Carbonic Acid Excess) Respiratory acidosis is characterized by an increased hydrogen ion concentration (a blood pH below 7.35), an NURSING ALERT Hyperalimentation The continuous use of total parenteral nutrition (TPN, hyperalimentation) without a magnesium supplement can cause hypomagnesemia. THINK ABOUT IT Intake of Phosphorus When the dietary intake of calcium from milk is sufficient to meet minimal requirements, phosphorus needs will also be met. How will you educate clients who either cannot or will not consume an adequate daily intake of milk to meet their calcium and phosphorus needs? Increased arterial carbon dioxide pressure (greater than 45 mm Hg), and an excess of carbonic acid. Respiratory acidosis is caused by hypoventilation or any condition that depresses ventilation (see the accompanying display). Hypoventilation can begin in the respiratory system, as occurs with respiratory failure, or outside the respiratory system, as occurs with drug overdose. Common drugs that can cause central nervous system depression and place the client at risk for respiratory acidosis are narcotics, barbiturates, and anesthetic agents. Clients with respiratory acidosis experience neurologic changes resulting from the acidity of the cerebrospinal fluid and brain cells. Hypoventilation causes hypoxemia (decreased oxygen levels), which causes further neurologic impairments; refer to Chapter 32 for a complete discussion of hypoxemia. Hyperkalemia may accompany acidosis. See Table 37-4 for the clinical manifestations and nursing interventions used to treat respiratory acidosis. Respiratory Alkalosis (Carbonic Acid Deficit) Respiratory acidosis is characterized by a decreased hydrogen ion concentration (a blood pH above 7.45) and a decreased arterial carbon dioxide pressure (less than 35 mm Hg). Respiratory alkalosis is caused by hyperventilation (excessive exhalation of carbon dioxide) resulting in hypocapnia (decreased arterial carbon dioxide concentration). Hyperventilation can be triggered by hypoxia at high altitudes, anxiety, fear, pain, fever, and rapid mechanical ventilation. Other causes of hyperventilation, which involve overstimulation of the respiratory center, include salicylate poisoning, hyperthyroidism, pneumonia, atelectasis, asthma, adult respiratory distress syndrome, congestive heart failure, pulmonary edema and embolus, brain tumors, meningitis, and encephalitis; refer to Table 37-4 for the clinical manifestations and treatment. Metabolic Acidosis (Bicarbonate Deficit) Metabolic acidosis is characterized by an increase in hydrogen ion concentration (blood pH below 7.35) or a decrease in bicarbonate concentration. Causes of metabolic acidosis can be divided into two categories: loss of base and gain in metabolic acids. Chronic diarrhea causes an excessive loss of bicarbonate and sodium ions from the small intestines. With the loss of sodium ions, chloride ions are in excess and combine with hydrogen to produce a strong acid (hydrochloric acid). Clients with certain medical diagnoses are at risk for metabolic acidosis. Such conditions include: 1. Diabetic ketoacidosis: The cells are deprived of glucose (decrease or absence of insulin) for metabolism; the liver, in response to the needs of the cells, increases the metabolism of fatty acids, which causes an increase in ketone bodies, making the extracellular fluid more acidic. 2. Renal failure: The normal mechanism of the kidneys to conserve sodium and water and excrete hydrogen is compromised. 3. Anaerobic metabolism: Cellular catabolism and acid accumulation occur with starvation, severe malnutrition, infection, fever, trauma, shock, and excessive exercise. 4. Drug overdose: Acid accumulation results from excessive ingestion of salicylate, paraldehyde, and methanol In response to metabolic acidosis, the respiratory center is stimulated, causing an increase in the rate and depth of respirations (Kussmaul breathing), to lower the acid concentration in extracellular fluid by increasing the exhalation of carbon dioxide. The respiratory compensatory mechanism is usually ineffective in decreasing acids, especially if the client has chronic obstructive pulmonary disease or is in ketoacidosis. Refer to Chapter 32 for additional information on these diagnoses. The renal compensatory mechanism tries to increase the pH by exchanging sodium ions with hydrogen ions to increase the excretion of hydrogen; refer to Table 37-4 for the clinical manifestations and treatment of metabolic acidosis. Metabolic Alkalosis (Bicarbonate Excess) Metabolic alkalosis is characterized by an increased loss of acid from the body or a gain in base (increased levels of bicarbonate). The blood pH is above 7.45. A gain in base may result from excessive ingestion of antacids. These substances neutralize acids, producing alkalosis and hypercalcemia. The excessive oral or parenteral administration of sodium bicarbonate or other alkaline salts (e.g., sodium or potassium acetate, lactate, or citrate) increases the amount of base in extracellular fluids. The following clinical conditions can place clients at risk for metabolic alkalosis: 1. Vomiting and nasogastric suctioning or lavage cause a loss in hydrochloric acid and chloride; with the loss of the hydrogen and chloride ions, bicarbonate ions are absorbed, unneutralized, into the bloodstream and the pH of the extracellular fluid rises (alkalosis). 2. Diarrhea, and steroid or diuretic therapy can cause the excessive loss of potassium, chloride, and other electrolytes; the potassium deficit causes the kidneys to exchange hydrogen ions (instead of potassium ions) for sodium ions, which promotes the loss of hydrogen, thereby increasing bicarbonate level. Hydrochlorothiazide, a thiazide diuretic, blocks the reabsorption of sodium in the cortex in the distal tubule causing sodium to be excreted in greater amounts than water (hyponatremia). Thiazides also cause hypokalemia because of the loss of urinary potassium. The secondary effects of thiazides lead to metabolic alkalosis because of a depletion in volume, chloride, potassium, and hydrogen ions (DeJong, 1998). The respiratory and renal compensatory mechanisms respond to an increased bicarbonate–carbonic acid ratio. The rate and depth of respirations are decreased in an effort to retain carbon dioxide. The arterial carbon dioxide concentration rises, creating respiratory acidosis, to counter the pH imbalance of metabolic alkalosis. A normal serum potassium level is a prerequisite to renal compensation. In alkalosis, potassium ions enter the cells in exchange for hydrogen ions, causing hypokalemia. Hypokalemia further potentiates metabolic alkalosis because the kidneys conserve hydrogen ions by excreting potassium ions in exchange for sodium ions. When hypokalemia is present, the kidneys cannot function as a compensatory mechanism; therefore, they continue to excrete hydrogen, and bicarbonate excess continues. Refer to Table 37-4 for the clinical manifestations and treatment of metabolic alkalosis. ASSESSMENT Assessment data are used to identify clients who have potential or actual alterations in fluid volume. Clients receiving certain treatments, such as medications and IV therapy, are at risk for developing imbalances. The key nursing assessment indicators that identify imbalances are daily weights, vital signs, intake and output, and the physical findings of the skin, oral cavity, eyes, venous filling, and neuromuscular system. Health History The nursing history should elicit data specific to fluids (see the accompanying display for sample topics to direct the interview). Physical Examination The nurse performs a complete physical examination and identifies all abnormalities because fluid alterations may affect any body system. The physical assessment of clients with altered fluid status is discussed in this section: refer to Chapter 27 for procedures on weight and vital sign measurement. Daily Weight Changes in the body’s total fluid volume are indicated by weight; for instance, each kilogram (2.2 lb) of weight gained or lost is equivalent to one liter (1000 ml) of fluid gained or lost. Accurate measurement of daily weight requires the nurse to implement the agency’s protocol to control certain variables. For example, the nurse should obtain the measurement at the same time each day, using the same scale. Vital Signs Measurement of vital signs provides the nurse with information regarding the client’s fluid, electrolyte, and acid-base status and the body’s compensatory response for maintaining balance. An elevated temperature places the client at risk for dehydration caused by an increased loss of body fluid. HEALTH HISTORY • Lifestyle (sociocultural and economic factors, stress, exercise) • Dietary intake (recent changes in the amount and types of fluid and food, increased thirst) • Religion (whether illness has had an effect on beliefs or religion; query whether the client would like a visit from his or her religious counselor) • Weight (sudden gain or loss) • Fluid output (recent changes in the frequency or amount of urine output) • Gastrointestinal disturbances (prolonged vomiting, diarrhea, anorexia, ulcers, hemorrhage) • Fever and diaphoresis • Draining wounds, burns, trauma • Disease conditions that could upset homeostasis (renal disease, endocrine disorders, neural malfunction, pulmonary disease) • Therapeutic programs that can produce imbalances (special diets, medications, chemotherapy, administration of intravenous fluid or total parenteral nutrition, gastric or intestinal suction) Changes in the pulse rate, strength, and rhythm are indicative of fluid alterations. Fluid volume alterations may cause the following pulse changes: • Fluid volume deficit (FVD): increased pulse rate and weak pulse volume • Fluid volume excess (FVE): increased pulse volume and third heart sound Respiratory changes are assessed by inspecting the movement of the chest wall, counting the rate, and auscultating the lungs. Changes in the rate and depth may cause respiratory acid-base imbalances or may be indicative of a compensatory response in metabolic acidosis or alkalosis, as previously discussed in Table 37-4. Blood pressure measurements can be used to assess the degree of FVD. FVD can lower the blood pressure with or without orthostatic hypotension. A narrow pulse pressure (less than 20 mm Hg) may indicate FVD that occurs with severe hypovolemia. Intake and Output Measure and record the client’s intake and output for a 24-hour period to assess for an actual or potential imbalance. A minimum intake of 1,500 ml is essential to balance urinary output and the body’s insensible water loss. Intake includes all liquids (e.g., ice cream, soup, gelatin, juice, and water) taken by mouth and liquids administered through tube feedings (nasogastric or jejunostomy) and parenterally (IV fluids and blood or its components). Output includes urine, diarrhea, vomitus, and drainage from tubes such as through gastric suction. The recording of intake and output data is usually referred to as the I&O. Thirst The most common indicator of FVD is thirst. With a decrease in extracellular fluid volume or an increase in the plasma osmolality, the hypothalamus triggers a thirst response. Food Intake The intake of food also contributes to maintaining extracellular fluid volume. One-third of the body’s fluid needs are met by ingested food. Food also provides the body with necessary electrolytes. See Chapter 38 for a complete discussion of metabolism. Edema Edema (the detectable accumulation of increased interstitial fluid) is the main symptom of FVE. Edema may be localized (confined to a specific area) or generalized (occurring throughout the body’s tissue). Localized edema is characterized by taut, smooth, shiny, pale skin. The body may retain 5 to 10 pounds of fluid before edema is noticeable (Bulechek & McCloskey, 1999). Inspect the dependent body parts—sacrum, back, and legs—to assess peripheral edema. Pitting edema is rated on a four-point scale: • +0'' no pitting • +1, 0''–1/4'' pitting (mild) • +2, 1/4''–1/2'' pitting (moderate) • +3, 1/2''–1'' pitting (severe) • +4, greater than 1'' pitting (severe) Skin Turgor Skin turgor is the normal resiliency of the skin. When the skin is pinched and released, it springs back to a normal position because of the outward pressure exerted by the cells and interstitial fluid. To measure the client’s skin turgor, grasp and raise the skin with two fingers as follows: • Adults: over the sternum, forehead, or inner aspect of the thigh • Children: over the abdominal area or medial aspect of the thigh Buccal (Oral) Cavity NURS I N G T I P Monitoring Water Balance The most accurate way to monitor water balance is through daily body weight measurement because water constitutes 45% to 75% of the body’s total weight. NURSING ALERT Dehydration in the Elderly The elderly are prone to a fluid volume deficit (dehydration), because the thirst mechanism in the medulla becomes less responsive with aging. NURS I N G T I P Skin Turgor in the Elderly With aging, there are fewer elastic fibers in the skin, resulting in reduced skin turgor. Assess the tongue for creases or furrows to monitor dehydration in the elderly (Hogstel, 2001). With dehydration there is a decreased skin turgor, as manifested by lax skin that returns slowly to the normal position. Increased skin turgor, which occurs with edema, is manifested by smooth, taut, shiny skin that cannot be grasped and raised. Inspect the buccal cavity. With FVD, there is a decrease in saliva, which causes sticky, dry mucous membranes and dry cracked lips. The tongue has longitudinal furrows. Eyes Inspect the eyes. FVD causes sunken eyes, dry conjunctiva, and decreased or absent tearing. Puffy eyelids (periorbital edema, or papilledema) are characteristic of FVE; the client may also have a history of blurred vision. Jugular and Hand Veins Circulatory volume is assessed by measuring venous filling of the jugular and hand veins. Place the client in a low Fowler’s position. Then: 1. Palpate the jugular (neck) veins: FVE causes a distention in the jugular veins (Figure 37-7). 2. Place the client’s hand below the heart level, and palpate the jugular veins; with FVD there is decreased venous filling (flat neck veins). Neuromuscular System Fluid and electrolyte imbalances may cause neuromuscular alterations: The muscles lose their tone and become soft and underdeveloped, and reflexes are diminished. Calcium and magnesium imbalances cause an increase in neuromuscular irritability. To assess for neuromuscular irritability perform the following tests: 1. Chvostek’s sign: Tap the facial nerve 2 cm anterior to the earlobe; unilateral twitching of the facial muscles (inclusive of the eyelids and lips) indicates a positive response (Figure 37-8). 2. Trousseau’s sign: Place a blood pressure cuff on the arm, inflate the cuff slightly above the systolic pressure, leave the cuff inflated 2–3 minutes, and deflate; carpal spasm or tetany indicates a positive response. A positive Chvostek’s sign and Trousseau’s sign may occur with hypocalcemia and hypomagnesemia. Other neurologic signs include inability to concentrate, confusion, and emotional lability, as previously discussed in Tables 37-3 and 37-4. Diagnostic and Laboratory Data Biochemical assessment is another essential source of objective data. Laboratory results can be used to detect imbalances before clinical symptoms are assessed in the physical examination. Laboratory tests used in assessing clients with common alterations in extracellular fluid volume are discussed next; refer to Chapter 28 for the normal values presented in this section. Hemoglobin and Hematocrit Indices The hematocrit is affected by changes in plasma volume. For instance, with severe dehydration and hypovolemic shock, the hematocrit is increased, whereas overhydration decreases the hematocrit. Hemoglobin levels are decreased with severe hemorrhage. Osmolality Osmolality is a measurement of the total concentration of dissolved particles (solutes) per kilogram of water. Osmolality measurements are performed on both serum and urine samples to determine alterations in fluid and
Figure 37-7 Positioning the Client to Assess Jugular Vein Distention electrolyte balance.
Osmolality can also be explained in relation to the specific gravity of body fluids. Specific gravity expresses the weight of the solution when compared with an equal volume of distilled water; the osmolality of a solution can be estimated by the specific gravity. Serum Osmolality Serum osmolality is a measurement of the total concentration of dissolved particles per kilogram of water in serum, recorded in milliosmoles per kilogram (mOsm/kg). The particles measured in serum osmolality include electrolyte ions, such as sodium and potassium, and electrically inactive substances dissolved in serum, such as glucose and urea. Water and sodium are the main entities that control the osmolality of body fluids. Serum sodium is responsible for 85% to 90% of the serum osmolality. The normal serum osmolality is 275 to 295 mOsm/kg (Fischbach, 2000). It can increase with dehydration and loss of body water and decrease with water excess. In clinical practice, the terms osmolality and osmolarity (the concentration of solutes per liter of cellular fluid) are often used interchangeably to refer to the concentration of body fluid. However, these terms are actually different, in that osmolality refers to the concentration of solutes in the total body water (solutes per kilogram of body weight) rather than in cellular fluid. Figure 37-9 relates osmosis to the osmolality of a solution. The appropriate term to use in intravenous fluid therapy is osmolarity (Bulechek & McCloskey, 1999). An osmolaritic solution is described as: • Hypotonic (hypo-osmolar) when there are less solutes in proportion to the volume of water than is the case in the body • Isotonic (iso-osmolar) when body water and solutes (sodium) are in amounts equal to those in the body • Hypertonic (hyperosmolar) when there are more solutes in proportion to the volume of water than is the case in the body Urine Osmolality Urine osmolality is a measurement of the total concentration of dissolved particles per kilogram of water in urine, recorded in milliosmoles per kilogram (mOsm/kg). The particles measured in urine osmolality come from nitrogenous waste (creatinine, urea, and uric acid), with urea contributing most. Urine osmolality varies greatly with diet and fluid intake and reflects the ability of the kidney to adjust the concentration of urine in order to maintain fluid balance. With normal kidney function, a dehydrated client will have an elevated urine osmolality, whereas clients with shock, hyperglycemia, hemoconcentration, and acidosis will have elevations in both urine and serum osmolality. Urine pH The measurement of the pH of urine reveals the hydrogen ion concentration of the urine to determine its acid or alkaline status. When the kidney buffering system is compensating for either metabolic acidosis or alkalosis, the pH of the urine should be within normal range (4.6–8.0). This is considered a sign of normal function. However, when the renal compensatory function fails to respond to the pH of the blood, the urine pH will increase with acidosis and decrease in alkalosis. Serum Albumin Albumin is synthesized in the liver from amino acids. Serum albumin plays an important role in fluid and NURS I N G T I P Urine Osmolality Urine osmolality is a more accurate indicator of hydration than is the specific gravity of urine. Some medications and the presence of protein and glucose solutes in the urine can give a false high specific gravity reading.
Figure 37-9 Osmosis as it relates to the osmolarity of a solution. The movement of water through a membrane from a lower concentration to a higher concentration is called osmosis. In a hypotonic solution, the water moves into the cells, causing them to swell and burst. The cells in the isotonic solution are normal in size and shape because the same amount of water is entering and leaving the cells. Cells in the hypertonic solution are losing water because water moves from a weaker concentration inside the cell to a greater concentration outside the cell membrane. electrolyte balance by maintaining the colloid osmotic pressure of blood, which prevents the accumulation of fluid (edema) in the tissues. However, serum albumin has a half-life of 21 days and fluctuates according to the level of hydration; therefore, it is not a good indicator of acute alterations in protein depletion. Clinically, this blood test is used to measure prolonged protein depletion, which occurs in chronic malnutrition. Refer to Chapter 38 for a discussion of serum albumin and pre-albumin. NURSING DIAGNOSIS In order to make a nursing diagnosis, the nurse must be able to interpret assessment and biochemical data and draw conclusions relative to the client’s imbalance. The primary nursing diagnoses for clients with fluid imbalances are presented in the accompanying display. Excess Fluid Volume Excess fluid volume (EFV) exists when the client has increased interstitial and intravascular fluid retention and edema. EFV is related to the excess fluid either in tissues of the extremities (peripheral edema) or in lung tissues (pulmonary edema). Factors that put the client at risk for EFV are: • Excessive intake of fluids (e.g., intravenous therapy, sodium) • Increased loss or decreased intake of protein (chronic diarrhea, burns, kidney disease, malnutrition) • Compromised regulatory mechanisms (kidney failure) • Decreased intravascular movement (impaired myocardial contractility) • Lymphatic obstruction (cancer, surgical removal of lymph nodes, obesity) • Medications (steroid excess) • Allergic reaction Assessment findings in the client with FVE include acute weight gain; decreased serum osmolality (less than 275 mOsm/kg), protein and albumin, BUN, Hgb, Hct; increased central venous pressure (greater than 12–15 cm H2O); and signs and symptoms of edema. The clinical manifestations of edema are relative to the area of involvement, either pulmonary or peripheral (see the accompanying display). Deficient Fluid Volume Deficient fluid volume (DFV) exists when the client experiences vascular, interstitial, or intracellular dehydration. The degree of dehydration is classified as mild, marked, severe, or fatal on the basis of the percentage of body weight lost. There are three types of dehydration based on the proportion of fluid and particles in the intracellular and extracellular spaces (see the accompanying display). Kleiner (1999) reports that a portion of the general population may be chronically mildly dehydrated based on the Nationwide Food Consumption Surveys. According to Sansevero (1997), approximately 1 millionelderly people a year are admitted to hospitals with iso- tonic dehydration, and 19% of emergency room admissions were prompted by dehydration, frequent falling, or failure to care for self. Mild dehydration, as little as 2% loss of body weight, results in impaired physiological and performance responses, and may be misinterpreted as a sign of aging and not hydration status (Kleiner, 1999). Assessment findings in the client with DFV include thirst and weight loss, with the amount varying with the degree of dehydration. With marked dehydration, the mucous membranes and skin are dry. There is poor skin turgor; low-grade temperature elevation; tachycardia; respirations 28 or greater; a decrease (10–15 mm Hg) in systolic blood pressure; slowing in venous filling; a decrease in urine (less than 25 ml per hour); concentrated urine; elevated Hct, Hgb, BUN, and an acid blood pH (less than 7.4). Severe dehydration is characterized by the symptoms of marked dehydration. Also, the skin becomes flushed. The systolic blood pressure continues to drop (60 mm Hg or below). There are behavioral changes (restlessness, irritability, disorientation, and delirium). The signs of fatal dehydration are anuria and coma that leads to death. NURSING DIAGNOSES FOR FLUID ALTERATIONS Excess Fluid Volume related to: • Excessive fluid intake secondary to excess sodium intake • Compromised regulatory mechanism (renal and cardiac dysfunction) • Inaccurate intravenous infusion rate Deficient Fluid Volume related to: • Excessive fluid loss secondary to vomiting, blood loss, surgical drains and tubes, diarrhea, and diuretics Risk for Deficient Fluid Volume related to: • Extremes of age (very young or old) and weight • NPO and fluid restrictions • Increased fluid output from normal routes: vomiting, diarrhea, urine • Increased fluid losses from drainage or suction routes: wounds, drains, indwelling tubes (e.g., urine catheter, nasogastric suction) • Loss of plasma associated with severe trauma and burns • Disorders that impair fluid intake or absorption (immobility, unconsciousness) • Chronic disorders: congestive heart failure, pulmonary edema, chronic obstructive lung disease, renal failure, diabetes, cancer, transplant candidates • Deficient knowledge related to factors influencing fluid requirements (hypermetabolic states, hyperthermia, and dry, hot environment) • Medications (e.g., diuretics) Risk for Deficient Fluid Volume Risk for fluid volume deficit exists when the client is at high risk of developing vascular, interstitial, or intracellular dehydration resulting from active or regulatory losses of body water in excess of needs. The multiple factors that can place the client at risk for FVD are listed in the preceding accompanying display. Other Nursing Diagnoses The relationship between the primary nursing diagnoses just discussed and the secondary diagnoses in clients with fluid imbalances are reciprocal: The primary diagnoses influence and are influenced by the secondary diagnoses. Holistic nursing requires that all diagnoses relative to clients be considered when developing their plan of care. Impaired Gas Exchange Impaired gas exchange related to a ventilation perfusion imbalance occurs when clients experience a decreased passage of oxygen or carbon dioxide between the alveoli of the lungs and the vascular system. This alteration is assessed by measuring the oxygen and carbon dioxide content through arterial blood gas analysis or pulse oximetry or both. Refer to Chapter 32 for further discussion of oxygenation. Decreased Cardiac Output Decreased cardiac output occurs when the blood pumped by a client’s heart is reduced so much that it is inadequate to meet the needs of the body’s tissue. This alteration may be caused by heart failure and various types of shock. Assessment findings may include low blood pressure; cool, clammy skin; weak, thready pulses; decreased urinary output; and a diminished level of consciousness. Risk for Infection Many disorders may place the client at risk for invasion by pathogenic organisms. Clients receiving IV therapy are at risk for an infection because their primary defense, the skin, is broken at the puncture site. Assessment findings indicative of IV site infection are client complaints of soreness around site, erythema, swelling at site, and foul-smelling discharge. Impaired Oral Mucous Membrane Altered oral mucous membrane occurs when a client experiences disruption in the tissue layers of the oral cavity. It is frequently related to dehydration. Assessment findings may include: oral pain or discomfort; stomatitis; and decreased salivation. NURSING ALERT Loss of Gastric Juices Clients who lose excessive amounts of gastric juices, either through vomiting or suctioning, are prone to develop not only DFV but also metabolic alkalosis, hypokalemia, and hyponatremia; gastric juices contain hydrochloric acid, pepsinogen, potassium, and sodium. Deficient Knowledge A knowledge deficit may exist to varying degrees in clients with fluid imbalances. Information obtained from a client’s health history may indicate the client’s level of understanding and perception of these alterations and direct teaching. Clients need to participate actively in their plan of care. PLANNING AND OUTCOME IDENTIFICATION Holistic nursing care for clients experiencing fluid imbalances requires that the nurse, in collaboration with each client, identify specific goals for the nursing diagnosis. These goals should be individualized to reflect the client’s capabilities and limitations and should be appropriate to the diagnosis as determined by the assessment data. During the planning phase, the nurse also selects and prioritizes nursing interventions to support the client’s achievement of expected outcomes based on the goals. For example, if vomiting and diarrhea, with a weight loss of 5% and dry mucous membranes, led to a diagnosis of Deficient Fluid Volume, then goals might include relief from vomiting and diarrhea and achievement of the proper fluid balance of intake and output. Expected outcomes for clients with fluid imbalances are not only specific to their primary diagnosis but also require inclusion of outcomes relative to interventions. An expected outcome for clients receiving IV therapy might read: IV site remains free from erythema, edema, and purulent drainage, because these clients are at risk for infection. Achievement of the goals and the client’s expected outcomes indicates resolution of the problem. IMPLEMENTATION Nurses have the responsibility to collaborate with and advocate for clients to assure that they receive care that is appropriate, ethical, and based on practice standards. Nurses rely heavily on the data obtained from the history in formulating expected outcomes and selecting appropriate nursing interventions to support the clients’ natural patterns as revealed in their history. The rationale for interventions related to alterations in either body fluid or electrolytes is based on the goal of maintaining homeostasis and regulating and maintaining essential fluids and nutrients. The nurse capitalizes on the clients’ adaptive capabilities by selecting interventions based on the clients’ perception of their support, strengths, and options. Bulechek and McCloskey (1999) address the importance of the nursing interventions relative to fluid therapy by identifying the nurse’s responsibilities to: • Understand the client’s metabolic needs and to make judgments concerning the outcomes of therapy • Perform frequent assessment and monitoring to recognize the adverse effects of fluid and electrolyte therapy and prevent complications • Prevent the rapid depletion of the body’s protein and energy reserves The nursing activities relative to assessment and implementation often require the same measurements: for example, weight and vital signs. Common interventions that promote attainment of expected outcomes to restore and maintain homeostasis are discussed next. Monitor Daily Weight Daily weight is one of the main indicators of water and electrolyte balance. The nurse is responsible for the accurate measurement and recording of daily weights; the health care practitioner uses these data with other clinical findings in determining the client’s fluid therapy. Measure Vital Signs The frequency of measuring the vital signs is dependent upon the client’s acuity level and clinical situation. For example, the vital signs of the typical postoperative client might be taken every 15 minutes until stable, whereas a client experiencing shock or hemorrhage should have vital signs monitored continuously. Vital sign measurements and other clinical data are used to determine the type and amount of fluid therapy. Measure Intake and Output Intake and output measurements are initiated to monitor the client’s fluid status over a 24-hour period (see Procedure 37-1 for information on how to measure the I&O). Agency policy relative to I&O may vary with regard to: • The time frames for charting (e.g., every 8 hours versus every 12 hours) • The time at which the 24-hour totals are calculated • The definition of “strict” I&O “Strict” I&O measurement usually involves accounting for incontinent urine, emesis, and diaphoresis and might require weighing soiled bed linens. Don gloves before handling soiled linen. The nurse reviews the client’s 24-hour I&O calculations to evaluate fluid status. Intake should exceed the output by 500 ml to account for insensible body loses. I&O and daily weights are critical components of intervention because these measurements are also used to evaluate the effectiveness of diuretic or rehydration therapy. Securing an accurate I&O requires the full support of the client and his or her family. The client and family members should be taught how to measure and record the intake (see the accompanying display for special home health care considerations). Provide Oral Hygiene The nurse is responsible for providing oral hygiene to promote client comfort and integrity of the buccal cavity. Refer to Chapter 31 for the procedure on oral hygiene. The frequency of oral hygiene depends on the condition of the client’s buccal cavity and the type of fluid imbalance. A client who is dehydrated or NPO for more than 24 hours may have decreased or absent salivation, coated tongue, and furrows on the tongue. These clients are at risk for developing oral diseases such as stomatitis, oral lesions or ulcers, and gingivitis. Initiate Oral Fluid Therapy Oral fluids may be totally restricted—a situation commonly referred to as nothing by mouth (NPO, which is from the Latin non per os)—or they may be restricted or forced, depending on the client’s clinical situation. For example, oral replacement therapy is often used for clients with mild dehydration. According to Hugger, Harkless, and Rentschiler (1998), oral rehydration therapy has a very high success rate in the treatment of childhood diarrhea with mild to moderate dehydration, and it has fewer complications when compared to intravenous replacement therapy. Severe dehydration in children is a medical emergency and must be treated with intravenous replacement therapy. Nothing by Mouth Clients are placed NPO status as prescribed by the health care practitioner. On the basis of agency policy and clarification with the health care practitioner, the client may be allowed small amounts of ice chips or medications with a sip of water when NPO. Common clinical situations that may require NPO status include the need to: • Avoid aspiration in unconscious, perioperative, and preprocedural clients who will receive anesthesia or conscious sedation • Rest and heal the gastrointestinal (GI) tract in clients with severe vomiting or diarrhea or when the client has a GI disorder (inflammation or obstruction) • Prevent the further loss of gastric juices in clients with nasogastric suctioning NPO clients should receive oral hygiene every 1 to 2 hours or as needed for comfort and to prevent alterations of the mucous membranes. APPLICATION: HOME CARE Considerations for Measuring I&O • Elicit client and family member input when selecting household items to be used for intake measurement. • Provide containers for measuring output; adapt the urinary container to home facilities, and include teaching relative to proper washing and storage. • Teach handwashing technique. • Provide written instructions on what is to be measured. • Provide sufficient I&O forms to last between the nurse’s visits. • Identify the parameters for evaluating a discrepancy between the intake and output and for notifying the nurse or health care practitioner. NURSING ALERT Remove Gloves before Charting Remove gloves and wash hands before recording the amount of drainage on the I&O form, to prevent the transfer of microorganisms when the form is removed from the client’s room. THINK ABOUT IT Oral Hygiene When you wake up in the morning, do you drink or eat anything before brushing your teeth? If you were sick, hospitalized, without family or significant other support, would you want to drink or eat if your mouth tasted sour? Many of your clients will feel the same way and will need supportive nursing care to maintain oral hygiene. Muscular weakness and difficulty swallowing are other problems that could compound the client’s dependency on you for oral hygiene. NURS I N G T I P Mouthwashes Avoid the use of alcohol and glycerin mouthwashes and glycerin swabs. These ingredients may feel refreshing, but they have a drying effect on the mucous membranes. Restricted Fluids Intake may be restricted to 200 ml over a 24-hour period; intake is commonly restricted in the treatment of EFV related to heart and renal failure. Client and family teaching and collaboration are the main nursing interventions in implementing this measure. How the nurse limits the fluids should be determined in collaboration with the client. For example: • Fifty percent of the allowed fluids might be taken at breakfast and lunch. • The remaining 50% might be taken with the evening meal, before bedtime, unless the client has to be awakened during the night for a medication. Forced Fluids Forcing or encouraging the intake of oral fluids, mainly water, may be done when treating elderly clients who are at risk for dehydration and clients with renal and urinary problems, for example, kidney stones. Compliance is obtained by client education and preference relative to timing and the type of liquids. A client might, for example, be requested to consume 2,000 ml over a 24-hour time period. If the client is intimidated on hearing this amount, which may sound very large, explain that the number of glasses to which this volume equates is only eight. Follow a similar time frame as set forth for restricted fluids, with the largest quantity of fluids administered with meals. Ice, gelatin, and ice cream count as liquid intake. Maintain Tube Feeding When the client cannot ingest oral fluids and has a normal GI tract, fluids and nutrients can be administered through a feeding tube as prescribed by a health care practitioner. Refer to Chapter 38 for a complete discussion of feeding tubes. Monitor Intravenous Therapy When fluid losses are severe or the client cannot tolerate oral or tube feedings, fluid volume is replaced parenterally through the intravenous route. Intravenous (IV) therapy is the administration of fluids, electrolytes, nutrients, or medications by the venous route. The health care practitioner prescribes IV therapy to treat or prevent fluid and electrolyte or nutritional imbalances. The nurse has specific responsibilities relative to IV therapy (see the accompanying Nursing Process Highlight). The Intravenous Nurses Society (INS) is the professional organization that establishes standards of practice to promote excellence in intravenous nursing to ensure the highest quality, cost-effective care for all individuals requiring infusion therapies (INS, 2000). INS standards of practice direct the development of agency policy/protocols in accordance with state and federal regulations and should complement the manufacturer’s direction for usage. The nurse should review the agency’s protocols before gathering the equipment. IV therapy requires parenteral fluids (solutions) and special equipment: administration set, IV pole, filter, regulators to control IV flow rate, and an established venous route. Parenteral Fluids The nurse confirms the type and amount of IV solution by reading the health care practitioner’s prescription in the medical record. IV solutions are sterile and packaged in plastic bags or glass containers. Solutions that are incompatible with plastic are dispensed in glass containers. Plastic IV solution bags collapse under atmospheric pressure to allow the solution to enter the infusion set. Plastic solution bags are packaged with an outer plastic bag, which should remain intact until the nurse prepares the solution for administration. When the plastic solution bag is removed from its outer wrapper, the solution bag should be dry. If the solution bag is wet, the nurse should not use the solution. The moisture on the bag indicates that the integrity of the bag has been compromised and that the solution cannot be considered sterile. The bag should be returned to the dispensing department that issued the solution. Glass containers are discussed in the section on equipment. IV solutions are usually packaged in quantities ranging from 50 to 1,000 ml. The nurse should select a container that has the prescribed amount of solution or select several containers that together contain the prescribed volume. At no time should the nurse select a container
Implementation of IV Therapy • Know why the therapy is prescribed. • Document client understanding. • Select the appropriate equipment in accordance to agency policy. • Obtain the correct solution as prescribed. • Assess the client for allergies: tape, iodine, ointment, or antibiotic preparations to be used for skin preparation of the venipuncture site. • Administer the fluid at the prescribed rate. • Observe for signs of infiltration (the seepage of substances into the interstitial tissue that occurs as the results of accidental dislodgement of the needle from the vein) and other complications that are fluid-specific. • Document implementation of prescribed IV therapy in the client’s medical record. whose volume is greater than that prescribed. For example, if the client is to receive 600 ml of normal (0.9%) saline, the nurse must not select a 1000 ml container, but rather two containers, 100 ml and 500 ml (containers are not prepared in volumes of 600 ml). Crystalloids (electrolyte solutions with the potential to form crystals) are used to replace concurrent losses of water, carbohydrates, and electrolytes. Sodium chloride and Ringer’s lactate are commonly used crystalloid solutions. There are three types of parenteral fluids that are classified in accord with the tonicity of the fluid relative to normal blood plasma. As previously discussed, an osmolar solution can be hypotonic, isotonic, or hypertonic. The type of solution is prescribed on the basis of the client’s diagnosis and the goal of therapy. The normal osmolarity of blood is between 280 and 295 mOsm/L, so the desired effect of the tonicity of the fluid is determined as follows: 1. Hypotonic fluid (hypo-osmolar, less than 290 mOsm/L) lowers the osmotic pressure and causes fluid to move into the cells; if fluid is infused beyond the client’s tolerance, water intoxication may result. 2. Isotonic fluid (iso-osmolar, 290 mOsm/L) increases extracellular fluid volume; if fluid is infused beyond the client’s tolerance, cardiac overload may result. 3. Hypertonic fluid (hyperosmolar, greater than 290 mOsm/L) increases the osmotic pressure of the blood plasma, drawing fluid from the cells; if fluid is infused beyond the client’s tolerance, cellular dehydration may result (Bulechek & McCloskey, 1999). Table 37-5 discusses the common types of intravenous solutions in terms of their tonicity, contents, and clinical usage. Crystalloid solutions can be isotonic (equal to the sodium chloride concentration of blood, 0.9%); hypotonic (less than the sodium chloride concentration of blood); and hypertonic (greater than the sodium chloride concentration of blood) (Kee & Paulanka, 2000). Colloids (nondiffusable substances) function like plasma proteins in blood by exerting a colloidal pressure to replace intravascular volume only. Examples of colloidal solutions are albumin, dextran, Plasmanate, and hetastarch (artificial blood substitute). During the administration of these solutions, the nurse should monitor the client for hypotension and allergic reactions (Bulechek & McCloskey, 1999; Kee & Paulanka, 2000). Blood transfusions are discussed later in this chapter. Equipment IV equipment is sterile, disposable, and prepackaged with user instructions. The user instructions are usually placed on the outside of the package, with a schematic that labels the parts, allowing the user to read the package prior to opening. The following discussion regarding intravenous equipment, inclusive of the frequency when to change disposal intravenous therapy equipment, is based on the revised 2000 Infusion Nursing Standards of Practice developed by INS. All intravenous equipment must be inspected by the nurse to determine the integrity of the IV product before, during, and after use. Product integrity refers to the sterility of the equipment. Products are assessed for integrity by visual examination of the product and checking the expiration date on the equipment. All products identified with a defect must be returned to the appropriate department within the agency with a written report identifying the defect. Since intravenous therapy provides a direct access into the vascular system, the nurse must understand the basic epidemiology principles and common organisms that may cause an infection and implement infection control measures to minimize the potential for infectious complications. The nurse uses aseptic technique and standard precautions when assembling and changing intravenous equipment. To decrease the risk of pathogen transmission, handwashing is required before and immediately after all IV procedures and upon removal of gloves. The frequency of changing sterile intravenous equipment not only reflects the national standards of practice but the agency’s established infection control policies. Infection control data may allow the agency to increase the time interval beyond the recommended standard provided the data verifies low infection rates. INS (2000) recommends that an organization that exhibits an increased rate of catheter-related bloodstream infection with the practice of 72-hour administration set changes should return to a 48-hour administration set change interval. Administration Set The administration set (infusion set) refers to the plastic disposal tubing that provides for the infusion of a solution. There are several types of infusion sets to accommodate the solution and the mode of administration: primary continuous; secondary; primary intermittent; and special tubing for certain solutions such as blood/blood components. There are several add-on devices, such as extension sets, filters, stopcocks, PRN adaptor, and needleless devices that are used in conjunction with the administration set and changed whenever the set is changed. Administration sets are changed at established time intervals and immediately upon suspected contamination or when the integrity of the set has been compromised. The administration set contains an insertion spike with a protective cap, a drip chamber, tubing with a slide clamp and regulating (roller) clamp, a rubber injection port, and a protective cap over the needle adapter (Figure 37-10). The protective caps keep both ends of the infusion set sterile and are removed only just before usage. The insertion spike is inserted into the port of the IV solution container. Infusion sets can be vented or nonvented. The nonvented type is used with plastic bags of IV solutions and vented bottles. The vented set is used for glass containers that are not vented (Figure 37-11). Glass containers require an air vent so that air can displace fluid from the container into the IV tubing.
Some glass bottles are vented with an inside tube that exits the bottle into a rubber stopper in the neck of the bottle; if the bottle is not vented, then the nurse needs to select a vented infusion set. The drip chamber is calibrated to allow a predictable amount of fluid to be delivered. There are two types of drip chambers: a macrodrip, which delivers 10 to 20 drops per milliliter of solution, and a microdrip, which delivers 60 drops per milliliter. The drip rate varies with the manufacturer as indicated on the package. The administration set has a manual flow-control device such as a slide clamp (Figure 37-10), a roller clamp, or a screw to regulate a prescribed infusion rate. Follow the manufacturer’s guidelines when using the manual flow-control device to regulate the prescribed infusion rate. The end of the IV tubing contains a needle adapter that attaches to the sterile device inserted in the client’s vein. Extension tubing may be used to lengthen the primary tubing. A primary continuous administration set is used to administer routine solutions prescribed to infuse continuously over a 24 hour period. The primary administration set, inclusive of the add-on devices, is changed every 48 to 72 hours in conjunction with the peripheral cannula change. A bag of intravenous solution should not hang longer than 24 hours. Secondary administration sets are often referred to as “piggyback” administration sets. The secondary tubing is connected into the primary tubing at an injection site (see Figure 37-11) and allows for the administration of a second solution such as medication. Secondary administration sets are also changed every 48 to 72 hours. Primary intermittent administration sets are used to deliver medications at prescribed intervals through an injection/access port and are changed every 48 to 72 hours; all add-on devices such as extension sets, filters, PRN adaptors, and stopcocks are changed with the intermittent administration set. A sterile needle/ needleless device should be aseptically attached to the intermittent administration set prior to administering the medication and removed immediately after each use. Health Hazard A Health Alert from Health Care Without Harm (HCWH) (1999) cautioned the public about the potential risks of exposure to diethylhexyl phthalates (DEHP) from medical products such as IV bags and tubing. More than 500 million IV bags are used in the United States every year to deliver blood, medication, and other essential solutions to clients (HCWH, 1999). Eighty percent of the IV bags are made with polyvinyl chloride (PVC), which requires a plasticizer to make the bags soft and flexible. DEHP is the softener used in PVC products. DEHP has been shown to leach from IV bags into the solutions they contain and directly into the client’s bloodstream. The Environmental Protection Agency has classified DEHP as a probable human carcinogen and HCWH claims that studies have shown that DEHP can damage the heart, liver, testes, and kidneys and interfere with sperm production. Certain drugs such as Taxol (used to treat breast cancer) and Taxotere (used to treat ovarian and breast cancer and AIDS-related Kaposi’s sarcoma) have been shown to increase the leaching of DEHP from PVC plastics into the solution (Stewart, 1999); see the accompanying display for additional drugs that can increase leaching of DEHP from PVC IV products. Although one leading producer of intravenous vinyl IV bags containing DEHP plans to develop an alternative to polyvinyl chloride or PVC for their products, no time frames were given to totally remove these products from the market. A second health hazard is inherent in the use of DEHP. The disposal of medical products containing DEHP releases highly toxic and endocrine-disrupting dioxins. According to the ANA (1999), PVC is the only plastic linked both to phthalate chemical leaching and to the production of dioxin. Intravenous Filters Intravenous filters prevent the passage of undesirable substances such as particulate matter and air from entering the vascular system. Particulate matter filters are utilized when preparing infusion medications for administration to prevent obstruction in the vascular/pulmonary systems, irritation and phlebitis (inflammation of a vein). Aireliminating filters are used for the delivery of infusion therapy to decrease the potential of air emboli; the filter should be located as close as possible to the cannula site. IV filters come in various sizes; the finer the filter, the greater is the degree of solution filtration. Although studies have shown that IV filters reduce the risk of bacteremia and phlebitis as much as 40%, some agencies do not use IV filters because of cost. Many IV catheters contain an in-line filter; if the catheter has an in-line filter, it is not necessary to add a filter to the tubing. Needles and Venous Peripheral-Short Catheters Needles and peripheral-short catheters provide access to the venous system. A variety of devices are available in different sizes to complement the age of the client, the type and duration of the therapy, and to protect the user from injury (Figure 37-12). As with any gauge needle, the larger the number, the smaller the lumen. The nurse considers the client’s age, body size, and the type of solution to be administered when selecting the gauge of the needle or catheter: • Infants and small children, 24 gauge • Preschool through preteen, 24 or 22 gauge DRUGS THAT INCREASE LEACHING OF DEHP FROM PVC PLASTICS • Chemotherapeutic agents: Etoposide (VePesid) and Teniposide (Vumon) • Antianxiety agents: Chlordiazepoxide HCl (Librium) • Antifungal agents: Miconazole (Monistat IV) • Immunosuppressive agents: Cyclosporine (Sandimmune) and Tacrolimus (Prograf) • Nutritional solutions: Fat emulsions and vitamin A NURS I N G T I P Age Considerations forChoosing IVs and Equipment Neonates, infants, and children are at risk for Altered Fluid Balance: Overload, related to rehydration. IV tubing with a microdrip and special volume control chambers is used to regulate the amount of fluid to be administered over a specific time interval. Armboards and soft restraints are used to stabilize peripheral infusions by immobilizing the extremity to prevent accidental removal of infusion devices.
• Teenagers and adults, 22 or 20 gauge • Geriatric, 22 or 24 gauge Butterfly (scalp vein or wing-tipped) needles are short, beveled needles with plastic flaps attached to the shaft. The flaps (which are flexible) are held tightly together to facilitate ease of insertion and then flattened against the skin to prevent dislodgement during infusion. These needles are commonly used for short-term or intermittent therapy and for infants and children. There are several types of short catheters used to access peripheral veins. Short peripheral venous catheters vary in length from 3/4 to 1 1/4 inches. During insertion, some of these catheters are threaded over a needle, and others are threaded inside a needle. Intracath is a term used to refer to a plastic tube inserted into a vein. An angiocatheter is a type of intracath with a metal stylet to pierce the skin and vein, after which the plastic catheter is threaded into the vein and the metal stylet is removed, leaving only the plastic catheter in the vein. Short venous catheters can have safety devices to reduce the risk of accidental needlesticks. These devices are designed to allow for easy insertion of the catheter while providing a built-in safety feature for the user. As the catheter is threaded over the needle and advanced into the vein, the built-in needle guard advances forward toward the tip of the needle; when the catheter hub is removed from the device, the entire needle is encased within the needle guard. Peripheral Intravenous (PI) and Heparin Locks Peripheral intravenous (PI) and heparin locks are devices that establish a venous route as a precautionary measure for clients whose condition may change rapidly or who may require intermittent infusion therapy. A butterfly needle or peripheral catheter is inserted into a vein and the hub is capped with a lock port, also called a Luer lock (Figure 37-13). Needle-Free System Safety is a concern associated with IV therapy; refer to Chapter 31. Accidental needle-stick injuries and puncture wounds with contaminated devices increase the employee’s risk for infectious diseases such as AIDS, hepatitis (B and C), and other viral, rickettsial, bacterial, fungal, and parasitic infections. Most health care agencies now use totally needle-free IV systems (Figure 37-14) to decrease the risk of employee injuries. Vascular Access Devices Vascular access devices (VAD) include various catheters, cannulas, and infusion ports that allow for long-term IV therapy or repeated access to the central venous system. The kind of VAD used depends on the client’s diagnosis and the type and length of treatment (see Table 37-6). Site selection and insertion of central catheters, other than peripherally inserted central catheters, is a medical act performed by a practitioner. Although there are many types of catheter materials, insertion techniques and kinds of central catheters, all central catheters must be radiopaque to allow for radiographic verification of placement of the catheter and its tip prior to the administration of any solution. Central catheters are usually inserted into the internal jugular and subclavian veins with the distal tip located in the superior vena cava to minimize vessel irritation and sclerosis. The femoral vein can be used for central venous access when there is thrombosis of the internal jugular or subclavian veins; correct tip location should be in the inferior vena cava. Insertion of a central catheter can be performed either percutaneously or surgically. Surgically, a central catheter is either placed
N . An implantable port is a device made of a radiopaque silicone catheter and a plastic or stainless steel injection port with a self-sealing silicone-rubber septum. The health care practitioner inserts the device into a subcutaneous pocket, usually over the third or fourth rib, lateral to the sternum. The distal tip of the catheter is surgically tunneled in the cephalic or external jugular vein, with the proximal end of the catheter tunneled through the subcutaneous tissue into the injection port of the device. Implanted ports and pumps are vascular access devices that provide for the delivery of prescribed parenteral therapies. Accessing these devices requires the use of aseptic technique. Noncoring needles such as a Huber needle are used to access an implanted port/pump and should be changed at least every 7 days. The smallest gauge noncoring needle that can deliver the prescribed therapy should be used when accessing the port/pump. Nurses caring for clients with implanted ports/pumps must have a thorough knowledge of the design features of the device, as explained in the manufacturer’s guidelines, to ensure correct access and administration techniques, maintenance, and potential complications. Implanted pumps have a reservoir designed to continuously infuse a specific volume of solution over a preset period of time; the pump must be routinely emptied and refilled at established intervals. Some pumps have an additional feature, a side port designed for administration of intermittent medication. The flow rate of some pumps is sensitive to changes in atmospheric pressure, body temperature, blood pressure and the viscosity of the medications. Clients are instructed to report changes in their lifestyle and physical condition that may affect the pump’s flow rate. Only nurses who have been specially trained are allowed to access an implanted port/pump because of the risk of infiltration into the tissue if needle placement is incorrect. A peripherally inserted central catheter (PICC) is thegeneric name for 11 different devices. A PICC is a silicone or polyurethane catheter inserted into one of the major veins in the antecubital fossa. Although the length of the catheter varies, on an average a PICC is 52 cm long, and its tip resides in the lower-third section of the superior vena cava. A PICC can be trimmed at the time of insertion to a specific length that is determined by the approximate distance between the insertion site and the superior vena cava. The majority of state boardsof registered nurses allow specially trained nurses to insert the PICC. Placement of the catheter’s tip is confirmed by x-ray prior to the administration of any solution. The registered nurse that inserts the PICC must document the type of PICC inserted and the total length of the inserted catheter, and record if the length of the catheter was trimmed prior to insertion. Preparing an Intravenous Solution To prepare an IV solution, read the agency’s protocol and gather the necessary equipment. Because IV equipment and solutions are sterile, check the expiration date on the package prior to usage. The solution can be prepared at the nurses’ work area or in the client’s room (Procedure 37-2). The nurse prepares and applies a time strip to the IV solution bag to facilitate monitoring of the infusion rate as prescribed by the health care practitioner (Figure 37- 19). The IV tubing is tagged with the date and time to indicate when the tubing replacement is necessary. IV tubing is changed every 48 to 72 hours in accord with the agency’s protocol. The nurse initials the time strip and IV tubing tag.
NURSING ALERT Marking an IV Bag Do not use a felt-tip pen to mark an IV bag; the ink from the pen can leak through the plastic and contaminate the solution. Do not label bag with time strip made of adhesive/silk/paper tape, as the adhesive will leach into the bag. Use only labels appropriate for IV bags. Initiating IV Therapy When initiating IV therapy, the nurse should assess for a venipuncture site. Figure 37-20 presents the common peripheral sites for starting IV therapy in pediatric, adult, and geriatric clients (see Chapter 28, Procedure 28-1, Venipuncture). When assessing clients for potential sites, consider their age, body size, clinical status and impairments, and the skin condition (see the accompanying display for contraindications when selecting a site). Lowerextremity veins are used for IV therapy only when so prescribed by the health care practitioner; circulating
Figure 37-20 Peripheral Veins Used in Intravenous Therapy. A. Armand Forearm; B. Dorsum of the Hand; C. Dorsal Plexus of the Foot blood in the lower extremities is likely to pool and clot, which may result in an embolism. Because contact with blood is likely, venipuncture requires the implementation of Standard Precautions. Refer to Chapter 31 for a complete discussion of Standard Precautions. Select a vein for puncture at its most distal end to maintain the integrity of the vein, because venous blood flows with an upward movement toward the heart. When a vein is punctured with an instrument, such as a needle, fluids can infiltrate (leak from the vein into the tissue at the site of puncture). If IV therapy has to be discontinued for any reason, such as infiltration, it can be restarted above the initial puncture site only. Vein Finder A vein finder is a device used to locate hard-to-find veins. It is helpful, for example, in working with obese clients whose superficial veins are difficult to locate. A Venoscope (Figure 37-21) is a type of vein finder with adjustable fiberoptic arms that reveal veins. The room is dimmed, and the disposable skids are placed flush against the skin. The nurse slowly moves the Venoscope along the extremity until a dark, shadowy line is seen between the fiberoptic arms. Once the vein is identified, it can also be checked to determine whether it is sclerotic. To assess for sclerotic veins, apply a downward pressure over the fiberoptic arms and observe the vein when pressure is applied then released. A nonsclerotic vein will disappear with pressure and reappear when pressure is released. Administering IV Therapy Once the solution is prepared for administration, the nurse calculates the rate and explains the procedure to the client (see Procedure 37-3 for the administration of IV therapy). There are three ways to administer solutions: 1. Initiate the infusion by performing a venipuncture. 2. Use an existing IV system: catheter, heparin or PI lock, central line, or implanted port. 3. Add a solution to a continuous-infusion line.
Fluid administration can be continuous, ongoing over a 24-hour period, or intermittent, 1000 ml ordered once in a 24-hour period. Although fluids may be continuous, the type of fluids can alternate over a 24-hour period; for example, an order might be add 40 mEq of KCl to first bag of 1000 ml of normal saline. IV medications may be piggybacked, added to an existing intravenous solution to infuse concurrently. IV solutions and medications that have been refrigerated should
Flushing Flushing refers to the instillation of a solution into an intravenous cannula. Flushing is performed to assess and maintain cannula patency and prevent the mixing of incompatible medications and/or solutions, following the conversion of continuous IV therapy to intermittent IV therapy, and to maintain intermittent cannula patency following IV medication administration and blood sampling. The type of solution and frequency of flushing an intermittent intravenous cannula is determined by the agency’s policy/protocol. According to the INS (2000), flushing a cannula at established intervals with saline (0.9% sodium chloride injection) is the accepted solution to ensure and maintain patency of an intermittent PI cannula, while a heparin flush solution is the accepted solution to maintain patency of an intermittent central venous devices. The volume of flush is equal to the volume capacity of the cannula and add-on devices times two (INS, 2000). Consideration is also given to the volume and frequency of heparin flush in order to prevent an alteration in the client’s clotting factors. When flushing a cannula positive pressure within the lumen of the catheter must be maintained to prevent the reflex of blood into the cannula lumen. Use the manufacturer recommended maximum pressure limits (pounds per square inch) when selecting the size of the syringe to use for flushing since the smaller the syringe the greater the pressure generated; excessive internal pressures in the device increase the potential for cannula damage and/or progressive internal cannula weakening over the life of the device (INS, 2000). If resistance is met when flushing a cannula, do not exert pressure in an attempt to restore patency of an occluded cannula since this action may result in the dislodgement of a clot into the vascular system and/or rupture of the catheter. Regulating IV Solution Flow Rates Infusion sets with macrodrip chambers are often used for adult clients, whereas microdrip chambers are used for volume-sensitive clients, such as geriatric or pediatric clients. Pediatric and geriatric clients usually require some type of device to regulate the fluids as a safety factor to prevent overload. Devices such as controllers and pumps are commonly used to regulate the rate of infusion. Calculation of Flow Rate The flow rate is the volume of fluid to infuse over a set period of time as prescribed by the health care practitioner. The health care practitioner will identify either the amount to infuse per hour (such as 125 ml per hour or 1000 ml over an 8-hour period). Calculate the hourly infusion rate as follows: For example, if 1000 ml is to infuse over 8 hours: Calculate the actual infusion rate (drops per minute) as follows: For example, if 1000 ml is to infuse over 8 hours with a tubing drop factor of 10 drops per milliliter: Another way to calculate the actual infusion rate is to use the hourly infusion rate; for the example just given: Flow-Control Devices Flow-control devices are used to regulate the infusion at the prescribed administration rate. Safety factors such as the client’s age and condition, prescribed therapy, and setting are considered when selecting a flow-control device. There are two basic types of flow-control devices: manual flow-control devices and electronic infusion devices. Manual flow-control devices include roller, screw, and slide clamps and may include volume control devices such as Buretrol. These devices are used routinely to regulate the accurate delivery of most prescribed IV therapy. Electronic infusion devices are operated either by electricity or battery and are used to administer IV fluids and medications and should be considered on all central access devices (INS, 2000). Electronic infusion pumps have audible alarms that sound when the solution has infused, the infusion tubing contains air or is kinked, or the cannula is clotted. There are two types of electronic infusion devices: controllers and pumps. Controller infusion devices generate flow by gravity and are capable of maintaining a constant preset flow rate either by drop counting or volumetric delivery. The nurse sets the flow rate, and the specific gravity of the solution and the height of the bag determine the maximum delivery pressure. Fluids with low-viscosity are usually infused by electronic controllers. Infusion pumps maintain the flow rate under positive pressure. Pumps counter the effects of resistance in the delivery system and pressure fluctuations at the infusion site (McConnell, 1999). Positive pressure infusion devices are classified as either volumetric or syringe pumps, and are used to deliver viscous fluids or large volumes of fluids. Volumetric pumps use either a peristaltic pumping action or a pumping cassette or chamber to delivery a fixed volume over a specified period of time. Syringe infusion pumps rely on a syringe or cartridge to deliver the fluid at a specific set rate. Managing IV Therapy IV therapy requires frequent client monitoring by the nurse to ensure an accurate flow rate and other critical nursing actions; refer to Procedure 37-4. These other actions include ensuring client comfort and positioning; checking IV solution for correct solution, amount, and timing; monitoring expiration dates of the IV system (tubing, venipuncture site, dressing) and changing as necessary; and being aware of safety factors. Coordinate client care with the maintenance of IV lines. Clients with IV therapy usually require assistance with hygienic measures, such as changing a gown (see Procedure 37-4). Change IV tubing when doing site care to decrease the number of times the access device is manipulated, thereby decreasing the risk for infiltration and phlebitis. PI devices are changed every 72 hours as directed by the Centers for Disease Control and Prevention (CDC) guidelines. Hypervolemia Hypervolemia (increased circulating fluid volume) may result from rapid IV infusion of solutions. This causes cardiac overload, which may lead to pulmonary edema and cardiac failure. Monitor the infusion rate hourly and refer to the Nursing Care Plan, Client with Fluid Volume Excess, for the assessment and interventions for a client experiencing fluid volume excess. Total volume Number of hours to infuse = ml/hour infusion rate 1000 8 = 125 ml/hour Total fluid volume Total time (minutes) drop factor = drops per minute 1000 ml 8(60) min10 drops/ml = 10,000 drops 480 min = 20.8 or 21 drops/min 125 ml 10 drops/ml 60 min = 20.8 or 21 drops/min NURSING ALERT Catheter Sepsis If client complains of chills and fever, check length of time that this IV solution has been hanging and the needle or catheter has been in place; assess client’s vital signs, and assess for other symptoms of pyrogenic reactions, such as backache, headache, malaise, nausea, and vomiting. Unexplained fever may be related to catheter sepsis. Pulse rate increases and temperature is usually above 100°F if IV-related sepsis occurs. Stop infusion, notify health care practitioner, and obtain blood specimens if prescribed.
If a solution infuses at a rate greater than prescribed, decrease the rate to keep vein open (KVO) and immediately notify the health care practitioner. Report the amount and type of solution that infused over the exact time period and the client’s response. Infiltration Infiltration may be caused by inserting the wrong type of device, using the wrong-gauge needle, or dislodgement of the device from the vein. When a drug or solution is administered under high pressure by a pump, it may also cause infiltration or vein irritation. Infiltration results in the leaking of fluids or medications into the surrounding tissue. The client usually complains of discomfort at the IV site. Inspect the site by palpating for swelling, and feel the temperature of the skin (coolness and paleness of skin are indications of infiltration). The nurse confirms that the needle is still in the vein by pinching the IV tubing; this action should cause a flashback (blood should rush into the tubing if the needle is still in the vein). If a flashback does not occur, aspirate the injection port nearest the device as explained in Procedure 37-4. Discontinue the needle or catheter if it cannot be aspirated and apply a sterile dressing to the puncture site. After the IV has been removed, the puncture site may ooze or bleed (especially in clients receiving anticoagulants). If oozing or bleeding occurs, apply pressure and reapply a sterile dressing until it stops. Accurately assess and document the degree of edema. Clients may be injured by infiltration. If the IV site becomes grossly infiltrated, the edema in the soft tissue may cause a nerve compression injury with permanent loss of function to the extremity. If a vesicant (medication that causes blistering and tissue injury when it escapes into surrounding tissue) infiltrates, it may cause significant tissue loss with permanent disfigurement and loss of function. Phlebitis Phlebitis may result from either mechanical or chemical trauma. Mechanical trauma may be caused by inserting a device with too large a gauge, using a vein that is too small or fragile, or leaving the device in place for too long. Chemical trauma may result from infusing too rapidly, or from an acidic solution, hypertonic solution, a solution that contains electrolytes (especially potassium and magnesium), or other medications. Phlebitis may be a precursor of sepsis. Listen for client complaints of tenderness, the first indication of an inflammation. Inspect the IV site for changes in skin color and temperature (a reddened area or pink or red stripe along the vein, warmth, and swelling are indications of phlebitis). If phlebitis is present, discontinue the IV infusion. Before removing and discarding the venous device, check the agency’s protocol to see whether the tip of the device needs to be cultured and sent to the laboratory for a culture and sensitivity. After removing the device, apply a sterile dressing to the site and wet warm compresses to the affected area. Document in the nurses’ notes the time, symptoms, and nursing interventions. Hypertonic solutions may cause irritation necessitating frequent IV site changes. Observe site for symptoms of postinfusion phlebitis following IV removal. This may occur in response to either chemical or mechanical factors of the preexisting IV. Postinfusion phlebitis is treated with hot compresses to the site and elevation of the extremity. Intravenous Dressing Change IV dressing changes require the use of Standard Precautions and aseptic technique; refer to Procedure 37-4. Institutional protocol and the type of intravenous access device and dressing determine the frequency of care: 1. Nontransparent (gauze) dressing may be used for a PI. It is changed every 24 hours. 2. Transparent dressings (Bioclusive, OpSite, Tegaderm) allow visualization of the IV site; these dressings are changed every 48 hours. Persistent drainage at the IV site may require dressing changes more frequently or necessitate changing the IV site. Discontinuation of Intravenous Therapy Intravenous therapy is discontinued on health care practitioner order as determined by the client’s need or response to therapy. The removal of a short peripheral catheter is a nursing intervention to minimize the complication risks related to infusion therapy or to implement the health care practitioner’s order. Peripheral catheters are removed every 48 hours and immediately upon suspected contamination or complications. Pressure and a dry sterile dressing are applied to the site upon removal of the catheter; refer to Procedure 37-4. The integrity of the catheter and insertion site should be assessed with observations and actions documented to the client’s medical record. The removal of a PICC is usually a simple procedure; however, research suggests that, in 7% to 12% of PICC removals, difficulties can arise (Macklin, 2000). Only nurses who have been trained in the insertion of a PICC line should remove the catheter. Since the catheter is completely inserted in the vascular system and invisible, the nurse must feel for resistance during removal. If resistance is felt, the nurse stops and assesses for certain complicating factors: venous spasm, vagal reaction, phlebitis, thrombosis, and knotting of the catheter. Prior to removal, the nurse must verify in the client’s medical record the type and the specific length of the inserted PICC. Blood Transfusion The purpose of a blood transfusion is to replace blood loss (deficit) with whole blood or blood components. NURSING ALERT IVs and the Critically Ill Never remove a functioning intravenous device from a critically ill client until another successful venipuncture has been performed; an established intravenous route may be needed for the administration of solutions, medications, or blood components. NURS I N G T I P Phlebitis Tenderness, not redness, is the earliest sign of peripheral IV-site phlebitis. administer, either whole blood or a component of whole blood, such as packed red blood cells. Whole Blood and Blood Products Clients with a demonstrated deficiency in either whole blood or a specific component of blood are given a blood transfusion. Whole blood contains red blood cells (RBCs) and plasma components of blood. It is used when the client needs all the components of blood to restore blood volume after severe hemorrhage and to restore the capacity of the blood to carry oxygen. Various types of blood components are used in the clinical setting (Table 37-7). Packed RBCs are more commonly prescribed than whole blood. Plasma or fresh frozen plasma is separated and frozen within 8 hours after blood collection. Albumin (protein colloid) is a volume expander that maintains the colloid osmotic pressure of the blood. Albumin, hetastarch, and dextran (nonprotein colloids) are agents that increase intravascular volume in order to maintain hemodynamic stability and to provide adequate tissue perfusion. Cryoprecipitate is the most expensive of all blood components because it is constituted from many units of whole blood. When the health care practitioner prescribes the administration of whole blood or a blood product, the client’s blood is typed and crossmatched; refer to Chapter 28 for a complete discussion of blood groups and Rhesus (Rh) factor. Check with the family for donors if time and the client’s condition permit. The blood is stored in the blood bank after typing and crossmatching until the nurse is ready to administer. Although whole blood has a refrigerated shelf life of 35 days, platelets must be administered within 3 days after they have been extracted from whole blood. If the RBCs and plasma are frozen, their shelf life can be extended up to 3 years (Kee & Paulanka, 2000). Initial Assessment and Preparation The nurse must perform an initial assessment before administering blood (see the accompanying display). The viscosity of whole blood usually requires the use of an 18- or 19-gauge needle or catheter to prevent damage to the red cells. BLOOD TRANSFUSION, INITIAL ASSESSMENT • Verify that client has signed a blood administration consent form and that this consent matches what the health care practitioner has prescribed. • Verify whether the client has an 18- or 19-gauge needle or catheter in the vein; if the blood is to be infused quickly, a 14- or 15-gauge device must be used. Pediatric and elderly clients may require a 23- gauge device because of smaller or thin-walled veins. • Ensure patency of the existing IV site. • Establish baseline data for vital signs, especially temperature, and assess skin for eruptions or rashes. • Check client’s blood type against the label on the whole blood or blood component prior to administration, to ensure compatibility. • Assess client’s age. If the client is at risk for circulatory overload (pediatric, elderly, or malnourished clients), notify the blood bank to divide the 500-ml bag of blood into two 250-ml bags or discuss with the health care practitioner other alternatives, such as packed RBCs rather than whole blood.
Scheduled IV medications should be infused before blood administration. This sequence prevents a reaction to a medication while blood is infusing; if a reaction were to occur, the nurse would not be able to discern which infusate was causing the reaction. Administering Whole Blood or a Blood Component The agency’s blood protocol may require that a licensed person sign a form to release the blood from the blood bank and that a blood product be checked by two licensed personnel prior to infusion. The following information must be on the blood bag label and verified for accuracy: the client’s name and identification number, ABO group and Rh factor, donor number, type of product ordered by the practitioner, and the expiration date. Observe the blood bag for any signs of puncture, gas bubbles, color, and consistency (RBCs clumping). When the information has been verified, both licensed personnel sign the appropriate form. If any of the information does not match exactly or if the product has expired, return the product immediately to the blood bank. Blood should be administered within 30 minutes after it has been received from the bank, to maintain RBC integrity and to decrease the chance of infection. Whole blood should not go unrefrigerated for more than 4 hours. Room temperature will cause RBC lysis, releasing potassium and causing hyperkalemia (Procedure 37-5). Safety Measures As discussed in Procedure 37-5, the client should be observed for the initial 15 minutes for a transfusion reaction. Vital signs are usually taken every 15 minutes for the first hour, then every hour while the blood is transfusing. To prevent blood contamination, change the blood tubing and filter every 4 hours or after each unit of blood. Transfuse each unit of blood over a 2- to 4-hour interval. NURSING ALERT Transfusion Reaction The severity of a transfusion reaction is relative to its onset. Severe reactions may occur shortly after the blood starts to infuse. At the first sign of a reaction, stop the blood infusion immediately. NURSING ALERT Blood Transfusion Incompatibility Use only normal saline with a blood product. Blood transfusions are incompatible with dextrose and with Ringer’s solution. Together, they cause hemolysis, clumping of RBCs.
As a precaution against a blood transfusion reaction, prepare a bag of normal saline, as directed by protocol. The normal saline is prepared as a secondary infusion system; it should not be connected to the Y-set tubing that is transfusing blood. If the client has a reaction, and the blood is discontinued, the secondary bag of normal saline should be connected and infused. This action prevents the client from receiving all the blood that is in the Y-set tubing, approximately 20 to 30 ml. Even though the procedure for infusing packed cells, and sometimes whole blood, requires a Y-set for coadministering normal saline, the secondary bag of normal saline is a precautionary measure for transfusion reactions. There are three basic types of transfusion reactions: allergic, febrile, and hemolytic. Other complications include sepsis, hypervolemia, and hypothermia. An allergic reaction may be mild or severe, depending on the cause. Hemolytic reactions may be immediate ordelayed up to 96 hours, depending on the cause of the reaction. The classic symptoms of a reaction and sepsis are fever and chills. The immediate nursing actions for all types of reactions and complications are: stop the transfusion, keep the vein open with normal saline, and notify the health care practitioner. Other measures include sending the IV tubing and bag of blood back to the blood bank; obtaining a blood and urine specimen; labeling the specimen “Blood Transfusion Reaction”; processing a transfusion reaction report; monitoring vital signs every 15 minutes for 4 hours or until stable; and monitoring the intake and output. A delayed hemolytic reaction results when the donor and client’s anti-A or anti-B agglutinins are mismatched or when there has been improper storage of the blood unit. This reaction causes the cells to clump and form plugs in small blood vessels. Within a few hours or days, the phagocytic WBCs and the reticuloendothelial sys- tem destroy agglutinated cells, releasing hemoglobin into the plasma. The client is monitored for jaundice, persistent anemia or fever, oliguria, flank pain, and abnormal bleeding. An immediate hemolytic reaction is a rare occurrence. It results from a mismatch of donor and client’s blood, causing immediate hemolysis of RBCs. The antibodies cause lysis of RBCs, which release proteolytic enzymes that rupture the cell membranes. The clinical manifestation are headache, dyspnea, cyanosis, chest pain, and tachycardia. Febrile reactions are common and result from the client’s sensitivity to WBCs, platelets, or plasma proteins. Warm, flushed skin, headache, muscle pain, and anxiety are the symptoms of a febrile reaction. It is treated with antipyretic medication. To help prevent a febrile reaction, keep the client warm during the transfusion. Make sure that the tubing has a leukocyte-reduction filter. The leukocyte-reduction filters also reduces the risk of transmitting cytomegalovirus (CMV) (a DNA virus that causes intranuclear and intracytoplasmic changes in infected cells). Approximately 10% of seropositive donors are capable of transmitting CMV infection. Mild allergic reactions are common, resulting from a sensitivity to infusing plasma proteins. Allergic reactions cause a rash, itching, hives (urticaria), and wheezing. Clients with these symptoms should be monitored for anaphylactic shock. Antihistamines may be prescribed to counter the allergic response. Severe allergic reaction results from an antibody-antigen response as demonstrated by shortness of breath and chest pain; if untreated, it may cause circulatory collapse and cardiac arrest. If this occurs, initiate CPR after the blood has been discontinued. Sepsis results from the administration of contaminated blood (containing gram-negative bacteria). It is a serious complication. Clinical manifestations include chills and fever, vomiting, abdominal cramping, diarrhea, shock, and renal failure. It is treated with broadspectrum antibiotics and steroids. Nursing measures are directed toward maintaining hydration and monitoring intake and output to evaluate renal function. Hypervolemia from fluid overload is a preventable complication. Clients at risk for FVE are placed in a sitting position. The blood is transfused at a reduced flow rate; request the blood laboratory to divide the unit into 2 containers of blood so that none of it is unrefrigerated for more than 2 hours during transfusion. Clinical manifestations of hypervolemia are similar to those of FVE (dyspnea, cough and rales, distended neck veins, hypertension, tachycardia, and pulmonary edema). Administer oxygen and IV diuretics as prescribed to treat circulatory overload. Clients needing rapid transfusions are at risk for transfusion-induced hypothermia. Such clients may include neonates needing exchange-transfusions and trauma victims who require large volumes of whole blood. A blood-warming device may be prescribed to prevent transfusion-induced hypothermia. The symptoms of transfusion- induced hypothermia result from the rapid transfusion of large amounts of cold blood. If the infusing blood temperature is below 30°C (86°F), the myocardial temperature decreases, causing hypotension and myocardial irritability that may rogress to ventricular fibrillation and cardiac arrest. Nursing interventions are directed toward warming the client with temperature-regulating blankets after the transfusion has been stopped. Obtain an ECG to assess for cardiac arrhythmias. Which buffer system acts immediately?The carbonic acid-bicarbonate buffer system is the fastest acting of all the compensatory mechanisms.
What causes respiratory alkalosis?Respiratory alkalosis occurs when high levels of carbon dioxide disrupt the blood's acid-base balance. It often occurs in people who experience rapid, uncontrollable breathing (hyperventilation). Treatment includes supplemental oxygen and therapies to reduce the risk of hyperventilation.
Which client is at the greatest risk for developing an acid base imbalance of electrolyte disorder?Those who have cancer and receive a bone marrow transplant—which increases the risk of infections and fever—or take chemotherapy medications that cause kidney problems are also at higher risk of developing a fluid and electrolyte imbalance.
Which client may have respiratory alkalosis?Breathing too fast can cause a person to go into respiratory alkalosis. This occurs when a person's pH level is higher than 7.45. A person may breathe too fast due to anxiety, overdosing on certain medications, or using a ventilator.
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When caring for a client with hypomagnesemia, the nurse prioritizes assessment of which body system?
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