A client is receiving total parenteral nutrition through a subclavian vein the nurse should

Vascular Access

Solutions for peripheral parenteral nutrition are hypertonic to blood, and their osmolality should not exceed 900 mOsm/L. When solution osmolality exceeds 900 mOsm/L, the incidence of phlebitis, inflammation, and pain is clearly increased. Adding 5000 units of heparin to a peripheral parenteral nutrition solution may prolong the duration of the peripheral line.

In most cases, parenteral nutrition is delivered through a central venous access. The selection of the site for catheter insertion and the type of catheter needs to be individualized. If the aim of the intervention is to provide an access for parenteral nutrition only, a single-lumen catheter is preferred. In general, the favored site for insertion is the subclavian vein. Placement in the internal jugular vein, compared with the subclavian vein, appears to be associated with a slightly higher risk of infection and a clearly higher risk of thrombosis. It is also less comfortable for mobile patients. Placement in the subclavian vein is associated with a small risk of pneumothorax and a slightly higher risk of stenosis. The femoral vein should be used only when placement in the jugular or subclavian vein is contraindicated or not possible. A femoral vein access is associated with the highest risk of infection or thrombosis. Most catheters are introduced by skin puncture; catheters intended for long-term use are placed surgically. Peripherally inserted catheters are inserted through a peripheral, usually antecubital, vein and then advanced into a central vein. They can be placed if the intended duration of parenteral nutrition is more than 2 weeks, and they can be used for up to 6 months in stable patients. The main advantage of these catheters is the avoidance of the risks associated with the puncture of a central vein, but they may lead to a higher rate of phlebitis.

Before placement of a vascular access, patients should be well hydrated and the coagulation status checked. Strict aseptic technique is necessary, and correct positioning of the catheter should be controlled by a chest radiograph before central parenteral nutrition is initiated. Proper catheter care includes regular inspection of the insertion site and dressing with gauze or transparent, semipermeable dressings.

Mechanical complications during placement include arterial puncture, pneumothorax, and hematoma. Infectious complications related to a central venous access occur in 4 to 20% of hospitalized patients, especially in immunocompromised patients and in critically ill patients. In patients with central parenteral nutrition, any sign of fever or sepsis should prompt the thought of catheter-related septicemia or catheter infection. Thrombosis detected by ultrasound examination is frequent, but its clinical relevance remains unclear.

Complications

The complications of PPN and TPN include phlebitis and other local reactions to infusion, maintenance of venous access, infection, air embolism, and refeeding syndrome. The refeeding syndrome is more common with TPN and may result in sudden death, more often affecting severely malnourished patients as they transition suddenly from deriving energy from stored fat to obtaining energy from infused glucose. This can cause a sudden depletion of phosphate stores, resulting in cardiac dysfunction. Patients who have lost more than 30% of their body weight should undergo gradual repletion of nutrients, with a slow increase in the rate of TPN over several days.

EVIDENCE-BASED SUMMARY

To determine total daily calorie needs, multiply the basal metabolic rate (BMR) by the appropriate activity factor:

Sedentary (little or no exercise; mild stress): BMR × 1.2

Light activity (light exercise, sports 1-3 days/wk; moderate stress): BMR × 1.4

Moderately active (moderate exercise, sports 3-5 days/wk; severe stress): BMR × 1.6

Very active (hard exercise, sports 6-7 days/wk): BMR × 1.725

Extra active (very hard exercise, sports + physical job or cross-training): BMR × 1.9

To determine the BMR or basal energy expenditure (BEE), use the on-line calculator (http://www.calculator.org/bmr.html).

Whenever possible, nutritional supplementation should be through the enteral route rather than parenteral.

Venous access

The type of venous access varies depending on the nutritional needs of the patient. Although peripheral PN may be used for a limited number of days, the high risk of using peripheral veins is extravasation of the solution with a subsequent inflammatory response and potential skin necrosis. Since the mid-1990s, a percutaneous intravenous catheter (or PIC-line) has been used. These catheters are relatively small in diameter (2-Fr or 22-gauge). They are placed through the child's peripheral veins, in the upper or lower limbs, and passed into the central venous system. These catheters are extremely well tolerated in adults and children; they can often be maintained for several weeks with reasonably low infection rates.115,116 Unlike the placement of a Broviac-type catheter, which requires local or general anesthesia, PIC-lines can generally be placed in the neonatal intensive care unit (NICU) with minimal sedation. Another advantage of these catheters is avoidance of pneumothorax, because access is through the extremities rather than the chest. The cost of the peripheral access devices is considerably less than that of Broviac-type catheters; however, PIC-lines have similar or higher incidences of venous thrombosis, and comparable rates of infection and complications.117

For infants and children who require longer durations of infusion, central venous PN may be administered through a tunneled Silastic catheter (e.g., Broviac, 2.7- or 4.0-Fr). Such a catheter often has a woven Dacron cuff. Although the tunneling of the catheter and cuff has not been shown to reduce catheter sepsis, the use of a cuff can prevent accidental dislodgement.118 The catheter may be placed into the superior or inferior vena cava. The ideal position for the tip of the catheter is the junction of the right atrium and the superior vena cava. The child's facial, external jugular, subclavian, or saphenous veins are ideal locations for access. In children who weigh less than 750 g, the internal jugular or femoral vein may need to be used because of the small caliber of other vessels.

B. Parenteral Access

The composition of the parenteral nutrition solution is dependent on the location of the vein in which it is delivered. Peripheral parenteral nutrition (PPN) is usually reserved for patients requiring short-term therapy who are not markedly hypermetabolic or fluid restricted and have adequate peripheral venous access. Hypertonic solutions may contribute to phlebitis; therefore, the osmolarity of the parenteral nutrition solution should be less than 900 mOsm/L [116]. This generally necessitates the use of a three-in-one or total nutrient admixture (TNA), where the amino acids, dextrose, and intravenous lipid emulsion are compounded in one container.

Central parenteral nutrition is indicated for patients requiring long-term parenteral nutrition who have increased nutritional and metabolic requirements and/or are fluid restricted. Because the parenteral nutrition solution is delivered centrally, where there is high and rapid blood flow, osmolarity is not a consideration. The solutions may be dextrose based (dextrose and amino acids) or TNA.

Formulating a Regimen

Once the decision has been made to start the patient on PN, it is important to determine whether the patient will require central or peripheral PN. The patient who will require PN for a short time, who has low to average energy, protein and electrolyte needs and has adequate nutritional status should be given PN administered through a peripheral intravenous catheter, called peripheral PN (PPN). The patient with increased fluid, caloric, protein, and energy needs who is malnourished and who will need PN for more than 1 week should be given PN that is administered through a central line. Maintenance fluid requirements can be calculated using body weight or surface area. Fluid needs are not only influenced by age and weight, but also by insensible losses, as well as the underlying medical condition or disease state. Allowances will need to be made for ongoing losses. Some patients with renal failure or fluid overload, as well as neonates with bronchopulmonary dysplasia or patent ductus arteriosus or who are receiving high-volume intravenous medications, may require fluid restriction and smaller volumes of concentrated PN. PN should not be used as a replacement solution for the patient with excessive fluid losses, because this will result in the excessive delivery of some nutrients. In these circumstances, we recommend using specifically designated replacement solutions. A common method for determining fluid requirements is as follows: 100 mL/kg for each of the first 10 kg of body weight, then an additional 50 mL/kg for the each of the next 10 kg of body weight, up to 20 kg. Patients whose weight is above 20 kg have an additional 20 mL/kg for every kilogram over 20 kg. Alternatively, 1600 mL/m2 can be used if body surface area can be determined. Whatever the method chosen, the patient should always be examined for excessive or inadequate fluid intake by evaluating fluid intake and output data, weight, and urine specific gravity and by physical examination. The next step in formulating a PN regimen is to determine the goal for the patient’s caloric and protein needs. Depending on the current nutritional status, a patient can usually receive calories equaling the REE or 75 to 85% of goal calories and then be increased to goal calories incrementally over the next 2 to 3 days. Patients at risk for refeeding syndrome should have their PN regimen advanced more slowly. A dextrose solution of 10% is used initially; if it is tolerated and central access is present, a more concentrated dextrose solution of up to 30 to 35% can be used if needed. Most patients receive dextrose concentrations of less than 20%. Once the fat and protein calories have been calculated, the balance of calories is provided as intravenous carbohydrate. It is important to make sure the final PN solution is balanced to prevent complications of overfeeding as well as excessive administration of any macronutrient. Current literature suggests am macronutrient mixture of 50 to 60% carbohydrate, 10 to 20% protein, and 20 to 30% fat to reduce the risk of parenteral nutrition associated liver disease (PNALD).81

It is also important to calculate the GIR and make sure that it does not exceed the recommended ranges. After a baseline chemistry panel is reviewed, appropriate amounts of electrolytes and minerals are added. Serum electrolyte levels should initially be monitored daily, until a stable regimen has been reached. A triglyceride level should be checked whenever intravenous fat intake is increased. In addition, patients with sepsis may have problems with triglyceride clearance and need to have values checked periodically. A weekly measurement of prealbumin may be a is a useful test of protein status and the caloric adequacy of the PN regimen, if C-reactive protein is less than 1 mg/L and the patient is not on steroids.

Feeding Approaches

There are four approaches to supplying nutrients, using two major routes (Fig. 11-1): The enteral routes include oral and tube feeding, and the parenteral routes include central and peripheral parenteral nutrition. Central parenteral nutrition can be infused through a centrally inserted catheter or a peripherally inserted central catheter (PICC), which reaches from an arm vein to the superior vena cava or right atrium of the heart. Every patient can be nourished by at least one of these approaches. Because they are not mutually exclusive, in many cases two or more complementary approaches can be used. Patients should not be completely unfed for more than 5 to 7 days before tube feeding or total parenteral nutrition (TPN) is instituted. Clinical judgment regarding when to intervene must be exercised if there is food intake but it is insufficient to meet the patient's needs.

The most feasible physiologic feeding approach should always be used. This means that enteral feeding, whether oral or by tube, is always preferred over parenteral feeding unless a contraindication is present. (If the gut works, use it.) The reasons for preferring the enteral route (Box 11-1) go beyond the obvious fact that it is the most “normal” way to ingest nutrients. The physiologic responses to enteral feeding differ significantly from those of parenteral nutrition because the latter bypasses the intestinal tract and portal circulation through the liver. Among other things, enteral feeding stimulates gut hormones, subjects nutrients to the absorptive and metabolic controls of the intestinal tract and liver, and produces less hyperglycemia, which allows for better immune function and decreases the risk of systemic infection. The buffering capacity of enteral feeding can improve resistance against stress ulcers. The cost of enteral feeding is only a fraction of that of parenteral. Finally, there is evidence that the intestinal mucosa undergoes atrophy during parenteral nutrition, whereas enteral feeding maintains a healthier mucosa. Although not established in humans, this may enhance mucosal resistance to the translocation of bacteria and endotoxins and reduce the risk of sepsis, multiple organ system failure, and gastrointestinal bleeding. Although it is sometimes tempting to feed a patient parenterally when a central venous catheter is already present, convenience alone does not justify this route. Because of the benefits of enteral feeding, aggression in gaining enteral access for feeding is warranted (Chapter 13).

Of the enteral options, oral feeding is preferred over tube feeding. Nasogastric or nasointestinal tube feeding is effective in many patients who have inadequate nutrient intake as a result of depressed appetite or the inability to eat. However, if the gastrointestinal tract is not able to be used or is unreliable for more than 5 to 7 days, parenteral nutrition should be used.

Parenteral Nutritional Repletion

In the older person with a nonfunctioning gastrointestinal tract, parenteral nutrition may be unavoidable. All patients receiving parenteral nutrition must be monitored closely for adverse effects. For short-term intravenous nutritional repletion, peripheral parenteral nutrition may be used. Low osmolality nutritional preparations, with a low risk of toxicity to soft tissue, are best suited for this purpose. There is a paucity of data regarding the safety and efficacy of most peripheral parenteral nutritional products for periods exceeding 14 days. Thus, where longer periods of intravenous feeding are required, total parenteral nutrition through a large central vein is indicated. Standard total parenteral formulations comprising 25% dextrose, 5% amino acids, electrolytes, and trace elements in optimal amounts are suitable for use in most patients. During prolonged parenteral nutrition, lipid emulsion supplements should be added to prevent deficiency of essential fatty acids.

Route

Compounding and Technical Requirements for PN

Macronutrients