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Special Populations Patients with pre-existing conditions may have special considerations in the formulation, administration, and monitoring protocols for parenteral nutrition support.
Diabetes As the prevalence of diabetes increases, it is likely that many more patients will need special consideration for parenteral support. The primary concern is adequate blood glucose control. Chronic hyperglycemia can compromise the benefits of parenteral nutrition as well as complicate fluid balance, immune function, and nutrient metabolism. Diabetes is not a contraindication, but does require some additional considerations for the dextrose content and infusion rate as well as for monitoring changing insulin requirements during parenteral nutrition support.
Congestive Heart Failure Patients with a history of heart disease, particularly of congestive heart failure, require special attention to volume and calorie overload. Care should be taken to prevent overfeeding and fluids may be restricted, particularly during the first few days to weeks of infusion. In congestive heart failure patients, volume may be limited to 1-1.5 liters per day.
Pulmonary Dysfunction Pulmonary dysfunction, particularly with catabolism and loss of pulmonary muscles, requires a careful balance between assuring adequate energy and protein intake while assuring that carbohydrate administration is well within the individual’s tolerance level. It will be especially important to spare protein through the provision of adequate calories from carbohydrate and fat sources. Carbohydrates may be restricted to 4 mg/kg/minute or less to prevent further respiratory compromise, hypercapnia, and increased breathing effort.
Acute Renal Dysfunction In cases of acute renal failure it will be important to meet the increased calorie and protein needs within protein tolerance levels as much as possible. Protein should be provided to reduce the effects of catabolism and the often-associated instability of a catabolic state. While not a contraindication, special care should be taken with protein administration in patients with azotemia. In some cases, short-term dialysis may be required as the condition stabilizes.
Hepatic Disease Liver diseases are particularly problematic in parenteral nutrition because of the liver’s primary role in processing nutrients and medications, and its role in facilitating other metabolic processes. Changes in carbohydrate, protein, fat, and micronutrient metabolism are common. The malnutrition that often accompanies liver disease, especially with any additional stress such as infection or injury, can be difficult to address while considering the numerous metabolic alterations that affect parenteral nutrition.
Carbohydrate intolerance and insulin resistance may occur in up to 80% of patients with cirrhosis. Special care is required to maintain reasonable glucose levels and prevent overfeeding and refeeding syndrome.
Protein requirements are fairly high at around 1.5 g/kg and protein intolerance can present some limitations if symptoms of encephalopathy are present. In some cases, protein administration can be reduced to 1.0 g/kg and branched chain amino acids (BCAAs) are used to reduce the dependence on hepatic metabolism of protein and has been used in patients with significant encephalopathy. Typically, triglycerides may be elevated because of impaired fat clearance.
Fat clearance is often impaired with a reduction in fat breakdown and clearance of fatty acids. Hypertriglyceridemia can occur and may make it difficult to supply energy through fat emulsions in TPN.
Just as the initiation of TPN requires careful planning and monitoring, discontinuation through transitional feeding will also require due consideration. In adults who maintain reasonably good nutritional status, the discontinuation of TPN is often relatively abrupt, but may include a gradual tapering of feeding to prevent hypoglycemia. Other patients who may require transitional feeding or a more gradual transition to enteral feeding or solid food intake include the malnourished, the elderly, pediatric patients, cancer patients and those at risk for aspiration. Calorie counts to document adequate enteral and oral intake can help to reduce the time to discontinue TPN. In pediatric patients the process may take longer with transitional enteral and/or oral feedings to make sure that nutrient intake is not compromised in the process. Additional partial support with peripheral parenteral nutrition (PPN) or intravenous hydration and electrolytes can be used to ease the transition from TPN to enteral/oral feeding.
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