Special considerations required for the formulation and administration of total parenteral nutrition therapy in the elderly patient.

Providing total parenteral nutrition (TPN) to hospitalised patients is not a benign procedure and can be associated with appreciable risks including the development of septic, mechanical and/or metabolic complications. In the older patient, the risks are heightened due to the effects of aging on vital organ function, as well as on the body's ability to respond to injury and infection. In addition, the existence of co-morbid disease will increase the rate of complications. The design of nutritional regimens must account for the changes in body composition and function with age in order to reduce the risks of nutrition-related complications. As a consequence of the reduction in lean body mass and organ function, coupled with the need to mobilise endogenous protein during acute metabolic stress, it is prudent to provide protein intakes of 1.5 g/kg/day, similar to amounts given to younger adult populations. In contrast, the caloric intake should be reduced by as much as 30% from amounts given younger adults of equivalent height and weight in order to avoid the dangers of overfeeding. Single-fuel systems may be better choices in those with acute cardiovascular disease, as glucose is a preferred fuel in this setting, whereas a mixed-fuel system will generally allow improved glucose homeostasis in the diabetic patient. Once TPN is instituted, metabolic management may be as important as nutritional support. Critical illness is associated with a variety of electrolyte disorders which are often accentuated by concurrent drug therapy and pre-existing co-morbid disease. The older patient is often less able to withstand abrupt changes in metabolic homeostasis. These points underscore the importance of the careful application of TPN therapy in the older patient.