The provision of carbohydrate, fat and proteins by intravenous administration. In severely ill patients – especially those who have had major surgery or those with SEPSIS, burns, acute PANCREATITIS and renal failure as well as very premature newborns, the body's reserves of protein may become exhausted. This results in weight loss; reduction in muscle mass; a fall in the serum albumin (see ALBUMINS) and impairment of cellular IMMUNITY. Severely ill patients are unable to take adequate food by mouth to repair the body protein loss parenteral nutrition may be required.

The preferred route for the infusion of hyperosmolar solutions is via a central venous catheter (see CATHETERS). If parenteral nutrition is required for more than two weeks, it is advisable to use a long-term type of catheter such as the Broviac® or Hickman® type, which is made of silastic material and is inserted via a long subcutaneous tunnel; this not only helps to fix the catheter but also minimises the risk of infection entering the body through the cannula or its insertion site.

Dextrose is considered the best source of carbohydrate used as a 20 per cent or 50 per cent solution. AMINO ACIDS should in the laevo form are designed to contain the correct proportion of essential (indispensable) and non-essential amino acids. Preparations are available with or without electrolytes and with or without fat emulsions.

The main hazards of intravenous feeding are blood-borne infections made possible by continued direct access to the circulation through the cannula and biochemical abnormalities related to the composition of the solutions infused. The continuous use of hypertonic solutions of glucose can cause HYPERGLYCAEMIA and glycosuria and the resultant POLYURIA may lead to dehydration. Treatment with INSULIN is needed when hyperosmolality occurs, and in addition the water and sodium deficits will require to be corrected.