Nutrition in the critically ill patient: part III. Enteral nutrition

To review the human nutrition in the critically ill patient in a three-part presentation.

Articles and published peer-review abstracts and a review of studies reported and identified through a MEDLINE search of the English language literature on enteral nutrition.

Enteral nutrition is indicated in the critically ill patient when there is an inability to ingest adequate nutrients by mouth and where the gastrointestinal tract is otherwise normal. The commonly used polymeric feeding solutions provide a mixture of nutrients similar to that encountered in the normal diet, usually as an iso-osmolar low residue solution. Because lactose intolerance may be encountered during critical illness, most formulations are lactose free. Special glutamine formulations and immune enhancing enteral formula (e.g. enriched with 3 fatty acids, arginine and ribonucleic acids) have been used in critically ill patients. However there have been few studies to indicate that these diets are of greater benefit compared with normal enteral formulations. The daily nutritional requirements are often not met in critically ill patients largely due to delayed gastric emptying or diarrhoea. Prokinetic agents, special formulations containing fibre and probiotics, have been used in an attempt to improve the tolerance to the formulations, although there have been no comparative studies that allow firm recommendation to be made. In general, a standard enteral solution is usually prescribed first and instilled into the stomach using a fine bore nasogastric tube. If gastric emptying is delayed prokinetic agents are tried before a transpyloric tube or enterostomy tube feeding is considered.

Nutritional requirements for the critically ill patient should be delivered enterally in patients who have a normally functioning gastrointestinal system. A standard formulation is usually prescribed and instilled into the stomach using a fine bore tube. If gastric emptying is delayed prokinetic agents are tried before a transpyloric tube or enterostomy tube feeding is considered. Diarrhoea caused by enteral pathogens may require specific treatment. If pathogens are excluded then fibre and probiotics may be considered. Motility reducing agents (e.g. opiates) may cause abdominal bloating.