Severe protein-calorie malnutrition is a major problem in many intensive care (ICU) patients, due to the increased catabolic state often associated with acute severe illness and the frequent presence of prior chronic wasting conditions. Nutritional support is thus an important part of the management of these patients. Over the years, enteral nutrition (EN) has gained considerable popularity, due to its favorable effects on the digestive tract and its lower cost and rate of complications compared to parenteral nutrition. However, clinicians caring for ICU patients are often faced with contradictory data and difficult decisions when having to determine the optimal timing and modalities of EN administration, estimation of patient requirements, and choice of formulas. The purpose of this paper is to provide practical guidelines on these various aspects of enteral nutritional support, based on presently available evidence.

Oral supplements of arginine and citrulline increase local nitric oxide (NO) production in the small intestine and this may be harmful under certain circumstances. Gastrointestinal toxicity was therefore reviewed with respect to the intestinal physiology of arginine, citrulline, ornithine, and cystine (which shares the same transporter) and the many clinical trials of supplements of the dibasic amino acids or N-acetylcysteine (NAC). The human intestinal dibasic amino acid transport system has high affinity and low capacity. L-arginine (but not lysine, ornithine, or D-arginine) induces water and electrolyte secretion that is mediated by NO, which acts as an absorbagogue at low levels and as a secretagogue at high levels. The action of many laxatives is NO mediated and there are reports of diarrhea following oral administration of arginine or ornithine. The clinical data cover a wide span of arginine intakes from 3 g/d to>100 g/d, but the standard of reporting adverse effects (e.g. nausea, vomiting, and diarrhea) was variable. Single doses of 3-6 g rarely provoked side effects and healthy athletes appeared to be more susceptible than diabetic patients to gastrointestinal symptoms at individual doses>9 g. This may relate to an effect of disease on gastrointestinal motility and pharmacokinetics. Most side effects of arginine and NAC occurred at single doses of >9 g in adults (>140 mg/kg) often when part of a daily regime of approximately>30 g/d (>174 mmol/d). In the case of arginine, this compares with the laxative threshold of the nonabsorbed disaccharide alcohol, lactitol (74 g or 194 mmol). Adverse effects seemed dependent on the dosage regime and disappeared if divided doses were ingested (unlike lactitol). Large single doses of poorly absorbed amino acids seem to provoke diarrhea. More research is needed to refine dosage strategies that reduce this phenomenon. It is suggested that dipeptide forms of arginine may meet this criterion.

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Data on the prevalence of malnutrition among patients with spinal cord injuries (SCI) are lacking. The aim of the present study was to assess nutritional risk at admission, and the status of nutritional support in the UK SCI Centres (SCIC); a cross-sectional, multicentre study in four SCIC. A standardised questionnaire was used and distributed to the participating SCIC. After obtaining informed consent, baseline demographic data, nutritional risk score by the 'Malnutrition Universal Screening Tool', BMI and routine blood biochemistry were collected from every patient admitted to an SCIC. The four SCIC, comprising 48·2 % of the total UK SCI beds, contributed data from 150 patients. On admission, 44·3 % of patients were malnourished or at risk of undernutrition. Nutritional risk was more common in patients with acute high cervical SCI than those with lower SCI (60·7 v. 34·5 %), and nutritional risk was more common in those with additional complications including ventilatory support (with tracheostomy, 56·3 v. 38·7 %). Also, 45 % of patients were at risk of overnutrition (BMI $ 25 kg/m 2 ). The prevalence of malnutrition in SCI patients admitted to SCIC is higher than national figures focused on general hospitalised patients, indicating that SCI patients are particularly vulnerable to malnutrition. Patients with SCI who have a tracheostomy may need additional attention. Given the potential negative impact of malnutrition on clinical outcomes, an emphasis on mandatory nutrition screening, followed by detailed assessment for at-risk individuals should be in place in the SCIC.