[[ International Symposium�F04 ]]

Specialty Nutrients in Critical Illness Brian J Rowlands M.D. FRCS FACS Professor of Surgery Queen's University of Belfast, Northern Ireland, U.K.

In the past 25 years, numerous scientific studies have documented the value of nutrient support in critically ill patients. Sepsis, systemic inflammatory response syndrome (SIRS) and multiple organ dysfunction syndrome (MODS) complicate several surgical diseases and their treatment by surgical, endoscopic, medical and radiological techniques. Many patients who are treated for sepsis receive either intravenous or enteral nutritional support. Administration of these regimen is governed by a sound understanding of the metabolic response to trauma and basic nutritional principles. Strict protocols for administration minimise the technical, mechanical, metabolic, biochemical, haematological and septic complications. Several diseases have a high incidence of septic complications, SIRS and MODS.[1] These include major trauma, obstructive jaundice, inflammatory bowel disease, acute pancreatitis and major intra-abdominal sepsis. These clinical conditions and their septic complications are characterised by a state of "hypermetabolism" which leads to a rapid consumption of endogenous stores of protein and energy, immunological dysfunction and deterioration of organ function.[2] These changes which affect the liver, kidney, gastrointestinal tract, heart and lungs are orchestrated by a series of neuroendocrine events and the release of cytokines, activators and mediators of the systemic metabolic response. The "gut-liver axis" appears to have a central role in these responses which may be modified by parenteral and enteral nutrient substrates.[3,4] In recent years there have been two major trends in the use of nutritional support. First, there is a major shift from intravenous administration of nutrients to enteral feedings which is supported by evidence from controlled clinical trials.[5,6] Second, the quantity of nutrients being administered is decreasing and the quality of the nutrient mix is improving. Enteral feeding may be delivered using normal oral nutrition, standard enteral diets and supplementary enteral nutrition with novel substrates. Substrates suggested as capable of enhancing intestinal integrity and supporting immune function include amino acids (glutamine, arginine and ornithine), fatty acids (short chain and omega-3 polyunsaturated) and nucleotides (RNA).[7] Enteral nutrients produce their beneficial effects in several ways: support of generalised immune function enhancement of mucosal barrier reduction of bacterial translocation modification of hepatic Kupffer cell function cytokine release acute phase protein production by the liver Enteral diets maintain the structural and functional integrity of the small and large bowel by stimulation of gastrointestinal hormone release, motility and mucus production. In addition, maintenance of the luminal milieu of nutrients, micro-organisms and trophic factors are important for normal digestive and barrier function.[8] This presentation will discuss the experimental evidence and clinical significance of gut mucosal barrier dysfunction and therapeutic strategies for the prevention and treatment of gut-derived sepsis. The major focus will be the evaluation of individual specialty nutrients (novel substrates) which have a selective action on the maintenance of gut mucosal integrity (selective gut nutrients).[9] Their metabolism in health and disease will be discussed together with their effects on gut mucosal structure and function and the experimental evidence for their therapeutic use. The rationale for clinical use and evidence for clinical efficiency will also be considered. In the future, the use of specialty nutrients in the critically ill patient may have beneficial effects on nutritional, metabolic and immune status producing reductions in complications, length of hospital stay and mortality: Carefully conducted clinical trials will be necessary to identify those groups of patients who are most likely to benefit from these nutritional interventions.[10] REFERENCES l. McCrory DC, Rowlands BJ. Septic syndrome and multiple system organ failure. Current Practice of surgery 1993: 5: 211-215 2. Cerra FB. Hypermetabolism: organ failure and metabolic support. Surgery 1987; 101: 1-14. 3. Cerra FB. Nutrient modulation of inflammatory and immune function. Amer J Surg 1991; 161: 230-234 4. Wilmore DW. Catabolic illness: strategies for enhancing recovery. N Engl J Med 1991; 325: 695-702. 5. Kudsk KA, Groce MA, Fabian TC et al. Enteral versus Parenteral Feeding: effects of septic morbidity after blunt and penetrating abdominal trauma. Annals of Surgery 1992; 215: 503-513 6. Moore FA, Feliciano DV, Andrassy RJ et al. Early enteral feeding, compared with parenteral reduces postoperative septic complications - the results of a meta-analysis. Annals of Surgery 1992; 216: 172-183 7. Daly JM, Leibermann MD, Goldfine J et al. Enteral nutrition with supplemental arginine, RNA and omega-3-fatty acids in patients after operation: immunological, metabolism and clinical outcome. Surgery 1992; 112: 56-67 8. Silk DBA, Grimble GK (eds). Gut mucosal nutritional support: enteral nutrition as primary therapy? Gut 1994 suppl 1; 35: S1-S80 9. Gardiner KR, Kirk SJ, Rowlands BJ. Novel substrates to maintain gut integrity. Nutritional Research Reviews 1995; 8: 43-66 10. Souba WW. Nutritional support. N Engl J Med 1997; 336: 41-48