Protéines nutritionnelles et catabolisme musculaire chez le brûlé grave. Effets comparatifs de petits peptides ou d'acides aminés libres

Abstract

The beneficial effects of hight caloric and protein enteral diet on wound healing and prevention of infection in severly burned patients is well documented. However, the relative proportion of each nutrient and especially the form of nitrogen supply have not yet been clearly established. The aim of this study was to compare, in severely burned patients, the efficiency of a partial protein hydrolysate and free amino acid formula during a 15-day enteral feeding. Twenty burned patients ranging in age from 18 to 67 years with a mean burn size of 40 ± 12 % of total body surface area, of which 31 ± 14 % was deep dermal, were studied prospectivly and randomised in two groups. Group A received the free amino acid diet which was obtained by hydrolysis of the protein hydrolysate given to Group B (60 % small peptides). All diets contained a nitrogen source of similar amino acid composition. Nitrogen balance was measured daily and serum protein concentrations were determined on days 0, 4, 8, 11 and 15. Anthropometric parameters, urinary 3 methylhistidine/creatinine ratio and plasma amino acid concentration were assessed on days 0, 8 and 15. Daily and cumulative nitrogen balance at D15 did not differ between the two groups. In group A, the circulating visceral proteins increased at all times of the study without decrease of acute phase reactant, whereas only transthyretin and retinol binding protein increased at D11 and D15 with a significant decrease of C-reactive protein at the same time in the other group. In group A, the musculary circumference had decreased at D8 and D15 without change of the 3 methylhistidine/creatinine ratio, whereas in group B the anthropometric parameters did not change with a decrease of the 3 methylhistidine/creatinine ratio at D8. Comparisons of D8 or D15 with D0 values showed that 14 amino acids, from which 6 essential amino acids increased significantly with the free amino acid diet, but only one amino acid increased with the protein hydrolysate diet. We conclude that in severely burned patients, enteral feeding with small peptides decreases muscular breakdown without change in hepatic protein synthesis. The enteral support containing free amino acids is more effective on serum protein levels, probably by increasing the production of endogenous amino acids.