A double-blind, prospective, randomized study of glutamine-enriched compared with standard peptide-based feeding in critically ill patients

Arterial and venous plasma amino acids were determined in 28 intensive care patients randomly assigned to receive 10 d of isoenergetic, isonitrogenous feedings that differed sixfold in glutamine content. Subjects were generally well-matched for age, injury severity, and disease diagnoses. Nasojejunal feedings were started within 48 h of admission. Data were analyzed from those 19 subjects still receiving ≤ 50 mL feeding/h on day 5. Both groups had comparable gastric residuals, stool frequency, and delivered nitrogen and energy. At study initiation, all subjects had relative hypoaminoacidemia, with day 1 venous glutamine concentrations down 26% compared with reference values. Plasma glutamine rose to comparable concentrations with feeding of either diet. There were, however, significant (P < 0.05) increases in arterial or venous plasma total, indispensable, and branched-chain amino acids of 125-144% by day 5 only in patients fed the standard control diet. The phenylalanine-tyrosine ratio was elevated on day 1 in both groups (1.3-1.4) but decreased significantly only in the glutamine- supplemented group (1.1 compared with 1.4) by day 5. Glutamine supplementation blunted the hyperaminoacidemia and elevated aromatic amino acid response to injury.