Metabolic effects of arginine addition to the enteral feeding of critically ill patients.
BACKGROUND
Some studies have suggested that the addition of arginine to enteral feeding solutions may improve outcome in critically ill patients, but the mechanism is incompletely explained. In particular, the availability and utilization of arginine administered enterally is not well defined.


METHODS
This prospective, randomized, double-blind, placebo-controlled study performed in a Department of Medicosurgical Intensive Care included 51 patients likely requiring long-term enteral feeding. Thirty-seven patients (57 +/- 7 years, SAPS II 33 +/- 6) completed the 7-day study, of whom 20 received the formula enriched with free arginine (6.3 g/L) and 17 received an isocaloric and isonitrogenous control solution. Arginine absorption was assessed from plasma arginine concentrations in serial samples. Three pathways of arginine utilization were explored: (1) the production of nitric oxide, assessed by the plasma concentration of nitrite/nitrate (NOx) and citrulline, and 24-hour urinary excretion of NOx; (2) the protein turnover, estimated by the phenylalanine concentrations; and (3) the activity of arginase, reflected by the ornithine concentration.


RESULTS
The plasma concentrations of arginine and ornithine increased in the group fed with the enriched formula (from 55 +/- 9 micromol/L to 102 +/- 9 micromol/L and from 57 +/- 7 to 135 +/- 11 micromol/L, respectively, p < .05), but not with the control formula. There was no difference between groups in either NO production or phenylalanine concentration.


CONCLUSIONS
Supplemental arginine in enteral feeding is readily absorbed, and mainly metabolized into ornithine, presumably by the arginase enzyme.
Preiser
J C
JC
Department of Intensive Care, Erasme University Hospital, Free University of Brussels, Belgium.
Berré
P J
PJ
Van Gossum
A
A
Cynober
L
L
Vray
B
B
Carpentier
Y
Y
Vincent
J L
JL
D001119:Arginase / Q000378:metabolism; D001120:Arginine / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D001682:Biological Availability; D016638:Critical Illness / Q000628:therapy*; D004311:Double-Blind Method; D004750:Enteral Nutrition; D005260:Female; D006801:Humans; D007408:Intestinal Absorption; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000032:analysis; D009952:Ornithine / Q000097:blood; D010649:Phenylalanine / Q000097:blood; D011446:Prospective Studies
D009569:Nitric Oxide; D010649:Phenylalanine; D001120:Arginine; D009952:Ornithine; D001119:Arginase