Effects of glutamine supplementation, GH, and IGF-I on glutamine metabolism in critically ill patients

During critical illness glutamine deficiency may develop. Glutamine supplem entation can restore plasma concentration to normal, but the effect on glut amine metabolism is unknown . The use of growth hormone (GH) and insulin-li ke growth factor I (IGF-I) to prevent protein catabolism in these patients may exacerbate the glutamine deficiency. We have investigated, in criticall y ill patients, the effects of 72 h of treatment with standard parenteral n utrition (TPN; n = 6), TPN supplemented with glutamine (TPNGLN; 0.4 g.kg(-1 ).day(-1), n = 6), or TPNGLN with combined GH (0.2 IU.kg(-1).day(-1)) and I GF-I(160 mu g.kg (-1).day(-1)) (TPNGLN+GH/IGF-I; n = 5) on glutamine metabo lism using [2-N-15]glutamine. In patients receiving TPNGLN and TPNGLN+GH/IG F-I, plasma glutamine concentration was increased (338 +/- 22 vs. 461 +/- 2 4 mu mol/l, P < 0.001, and 307 +/- 65 vs. 524 +/- 71 mu mol/l, P < 0.05, re spectively) and glutamine uptake was increased (5.2 +/- 0.5 vs. 7.4 +/- 0.7 mu mol.kg(-1).min(-1), P < 0.05 and 5.2 +/- 1.1 vs. 7.6 +/- 0.8 mu mol.kg( -1).min(-1), P < 0.05). Glutamine production and metabolic clearance rates were not altered by the three treatments. These results suggest that there is an increased requirement for glutamine in critically ill patients. Combi ned GH/IGF-I treatment with TPNGLN did not have adverse effects on glutamin e metabolism.