GROWTH-HORMONE SUPPRESSION AND GLUTAMINE FLUX ASSOCIATED WITH CARDIAC-SURGERY

Pharmacological doses of growth hormone (GH) in humans and rats increa se plasma and muscle glutamine values. As major surgery results in a p hysiological rise in serum GH concentration, we investigated whether t his physiological increase in GH altered glutamine metabolism. Eightee n patients undergoing coronary artery bypass graft (CABG) surgery were randomly assigned to receive somatostatin, 100 mu g subcutaneously at induction of anaesthesia and 8 hourly for 48 h, or placebo. Somatosta tin effectively blocked the physiological surge of GH following injury but did not affect plasma or muscle glutamine concentrations, which f ell significantly in both groups. Plasma glutamine decreased by 31% (P <0.01) and 28% (P<0.01) in the control and somatostatin groups respect ively. Muscle glutamine was reduced 45% (P<0.001) in the control group and 50% (P<0.001) in the somatostatin group. There was no difference in muscle or circulating glutamate, alanine or branched chain amino ac id concentrations or in metabolite values between the somatostatin-tre ated patients and the control group. There was no relationship between the GH response to surgery and glutamine metabolism following major s urgery.