Both Glucose-Insulin-Potassium and Glutamine in Warm Blood Cardioplegia Increase the Rates of Myocardial Glucose and Free Fatty Acid Oxidation

Abstract

Objective -- We wanted to assess the effect of glucose-insulin-potassium (GIK) and glutamine on the oxidative metabolism during and after prolonged warm continuous blood cardioplegia (WB). Design -- WB was given to 21 pigs divided into three equally sized groups: WB (control), WB and GIK, or WB and glutamine. Oxidation rates of radiolabeled glucose ( 14 C) and free fatty acid (FFA) ( 3 H) were assessed before, during, and at 30 and 60 min after 3 h of cardiac arrest with WB. Results -- During standstill the substrate oxidation dropped markedly (<60%), glucose oxidation was highest in the WB + GIK group ( p < 0.05) and FFA oxidation highest in the WB + glutamine group (NS). During recovery the GIK group had an elevated glucose oxidation (47 and 40% vs WB at 30 and 60 min recovery, respectively - p < 0.05). Following 30 min recovery the addition of GIK suppressed FFA oxidation some 60%. Glutamine increased the oxidation of both glucose (30%) and FFA (150%) following 60 min recovery ( p < 0.05). During the whole recovery phase the relative FFA oxidation was significantly lowered in the GIK group. There were no differences between the groups regarding arterial levels or uptake of substrates, except for a higher myocardial oxygen consumption (MVO 2 ) during cardioplegia in the glutamine group. All the hearts performed similarly. Conclusion -- Addition of GIK or glutamine to the well-perfused and oxygenated heart during WB led to a postcardioplegic increase in oxidative metabolism and MVO 2 . GIK resulted in a significant metabolic shift from FFA to glucose.