Insulin(GIK) improves myocardial metabolism in patients during blood cardioplegia.

The aim of this study was to test the hypothesis that abnormalities of myocardial substrate metabolism during blood cardioplegic aortic cross-clamping and early reperfusion are attenuated further by insulin(GIK) than by alpha-ketoglutarate enrichment of blood cardioplegia alone. Twenty-eight males (47 to 78 years) undergoing coronary artery bypass grafting (CABG) participated in a prospective, controlled, randomized study. All patients had alpha-ketoglutarate-enriched blood cardioplegia. Insulin(GIK) was infused in 13 patients during aortic cross-clamping. Insulin(GIK) prevented lactate release during cardioplegia (1.5+/-15 vs -44+/-14 micromol/min, p = 0.04), and a significant extraction of lactate was induced shortly after declamping the aorta (15+/-3 vs 2+/-1%, p = 0.001). Free fatty acid uptake was reduced after cardioplegic cross-clamping (5.7+/-1.6 vs 16.0+/-3.8 micromol/min, p = 0.02). More positive/less negative levels of alanine, aspartate, glutamine, glycine, ornithine, taurine and tyrosine were found in all the insulin-treated patients. We conclude that insulin(GIK) attenuates abnormalities of myocardial substrate metabolism during blood cardioplegic aortic cross-clamping and early reperfusion further than is obtained with alpha-ketoglutarate enrichment of blood cardioplegia alone.