Myocardial Protection During Elective Coronary Artery Bypass Grafting Using High-Dose Insulin Therapy

Abstract

Coronary artery bypass grafting (CABG) with cardioplegic cardiac arrest and cardiopulmonary bypass (CPB) is associated with myocardial injury. The aim of this study was to investigate whether high-dose insulin therapy has a myocardial protective effect by enhancing early metabolic recovery of the arrested heart during revascularization. A total of 44 patients undergoing elective CABG were randomized to receive intraoperative titrated intravenous insulin infusion (n = 22) or a fixed high-dose systemic insulin infusion at 5 mU/kg/min (n = 22). Blood samples were collected simultaneously from the radial artery and the coronary sinus before starting CPB and at 5 and 10 minutes after the release of the aortic cross-clamp to determine lactate, oxygen saturation, and hemoglobin concentration. Lactate extraction/excretion and myocardial oxygen extraction were calculated and compared between the two groups. The change in cardiac indices was determined immediately postoperatively as a measure of functional recovery, and the troponin I level was measured 4 hours postoperatively as an indicator of myocardial protection. Operative characteristics, including CPB and aortic cross-clamp time, were similar between the two groups. Arterial oxygen content was similar in both groups. The high-dose insulin therapy group had early extraction of lactate and higher oxygen extraction immediately postoperatively compared with the standard group. In addition, the high-dose insulin group had a lower troponin I level 4 hours postoperatively, with greater improvement in cardiac indices. High-dose insulin therapy promotes early metabolic recovery of the heart during elective CABG, leading to better myocardial protection and functional recovery.