Myocardial protection during elective coronary artery bypass grafting using high-dose insulin therapy

Background. 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. Methods. 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. Results. 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. Conclusions. High-dose insulin therapy promotes early metabolic recovery of the heart during elective CABG, leading to better myocardial protection and functional recovery.