GIK in cardiac surgery.

Abstract

Prof. Dr. Joachim Boldt, Abteilung für Anästhesiologie und operative Intensivmedizin, Justus-Liebig-Universität Gießen Klinikstraße 29, D-35392 Gießen (Germany) In 18-78% of patients undergoing coronary artery bypass grafting (CABG), evidence of myocardial ischemia is diagnosed after finishing cardiopulmonary bypass (CPB) [1-3]. In addition to various cardioplegic solutions, several pharmacological approaches have been proposed in the prebypass period of cardiac surgery patients to reduce the incidence of perioperative myocardial ischemia, to avoid or reverse myocardial ischemia/reperfusion injury, and to improve myocardial function after CPB. Nitroglycerin [4], Ca++ channel blockers [5], acadesine [6] ‚ and other pharmacological compounds have been recommended to attenuate the sequelae of ischemia in these patients. Infusion of glucose/insulin in combination with potassium (GIK) is another technique for improving myocardial preservation at this time [7-9]. Since its first description by Sodi-Palares et al. [10] in 1965, we have gained a massive increase in knowledge related to the mechanisms of GIK: An increase in intracellular cardiac glycogen results in an increased glycolytic reserve and an improved resistance to ischemia most likely due to an enhanced glycolytic and anaerobic ATP production [11]. Additional beneficial effects of GIK include a reduction in circulating free fatty acids (FFAs), which are reported to have deleterious effects on myocardial function and metabolism during ischemia [12]. GIK was able not only to protect the ischemic myocardial cell, but also to improve global and segmental function of the myocardium, particularly in patients with impaired ventricular function [13]. The paper of Wistbacka et al. [14] published in this issue of INFUSIONSTHERAPIE und TRANSFUSIONSMEDIZIN also deals with the effects of GIK infusion prior to CPB in patients undergoing coronary artery bypass grafting (22 GIK-treated versus 22 nontreated patients). Aspartate/glutamate was added to the GIK infusion in this study, which is suggested to improve myocardial energy metabolism during and after ischemia [15]. Markers of reduced myocardial ischemia and/or improved myocardial function in the paper of Wistbacka et al. were CK-MB enzyme plasma levels and various hemodynamic data. The authors concluded from their results that GIK/ apartate/glutamate infusion prior to CPB was associated with beneficial effects in cardiac function thereafter. In spite of some potential value of this technique, it has produced conflicting results varying from enthusiastic to discouraging reports, which even dispute any positive effect. Interestingly, Wistbacka and his group published a paper in 1992 dealing with the use of GIK in 32 elective coronary artery bypass patients [16]. Looking at CK-MB enzyme fraction, ECG and hemodynamic changes, they concluded in that paper that prebypass infusion of GIK entailed no clinical benefit in comparison to a control group, who had received Ringer’s acetate. Inotropic support, incidence of arrhythmias, and duration of intensive care stay were not different between these two groups either. Thus the question arises whether this technique can be recommended in cardiac surgery