[Improved myocardial protection in open heart surgery by massive preoperative insulin supply (author's transl)]

In this study we investigated, whether in addition to cooling and cardioplegia, preventive administration of massive doses of insulin with glucose exerts a protective effect on the myocardium by increasing myocardial glycogen stores and shifting myocardial metabolism towards (primarily anaerobic) glycolysis. Experiments were done on two groups of 5 dogs each (average 27 kg) undergoing experimental extracorporeal circulation (ECC) with 90 min aortic clamping, under cooling and cardioplegia. Cardiac output (CO), systolic ventricular blood pressure (Pventr), heart rate (HR) and mean central venous pressure (CVP) were recorded at LA-levels of 5, 10, 15 and 20 mm Hg before onset of ECC (preop. value), after termination of ECC, and after 2 periods of a 10 min. reperfusion. While the 1st group served as control, the 2nd group received a massive i.v. insulin supply (total 20 U/kg) every 10 min, as well as glucose to keep blood sugar level stable within 60 min. prior to the onset of ECC. It was shown that in the control group after termination of ECC and after 1st reperfusion Pventr and CO were significantly below the preop. values, and only after the 2nd reperfusion within the preop. range. In the insulin group, however, Pventr and CO were already within the preop. range at termination of the ECC. After the 1st and after the 2nd reperfusion CO was in part significantly above the preoperative value. HR and total peripheral resistance (TPR) were not significantly changed. It is concluded that preventive insulin application produces a more vital myocardial cell function immediately after termination of ECC, indicating increased myocardial protection and improved ischaemic tolerance.