[Myocardial stress of different surgically induced types of cardiac arrest in dogs evaluated by myocardial potassium and acid-base balance (author's transl)].

In mongrel dogs myocardial stress of the following types of artificial cardiac arrest in moderate hypothermia and cardiopulmonary bypass was compared: 1. Ischemic arrest after aortic occlusion lasting 30 or 45 minutes. 2. Injection-cardioplegia according to Kirsch lasting 90 minutes. 3. infusion-cardioplegia according to Bretschneider lasting 90 minutes. The following parameters were compared: extracellular potassium activity ([K+]e) during cardiac arrest and [K+] in arterial and coronary venous blood during reflow, total [K+] and acid-base balance during reflow, time course of [K+] and lactic acid release and uptake during reflow after cardiac arrest. In our experimental conditions the lowest alterations of myocardial [K+] and acid-base balance were observed after infusion-cardioplegia according to Bretschneider. Injection-cardioplegia according to Kirsch was less protective for the heart as evidenced by more intensive acidosis, enlarged [K+] loss and prolongation of [K+] uptake during reflow. Ischemic cardiac arrest in moderate hypothermia was the worst type of artificial standstill indicated by development of fatal myocardial acidosis.