Myocardial "equilibration processes" and myocardial energy turnover during initiation of artificial cardiac arrest with cardioplegic solution - reasons for a sufficiently long cardioplegic perfusion.

In canine hearts the myocardial equilibration processes (temperature, pO2, pCO2, Na+, K+) and the myocardial energy turnover were analyzed at the beginning of a cardioplegically induced cardiac arrest during a coronary perfusion of 10 minutes. The investigated hearts (n = 10) were perfused with the Bretschneider histidine-buffered cardioplegic solution according to the recommendations worked out for clinical use. The results show that during the cardioplegic coronary perfusion of 10 minutes the cooling and temperature equilibration of the myocardium occur considerably faster than the establishment of a new energy steady-state at a very low level. The minimalization of the coronary resistance and of the myocardial O2 consumption are only reached after an extended perfusion period of 7 to 9 minutes. In consequence of the results, the following recommendations can be given for the clinical use of the Bretschneider cardioplegic solution: a) the solution should be used at a temperature of between 5 degrees and 10 degrees C, b) the cardioplegic coronary flow should be between 60 and 80 ml/min . 100 gww, c) the human heart should be perfused for 8 to 10 minutes and, d) the perfusion pressure should be maintained at 40 to 50 mmHg after cardiac arrest has set in. So far the action of equilibration procedures when using the Bretschneider cardioplegic method has not been compared with that of other cardioplegic methods.