Influence of moderate hypothermia and deep local hypothermia with or without cardioplegia on intramyocardial oxygen tension during ischemic cardiac arrest.

The effect of ischemic cardiac arrest on intramyocardial oxygen tension (MpO2) in hearts of dogs under normothermia, moderate hypothermia as well as in heart in deep local hypothermia and in hearts subjected to deep local hypothermia combined with Bretschneider cardioplegia was examined. In the last mentioned condition the myocardial oxygen depletion was slowest and even at the end of 30 minutes of anoxia MpO2 was significantly higher in comparison with the other groups. Release of myocardial ischemia resulted in an immediate rise of MpO2 to overshoot levels in animals in normothermia and with deep local hypothermia alone, while in animals in moderate hypothermia and with combination of local hypothermia with cardioplegia reversed only to preanoxic values. On the basis of MpO2 measurements and of postischemic recovery of cardiac function the authors conclude that the combination of deep local hypothermia with cardioplegia is superior for myocardial protection to other used techniques.