INFLUENCE OF SYSTEMIC HYPOTHERMIA ON SYSTOLIC AND DIASTOLIC FUNCTIONAL RECOVERY AFTER CONTINUOUS WARM ANTEGRADE BLOOD CARDIOPLEGIA

Experimental observations in our laboratory indicate that myocardial r ecovery is similar following warm or cold antegrade blood cardioplegia when the core temperature is maintained at 37-degrees-C. To determine the effects of hypothermia on myocardial recovery, 15 adult mongrel d ogs were randomized to normothermic or hypothermic bypass (28-degrees- C) during 60 min of continuous warm antegrade blood cardioplegia. The hypothermic group was rewarmed after releasing the aortic cross-clamp and bypass was discontinued at 30 min in both groups. Myocardial recov ery was assessed at 60, 90, and 120 min after the arrest. Core tempera ture was maintained in the normothermic group but gradually decreased after bypass in the hypothermic group, reaching a low of 33.8 +/- 1-de gree-C at 120 min. Myocardial functional recovery was preserved after normothermic bypass. The decrease in core temperature, however, that w as observed after systemic hypothermia, was paralleled by significant decreases in the maximum rate of left ventricular pressure rise (dp/dt ), the maximum elastance of the left ventricle, and preload recruitabl e stroke work. Diastolic function decreased slightly, but not signific antly, during reperfusion following systemic hypothermia but was unalt ered after normothermic bypass. Myocardial oxygen consumption was unch anged in both groups. Myocardial ultrastructure was preserved after no rmothermic bypass. In contrast, cellular oedema and mild ultrastructur al changes were evident after systemic hypothermia. We therefore concl ude that the use of systemic hypothermia during bypass is associated w ith lower core temperatures during early recovery which results in imp aired functional recovery.