EXPERIMENTAL HYPOTHERMIA - EFFECTS OF CORE COOLING AND REWARMING ON HEMODYNAMICS, CORONARY BLOOD-FLOW AND MYOCARDIAL-METABOLISM IN DOGS

Conflicting results have been reported as to the extent that cardiovas cular function can be reestablished after rewarming from hypothermia. We measured hemodynamic function, myocardial metabolism and tissue wat er content in dogs core-cooled to 25 degrees C and later rewarmed. At 25 degrees C left ventricular (LV) systolic pressure (LVSP) was 54% +/ - 4%, maximum rate of LV pressure rise (LV dP/dt(max)) 44% +/- 5%, aor tic pressure (AOP) 50% +/- 6%, heart rate (HR) 40% +/- 0%, cardiac out put (CO) 37% +/- 5%, myocardial blood flow (MBF) 34% +/- 5%, and myoca rdial oxygen consumption (MVo(2))8% +/- 1%, compared to precooling. St roke volume (SV) and LV end-diastolic pressure (LVEDP) were unchanged. As normothermia (37 degrees C) was reestablished, the depression of c ardiac function and myocardial metabolism remained the same as that at 25 degrees C:LVSP 71% +/- 6%, LV dP/dt(max) 73% +/- 7%, SV 60% +/- 9% , AOP 70% +/- 6%, CO 57% +/- 9%, MBF 53% +/- 8%, and MVo(2) 44% +/- 8% . HR, in contrast, recovered to precooling values. The arterial concen trations of glucose and free fatty acids (FFA) did not change signific antly during the experimental period, whereas an increase in lactate o f nonmyocardial origin appeared after rewarming. Increased myocardial contents of creatine phosphate and water were found during both hypoth ermia and rewarming. The present study demonstrates a persistent depre ssion of cardiac function after hypothermia and rewarming in spite of adequate energy stores. Thus, a direct influence on myocardial contrac tile function by the cooling and rewarming process is suggested.