[The effect of dobutamine on hemodynamics, critical cooling, and myocardia excitability during simple deep...

The effects of dobutamine (DOB) on hemodynamics, critical cooling, and myocardial excitability were studied in dogs under simple deep hypothermia. Hypothermia was induced by surface cooling after the animals had been anesthetized with ether and triflupromazine (conventional method, group I). Continuous intravenous administration of DOB was combined with conventional method in group II, and surface cooling was performed with thiamylal in group III. The following results were obtained. The mean lowest temperature reached was 15.6 degrees C in group II. MAP, CO and V max of group II were maintained significantly higher than those of group I during cooling. Decrease in BE in group II was mild compared with group I. Catecholamine release during cooling was suppressed completely in group I and II, but increased markedly in group III. Myocardial threshold to artificial pacing in group II was elevated as the temperature fell, and restored during rewarming, while that of group III was unchanged during cooling. Ventricular fibrillation occurred by stimulation of pacemakers in some cases. Our results suggest that even in case of hypothermia, DOB retains a selective inotropic effect with no threat of arrhythmogenicity, and produces stable hemodynamics. These characteristics of DOB allow cooling down to 15 degrees C.