Hemodynamic and metabolic effects of hypothermia and rewarming

There is a lack of detailed knowledge of the pathophysiologic mechanisms initiated during and after rewarming. To study cardiac function after rewarming from hypothermia sodium pentobarbital anesthetized open chest-dogs were cooled to 25 degrees C and rewarmed. Myocardial blood flow was measured at different temperatures, and blood samples were drawn from the aorta and the coronary sinus for metabolic measurements. Mean aortic blood pressure (AOP) and aortic blood flow were recorded. Compared to precooling, AOP and heart rate were both significantly reduced during hypothermia. During rewarming stroke volume (SV) decreased significantly. At the end of rewarming AOP and SV were significantly lower than before cooling and myocardial blood flow, as well as oxygen and lactate uptake were only 50% of precooling levels. The present study demonstrated that hypothermia and rewarming depress cardiovascular function. Changes in peripheral vascular function, myocardial metabolism and contractility, may lead to the observed reduction in recovery upon rewarming.