Effects on dogs of surface-induced hypothermia and rewarming on the right heart function and pulmonary circulation

Hypothermia is commonly found in accidents on land and at sea, yet its pulm onary circulatory effects have not been studied before. To study the effect s of hypothermia on the right heart function and pulmonary circulation, car diac catheterization was carried out on nine anaesthetized beagle dogs. The dogs were cooled between ice bags until the temperature in the pulmonary a rtery was 25 degrees C and then rewarmed using a heating box especially con structed for this purpose. Heart rate decreased significantly (P < 0.01) du ring cooling. Cardiac output also diminished mainly because of decreased he art rate. Total pulmonary resistance increased in the cold (P < 0.05) and r eturned to the initial level during rewarming. The peak rate of increase in pressure (dP/ dt(max)) of the right ventricular pressure curve did not sho w any significant change. Retardation in relaxation in hypothermia was indi cated by an increase(P < 0.01) in the peak negative dP/dt of the right vent ricular pressure curve. According to our results, the contraction rate did not change, but the relaxation rate decreased significantly during cooling. No signs of heart failure were observed and all parameters returned to nor mal during rewarming. In conclusion, right ventricular function was not com promized even during deep hypothermia.