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

Abstract

Hypothermia is commonly found in accidents on land and at sea, yet its pulmonary circulatory effects have not been studied before. To study the effects of hypothermia on the right heart function and pulmonary circulation, cardiac catheterization was carried out on nine anaesthetized beagle dogs. The dogs were cooled between ice bags until the temperature in the pulmonary artery was 25 degrees C and then rewarmed using a heating box especially constructed for this purpose. Heart rate decreased significantly (P < 0.01) during cooling. Cardiac output also diminished mainly because of decreased heart rate. Total pulmonary resistance increased in the cold (P < 0.05) and returned to the initial level during rewarming. The peak rate of increase in pressure (dP/dtmax) of the right ventricular pressure curve did not show any significant change. Retardation in relaxation in hypothermia was indicated by an increase (P < 0.01) in the peak negative dP/dt of the right ventricular 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 normal during rewarming. In conclusion, right ventricular function was not compromised even during deep hypothermia.

Effect of perfusate temperature on pulmonary vascular resistance and compliance by arterial and venous occlusion in the rat

“…This study shows a direct dependence on T of the hydraulic resistance of all the pulmonary vascular bed areas, while similar results were previously found for venous resistance only (De Pasquale et al 1965;Greenlees et al 1985); according to present results, the pulmonary vascular area which exhibited the highest sensitivity to T changes was the venous area, followed by the capillary area, while less sensitivity was observed for the arterial area (Table 2). Similar percentage changes in PVR may be calculated from data reported by other authors in different animal species (Goetz et al 1962;Pennington et al 1971;Martinez-Ruiz et al 1996), while higher figures are reported by others, again in different experimental animals (Stern and Braun 1970;Chen and Chien 1978;Palo et al 2000).…”

“…Indeed, while most authors describe a decrease in pulmonary vascular resistance (PVR) with increasing blood temperature (Goetz et al 1962;De Pasquale et al 1965;Stern and Braun 1970;McMurtry et al 1975;Chen and Chien 1978;Will et al 1978;Greenlees et al 1985;Palo et al 2000), some reports record no change (Fuhner and Starling 1913), or even an opposite effect (Pennington et al 1971;Martinez-Ruiz et al 1996).…”

Prewarming Followed by Active Warming is Superior to Passive Warming in Preventing Hypothermia for Short Procedures in Adult Rats (Rattus norvegicus) Under Isoflurane Anesthesia

“…15,30,34 Hypothermia in animals has been linked to cardiovascular compromise, coagulopathy, increased data variability in biomedical research, and longer recoveries from anesthesia. 18,22,23,31,35,38 Hypothermia is a well-recognized and extremely frequent anesthetic complication in animals, affecting as much as 84% to 97% of dogs and cats undergoing surgical procedures. 24,25,27 The rapid onset of hypothermia in anesthetized laboratory rodents suggests that a high incidence of hypothermia is likely if active warming is not provided.…”