Renal, Cardiovascular and Respiratory Responses and Their Interrelations During Hypothermia

Abstract

The renal circulation and its relationship to cardiovascular and respiratory functions during progressive reduction of rectal temperature and during a period of low, stable temperature was studied in eight dogs. Hypothermia was induced by total immersion of the animals in an ice-bath. The results demonstrated an exponential reduction of the gomerular filtration rate, renal blood flow, urine volume, minimal tubular excretory capacity of PAH and heart rate with the fall in rectal temperature. Respiratory rate and oxygen consumption also fell exponentially with temperature, but tended to return towards control levels during the stable phase of reduced body temperature. The filtration fraction was increased upon cooling, but declined abruptly during the period of stabilized rectal temperature. The tubular reabsorption of water and the hematocrit remained unaltered during the experiments. Blood pressure changes were variable, although the over-all trend indicated a decrease upon cooling and a recovery during the stable period. This study suggested a direct, depressant effect of cold upon the kidney, accompanied by concomitant cardiovascular and metabolic changes. These effects, however, did not appear to be functionally correlated in every case; rather, they were the simultaneous result of the influence of cold on all body tissues in accordance with van't Hoff's law.