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lnspite of the extensive literature on the subject to hypothermia, little data has been published concerning the actual quantitative determination of the renal function during this state. The observations of renal function include the measurement of renal blood flow, renal plasma flow, glomerular filtration rate and renal excretion of sodium and potassium. Twenty-eight healthy mongrel dogs of both sexes, ranging in weight from 12 to 18kg, were used in the study. At the beginning of the experiments, the animals were anesthesized with intravenous injections of pentobarbital sodium [30mg/kg body weight]. Two polyethylene catheters were placed in the femoral artery and vein. The animals have been divided into 4 groups, each group consisted of 7 animals and used for a different type of observation. Group 1: The effect of pentobarbital sodium anesthesia alone on renal function during normothermia was observed for control group. Observations were made at approximately the same time lapse after the hypothermic dogs in group 2 attained to the corresponding body temperature. Group 2: The effect of reduction and rewarming of body temperature was observed. Following suitable control observations, the body temperature was reduced to 28degree and rewarmed to control levels immediately after the observations at hypothermic levels were completed. Group 3: The response to noradrenaline during hypothermia was observed. During administration of noradrenalin, the reduced blood pressure was returned to approximately control values. Following rewarm to control level of body temperature, final observation was carried out. Group 4: The effect of progressive reduction of body temperature on renal function was observed. Observations during hypothermia were made at 30degree, 25degree, and 20degree. The dogs were infused with normal saline, 10ml/kg of body weight, and 3mg/kg of heparin sodium through the implanted femoral venous canula, 50 minutes prior to study. All arterial blood samples were obtained at appropriate intervals from the femoral artery. The body temperatures were checked with the mercury thermometer inserted into esophagus. The record of mean arterial blood pressure was obtained from U-shaped mercury manometer by femoral artery canula. Creatinine clearance was used to measure glomerular filtration rate, the single injection method of Hippuran I131 of Pritchard for renal blood flow, and Coleman flame photometer for measurement of sodium and potassium levels. Renal plasma flow was calculated from renal blood flow and hematocrit. Dogs were ventilated with respirator when animals were cooled below the esophageal temperature of 28degree. Results were summarized as follows: 1]Progressive reduction in mean blood pressure was observed during hypothermia. As the body temperature was reduced to 30degree, 28degree[group 2 and 3], 25degree and 20degree [group 4], the mean blood pressure was progressively decreased to approximately 84%, 72-69%, 69% and 44% of the control value. On the other hand, no significant changes during pentobarbital sodium anesthesia alone was observed. 2]The reduction of blood pressure was associated with a marked reduction in glomerular filtration rate and also parallel reduction of renal blood flow and renal plasma flow. The rates of decrease in renal plasma flow were more marked than in glomerular filtration rates at 30degree [group 4], 28degree[group 2] and 25degree[group 4], and consequently filtration fractions were increased during these stage, while filtration fraction was sharply dropped during rewarming [group 2] and final observation at 20degree of hypothermia [group 4]. 3]The reduction of renal blood flow, renal plasma flow and glomerular filtration rate was not improved when the blood pressure was raised to control values with an infusion of noradrenaline. 4] Urine flow per minute was decreased during hypothermia from 1.18 cc/min [control value] to
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