RENAL FUNCTION— MOVER, MORRIS and DE BAKEY 201 



In the animals in subgroup 2C, the aorta was occluded above the renal artery 

 for two hours with a Potts clamp and at the same time, the left renal artery 

 was occluded with the bulldog clamp. During this procedure, then, the right renal 

 artery was open to any retrograde flow that might occur through the collateral 

 circulation into the aorta below the Potts clamp, but the left kidney was com- 

 pletely blocked of any circulation from the aorta. Following occlusion of the aorta 

 above the renal arteries (subgroups 2B and 2C), the blood pressure distal to the 

 occlusion ranged between 15 and 34 mm. Hg (average 28 mm. Hg), due to the 

 collateral circulation into the distal aorta. The renal artery and the aorta were oc- 

 cluded for two hours in each instance (subgroups 2B and 2C). After the occlusion, 

 the animals were allowed to recover and were placed in their cages. Three days 

 later, the animals were again anesthetized with 30 mg/kg of pentobarbital. Each 

 ureter was then catheterized and observations on renal function were again re- 

 peated. At the same time water and electrolyte excretion studies were carried out. 

 This allowed us to determine renal blood flow, glomerular filtration rate, and water 

 and electrolyte excretion for each kidney separately, and thus to compare the 

 degree of damage between the right and the left kidneys as reflected in the altera- 

 tions in renal hemodynamics. 



The effect of renal ischemia during hypothermia. Seven animals were 

 studied in which the temperature was reduced to 25 to 27° C. Then the aorta was 

 occluded above the renal arteries. At the same time the left renal artery was oc- 

 cluded similar to the animals in group 2C. After two hours of occlusion, the 

 clamps were removed and the dogs were warmed up to control levels. Three days 

 later, the ureters were catheterized and observations were made on renal function 

 for each kidney. These were then compared to the observations made in the animals 

 in which the blood supply to the kidneys had been interrupted (subgroup 2C) under 

 normothermic conditions. 



RESULTS 



The effects of hypothermia on renal hemodynamics and water and elec' 

 trolyte excretion. Figure 2 summarizes the effect of progressive hypothermia on 

 renal function. The observations are expressed in per cent of the control observa- 

 tions made prior to reducing the temperature. As the temperature was reduced to 

 approximately 90° F. (30 to Z2° C.) the average mean blood pressure decreased 

 to 90 per cent of the control levels. This was associated with a reduction in 

 glomerular filtration rate to 58 per cent of the control values and in renal blood 

 flow to 69 per cent of the control level. There was no effect on the hematocrit in this 

 group of animals. When the temperature was reduced to 80° F., i.e. 25 to 27° C, 

 the average mean blood pressure decreased further to about 75 per cent of the 

 control values and the glomerular filtration rate and renal blood flow to 31 per cent 

 and 28 per cent of the control values respectively. The average absolute values 

 for these observations are recorded within the bar graph for each of the func- 

 tions studied in figure 2. 



Associated with the reduction in glomerular filtration rate, there was no con- 

 current reduction in urine volume or in sodium excretion (fig. 3). This is of 

 interest since under normothermic conditions if the glomerular filtration rate is 



