204 



PHYSIOLOGY OF INDUCED HYPOTHERMIA 



ever, glomerular filtration rate and renal blood flow increase more slowly, being- 

 only about I of the control levels immediately after normothermic levels are 

 reached. When these observations were repeated 24 hours later, all of the functions 

 had returned approximately to control values. 



As with glomerular filtration rate and renal blood flow, prolonged hypothermia 

 had no additional effect on water and electrolyte excretion as compared to obser- 

 vations made immediately after reduction in temperature. There was no change 

 or increase in urine volume and sodium excretion. Potassium excretion was uni- 

 formly depressed (fig. 5). In this group of animals it seemed that the effect on water 

 excretion was more pronounced after prolonged hypothermia than it was imme- 

 diately after the reduction in temperature. When the temperature returned to the 

 control values, sodium excretion remained elevated. 



When the blood pressure was raised to control levels with norepinephrine during 

 hypothermia, glomerular filtration rate and renal blood flow were not increased 

 (fig. 6). This suggests that the reduction in renal function is a direct result of 

 hypothermia, not a result of the hypotension. When the temperature was returned 

 to control levels, glomerular filtration rate and renal blood flow both increased. 



The effect of renal ischemia on renal hemodynamics and water and elec- 

 trolyte excretion. In the group of animals in which the aorta was occluded above 

 the renal arteries (subgroup 2A) no alteration in renal function was observed 

 three days after the occlusion. This indicates that a pressure as low as 15 to 32 

 mm. Hg for a period of two hours is adequate to protect the kidneys against renal 

 damage. 



129 



186 



154 



Urine 

 cc / 



Volume 

 min. 



Hypothermia 



After 2 hours at80»F 



Normothermio 



Sodium Excretion 

 >iEq./min. 



Potassium Excretion 

 /i Eq./min. 



Fig. 5.— Tlie effect of prolonged hypothermia on urine and electrolyte excretion as compared 

 to the immediate response to temperature reduction. 



