220 PHYSIOLOGY OF INDUCED HYPOTHERMIA 



returned to normal with warming. In contrast, 9 per cent of filtered potassium was 

 excreted at 37° C, while 36 per cent was excreted at 22° C. This returned to 

 normal with rewarming. 



The urine composition thus assumed the composition of plasma ultrafiltrate 

 where U/P ratios approached unity as cooling progressed. The clearance of sub- 

 stances normally reabsorbed by the kidney tubules, such as H2O, Na and CI were 

 increased, while clearances of nonreabsorbable solutes such as endogenous or 

 exogenous creatinine were reduced. The clearances of substances believed to be 

 secreted by the tubular cells were also reduced. 



We therefore believe that distal tubular function is greatly reduced during cool- 

 ing and nearly eliminated at 22° C, while proximal tubular activity is little affected 

 by hypothermia. 



