THE EFFECT OF HYPOTHERMIA ON THE PERIPHERAL 



SERUM LEVELS OF FREE IZ-HYDROXYGORTIGOIDS 



IN THE DOG, AND IN MAN 



WILLIAM F. BERNHARD 



The experimental investigation and clinical application of hypothermia in the 

 care of surgical patients has become increasingly important. Technical advances 

 have predominated so far, while the metabolic response of the organism to opera- 

 tive stress in hypothermia has not as yet been clearly defined. Recently, direct 

 methods for measurement of 17-hydroxycorticoids were made available, and studies 

 have been carried out in normal individuals, and in patients during and after 

 surgery at normal body temperature. Utilizing these techniques in the experimental 

 animal, data have been presented demonstrating an inhibition of the adrenocortical 

 17-hydroxycorticoid output at low temperatures. It was found that there was a 

 marked reduction in adrenal venous blood flow without a compensatory rise in 

 corticoid concentration, and thus a low corticoid minute output resulted. 



The level of 17-hydroxycorticoids in the arterial blood plays a major role in 

 regulating the metabolic response of the organism. This level is determined not only 

 by adrenocortical production of these substances, but also by their rate of utiliza- 

 tion, conjugation, and excretion. Concomitant depression of these three processes 

 may be anticipated in hypothermia, since cooling depresses tissue metabolism 

 throughout the organism. 



Peripheral 17-hydroxycorticoids in the dog. A group of adult mongrel dogs 

 were anesthetized with pentobarbital sodium, intubated, and hyperventilated with a 

 positive pressure apparatus. A polyvinyl cannula was inserted into a femoral artery, 

 permitting arterial blood sampling. An initial laparotomy was then carried out and 

 closed, following which the first peripheral blood sample was obtained. This rep- 

 presented the control level from a surgically stressed normal animal. Hypothermia 

 was then induced and after a period of stabilization, a second laparotomy was 

 performed and the second arterial blood sample collected. In all animals the in- 

 ferior mesenteric, superior mesenteric, celiac axis, hepatic artery and portal vein 

 were then isolated and occluded with bulldog clamps, permitting complete exclusion 

 of the liver from the circulation. The occlusions were maintained for one hour and 

 then the third arterial blood sample was obtained. The clamps were then released, 

 the incision closed and the animals rewarmed in a warm water bath. The final 

 arterial blood sample was obtained when the body temperature returned to normal. 

 Free plasma 17-hydroxycorticoids were determined by the method of Silber and 

 Porter. 



The mean 17-hydroxycorticoid levels (fig. 1) in the arterial plasma of the dogs 

 studied revealed a plasma corticoid level of 17.8 ±1.5 gamma per cent after the 

 control laparatomy at normal body temperature. Following the induction of hypo- 

 thermia and stabilization of the animal's temperature at 25° C. a second laparotomy 

 was performed. The mean corticoid concentration at the end of this procedure was 

 24.8 ±3.5 gamma per cent. After one hour of exclusion of the liver from the cir- 



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