176 



PHYSIOLOGY OF INDUCED HYPOTHERMIA 



ANESTHESIA- PENTOTHAL- ETHER 

 HYPERVENTILATION 



30 



24.8 



20 



PLASMA 



17-HYDROXYCORTICOID 



LEVEL 



r % 



25.0 



17.8 



FIRST 



LAf»ROT0MY 



AND 



CLOSURE 



SECOND 

 LAWVRO- 

 TOMY 



r I 



23.7 



HEPATIC 

 AFFERENT 

 OCCLUSION 

 ONE HOUR 



CLOSURE 

 SECOND 



LAPAROTOMY 



37" 37«-C00LING-»25" 25° l»-REWARMING->37'' 



TEMPERATURE °C 



12 3 4 5 



TIME - HOURS 



Fig. 1. 



dilation, the level was 23.7 ±3.6 gamma per cent. Finally, after rewarming to 

 normal body temperature, the level was 25.0 ±2.8 gamma per cent. 



The half life of hydrocortisone in the blood of the normal animal is less than 

 one hour, the hormone being conjugated by the liver, excreted in the urine and 

 possibly utilized by the tissues. The fact that the arterial corticoid levels in the ani- 

 mals studied increased rather than decreased after two hours of cooling and fur- 

 ther trauma suggests that depression of these mechanisms is ecjual to or greater 

 than the fall in adrenocortical production of the hormones. This conclusion was 

 strengthened by the fact that exclusion of the liver from the general circulation 

 failed to produce a change in arterial corticoid levels. If the liver were conjugating 

 steroids at a normal rate in the hypothermic animal, an appreciable fall in plasma 

 corticoid levels would have resulted. It is evident, therefore, that the marked re- 

 duction in adrenocortical hormone production in hypothermia is more than balanced 

 by the concomitant depression of mechanisms which normally tend to reduce this 

 level. 



Peripheral 17-hydroxycorticoids in man. A small group of patients under- 

 going surgery with hypothermia were also studied (two examples shown in figin"es 

 2 and 3). Peripheral venous blood samples were obtained before, during and for 

 7 to 13 days following surgery. Blood was collected in dry test tubes, allowed to 

 clot, and the serum removed. Samples were stored in a deep freeze until analvzed, 

 at which time the corticoid determinations were carried out by the method of 

 Nelson and Samuels. 



The normal range for peripheral 17-hydroxycorticoids in this laboratory is 15 to 

 18 gamma per cent with a mean of 12 gamma per cent. Additional ])atients under- 



