16 



PHYSIOLOGY OF INDUCED HYPOTHERMIA 



^ 



-247' 

 Heol Conlent Coloriei 690 



Tlm« In Cold Hours Control 



^^^^ Storoga 



[ I Metobolism 



Rodiotlon and Convection 



^^ 



Time -hr«. 

 Control 



2-35.5 

 35.5-38 



Ambl«nt-T«mp-'C 

 25.0' 

 -8.0* 

 21.0* 

 15.0* 



466 

 9 



470 

 10 



Fig. 6. — Heat balance of the dog in fig. 4. This animal was breathing room air spontaneously 

 throughout the course of the experiment. Heat content should read Cal./M-. 



only 4° C. is some 90 times greater than that required at normal l:)ody temperatures. 

 Cassidy et al.^° demonstrated a delay in the drop of the blood sugar following 

 insulin administration in dogs cooled to 25° C. The enzymatic detoxification of 

 epinephrine is slower at low temperatures, a given dose resulting in a longer and 

 more intense action during hypothermia. This is in contrast to studies on isolated 

 tissues where epinephrine effect is greatest at temperatures of approximately 37° C. 

 Substances which are chemically detoxified by the tissues may have their action 

 prolonged l)y hypothermia while drugs not detoxified may be uninfluenced by the 

 temperature change. A number of factors must be considered l)efore critical evalua- 

 tion of drug action can l)e made. The accumulation of such data must take into con- 

 sideration such matters as rates of absorption and distribution to effector areas, 

 permeability changes (selective) of the cell, rate of destruction, effective ratios of 

 concentration of drug and substrate at point of action, response of tissue to concen- 

 tration and the intracellular enzymatic mosaic alterations resulting from changes in 

 local temperature. This local temperature effect may also be modified by the differ- 

 entiated action of temperature upon adjacent cells which may respond in an entirely 

 different manner. 



