HEMORRHAGIC SHOCK— FRIEDMAN, DAVIDOFF and FINE 377 



The acidosis of hypothermia resuUino- from liyiKM-capnia'''' apparently does not 

 occm- in shocked dogs. This is douhtless ])ecaiisc the level of metaholic activity is so 

 low that the correspondingly low ventilatory volume is sufficient to discharge the 

 CO2 produced. That the death of hypothermic shocked dogs which did not receive 

 antihiotics at the time of transfusion was not related to hypercapnia is ohvious from 

 the fact that death was regularly prevented by antibiotic therapy. 



Fisher et al}* observed hypoglycemia and prolonged clotting time as a result of 

 hypothermia of 5 to 10 hours duration. Firor^-^ observed altered cell morphology in 

 tissue cultures grown at 28° C. Within the limits and duration of hypothermia 

 which we employed these and other deleterious effects of hypothermia are not 

 dominant features in the shocked dog. On the one hand, the protective action of 

 hypothermia is impressively demonstrated by (1), the experiments of Allen/" who 

 found that hypothermic rats survive a dose of total body X-radiation which is fatal 

 to normothermic rats, (2), by experiments showing that hypothermia prevents the 

 swelling of the hind limbs following removal of tourniquets applied for 4-5 hours, 

 and (3), the observation that hypothermia protects the abdominal viscera from an 

 otherwise fatal exposure to total ischemia.- ^' "■'' ^^' ^^ Similarly, we have observed 

 that hypothermia reduces the volume of peritoneal exudate in experimental fecal 

 peritonitis in dogs.-° This may be due to decreased capillary permeability or to 

 vasoconstriction. Presumably the relatively bloodless state of surgical wounds dur- 

 ing hypothermia is due to slow flow through the peripheral vessels because of vaso- 

 constriction, lowered blood pressure and reduced cardiac output. Additional bene- 

 ficial effects of hypothermia, as our observations on hemorrhagic shock demonstrate, 

 are the suppression of bacterial activity, and the support given to the maintenance 

 of the integrity of the antibacterial defense mechanism.^ AH of these positive 

 qualities of hypothermia are derived from its capacity to reduce the tissue re- 

 quirements for oxygen and blood supply. When applied within certain limits of 

 degree and duration for certain specific objectives the protective properties of 

 hypothermia outweigh its dangers. 



SUMMARY AND CONCLUSIONS 



(1) The dog's capacity to tolerate severe hemorrhagic shock is substantially in- 

 creased by precooling to 28° C. Used alone it does not effect survival, but when 

 combined with antibiotic therapy, it results in 100 per cent survival. 



(2) The increased resistance to hemorrhagic shock is due to the protection of 

 the antibacterial defense mechanism, which disintegrates rapidly in the normo- 

 thermic dog. 



(3) The very low level of respiratory activity does not result in hypercapnia, or 

 deficiency in oxygen supply because of the extreme reduction in the rate of meta- 

 bolic activity. This accounts for the fact that survival is possible even though the 

 cardiac output and peripheral flow are at levels far below those consistent with 

 survival of normothermic dogs, 



REFERENCES 



1. Ricca, R. A., Fink, K., Katzin, L., and Warren, S. L. : The effect of environmental tem- 

 perature on experimental traumatic shock, J. Clin. Invest. 24: 127, 1945. 



