430 



PHYSIOLOGY OF INDUCED HYPOTHERMIA 



51. Covino, B. G., and Hegnauer, A. H. : Ventricular excitability cycle: Its modification by pH 

 and hypothermia, Am. J. Physiology 181: 471, 1955. 

 Berne, R. M. : The effect of immersion hypothermia on coronary blood flow, Circ. Research 



2: 236, 1954. 

 Edwards, W. S., Tuluy, S., Reber, W. E., Siegel, A., and Bing, R. J. : Coronary blood flow 

 and myocardial metabolism in hypothermia, Ann. Surg. 139: 275, 1954. 

 54. Covino, B. G., Charleson, D. A., and D'Amato, H. E. : Ventricular fibrillation in the hypo- 

 thermic dog, Am. J. Physiology 178: 148, 1954. 



52. 



53 



DISCUSSION 



Dr. J. Adams-Ray: A new method for prodticing hypothermia has been elaborated 

 in team work with engineer P. O. Persson at the Royal Institute of Technology, 

 Stockholm.^ Cold air with a velocity of 5-6 meters per second is fanned over the 

 dog or patient, lowering the rectal temperature by 0.1° C. per minute, much as is 

 done with icewater. Heating elements provide warm air for the rewarming period. 



As we all know, it may be difficult to keep the rectal temperature stable, and 

 drift may be dangerous. When studying the effect of hypothermia on burns with 

 Dr. B. Johansson and L. Troell we worked out a technique for the automatic con- 

 trol of the rectal temperature. A thermocouple adjusted for the desired rectal 

 temperature is inserted in the rectum. \Vhen the temperature has come down to 

 31° C, the automatic-control thermocouple is activated. The rectal temperature 

 can be held at a constant level very easily (fig. 1), in this case a 24-hour experi- 

 ment. The oscillation of the air-temperature can be adjusted by a maximum-mini- 

 mum control (see the adjustment at 12 hours). 



An apparatus built on these principles and that can be used for experiments or 

 as a cooling bed or operating table is now manufactured by the Heljestrand Cy. 

 Eskilstuna, Sweden (fig. 2). The air temperature can be varied from — 10° C. to 



2 4 6 8 W 12 U 16 18 20 22 24 h 



Fig. 1.— IMaintcnancc of constant rectal tcnipcraUu-e by automatic control of air temperature. 



