EFFECTS OF COLD ON THE NERVOUS SYSTEM 



J. D. McyUEEN 



I would like first to outline in a general way the development of our knowledge 

 of the effects of induced cold on the functioning of central and peripheral nervous 

 tissues, and second to consider the specific etifects of peripheral ner\e and cerehral 

 cortex. 



Simpson^'- ^"^ stands virtually alone as the pioneer in this field ; however, j^rior to 

 his work, W'alther" in 1862 had cooled the rahl:>it to a temperature of 20° C. with 

 successful rewarming. and Horvath^** in 1881 similarly studied the hihernator to a 

 temperature just above 0° C. Horvath, as well, did, during the period of hypo- 

 thermia, elicit muscular response upon stimulation of the appropriate motor nerve. 



Sutherland Simpson in 1902-'' was able to cool one monkey to a rectal tempera- 

 ture of 14° C. He rewarmed this animal and examined it thereafter for a period 

 of one month. His description reads, "There was no evidence whatever of any bad 

 effect having followed." With Herring in 1905-'* he pursued this work in the cat 

 and established a lethal temperature of 16° C. for this animal. He introduced both 

 terms "cold narcosis" and "artificial hibernation" at this time, the connotation of 

 the latter term being quite distinct from that introduced more recently by Laborit 

 and his co-workers.-^ He found that, at a temperature estimated to be between 23° 

 and 25° C. for both animals, the heat regulating mechanisms w^ere completely sup- 

 pressed. Simpson thus rather early defined the narcotic action of cold. He perhaps 

 correctly localized such action in the brain stem, for the term "highest centers" 

 does appear in his description. Britton,^ some two decades later contested this con- 

 cept of artificial hibernation on the basis of Simpson's brief periods of observation. 

 He did show, that after periods of 6 to 12 hours under favorable conditions, the 

 animal could restore heat regulation. Both workers considered in detail during the 

 rewarming period, the temperature course of recovery from neurologic deficit. 

 These are listed in table I. 



Not until 1940 was general refrigeration employed in the human. Temple Fay^° 

 first employed this technique and did so specifically in the treatment of advanced 

 malignancy. Forty-two patients were so treated to a minimum temperature of 25° C. 

 and for periods as long as 150 consecutive hours. xA.biding neurological deficits were 

 not observed, nor did subsequent microscopic examination of these brains by Sano 

 and Smith^^ reveal significant pathology. Talbott"'' reported on a group of similarly 

 treated psychotic patients in 1941, and Laufman in 1951-^ presented the best docu- 

 mented case of accidental hypothermia. From these cases, the neurological status at 

 the various recorded temperatures can be tabulated, although the detail has never 

 been comparable to that of the animal experiments. 



It is recognized that no rigid temperature level exists for disappearance of a 

 response on cooling nor reappearance of the same response on rewarming. Un- 

 fortunately, the temperatures recorded were rectal and not tissue temperatures, and 

 non- volatile anaesthetic agents were routinely used. In the human at a temperature 

 at about 34° C. amnesia is established for the period of cooling Ijelow this level. 



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