JAMES A. MILLER, JR. 237 



and organs described earlier. It appears likely that the differences are due 

 to two facts: 1} the temperatures currently used in hypothermia studies 

 (25°-30°C) are sufficiently high to permit appreciable metabolic activity 

 in organs such as the liver and kidney. Bigelow et al. (33j found a 

 residual metabolism of 56% in a dog at 28°C and it is possible that the 

 metabolism of organs such as the liver, kidney and adrenals may not 

 fall as rapidly as the body as a whole. 2) Because of vasoconstriction, 

 hypotension, and reduced cardiac output, such structures may suffer 

 from increasing anoxia as the period of cooling is prolonged. In the 

 course of 2^/2 hours at this temperature (the time used by Miss Krocker) 

 serious damage can occur. Evidence in favor of this interpretation is 

 found in the experiments of Falkmer and Kjellgren (63) who by the use 

 of intra-abdominal coils cooled the liver 5° to 10° lower than the rest 

 of the body. In their histological studies only very mild liver injury 

 was found and restitution appeared to be complete within 24 hours. This 

 might also explain the fact that tissue damage has not been demonstrated 

 in limbs in which temperatures approaching 0°C were induced prior to 

 amputation. 



That there is nothing inherently dangerous to organs such as the liver, 

 adrenals and kidneys from low temperatures is illustrated by studies on 

 deep hypothermia by the group at the National Institute for Medical 

 Research in London. With the aid of glycerol and — 79°C they have 

 developed methods of preserving both motility and fertility of spermatozoa 

 for long periods (135-137, 151, 172, 147-150, 159). With a modification 

 of this technique, red blood corpuscles can be frozen, stored for months 

 and reinjected (165-168, 128, 129, 107-110). Even more remarkable have 

 been the demonstrations that ovaries and testes not only do not disin- 

 tegrate at — 79°C, but can be shown to secrete appropriate hormones 

 upon reimplantation after long sojourns at — 79°C outside the body (138- 

 140, 169-171, 53-55). In the case of the testis, active grafts were obtained 

 after 227 days and if imjilanted into the scrotum produced motile sperma- 

 toza (54). Ovaries stored for one year at — 190°C still retained capacity 

 to form functional grafts (139). Other applications of their technique for 

 longtime storage of vital tissues include skin (400 days with subsequent 

 successful grafting — ref. 34), arteries (93, 92) and corneas (156). From 

 these facts the impression is gained that the temperature range which 

 is currently employed in generalized hypothermia probably will eventually 

 be included in the so-called 'danger zone'. Wlien the causes of ventricular 

 fibrillation are better understood and controlled, it appears likely that 

 the range between 10° and 0°C will be utilized. As noted above, in this 

 range metabolic requirements approach zero and long periods of total 

 interruption of blood supply or complete tissue anoxia can be tolerated. 



