JAMES A. MILLER, JR. 235 



pretation has been offered. This is the concept that circus movements 

 rather than ectopic foci are responsible for fibrillation (154). 



According to Gollan, the tendency to develop ectopic foci is aggravated 

 by increased pressure in the coronary system which causes ischemic 

 anoxia in the myocardium (76). This explanation may perhaps reconcile 

 the contradictory reports on the question whether or not myocardial 

 hypoxia plays a role in ventricular fibrillation. Those who find no evidence 

 that it does include Hegnauer and D'Amato (86), Badeer (25), Reissman 

 and Kapoor (155). Those who consider that hypoxia is important include 

 Bigelow et al. (32), Swan et al. (177) and Ramos (154). 



Vascular Effects. Hypothermia prolongs bleeding and clotting time 

 and reduces circulating plasma volume 10%-12% (52, 164). The fate of 

 the lost fluid is problematical, but it is the cause for the hemoconcentration 

 and for the large amount of fluids whicli profoundly hypothermic animals 

 require to maintain blood volume and fluidity (78). The great increase in 

 blood viscosity caused by low temperature (84) is a serious problem 

 at temperatures below 20°C. Laufman (103) mentions that the thick 

 consistency of the blood of his patient at 18°C rectal temperature 

 interfered with the taking of samples. Extreme peripheral vasconstriction 

 is a well-known effect of exposure to low temperature. In addition, con- 

 striction of deeply placed vessels occurs when cooled blood is returned 

 to the abdominal vessels (106). This causes renal ischemia and anuria, 

 reduced blood supply to the heart and liver (39) and other organs. 

 This may become a serious problem if hypothermia is prolonged in the 

 moderately low temperature range, between 25° and 30°C, in which 

 metabolism may be as high as 50% of normal. At 10°C or less, the oxygen 

 requirements are so low that organs can tolerate ischemia for extended 

 periods. 



Respiration. Respiratory rate and excursion decrease with decreasing 

 body temperature and in animals anesthetized with pentothal or Nembutal 

 artificial respiration is necessary below about 28°C (36). On the other 

 hand, with ether respiratory movements continue until after cardiac arrest 

 in most of the cases (85). Respiratory movements of etherized monkeys 

 continue to 20° (41). Since respiratory acidosis has been demonstrated and 

 has been found to reduce survivals, hyperventilation is generally employed 

 (176). Premedication with sodium bicarbonate also has been found to be 

 beneficial (132). Investigators are generally agreed that maintenance 

 of high blood pH gives better survivals (68) . 



Effects on the Embryo. Since our interest in hypothermia is pri- 

 marily as a means of combating asphyxia of the newborn, observations 

 with embryonal tissues are of significance. These show that temperatures 

 near zero are not merely tolerated; they are superior to higher tem- 



