REVIEW AND APPRAISAL OF PARTS I AND II— HORVATH 285 



Ian. The successful resuscitation of animals whose body temperatures were lowered 

 to 0° C. or below indicated that prior impressions of the lethal effects of lesser 

 hypothermic levels (16°-24° C.) need re-evaluation, Furthermore, the procedures 

 by which such extreme lowering of the body temperature were accomplished and 

 the relative lack of such complications as ventricular fibrillation, suggest that there 

 may be some misconceptions concerning the physiological mechanisms being in- 

 voked to account for the untoward incidences observed in animals subjected to mild 

 hypothermia. 



Problems which now recjuire clarification have to do with the development of 

 acidosis and electrolyte shifts, the use of forced (abnormal) ventilation with and 

 without oxygen and/or oxygen and carbon dioxide mixtures. The inability of the 

 discussants to come to a meeting of minds on these aspects of hypothermia was 

 evident. It may be partially due to the inability to control the variables mentioned 

 earlier or to the fact that the physiological adjustments by the organism were being 

 interfered with to varying degrees. For example, the supposition by certain in- 

 vestigators that animals with low body temperatures should be ventilated with 

 small quantities of air similar in volume and of the same or different composition 

 to those seen when they were normothermic hardly seems valid. It is obvious from 

 the data presented by others that the ventilatory requirements of the hypothermic 

 animal are not those of the normothermic. Furthermore, the lack of agreement 

 among different investigators regarding the significance of the electrolyte shifts 

 seems to be related, in part, to their employment of arbitrary ventilatory patterns. 

 The ultimate decision regarding the importance of electrolyte alterations would 

 seem to rest in the demonstration of their role in animals subjected to the And jus 

 procedure where complete cardiac and respiratory arrests were present for appre- 

 ciable periods of time. 



The fact that the And jus animal can be successfully resuscitated by applying 

 localized heat to the thoracic area suggests that these animals may go through 

 physiological adjustments similar to those exhibited by the poikilothermic animals 

 discussed by Lyman and Chatfield. The biochemical and physiological capacities of 

 this cooled heart muscle require extensive investigation. Brooks and Hoffman in 

 their discussions have made a step, but only a step, toward providing us with this 

 information. The difficulties inherent in this task are evident from their analysis of 

 our present stage of knowledge. 



The studies reported on the circulation of the cooled intact animal appear to be 

 complicated to more than the usual degree by variables in technique and experi- 

 mental approach. The major complicating factor in the study of the circulation is 

 the development of ventricular fibrillation. Since the factors conducive to ventric- 

 ular fibrillation are many and varied it would appear that further study with 

 Andjus' and Smith's preparation should provide some important clues. 



Reduction of the body temperature results in certain straightforward modifica- 

 tions of basal functioning, probably primarily related to the reduction of the 

 metabolic level and the influence of temperature on the basic enzymatic reactions. 

 Brown, Fuhrman, Brauer, and Gray have presented suggestive evidence of the 

 value of considering the relationship of temperature to enzyme-substrate interreac- 

 tion. While information on isolated systems can provide valuable information it 



