418 PHYSIOLOGY OF INDUCED HYPOTHERMIA 



Pleural perfusion. Pierpont and Blades^^ have induced hypothermia by perfus- 

 ing cold saline into the pleural cavity. During a thoracic operation such a technique 

 could be readily applied. It may also be quite helpful in rewarming (see Hughes, 

 Discussion, p. 412) . It has a disadvantage in that, generally, it is not as rapid as other 

 methods^* although Jaeger/^' using a closed circulating system, found that the 

 temperature could be decreased about 1° C. every five minutes. It does not seem to 

 be this rapid when cold saline is introduced into the open chest through a thoraco- 

 tomy wound during an operation. 



Peritoneal cooling. Jaeger^° has used peritoneal cooling in animals. One mush- 

 room catheter was introduced into the left flank to serve as tbe point of entry for 

 the coolant fluid while a sump drain was introduced into the right lower quadrant 

 for removal of the fluid. The intrapericardial temperature was 1.1° to 4.4° C. lower 

 than the rectal temperature. This was probably due to cooling of the blood flowing 

 not only through the vena cava but through the portal vascular bed and other ab- 

 dominal viscera returning blood to the heart. He thought tbe advantages of such a 

 method were that cooling and rewarming did not interfere witli the opening and 

 closing of the chest or performance of tbe operative procedure. It seemed to reduce 

 the temperature as rapidly as other methods. One animal died 48 hours after the 

 operation from an intestinal hemorrhage and another dog, sacrificed at that time, 

 showed, in the small intestine, punctate sub-serosal hemorrhage and edema of the 

 mucosa. In addition, one wonders about the introduction of infection and the de- 

 velopment of intestinal adhesions subsequent to this method of hypothermia. 



Intragastric balloon. This method has been investigated by Khalil and 

 MacKeitb.^'' They introduced a balloon through the esophagus into the stomach. 

 The balloon was filled via a connecting tube with 250 ml. cooled water (4° C). 

 Body temperature in rabbits could be lowered to 25° C. in two hours. The method 

 might conceivably be useful in infants and small children. It might have an ad- 

 vantage over skin cooling in that it would not be affected Ijy cutaneous vasocon- 

 striction occurring in response to cold. In animals profuse salivation and extrasys- 

 toles were noted. Tbere are no data as to whetber tbe heart might cool more than 

 the rest of the body. This would be undesirable. 



Rewarming. Rewarming may be accomplished by a number of methods. Immer- 

 sion in water at a temperature of 40-42° C. is useful. It is rapid, simple, and con- 

 trollable. It has the same disadvantages as immersion cooling. As already indicated 

 the blankets containing coils can also provide warmth. 



Diathermy has been used by Rigelow^' and Swan.- The chief advantage of tbis 

 method is tbat it appears to minimize tissue gradients between the superficial and 

 deep tissues because of its deep heating characteristics. In experimental studies, 

 Bigelow and associates^' did not encounter vascular collapse. This might be at- 

 tributable to a more uniform heating of deep and superficial tissues. Burns occur 

 from tbis method, however, if there is inadeciuate insulation between the coil and 

 tbe patient. Onedialf incb of rubber was alleged to provide sufticit-nt insulation to 

 permit satisfactory heating and prevent burns. 



Air warming has been used by a number of iiuestigators. It is accomplisbed by 

 placing the patient in bed under a heat cradle. It is most useful when the tempera- 



