224 



PHYSIOLOGY OF INDUCED HYPOTHERMIA 



infarction." Occlusion of the inferior vena cava above the liver, necessary for a 

 so-called bloodless field and the prevention of air embolism, must be accompanied 

 either by a shunt or by aortic obstruction to prevent almost immediate shock. 

 Hypothermia permits prolonged thoracic aortic obstruction^^ and is in that sense 

 essential if the contemplated liver resection is to be performed on the isolated 

 organ. 



At our institution Raffucci preceded these researches with experiments directed 

 toward establishing the duration of afferent hepatic circulatory occlusion tolerated 

 l3y dogs. He concluded that 20 minutes was the maximum safe period of portal 

 vein and hepatic artery obstruction under normothermic conditions. ^*^' ^^ Simul- 

 taneous clamping of the superior mesenteric artery was the only measure taken to 

 prevent intestinal engorgement. In the light of our studies it would seem that the 

 deaths attributed to hepatic necrosis by Raffucci were in fact due to the effects of 

 portal obstruction with consequent shock and intestinal infarction. The beneficial 

 or protective effect of hypothermia, however, was clearly shown by Raft'ucci when 

 only 3 of 11 dogs succumbed after one hour of occlusion of the superior mesenteric 

 artery, celiac axis, portal vein, and hepatic artery.'^ No doubt less blood was iso- 

 lated from the circulation because of depressed collateral activity in response to 

 hypothermia. 



Clinical experience. Table IV is a summary of the results obtained in four 

 patients submitted to total right hepatic lobectomy under hypothermia. The same 

 technique of occlusion was used as in the experimental animals. Cooling, however, 

 was effected by means of refrigerated blankets rather than ice water immersion. 

 The raw surface of the liver after excision of the cancer was notably free of bleed- 

 ing. There was no evidence of the active collateral arterial supply so noticeable in 

 dogs. There was, however, a much greater postoperative blood loss, probably a 

 function of the increased surface area. One patient bled to death from an hepatic 

 vein which had been ligated but retracted from its ligature. Another patient, M, 

 was re-explored in the immediate postoperative period to secure hemostasis. His 

 course was further complicated by peritonitis, and death ensued 15 days after sur- 

 gery. Because of difficulties related to bleeding, the fourth patient was rewarmed 

 to 96° F. on the operating table by circulating hot solution through the blankets. 



TABLE IV 

 Occlusion and Total Right Hepatic Lobectomy under Hypothermia in Humans 



