DIFFICULTIES OF EPIDEMIOLOGICAL STUDIES 



the induction of cooling, the fact is, of course, that the human 

 being, himself being a heat exchanger and a very inefficient 

 one in many respects, produces a series of problems outside 

 of the infection which have resulted in very serious consequences, 

 sometimes death, and this is because the specific heat of the 

 various tissues are so different. When I say artificial cool- 

 ing, I am referring to hypoxia in the systems. When a patient 

 is cooled down, he winds up with some very serious gradients 

 in various tissues, the most serious of which is skeletal muscle. 

 The skeletal muscle is not cooled down very much. It is kept 

 quite warm, as a matter of fact. The liver is cooled down quite 

 considerably; also the brain. The net result is that when the 

 cooling process is stopped and the patient is presumably sta- 

 bilized at a particular level of hypothermia, and this is usually 

 guaged by the esophageal temperature, we begin working on 

 the patient. Of course, a lot of other things are going on, par- 

 ticularly, I think, in the skeletal muscle, which when we start 

 to rewarm the patient, results in a metabolic situation which 

 has made us very, very unhappy; and this is the metabolic 

 acidosis. 



Now, I am off the subject that you had raised. Dr. Mitchell. 

 With regard to infections per se, I am not aware of any. They 

 probably have developed and I can only reiterate the attempts 

 of culturing the equipment and, of course, the patient's blood 

 stream, but we have not found any bacteremia. The bacteria, 

 if present, would become overwhelming. This is a matter which 

 would require serious investigation, but then, I personally am 

 not terribly concerned about it because of the time factor. I 

 don't think much is going to happen in one or two hours. These 

 patients are cooled to 10° C in about twenty minutes. They are 

 warmed in about forty-five minutes, but time factors are very 

 short, and I can assure you that the deep level cooling main- 

 tained is very brief. Attempts to assay host mechanisms have 

 demonstrated that the period of cooling and rewarming has not 

 produced any longstanding effect on the host mechanisms in handling 

 bacterial infections. 



CAMPBELL: The anesthetic must play quite a role here, 

 as in allergic reactions which do not occur during anesthesia. 



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