Extravascular Local Cooling of the Brain in Man

W 'nEN we cool the homeothermic brain of man, we disturb its functions. In exchange for an improved ability to withstand ischemia, we hazard the little known factors of abnormal survival at subnormal temperatures. These hazards increase in direct proportion to the depth, duration and extent of cooling. The metabolic and cardiovascular dangers of surface cooling of the whole body below 30~ and the technical complexities of perfusion techniques are well known, s,l~ Bearing in mind that even the most specialized individual tissues are able to survive near freezing temperatures, it would appear that it is not the actual process of cooling the tissues that is hazardous, but rather it is the sequence of physiological changes in various parts of the body in response to cold. 2,6,H,~3 The recognition of these facts has led to the development of local cooling as an attempt to by-pass the general effects of hypothermia, particularly when deep hypothermia is required; i.e., in the terminology of Bigelow, 2 temperatures below ~8~ Fig. 1 is a suggested classification of hypothermia which will serve to guide our use of terms in this report. Local cooling of the nervous system has been achieved in animals by a number of workers 9,24,25,30,34,42 using pervascular methods. In man, a few reports using such methods also have appeared. 2~ However, extravascular local cooling has not, to our knowledge, received sufficient attention. In another study we have reviewed the earlier work in this field and reported our results with local extravascular cooling in animals? 9 I t was emphasized there that the pioneer observations of Trendelenburg 39-41 in 1910