Selective Cerebral Hypothermia

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Abstract
A safe suitable technique for producing selective brain cooling by a perfusion method is described. Of 15 dogs, 7 survived. The salient features aiding survival were discussed. The use of a direct vasodilator (papaverine) in the perfusate to relieve vasospasm markedly reduced cooling time and represented the most significant technical advance over previously described methods. An acid base analysis utilizing the Siggaard-Andersen curve nomogram was performed on 4 dogs and no significant acidosis noted during selective brain cooling. A definite arteriovenous lactic acid difference developed at hypothermic temperatures indicating the brain may metabolize this substance in preference to glucose at lowered brain temperatures, the reasons for which were discussed. The rate of disappearance of physically dissolved O2 (PO2), was measured in the brain following ischemia at different temperatures. The average rate of disappearance at 20[degree] C. was 40% of the rate at 37[degree] C. The discrepancy between this finding and the in vitro O2 utilization rate at the same temperature was discussed.