[Effect of pH adjustment in deep hypothermia and circulatory arrest (author's transl)]

In 14 puppies, body temperature was lowered to 22 degrees C with surface hypothermia, then to 16 degrees C with textracorporeal circulation. During 60 min of circulatory arrest all hearts were protected with the same multidose blood cardioplegic solution. In seven dogs pH was kept at 7.4 and in seven others pH was varied as in poikilotherms (i.e. 7.95 at 16 degrees C) principally by adjusting pCO2 during cooling and rewarming. Appropriate pH adjustment allowed higher cardiac output with normal systemic lactate metabolism. Raising pH by lowering pCO2 to 10 mm Hg allowed twice as much cerebral blood flow. Postischemic myocardial performance was depressed by 50% by retaining pH 7.4 and was normal when pH was varied appropriately. These findings have major implications for the routine management of hypothermia during cardiac operations.