Ectothermic philosophy of acid-base balance to prevent fibrillation during hypothermia
G. M. Kroncke, R. D. Nichols, J. T. Mendenhall, P. D. Myerowitz and J. R. Starling
In the ectotherms, or cold-blooded animals, carbon dioxide pressure
decreases (PCO2) and pH increases as body temperature falls. This tends to
increase coronary blood flow and prevent fibrillation. This concept was
investigated in 181 consecutive patients undergoing open heart surgery of
all types. In 121 cases, endothermic (warm-blooded) temperature-corrected
normal values of pH, PCO2, and oxygen pressure were maintained during
extracorporeal circulation as the perfusate temperature was lowered to 24
degrees C prior to aortic cross-clamping and administration of blood
cardioplegia solution. In 49 patients (40%), ventricular fibrillation
occurred prior to cross-clamping. In the other 60 consecutive cases, in
which the ectothermic principle of cooling was applied, the PCO2 was
allowed to decrease from 50 to 40 mm Hg and the non-temperature-corrected
pH rose from 7.28 to 7.42. Fibrillation occurred in only 12 (20%) of these
60 patients.
