ACID-BASE MANAGEMENT FOR OPEN-HEART SURGERY

An important part of managing patients during open-heart surgery is continuous monitoring of the acid-base status prior to, during, and following cardiopulmonary bypass. The use of a thermostatically controlled triple electrode system whereby arterial pH, pCO 2 , and pO 2 can be measured and base excess or base deficit quantitated by special application of the Astrup-Andersen nomogram is enthusiastically endorsed. In the opinion of the authors, respiratory alkalosis is to be avoided throughout the entire operation and postoperatively, as this appears to result in a base deficit, which is subsequently revealed as a metabolic acidosis. Particular consideration is given to the bypass phase when hypothermia is employed, since "optimal" pH appears to vary with temperature. Continued maintenance of good acid-base status with buffers is advocated. It is considered that buffer administration should be on a "titration" principle with frequent arterial blood gas analyses. Possible reasons are presented for the improved postoperative morbidity when optimal acid-base status is maintained throughout the operation and postoperatively.