Acid-base monitoring of open-heart surgery

The techniques and interpretation of acid-base studies on patients undergoing open-heart surgery with extracorporeal circulation are described. The ;normal' range and duration of changes in 35 surviving patients are given; these were essentially of respiratory rather than of metabolic origin, being a respiratory alkalosis induced by the anaesthetist before perfusion, and a respiratory acidosis after assisted respiration was stopped. Gross metabolic acidosis was seen only where clinically severe complications had occurred.