THE SUGGESTION of Bigelow1 that hypothermia might be used as an aid to intracardiac surgery has excited the interest of many surgeons. Like others, we have stopped the circulation of a group of dogs under hypothermic conditions and have performed experimental intracardiac operations. Also like others, we have found that ventricular fibrillation may seriously limit the usefulness of this technique. It is a relatively frequent complication and one which is not always readily overcome. Factors which probably contribute to the high incidence of fibrillation are (1) anoxia, (2) manipulation of the heart, and (3) hypothermia. It has been our impression that it is more difficult to abolish ventricular fibrillation in hypothermic than in normothermic dogs. The experiments described below were undertaken in an attempt to find out whether this impression could be confirmed under controlled conditions.
During experiments recently reported2 we developed a standardized technique for inducing