THE IMPACT OF REPEATED SHORT EPISODES OF CIRCULATORY ARREST ON CEREBRAL FUNCTION - REASSURING ELECTROENCEPHALOGRAPHIC (EEG) FINDINGS DURINGDEFIBRILLATION THRESHOLD TESTING AT DEFIBRILLATOR IMPLANTATION

The impact of circulatory arrest on EEG features during defibrillation threshold testing for implantation of a cardioverter defibrillator ha s been disputed. Cumulation of cerebral ischemic effects during thresh old testing has been observed, and consequently the advice was given t o avoid short intervals between tests and to limit the test number. Th is study investigated the duration of EEG signs of cerebral ischemia a s well as the occurrence of cumulation. EEGs were recorded during stan dardized general anesthesia. Subsequent tests were performed after rec overy of EEG, electrocardiogram, systemic arterial blood pressure, and heart rate. In 36 consecutive survivors of out-of-hospital cardiac ar rest 286 episodes of induced circulatory arrest were analyzed. Ischemi c EEG changes were present in all episodes of circulatory arrest, cons isting of slowing, progressing to absence of activity. The relation be tween the onset time or recovery time and the test number and test int erval was studied. A highly significant correlation between circulator y arrest and recovery time was found (P < 0.001). A significant negati ve correlation existed between test number and recovery time (P < 0.05 ). Test interval was not related with either onset or recovery time. W e conclude that repeated threshold tests which are monitored by assess ment of EEG and hemodynamics are not associated with cumulative EEG ch anges as a result of ischemia. Our results do not support the advice t hat the number of tests should be limited.