The impact of repeated short episodes of circulatory arrest on cerebral function. Reassuring electroencephalographic (EEG) findings during defibrillation threshold testing at defibrillator implantation.

The impact of circulatory arrest on EEG features during defibrillation threshold testing for implantation of a cardioverter defibrillator has been disputed. Cumulation of cerebral ischemic effects during threshold testing has been observed, and consequently the advice was given to avoid short intervals between tests and to limit the test number. This study investigated the duration of EEG signs of cerebral ischemia as well as the occurrence of cumulation. EEGs were recorded during standardized general anesthesia. Subsequent tests were performed after recovery of EEG, electrocardiogram, systemic arterial blood pressure, and heart rate. In 36 consecutive survivors of out-of-hospital cardiac arrest 286 episodes of induced circulatory arrest were analyzed. Ischemic EEG changes were present in all episodes of circulatory arrest, consisting of slowing, progressing to absence of activity. The relation between the onset time or recovery time and the test number and test interval was studied. A highly significant correlation between circulatory arrest and recovery time was found (P < 0.001). A significant negative correlation existed between test number and recovery time (P < 0.05). Test interval was not related with either onset or recovery time. We conclude that repeated threshold tests which are monitored by assessment of EEG and hemodynamics are not associated with cumulative EEG changes as a result of ischemia. Our results do not support the advice that the number of tests should be limited.