The role of microembolisation in cerebral injury as defined by functional magnetic resonance imaging.
BACKGROUND AND PURPOSE Microemboli have been implicated in the etiology of neuropsychological deficits after cardiopulmonary bypass. This study examined the incidence of high-intensity transcranial signals (microemboli) and their relation to changes in neuropsychological performance after surgery. METHODS Transcranial Doppler ultrasonography was used to measure middle cerebral artery blood flow velocity and detect microemboli. The number of high-intensity transcranial signals was determined and related to a neurological examination and absolute changes in neuropsychological performance as well as the number of patients considered to exhibit a neuropsychological deficit. Data were available on 100 consenting patients undergoing routine cardiopulmonary bypass. Fifty of the patients were randomly assigned to a procedure that included a 40-microns arterial line filter, and 50 had the procedure without any arterial line filter. RESULTS Significantly more patients were found to have neuropsychological deficits in the group without the arterial line filter at both 8 days (P < .05) and 8 weeks (P < .03) after surgery. In addition, more "soft" neurological signs were found in the nonfiltered group 24 hours after surgery (P < .05). More high-intensity transcranial signals were found in the nonfiltered group, and the number of high-intensity transcranial signals was found to be related to the likelihood of a patient having a neuropsychological deficit at 8 weeks. CONCLUSIONS These data suggest that neuropsychological deficits after routine cardiopulmonary bypass are related to the number of microemboli delivered during surgery. Furthermore, the numbers of microemboli may be reduced by including a 40-microns filter on the arterial line.