Reduced cerebral vasomotor reactivity as an indicator of postoperative confusion

Surgical intervention in elderly patients carries a high risk. A frequent problem with surgery in these patients is the occurrence of a temporary confusional state, which increases both the risk of postoperative complications and the need for intensive care. We hypothesised that, in part, temporary confusional state results from cerebral hypoxia occurring in response to blood pressure fluctuations during surgery. To assess whether disruption of autoregulation of cerebral blood vessels plays a role in temporary confusional state, we studied 31 patients over 55 years of age, using the Doppler-carbon dioxide test. We determined whether vasomotor reactivity could be used diagnostically to identify those patients most likely to experience temporary confusional state. Blood flow velocity in the middle cerebral artery was detected using Doppler ultrasound, and hypercapnia was induced by breathing carbon dioxide until an end-tidal concentration of 8.0% by volume was reached. Vasomotor reactivity was calculated on the basis of the changes in blood flow velocity in response to the increase in carbon-dioxide. Temporary confusional state was assessed using the Syndrome Short Test (Syndrom-Kurztest). We found that resting blood flow velocity was inversely related to age (p < 0.05). In addition, there was a significant inverse correlation between vasomotor reactivity and temporary confusional state (p < 0.05). These data indicate that vasomotor reactivity,:as measured by the Doppler-carbon dioxide test, is a reliable tool to identify patients at risk for postoperative psychological disturbances.