Effect of Dexmedetomidine on Dynamic Cerebral Autoregulation in Patients Undergoing Supratentorial Tumor Surgery

Background: Dexmedetomidine is gaining popularity in neuroanesthesia, but its effect on cerebral autoregulation (CA) is unclear. It is important to maintain CA in patients undergoing surgery for intracranial lesions. Previous studies have not examined the effect of dexmedetomidine on CA in anesthetized patients who have pre-existing intracranial pathology. Objective: The study was done to assess the effect of dexmedetomidine on dynamic CA (dCA) in patients with supratentorial tumors under sevoflurane anesthesia. Methods and Material: Forty American Society of Anesthesiologists physical status 1 and 2 patients with supratentorial tumors were randomized to receive either a bolus of dexmedetomidine (1 mu g/kg over 10 min) or a matching placebo. The middle cerebral artery (MCA) was insonated using a handheld transcranial Doppler probe and used to calculate the transient hyperemic response ratio, which is the surrogate measure of dCA. This test was repeated before and after administration of the test drug. Variables that can influence dCA like end-tidal carbon dioxide, blood pressure, and depth of anesthesia were tightly controlled throughout the conduct of Doppler studies. Results and Conclusion: The MCA flow velocity was comparable in both groups after administration of the test drug (58.05 +/- 7.41 cm/s vs 59.95 +/- 8.99 cm/s, P = 0.47). The transient hyperemic response ratio was also similar (1.30 +/- 0.11 vs. 1.26 +/- 0.07, P = 0.22). In anesthetized patients with supratentorial tumors, a bolus dose of dexmedetomidine does not affect dCA.