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NEUROSURGICAL ANESTHESIA

The Influence of Nicardipine-, Nitroglycerin-, and Prostaglandin E₁-Induced Hypotension on Cerebral Pressure Autoregulation in Adult Patients During Propofol-Fentanyl Anesthesia

Hiroshi Endoh, MD PhD^*, Tadayuki Honda, MD PhD^*, Satomi Ohashi, MD^*, Seiji Hida, MD^*, Chieko Shibue, MD, and Noboru Komura, MD

Departments of *Emergency and Critical Care Medicine and Anesthesiology, Niigata University Faculty of Medicine, Niigata, Japan

Address correspondence and reprint requests to Hiroshi Endoh, MD, PhD, Department of Emergency & Critical Care Medicine, Niigata University Faculty of Medicine, 1-757 Asahimachi, Niigata 951-8150, Japan. Address e-mail to endoh{at}med.niigata-u.ac.jp

We investigated the influence of drug-induced hypotension at a mean arterial pressure (MAP) of 60–70 mm Hg on cerebral pressure autoregulation in 45 adult patients during propofol-fentanyl anesthesia. Time-averaged mean blood flow velocity in the right middle cerebral artery (Vmca) was continuously measured at a PaCO₂ of 39–40 mm Hg by using transcranial Doppler ultrasonography. Hypotension was induced and maintained with a continuous infusion of nicardipine, nitroglycerin, or prostaglandin E₁. Cerebral autoregulation was tested by a slow continuous infusion of phenylephrine to induce an increase in MAP of 20–30 mm Hg. From the simultaneously recorded data of Vmca and MAP, cerebral vascular resistance (CVR) was calculated as MAP/Vmca. Furthermore, the index of autoregulation (IOR) was calculated as CVR/MAP, where CVR = change in CVR and MAP = change in MAP. The test was performed twice for each condition on each patient: baseline and hypotension. The IOR during baseline was similar among the groups. During nitroglycerin- and prostaglandin E₁-induced hypotension, IOR was not different from baseline. In contrast, during nicardipine-induced hypotension, IOR significantly decreased compared with baseline (0.37 ± 0.08 versus 0.83 ± 0.07, P < 0.01). In conclusion, nicardipine, but not nitroglycerin or prostaglandin E₁, significantly attenuates cerebral pressure autoregulation during propofol-fentanyl anesthesia.

IMPLICATIONS: Vasodilators may influence cerebral autoregulation by changing cerebral vascular tone. Nicardipine, but not nitroglycerin or prostaglandin E₁, attenuated cerebral pressure autoregulation in normal adult patients during propofol-fentanyl anesthesia.

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