• S Strebel, A M Lam, B Matta, T S Mayberg, R Aaslid, and D W Newell.
• Departments of Anesthesiology and Neurological Surgery, University of Washington, Seattle, USA.
• Anesthesiology. 1995 Jul 1;83(1):66-76.

BackgroundAlthough inhalation anesthetic agents are thought to impair cerebral autoregulation more than intravenous agents, there are few controlled studies in humans.MethodsIn the first group (n = 24), dynamic autoregulation was assessed from the response of middle cerebral artery blood flow velocity (Vmca) to a transient step decrease in mean arterial blood pressure (MABP). The transient hypotension was induced by rapid deflation of thigh cuffs after inflation for 3 min. In the second group (n = 18), static autoregulation was studied by observing Vmca in response to a phenylephrine-induced increase in MABP. All patients were studied during fentanyl (3 micrograms.kg-1.h-1)/nitrous oxide (70%) anesthesia, followed by, in a randomized manner, isoflurane, desflurane, or propofol in a low dose (0.5 MAC or 100 micrograms.kg-1.min-1) and a high dose (1.5 MAC or 200 micrograms.kg-1.min-1). The dynamic rate of regulation (dROR) was assessed from the rate of change in cerebrovascular resistance (MABP/Vmca) with the blood pressure decreases using computer modeling, whereas the static rate of regulation (sROR) was assessed from the change in Vmca with the change in MABP.ResultsLow-dose isoflurane delayed (dROR decreased) but did not reduce the autoregulatory response (sROR intact). Low-dose desflurane decreased both dROR and sROR. During 1.5 MAC isoflurane or desflurane, autoregulation was ablated (both dROR and sROR impaired). Neither dROR nor sROR changed with low- or high-dose propofol.ConclusionsAt 1.5 MAC, isoflurane and desflurane impaired autoregulation whereas propofol (200 micrograms.kg-1.min-1) preserved it.

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