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Arch Hellen Med, 28(5), September-October 2011, 611-620


The pathophysiology of cerebrovascular reactivity and its clinical approach

G.G. Tsaousi
"AHEPA" University Hospital of Thessaloniki, Thessaloniki, Greece

Cerebral blood flow autoregulation is the intrinsic ability of the cerebral vasculature to provide constant cerebral blood flow despite changes in the cerebral perfusion pressure or the systemic blood pressure. The underlying pathophysiology is rather complicated, and endothelial and myogenic vascular factors have been hypothesized as mechanisms responsible for control of this function. Although many physiological parameters modify cerebral autoregulation, the arterial blood carbon dioxide (CO2) tension is considered to be the most powerful determinant. Among intravenous anesthetic agents, propofol provides the best preservation of autoregulation. With the exception of sevoflurane, inhaled anesthetic agents appear to impair autoregulation in a dose-related manner, which is restored when hypocapnia is applied. Xenon is unique in retaining the cerebral autoregulation intact. Intraoperative cerebral autoregulation monitoring is considered an important issue for patients with impending or established neurologic disease. The introduction of transcranial Doppler technology in clinical practice has made possible continuous cerebrovascular autoregulation determination, especially when acute changes are involved. According to the cerebrovascular reactivity to slow or rapid changes of systemic blood pressure, cerebral autoregulation is distinguished into static (slow response) or dynamic (quick response), respectively, while its determination can be accomplished by spontaneous or evoked methods. So far there is no gold standard for the testing of cerebrovascular autoregulation. Pharmacological static cerebral autoregulation is the most robust and reproducible method used for this purpose, while dynamic autoregulation appears to be of clinical importance.

Key words: Cerebral blood flow, Dynamic cerebral autoregulation, Static cerebral autoregulation, Transcranial Doppler.

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