Cerebrovascular autoregulation and monitoring of cerebrovascular reactivity

Cerebrovascular autoregulation and reactivity are two important processes which maintain CBF at metabolically appropriate levels in response to fluctuations in cerebral perfusion pressure. Additionally, intact vascular reactivity protects the cerebral capillary bed against excessive hydrostatic pressures that may precipitate vasogenic oedema. The importance of vascular reactivity is amplified in the acute phase of injury by disruption to the integrity of the blood-brain barrier (BBB), known to occur even in mild cases of TBI. Monitoring of pressure reactivity in combination with measures of cerebrospinal compensatory reserve may assist in identifying those patients at risk for the development of vasodilatory, short-term increases in ICP. The state of pressure reactivity is also a robust, independent predictor of outcome after TBI. This chapter discusses CBF autoregulation, the careful regulation of vascular resistance, and the measurement of pressure reactivity in the cerebral vasculature.