Cerebral autoregulation refers to the physiological mechanisms that maintain blood flow at an appropriate level during changes in blood pressure. However, due to the important influences of arterial carbon dioxide levels, cerebral metabolic rate, neural activation, activity of the sympathetic nervous system, posture, as well as other physiological variables, cerebral autoregulation is often interpreted as encompassing the wider field of cerebral blood flow regulation. This field includes areas such as CO2 reactivity, neurovascular coupling and other aspects of cerebral haemodynamics.
This regulation of cerebral blood flow is achieved primarily by small arteries, arterioles, which either dilate or contract under the influence of multiple complex physiological control systems. Impairment of these systems may occur e.g. following stroke, trauma or anaesthesia, in premature babies and has been implicated in the development of subsequent brain injury. The non-invasive measurement of relevant physiological signals like cerebral blood flow, intracranial pressure, blood pressure, CO2 levels, cerebral oxygen consumption, etc. is challenging. Even more so is the subsequent assessment of the control systems. Much remains unknown about the physiology of blood flow control and the best clinical interventions to optimize patient outcome.