ABSTRACT
Cerebral function is dependent upon cerebral blood flow (CBF) and oxygenation. An understanding of the physiology of CBF regulation is essential in order to manage patients who may have decompensated intracranial pathology or injuries. A change in perfusion pressure results in a myogenic response in the cerebral vascular smooth muscle in order to maintain constant CBF. For example, a hypertensive response during exercise with an increase in mean arterial pressure results in cerebral vasoconstriction thus keeping CBF constant. A fall in mean arterial pressure will result in cerebral vascular smooth muscle relaxation causing vasodilatation thus maintaining CBF. CBF and cerebral metabolism are coupled, thus the regional CBF varies with metabolic activity. Brain injury can lead to loss of cerebral autoregulation in injury-affected areas of the brain, resulting in the development of a pressure-dependent perfusion area. A fall in cerebral perfusion pressure may lead to secondary ischaemic brain injury.
