The cerebral circulation

Introduction Management strategies for the prevention of secondary brain injury are based on maintaining the cerebral perfusion pressure. Anaesthetic and surgical interventions alter cerebrovascular physiology profoundly; hence, a good understanding of these changes is crucial to limit the damage following a brain injury. The brain is unique with a high metabolic rate, and its oxygen demand exceeds that of all organs except the heart. It is approximately 2% of body mass and receives 20% of the basal oxygen consumption and 15% of the resting cardiac output (700 ml min−1 in the adult). Mean resting cerebral blood flow (CBF) in young adults is about 50 ml (100 g brain tissue)−1 min−1. This mean value represents two very different categories of flow: 70 and 20 ml (100 g)−1 min−1 for grey and white matter, respectively. Regional CBF (rCBF) and glucose consumption decline with age, along with marked reductions in brain neurotransmitter content, and less consistent decreases in neurotransmitter binding.