Cerebral haemodynamics during anaesthesia

The human brain is dependent on uninterrupted blood flow, because it cannot store oxygen and other nutrients. The constancy of cerebral blood flow is regulated by a range of physiological mechanisms. Most notably, cerebral autoregulation protects the brain against blood pressure variability and cerebrovascular CO2 reactivity adjusts blood supply to (regional) metabolism. How changes in cardiac output influence cerebral blood flow is less clear. The regulating mechanisms that maintain systemic and cerebrovascular homeostasis may be affected during anaesthesia. Before conduction of our studies, it was already known that the sensitivity of the baroreflex, normally maintaining short-term blood pressure, is reduced during anaesthesia. However, how cerebrovascular regulation behaved during anaesthesia remained largely opaque. Anaesthesiologists strive to safeguard cerebral blood flow during surgery. Wry enough, they also interfere with the most important monitor of adequate brain perfusion: consciousness. And since cerebral blood flow is notoriously difficult to measure – let alone optimise – anaesthesiologists need to rely on physiological concepts to guide them. The studies on which this thesis is based focused on increasing the knowledge about the regulating mechanisms of cerebral blood flow in awake and anaesthetised patients. At present, around 1% of all patients experiences a clinical overt stroke after non-cardiac surgery, while the incidence of covert stoke may be much higher (~10% in elderly patients)