General Considerations Concerning the Effects of Anaesthetics on Cerebral Blood Flow and Metabolism

Abstract

With the exception of ketamine, and in experimental studies some of the synthetic analgetics (fentanyl, alfentanil and sufentanyl), all anaesthetics will induce a decrease in cerebral oxygen uptake. Concerning the hypnotic agents, including barbiturate, althesin, etomidate, benzodiazepines, neuroleptic agents and derivates of the fentiazines an associated decrease in CBF and CMRO₂ will occur. In contrast, inhalation agents like N₂O, halothane, enflurane and isoflurane generally give rise to a dissociation between CBF and oxygen uptake in the brain. These agents induce a fall in CVR, an increase in CBF and CBV, and a contemporary decrease in CMRO₂. The changes in ICP follow the changes in CBF and CBV. Thus inhalation agents will provoke an increase in CBF and ICP, and intravenous anaesthetics, with the exception of ketamine will result in a decrease in CBF and ICP.