Cerebrovascular and cerebral metabolic effects of commonly used anaesthetics.

: It is important to know the effects of anaesthetics on cerebral blood flow and cerebral metabolism to enable appropriate selection of agents for the brain injured patient. Thiopental possesses favourable cerebrovascular and metabolic properties but has not been shown to improve outcome in head injured patients. Propofol has properties similar to thiopental. Its rapid metabolism as well as its ability to reduce intracranial pressure and its antiemetic properties render it a very favourable drug. Despite controversies surrounding the effects of short-acting narcotics on intracranial pressure, they continue to be used because they provide stable haemodynamic conditions when used with care. Isoflurane is currently advocated as the best inhalational agent for neuroanaesthesia because of its lesser effects on cerebral blood flow and intracranial pressure. The effects of nitrous oxide on cerebral blood flow and intracranial pressure appear to vary according to the background anaesthetic used. Nitrous oxide is still widely used in most neuroanaesthetic practices, as its effects can be blunted by barbiturates, narcotics and/or hypocapnia. There is no convincing human study on the cerebral protective properties of anaesthetic agents although mild hypothermia has been shown experimentally to offer significant protection against global and focal ischaemia.