Perioperative brain protection refers to prophylactic measures instituted during the perioperative period to prevent or reduce ischaemic damage and to improve neurological outcome. In that context, strategies for protecting the brain rely on the control of physiological variables, anaesthesia, administration of non-anaesthetic pharmacological agents and preconditioning. Avoiding hyperthermia, hyperglycaemia and arterial hypotension are passive neuroprotective measures acknowledged in human beings. The protective effect of anaesthesia, compared to the awake state, is demonstrated in animals but remains to be validated in clinical practice. Laboratory studies investigating pharmacological neuroprotection have shown interesting results but most clinical trials have been disappointing except for a few drugs in specific settings. Preconditioning which results in the induction of some resistance to ischaemia appears as a promising strategy. Up to now, the translation of beneficial experimental results into clinical success is considered an entirely permissible hope but remains an unachieved objective.
Protecting the brain from ischaemia during the perioperative period is an important concern for anaesthesiologists. At the beginning of the third millennium and after 'the decade of the brain' in the 1990s, we are still wondering if such an objective should be considered an impossible dream or is becoming a tangible reality. Two factors may account for this perplexity. First, the understanding of a pathological entity and its consequences is an essential prerequisite to set up rational and efficacious measures of prevention. Cerebral ischaemia triggers a complex cascade of pathophysiological reactions, biochemical events, inflammatory response and gene transcriptions which are still incompletely understood and may therefore limit the efficacy of prevention. Secondly, we have to cope with this provoking paradox that any undeniable experimental success cannot be automatically translated into clinical benefit. Despite a huge amount of data demonstrating brain protection in animal models, similar proofs in human beings are still scanty. The purpose of this review is to discuss potential neuroprotective measures in the management of patients at risk of cerebral ischaemia, by focusing mainly on clinical trials.
Conceptually, brain protection may be passive and involve the avoidance of deleterious interventions, or active and refer to the application of beneficial strategies. The measures proposed for protecting the brain may be classified into four categories related to physiology, anaesthesia, pure pharmacology, and with some degree of overlapping, to preconditioning.