Minimum alveolar concentration: ongoing relevance and clinical utility

Abstract

SummarySince its introduction in 1965, minimum alveolar concentration (MAC) has served as the standard measure of potency for volatile anaesthetic agents. It is defined as the minimum alveolar concentration of inhaled anaesthetic at which 50% of people do not move in response to a noxious stimulus. Within the last 20 years, it has been discovered that volatile anaesthetics inhibit mobility largely through action on the spinal cord, whereas the amnesic and hypnotic effects are mediated by the brain. Studies suggest that the concentration of volatile anaesthetic needed to prevent explicit memory from developing, and to produce unconsciousness, is usually substantially lower than the concentration required to prevent movement in response to surgery. This review highlights the contributions and limitations of MAC and its derivatives as metrics of anaesthetic potency with respect to particular behavioural outcomes. Recent evidence is presented suggesting that a protocol that alerts anaesthetists whenever MAC falls to < 0.5 or 0.7 has the potential to decrease intra-operative awareness with explicit recall, possibly to a similar extent as does a protocol based on processed electroencephalography-driven alerting.

Non-instrumental clinical monitoring does not guarantee an adequate course of general anesthesia. A prospective clinical study

“…However, lower values of AAI during volatile anesthesia may indicate that volatile anesthetics were overdosed 27 . Intraoperative monitoring of level of anesthesia can reduce the consequences of neurotoxicity of anesthetics 14,15,43,44 . Clinical parameters during conduction of anesthesia varied, probably as a result of administered doses of anesthetics.…”

Effects of changing from sevoflurane to desflurane on the recovery profile after sevoflurane induction: a randomized controlled study

“…1 Maintaining anesthesia with sevoflurane in day surgery is popular because it has a relatively lower solubility than other volatile anesthetics and allows for rapid emergence and recovery. 2 Additionally, sevoflurane provides smooth volatile induction due to its lack of airway irritation, and it is often used as an induction agent.…”

Monitoring (un)consciousness: the implications of a new definition of ‘anaesthesia’

“…A single brain state is characterised by its own, singular pattern of neuronal activity (the 'neural signature'), which can be identified by The relationships shown are intended to be illustrative and not quantitative; re-drawn from Dilger [5].…”