Minimum alveolar concentration of an inhaled anesthetic is a marker of:
Correct Answer: Potency
Description: Ref: Miller Textbook of Anaesthesia. 7th ed.Explanation:Minimum alveolar concentration or MACll is a concept used to compare the strengths, or potency, of anaesthetic vapoursIt it is defined as the concentration of the vapour in the lungs that is needed to prevent movement (motor response) in 50% of subjects in response to surgical (pain) stimulus.A lower MAC value represents a more potent volatile anesthetic.Meyer-Overton hypothesisThe MAC of a volatile substance is inversely proportional to its lipid solubility (oil:gas coefficient)MAC is inversely related to potency i.e. high mac equals low potency.The hypothesis correlates lipid solubility of an anaesthetic agent with potency (1/MAC) and suggests that onset of anaesthesia occurs when sufficient molecules of the anaesthetic agent have dissolved in the cell's lipid membranes, resulting in anaesthesia.Common MAC valuesNitrous oxide - 104Xenon -72Desflurane - 6Ethyl Ether - 3.2Sevo flu rune - 2Enflurune - 1.7Isoflurane - 1.2Halothane - U.75Chloroform - 0.5M ethoxy flurane - 0.16
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