Minimum alveolar concentration (MAC) denotes:
Correct Answer: Potency
Description: Ans. B. PotencyExplanationMAC is an indicator of gas potency. The blood:gas partition coefficient is an indicator of solubility, which affects the rate of induction and emergence; it is NOT related to MAC.MAC: Alveolar concentration of a gas at which 50% of subjects do not respond to surgical incision.MAC of Inhaled Anesthetics GasBlood: Gas partition coefficient MAC*Halothane2.40.75% Enflurane1.91.7% Isoflurane1.41.2% Sevoflurane0.652.0% n2o0.47104% Desiflurane0.426.0% MAC values for adults 36--49 years old.Important points:Remarkably consistent across species.MAC is a population average; not a true predictor of an individual's response.MAC is an ED50 concentration. The ED95 is +- 25%, so at 1.3 MAC, 95% of patients will not respond to incision.MAC values are additive (e.g. 0.5 MAC isoflurane + 0.5 MAC N20 = 1 MAC)MAC-A wake (a.k.a. MAC-A ware): The MAC necessary to prevent response to verbal/tactile stimulation. - Volatiles: ~0.4 MAC; N20: -0.6 MACMAC-BAR: The MAC necessary to "blunt the autonomic response" to a noxious stimulus --1.6 MACMAC-intubation: The MAC necessary to prevent laryngeal response to "endotracheal intubation" --1.3 MAC
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Anaesthesia
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