Which anaesthetic agent has maximum MAC ?
Ans. is 'c' i.e., N20 Minimal alveolar concentration It is the lowest concentration of the anaesthetic in pulmonary alveoli needed to produce immobility in response to a painful stimulus (surgical incision) in 50% individuals. It is the measure of potency of inhalation GAs. Blood : gas paition cofficient It is the measure of solubility of agent in blood. It determines the speed of onset and recovery. Higher the blood : gas paition cofficient, lesser the speed of induction and recovary -4 more blood soluble agents have slower induction and recovery. Oil : gas paition cofficient It is the measure of lipid solubility of the agent, and therefore solubility in the fat - rich tissues of the CNS. This equates with the potency of individual agents. There is a direct relationship between the minimum alveolar concentration (MAC) value of inhaled anaesthetic agents and lipid solubility in terms of the oil/gas paition cofficient. Remember Maximum MAC -4 N20 Minimum MAC Halothane (Previously it was methoxyflurane, but it is not used now) Maximum blood : gas paition cofficient -4 Ether Minimum blood: gas paition cofficient Desflurane Maximum oil : gas paition cofficient Halothane (Previously it was methoxyflurane, but it is not used now) Minimum oil : gas paition cofficient -->N20deg
Ether
Methoxyfluorane
N20
Halothane