Anesthectic agent with least minimum alveolar concentration (MAC):
Ans: (b) IsofluraneRef: Stoelting's Pharmacology and Physiology in Anesthetic Practice, 4th editionMAC (MINIMUM ALVEOLAR CONCENTRATION)MAC is the concentration of inhalational agent in alveoli at 1 atm that prevents skeletal muscle movement in response to a supra-maximal painful stimulus (surgical skin incision) in 50% of patients.It is used to measure potency of inhalational agentsMAC[?]1/PotencyPotency is a measure of drug activity expressed in terms of the amount required to produce an effect of given intensity.Lesser amounts of drug required to produce maximum effect is called as more potent drug.For inhalational anaesthetic agents potency are measured by MAC valueLesser the MAC more is the potency (MAC [?]1 /Potency)Inhalational agents order from maximum potent to minimum potentMeth oxyflurane>Trilene>Halothane>Chloroform>Isoflurane>Enflurane>Sevoflurane>Ether>Sevoflurane>Xenon>N2O*MAC of Common Inhalational Agents:Inhalational agentsMACMethoxyflurane0.16Trilene0.2Halothane0.75Chloroform0.8Isoflurane1.17Enflurane1.63Sevoflurane1.8Ether1.9Desflurane6.6Xenon71N20104Factor Affecting MAC:Increase of MACDecrease of MACNo Change of MAC*. Hyperthermia*. Hypernatremia (|Na)*. Sympathomimetic drugs*. Cyclosporine*. Excessive pheomelanin production (red hair)*. Hypothermia*. Increasing age (6% per decade)*. Alpha 2 agonist agents*. Acute alcohol ingestion*. Pregnancy and postpartum upto 72 hours*. Lithium*. Lidocaine*. Hyponatremia*. Ketanserine*. Adrenergic antagonist agents*. BP<40 mm Hg*. PaO<38 mm Hg*. Chronic alcohol abuse*. Gender*. Duration of anaesthesia*. PaCO 15 - 95 mm Hg*. PaO>38 mm Hg*. BP>40 mm Hg*. Hyper or Hypokalemia*. Thyroid dysfunction*. Anaesthetic metabolism
Nitrous oxide
Isoflurane
Desflurane
Xenon
General Anesthesia