<prompt> Most potent analgesic agent among following:Nitrous oxideNitric oxideCO2Oxygen  <response>: Ans. a. Nitrous oxide Ref: Wiley and Churchill-Davidson A Practice of Anesthesia 7e p536; Miller 7e p813Out of the above options, most potent analgesic agent is Nitrous oxide.Nitrous oxide- 50:50 nitrous oxide and oxygen has revolutionized it as analgesic agent; it has been used as an analgesic agent in obstetric surgeries: dental procedures; in acute trauma; burn dressings and cardiac pain as well.- Wiley and Churehill-Davidson A Practice of Anesthesia 7e p536Miller says Nitrous oxide produce analgesia that is in part because of release of proenkephalin derived family of endogenous opioids.Physical properties of N2OIt is colourless, non-irritating and sweet smellingBoiling point is -89degCQ.Critical temperature is 36.5degCQ which is above room temperature, therefore it can be kept in liquefied state.Stored as liquid in blue color cylindersQ35 times more soluble than nitrogenQRemember: Anesthesia withNo analgesia HalothaneQOnly analgesia N2OQProfound analgesia KetamineQBestmaximum analgesia TrileneQ 