Session Key Points

  • The two commonly-used volatile anaesthetic agents isoflurane and sevoflurane are both halogenated ethers
  • Nitrous oxide is used as a carrier gas as it has both anaesthetic and analgesic properties
  • The minimum alveolar concentration (MAC) of a volatile anaesthetic agent is inversely proportional to is potency
  • The oil:gas (O:G) partition coefficient of volatile agents is related to potency: the higher the O:G partition coefficient, the greater the potency. Isoflurane is more potent than sevoflurane
  • The blood:gas (B:G) partition coefficient is related to the speed of onset of anaesthesia: the lower the B:G partition coefficient the more rapid the onset of anaesthesia. Sevoflurane has a faster speed of onset than isoflurane
  • The low B:G partition coefficient of nitrous oxide is responsible for diffusion hypoxia and the second gas effect