Which volatile anesthetic has the smallest blood–gas partition coefficient, contributing to the fastest onset and offset?

Which volatile anesthetic has the smallest blood–gas partition coefficient, contributing to the fastest onset and offset?

• A. Isoflurane
• B. Sevoflurane
• C. Desflurane
• D. Halothane

Answer: (C)

The speed of induction and emergence with a volatile anesthetic depends on how soluble it is in blood. The blood–gas partition coefficient measures this solubility: lower values mean the agent doesn't dissolve much in blood, so changes in alveolar concentration rapidly translate to brain concentration, giving a quick onset and a quick offset. Desflurane has the smallest blood–gas partition coefficient among common volatile anesthetics, so it equilibrates with the brain and arterial blood very quickly. That’s why it provides the fastest onset and offset. In contrast, agents with higher solubility stay dissolved in blood longer, slowing both induction and emergence. While desflurane is fastest, its use is balanced by practical considerations like airway irritation and the need for a specialized vaporizer; the other agents listed are slower to change brain concentrations because of their higher solubility.

The speed of induction and emergence with a volatile anesthetic depends on how soluble it is in blood. The blood–gas partition coefficient measures this solubility: lower values mean the agent doesn't dissolve much in blood, so changes in alveolar concentration rapidly translate to brain concentration, giving a quick onset and a quick offset. Desflurane has the smallest blood–gas partition coefficient among common volatile anesthetics, so it equilibrates with the brain and arterial blood very quickly. That’s why it provides the fastest onset and offset. In contrast, agents with higher solubility stay dissolved in blood longer, slowing both induction and emergence. While desflurane is fastest, its use is balanced by practical considerations like airway irritation and the need for a specialized vaporizer; the other agents listed are slower to change brain concentrations because of their higher solubility.