In general anesthesia, how does higher blood solubility of an agent affect its use?

In general anesthesia, how does higher blood solubility of an agent affect its use?

• A. More rapid onset
• B. More required for effectiveness
• C. No effect on onset
• D. Decreased duration

Answer: (B)

When an inhaled anesthetic has higher blood solubility, a larger portion of the drug dissolves in the blood, creating a bigger reservoir. Because the brain is reached only after enough of the agent leaves the blood and enters the brain, this reservoir slows the rise of brain concentration. To achieve surgical anesthesia promptly, you therefore need a higher inspired (alveolar) concentration or insist on a longer period for the brain to accumulate the necessary amount. That’s why higher blood solubility means more of the agent is required to reach effectiveness. Once effect is achieved, the same reservoir also slows recovery, since the drug must come out of the blood back into the lungs.

When an inhaled anesthetic has higher blood solubility, a larger portion of the drug dissolves in the blood, creating a bigger reservoir. Because the brain is reached only after enough of the agent leaves the blood and enters the brain, this reservoir slows the rise of brain concentration. To achieve surgical anesthesia promptly, you therefore need a higher inspired (alveolar) concentration or insist on a longer period for the brain to accumulate the necessary amount. That’s why higher blood solubility means more of the agent is required to reach effectiveness. Once effect is achieved, the same reservoir also slows recovery, since the drug must come out of the blood back into the lungs.