Anesthetic loss to the plastic and rubber components of the anesthetic circuit hindering achievement of an adequate inspired concentration is a factor with which of the following anesthetics?

Anesthetic loss to the plastic and rubber components of the anesthetic circuit hindering achievement of an adequate inspired concentration is a factor with which of the following anesthetics?

• A. Desflurane
• B. Nitrous oxide
• C. Sevoflurane
• D. Isoflurane

Answer: (D)

The main idea here is that some volatile anesthetics are taken up by the materials of the breathing circuit—rubber and plastic—so they don’t all reach the patient initially. This circuit uptake reduces the inspired concentration you actually deliver until the circuit equilibrates. Isoflurane tends to be absorbed more by these circuit materials than the other agents listed, so when you start delivery, a larger portion of the agent is sequestered in the tubing and components. That makes it harder to achieve the desired inspired concentration promptly, more so than with desflurane or sevoflurane, which have less uptake by the circuit. Nitrous oxide, being a gas with different diffusion characteristics, is less affected by circuit sorption, so it won’t cause this particular problem to the same extent.

The main idea here is that some volatile anesthetics are taken up by the materials of the breathing circuit—rubber and plastic—so they don’t all reach the patient initially. This circuit uptake reduces the inspired concentration you actually deliver until the circuit equilibrates. Isoflurane tends to be absorbed more by these circuit materials than the other agents listed, so when you start delivery, a larger portion of the agent is sequestered in the tubing and components. That makes it harder to achieve the desired inspired concentration promptly, more so than with desflurane or sevoflurane, which have less uptake by the circuit. Nitrous oxide, being a gas with different diffusion characteristics, is less affected by circuit sorption, so it won’t cause this particular problem to the same extent.