In transpulmonary shunt, the arterial rise in anesthetic partial pressure is reduced the most for which type of agents?

In transpulmonary shunt, the arterial rise in anesthetic partial pressure is reduced the most for which type of agents?

• A. Highly soluble
• B. Poorly soluble
• C. Moderately soluble
• D. Nitrous oxide

Answer: (A)

When a transpulmonary shunt is present, part of the blood bypasses ventilated alveoli and does not get exposed to the anesthetic gas. The arterial level that develops after starting anesthesia depends on how readily the agent transfers from alveolar gas into blood, which is governed by the blood–gas solubility (partition coefficient). Agents with high solubility dissolve readily in blood and tissues, acting as a large reservoir. Because a portion of blood never contacts the alveolar gas, the amount of anesthetic that actually reaches the arterial system is reduced more for these highly soluble agents than for poorly soluble ones. In contrast, poorly soluble agents require less uptake into blood, so their arterial rise is less diminished by the shunt. Nitrous oxide, being very poorly soluble, is affected least by the shunt.

When a transpulmonary shunt is present, part of the blood bypasses ventilated alveoli and does not get exposed to the anesthetic gas. The arterial level that develops after starting anesthesia depends on how readily the agent transfers from alveolar gas into blood, which is governed by the blood–gas solubility (partition coefficient). Agents with high solubility dissolve readily in blood and tissues, acting as a large reservoir. Because a portion of blood never contacts the alveolar gas, the amount of anesthetic that actually reaches the arterial system is reduced more for these highly soluble agents than for poorly soluble ones. In contrast, poorly soluble agents require less uptake into blood, so their arterial rise is less diminished by the shunt. Nitrous oxide, being very poorly soluble, is affected least by the shunt.