**Question:** 5 minutes before recovery from anesthesia, nitrous oxide is removed and 100% oxygen is administered to the patient to prevent -

**Core Concept:**
Nitrous oxide (N2O) is a commonly used inhalational anesthetic agent, often combined with other anesthetic agents like isoflurane or sevoflurane. When administered, nitrous oxide diffuses into the lungs and binds to hemoglobin, reducing its capacity to transport oxygen. When its concentration in the blood decreases just before recovery, oxygen saturation increases, and the risk of hypoxia is reduced. 100% oxygen administration is crucial during this transition to ensure adequate oxygenation of tissues and cells.

**Why the Correct Answer is Right:**
Nitrous oxide is a potent vasodilator, causing systemic vasodilation and decreased peripheral vascular resistance. This can lead to hypotension during recovery, potentially causing inadequate oxygenation. Removing nitrous oxide 5 minutes before recovery allows the vasodilatory effects to subside, preventing hypotension.

Additionally, administering 100% oxygen helps to increase oxygen saturation and maintain tissue oxygenation, reducing the risk of post-anesthesia complications.

**Why Each Wrong Option is Incorrect:**

A. This option is incorrect because nitrous oxide is removed 5 minutes before recovery, not replaced by oxygen. The focus is on reducing its vasodilatory effects and ensuring adequate oxygenation.

B. Although oxygen is vital during anesthesia, administering it immediately before recovery is not the main objective. Instead, the primary focus is on removing nitrous oxide and preventing hypotension.

C. This option is incorrect for the same reasons as option A and B. The primary concern is reducing nitrous oxide and preventing hypotension, not increasing oxygen saturation.

D. Although oxygen is essential post-anesthesia, administering it at this specific time is not the primary objective. The main focus is on reducing nitrous oxide and preventing hypotension.

**Clinical Pearl:**
In clinical practice, the transition from inhalational anesthesia to room air should be gradual, ensuring a smooth recovery. Monitoring vital signs and titrating oxygen supplementation based on oxygen saturation is crucial to prevent complications. This practice aids in a safe transition from anesthesia to the awake state and minimizes the risk of adverse effects, such as hypotension and hypoxia.