A 45-year-old patient requires maintenance of anaesthesia with sevoflurane. At 1 MAC, what percentage of sevoflurane in oxygen (FiO2 = 1.0) is required?

• A 1.0%
• B 2.0%
• C 2.4%
• D 1.8% ✓

Explanation

The MAC of sevoflurane in 100% oxygen is approximately 1.8% (range 1.71–2.05%). MAC represents the alveolar concentration at which 50% of patients do not move in response to a surgical skin incision. When FiO2 is 1.0 (pure oxygen) versus room air, MAC is slightly lower, but the standard cited value for sevoflurane is 1.8%. Desflurane MAC is 6–7%, halothane MAC is 0.75%, and isoflurane MAC is 1.15%.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

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