In a 3-year-old child undergoing adenotonsillectomy, sevoflurane induction is used. Compared with adults, children have faster inhalational induction primarily because of:

• A Lower blood-gas partition coefficient for sevoflurane in children compared to adults
• B Higher cardiac output relative to body weight accelerating alveolar-to-blood transfer
• C Greater hepatic expression of CYP2E1 in children, accelerating sevoflurane bioactivation
• D Higher alveolar ventilation relative to functional residual capacity (VA/FRC ratio) in children ✓

Explanation

Children have a higher alveolar ventilation-to-FRC ratio (approximately 5:1) compared to adults (approximately 1.5:1). This means they 'turn over' their FRC volume more rapidly with each breath, so the FA/FI ratio (alveolar to inspired concentration) rises much faster. The blood-gas partition coefficient for sevoflurane is similar in children and adults (~0.65). The higher cardiac output per unit weight in children does slightly increase uptake, but the dominant factor is the high VA/FRC ratio. This is why inhalational induction and recovery are both faster in children than adults.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.