A term neonate requires emergency laparotomy for necrotising enterocolitis. During anaesthesia, sevoflurane is used at 2 MAC. Compared to an adult, the neonate's MAC for sevoflurane is approximately:
- A Significantly lower (1.5%) due to immature neuronal myelination
- B Identical to adults (2.0%) as MAC is weight-independent
- C Higher (3.3%) due to immature GABA receptor density and higher metabolic rate ✓
- D Lower (1.8%) due to higher lipid content in neonatal brain tissue
Explanation
MAC is highest in neonates and infants (0–6 months) and decreases with age. For sevoflurane, MAC in neonates is approximately 3.3%, compared to adults at 2.0%. MAC peaks at 1–6 months of age and subsequently declines. The mechanism involves differences in GABA-A receptor subunit composition (immature receptors have different sensitivity to volatile anaesthetics), higher spinal cord plasticity, and developmental neurotransmitter profiles. The clinical implication is that neonates and infants require higher volatile concentrations for equivalent anaesthetic depth, though they are also more prone to cardiovascular depression, requiring careful titration.
Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.