A parturient at 36 weeks gestation requires emergency caesarean section under general anaesthesia. Regarding the pharmacology of suxamethonium in pregnancy, which statement is most accurate?

• A Suxamethonium is contraindicated in pregnancy due to risk of placental transfer causing neonatal apnoea
• B The dose of suxamethonium should be reduced to 0.5 mg/kg due to increased plasma cholinesterase in pregnancy
• C Plasma cholinesterase activity is reduced by approximately 25% in pregnancy, potentially prolonging suxamethonium duration, but the standard RSI dose (1–1.5 mg/kg) remains appropriate ✓
• D Suxamethonium is safe at standard doses and plasma cholinesterase activity is unchanged in pregnancy

Explanation

Plasma (pseudo)cholinesterase activity is reduced by approximately 25–30% during pregnancy and remains low for up to 6 weeks postpartum, due to haemodilution and reduced hepatic synthesis. Despite this reduction, the standard RSI dose of suxamethonium (1–1.5 mg/kg) is still appropriate because the modest enzyme reduction only marginally prolongs the duration of action clinically. Suxamethonium is highly ionised and does not cross the placenta in clinically relevant amounts at standard doses. In patients with known pseudocholinesterase deficiency, alternatives (rocuronium with sugammadex availability) should be considered.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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