A 70 kg parturient is receiving epidural anaesthesia for labour. The maximum recommended dose of lidocaine with adrenaline is 7 mg/kg. What is the maximum volume of 2% lidocaine with adrenaline that can be safely administered?
- A 15 mL
- B 20 mL
- C 24.5 mL ✓
- D 35 mL
Correct answer: C. 24.5 mL
Explanation
The maximum dose of lidocaine with adrenaline is 7 mg/kg. For a 70 kg woman, the maximum milligrams are 7 × 70 = 490 mg. Lidocaine 2% contains 20 mg/mL. Dividing 490 mg by 20 mg/mL gives 24.5 mL. The 35 mL option corresponds to 5 mg/kg, the limit for plain lidocaine, and is a common distractor. The 15 mL and 20 mL options are below the safe maximum.
Reference: Chestnut's Obstetric Anesthesia, 6th ed.
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