A 55-year-old man with chronic severe aortic regurgitation (LVEF 55%, LV end-systolic diameter 48 mm) is undergoing elective total knee replacement under combined spinal-epidural anaesthesia. Intraoperatively, his heart rate drops to 48 bpm and blood pressure falls to 85/50 mmHg. Which intervention is MOST appropriate?
- A Administer intravenous atropine 0.6 mg ✓
- B Administer intravenous phenylephrine 100 mcg
- C Start dobutamine infusion at 5 mcg/kg/min
- D Rapidly infuse 1 litre of normal saline
Correct answer: A. Administer intravenous atropine 0.6 mg
Explanation
In aortic regurgitation, bradycardia is harmful because it prolongs diastole, increasing the regurgitant volume and reducing forward cardiac output. The immediate treatment of symptomatic bradycardia is atropine. Phenylephrine would raise afterload and worsen regurgitation. Volume and inotropes are secondary considerations.
Reference: Miller's Anaesthesia, 9th ed.
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