Two hours after uncomplicated laparoscopic cholecystectomy, a patient develops polymorphic ventricular tachycardia with a twisting QRS axis. Serum magnesium is 1.3 mg/dL. Which is the FIRST-line drug?
- A Magnesium sulphate 2 g IV over 10 minutes ✓
- B Lignocaine 100 mg IV bolus
- C Amiodarone 300 mg IV bolus
- D Adenosine 6 mg rapid IV push
Correct answer: A. Magnesium sulphate 2 g IV over 10 minutes
Explanation
Torsades de pointes is treated first with IV magnesium sulphate 1 to 2 g even when the serum magnesium appears normal, because magnesium suppresses early afterdepolarisations independent of its blood level. Amiodarone and lignocaine are second line here and some antiarrhythmics that prolong the QT interval can worsen torsades. Adenosine does not terminate torsades. Underlying triggers such as hypokalaemia, bradycardia and drugs prolonging repolarisation must be corrected alongside.
Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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