From the Guidelines
The dose of magnesium sulfate for torsades de pointes is 1 to 2 g IV over 15 minutes.
Key Points
- The dose of magnesium sulfate can be repeated as needed to suppress ectopy and nonsustained VT episodes while precipitating factors are corrected 1.
- Magnesium sulfate can suppress episodes of torsades de pointes without necessarily shortening QT, even when serum magnesium is normal 1.
- The risk of magnesium toxicity is very small with the doses usually used to treat torsades de pointes, 1 to 2 g intravenously 1.
- Temporary pacing is highly effective in managing torsades de pointes that is recurrent after potassium and magnesium supplementation 1.
- Isoproterenol can also be used to increase heart rate and abolish postectopic pauses 1.
Important Considerations
- Monitoring high-risk patients during initiation of QT-prolonging antiarrhythmic medications and recognition of the syndrome when it occurs are the first steps in managing torsades de pointes 1.
- Potassium repletion to 4.0 mmol per L or more and magnesium repletion to normal values are beneficial in patients with torsades de pointes associated with acquired QT prolongation 1.
- The American Heart Association recommends the administration of intravenous magnesium sulfate to suppress the arrhythmia in patients with QT prolongation due to a medication, hypokalemia, hypomagnesemia, or other acquired factor and recurrent torsades de pointes 1.
From the Research
Dose of Magnesium Sulfate for Torsades de Pointes
The dose of magnesium sulfate for torsades de pointes varies depending on the patient population and the specific study.
- In adults, a bolus of 1.0 to 2.0 g MgSO4 25% has been shown to abolish torsades de pointes 2.
- In children, the optimal bolus dosage is 3 to 12 mg/kg, with infusion rates of 0.5 to 1.0 mg/kg/hr and serum magnesium concentration of 3 to 5 mg/dL 3, 4.
- Another study in children reported a bolus dosage of 5.9 +/- 3.8 mg/kg (range, 2.3-12 mg/kg) and continuous infusion at rates of 0.3-1.0 mg/kg per hour 4.
- A study in adults reported that a single bolus of 2 g of magnesium sulfate completely abolished torsades de pointes in 9 out of 12 patients, with the remaining 3 patients requiring a second bolus 5.
Administration and Efficacy
- Magnesium sulfate can be administered intravenously, with a bolus injection given over 1 to 2 minutes, followed by continuous infusion for several days 3, 4.
- The treatment has been shown to be effective in abolishing torsades de pointes without shortening the QT interval 2, 4.
- Magnesium sulfate has been recommended as the first line of therapy for torsades de pointes due to its efficacy and safety 6, 5.