From the Guidelines
The recommended dose of magnesium for treating torsades de pointes is 1 to 2 grams of magnesium sulfate administered intravenously over 15 minutes, as indicated by the most recent and highest quality study 1. This dose can be repeated as needed to suppress episodes of torsades de pointes, with the goal of titrating the dose to suppress ectopy and nonsustained VT episodes while correcting precipitating factors 1. Key considerations in the administration of magnesium for torsades de pointes include:
- Monitoring for signs of magnesium toxicity, including hypotension, respiratory depression, and loss of deep tendon reflexes 1
- Using caution in patients with renal impairment, as the dose may need to be reduced 1
- Correcting electrolyte abnormalities, particularly potassium, and addressing any underlying causes such as medication effects or structural heart disease 1 The use of magnesium in this context is supported by its mechanism of action, which involves stabilizing the cardiac cell membrane and shortening the QT interval, thereby helping to terminate and prevent recurrence of torsades de pointes 1.
From the Research
Recommended Dose of Magnesium for Torsades de Pointes
The recommended dose of magnesium for treating torsades de pointes is as follows:
- A bolus of 1.0 to 2.0 g MgSO4 25% can be effective in abolishing torsades de pointes 2
- A single bolus of 2 g of magnesium sulfate can completely abolish torsades de pointes within 1 to 5 minutes 3
- Doses of 1 to 3 g of magnesium sulfate by direct intravenous injection have been used to treat torsades de pointes 4
Administration and Efficacy
- Magnesium sulfate can be given safely even in patients with acute myocardial infarction, angina pectoris, or systemic hypertension 2
- The use of magnesium sulfate for torsades de pointes appears to be worthy of additional trials 2
- Magnesium sulfate is a very effective and safe treatment for torsades de pointes, and its application is rapid and simple 3
- The antiarrhythmic properties of magnesium salts are thought to be due to a direct antagonism of Mg++-K+ and/or Mg++-Ca++ 4
Comparison to Other Treatments
- Magnesium sulfate has advantages over other means of treatment of torsades de pointes, such as isoprenaline infusion or pacing, including innocuity, simplicity, and rapidity of administration, and almost immediate efficacy 4
- Magnesium sulfate is now regarded as the treatment of choice for torsades de pointes 5