From the Guidelines
Magnesium sulfate is indicated in cardiac arrest specifically for patients with torsades de pointes (polymorphic ventricular tachycardia with prolonged QT interval) or suspected hypomagnesemia, with a recommended dose of 1-2 grams of magnesium sulfate administered intravenously over 5-20 minutes during cardiac arrest resuscitation. The use of magnesium in cardiac arrest is supported by the 2018 American Heart Association focused update on advanced cardiovascular life support, which recommends considering magnesium for torsades de pointes (Class IIb; Level of Evidence C-LD) 1.
Key Points
- Magnesium sulfate is not recommended for routine use in cardiac arrest (Class III: No Benefit; Level of Evidence C-LD) 1
- The recommended dose for torsades de pointes is 1-2 grams of magnesium sulfate (2-4 mL of 50% solution) administered intravenously over 5-20 minutes during cardiac arrest resuscitation
- For torsades de pointes with a pulse, the same dose can be given but more slowly over 5-60 minutes
- Magnesium works by stabilizing cardiac cell membranes, reducing the triggered activity that can cause torsades de pointes, and correcting electrolyte imbalances that may contribute to arrhythmias
Administration and Monitoring
- When administering magnesium, monitor for hypotension, bradycardia, and signs of magnesium toxicity such as loss of deep tendon reflexes, respiratory depression, or heart block, especially in patients with renal impairment
- The 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care also support the use of magnesium for torsades de pointes, with a recommended dose of 1 to 2 g of MgSO4 bolus IV push (Class I, LOE C) 1
Evidence Summary
- The evidence from the 2018 American Heart Association focused update on advanced cardiovascular life support 1 and the 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care 1 supports the use of magnesium sulfate in cardiac arrest for specific indications, including torsades de pointes and suspected hypomagnesemia.
From the Research
Indications for Magnesium Use in Cardiac Arrest
The use of magnesium in cardiac arrest is indicated in several scenarios, including:
- Intractable ventricular tachycardia and fibrillation, whether hypo- or normomagnesemic 2
- Torsades de pointes 2, 3, 4
- Digitalis-toxic ventricular tachyarrhythmia 2
- Multifocal atrial tachycardia 2
- Hypomagnesemic atrial tachyarrhythmia 2
- Cardiac arrest due to hypokalemia and hypomagnesemia 3
Administration and Dosage
The recommended dosage of magnesium sulfate is 10-15 ml of 20% MgSO4 infused over 1 min, followed by 500 ml of 2% MgSO4 over 5 h 2. A second 500 ml over 10 h may be necessary. However, the use of magnesium should be contraindicated in cases of renal failure, disappearance of deep tendon reflex, rise in serum Mg above 5 mEq/l, drop in systolic blood pressure below 80, or drop in pulse below 60 2.
Role of Magnesium in Cardiac Arrest
Magnesium plays a critical role in the function of all cells and organs, and its disorder is associated with increased risk of cardiac arrest, as well as respiratory failure and acute coronary syndrome 5. However, the current evidence on the role of magnesium in cardiac arrest is limited, and more research is needed to fully understand its effects 6.