When do we stop magnesium sulfate in Advanced Cardiovascular Life Support (ACLS)?

Magnesium Sulfate in ACLS: When to Stop Administration

Magnesium sulfate should not be routinely used in ACLS and should be stopped immediately if administered for any indication other than torsades de pointes (polymorphic VT associated with long-QT interval). 1

Indications and Contraindications

• Magnesium sulfate is only indicated in ACLS for torsades de pointes, where it may be considered at a dose of 1-2g IV bolus diluted in 10mL D5W 1, 2
• Routine administration of magnesium sulfate in cardiac arrest is not recommended (Class III: No Benefit; Level of Evidence C-LD) 1
• Multiple randomized clinical trials have consistently shown no benefit of magnesium administration for cardiac arrest with any presenting rhythm or specifically for VF/pVT cardiac arrest 1
• Four small randomized trials with a total of 444 patients showed no increase in ROSC or survival to hospital discharge with magnesium administration 1

Evidence Against Routine Use

• The 2018 American Heart Association ACLS guidelines specifically state that magnesium should not be used routinely during cardiac arrest management 1
• Research studies have failed to demonstrate improved outcomes with magnesium administration in refractory ventricular fibrillation 3, 4
• A randomized trial of 105 patients with refractory VF showed no significant differences between magnesium and placebo for ROSC (17% vs 13%) or survival to hospital discharge (4% vs 2%) 3
• Another study of 67 patients found that high-dose magnesium as first-line drug therapy for out-of-hospital cardiac arrest was not associated with significantly improved survival 4

Proper Use in Torsades de Pointes

• For torsades de pointes, administer 1-2g IV magnesium sulfate diluted in 10mL D5W 1, 2
• Magnesium acts to prevent reinitiation of torsades rather than pharmacologically converting polymorphic VT 1
• The use of magnesium for torsades de pointes is supported by observational studies, though randomized controlled trials are lacking 1, 5
• In a small case series, bolus administration of 1.0 to 2.0g MgSO4 abolished torsades de pointes in patients where it was induced by medications 5

Potential Adverse Effects

• Magnesium can cause hypotension and bradycardia when administered rapidly 6
• In patients with post-ROSC hypotension, there is a trend toward increased post-ROSC hypotension with IV magnesium sulfate 7
• The FDA label cautions that the rate of IV injection should generally not exceed 150 mg/minute, except in severe eclampsia with seizures 6
• Administration of magnesium must be carefully adjusted according to individual requirements and response, and should be discontinued as soon as the desired effect is obtained 6

Clinical Decision Algorithm

1. Identify the cardiac rhythm accurately

   • If torsades de pointes (polymorphic VT with long QT): Consider magnesium sulfate 1, 2
   • If any other rhythm (VF, pVT, asystole, PEA): Do NOT administer magnesium 1

2. If magnesium was started inappropriately:

   • Stop administration immediately 1
   • Continue standard ACLS protocols with appropriate medications (amiodarone or lidocaine for shock-refractory VF/pVT) 1

3. If torsades de pointes is present:

   • Administer 1-2g IV magnesium sulfate diluted in 10mL D5W 1, 2
   • If torsades persists despite magnesium, consider increasing heart rate with pacing or isoproterenol 2

In conclusion, the evidence clearly demonstrates that magnesium sulfate should be stopped immediately if administered for any indication other than torsades de pointes during ACLS, as it provides no benefit for other arrhythmias and may potentially cause harm through hypotension and bradycardia.