Association Between Protocolized Magnesium Supplementation and Atrial Fibrillation or Flutter in Critically Ill Patients: A Multicenter Retrospective Cohort Study
Abstract
OBJECTIVES
Most ICUs use protocolized magnesium supplementation, yet the clinical effect of this practice is unknown.
DESIGN
Pseudo-randomized retrospective study comparing patients who were and were not assigned to receive magnesium supplementation, using a protocol where supplementation occurs when serum levels are less than or equal to 0.95 mmol/L (2.31 mg/dL). Primary outcome was atrial fibrillation or flutter within 24 hours. Secondary outcomes were tachyarrhythmia (supraventricular tachycardia or ventricular arrhythmia) and death within 24 hours.
SETTING
ICUs with a shared magnesium supplementation protocol, in five hospitals in Ontario, Canada, from January 1, 2022, to December 31, 2024.
PATIENTS
Adults (18 yr old or older) admitted to ICU with a magnesium protocol order, at their first magnesium level of 0.92-0.99 mmol/L (2.24-2.41 mg/dL). To minimize confounding, we included only patients with a level near the supplementation threshold.
INTERVENTIONS
None.
EXPOSURE
Magnesium level 0.92-0.95 mmol/L (2.24-2.31 mg/dL, supplementation group) vs. 0.96-0.99 mmol/L (2.32-2.41 mg/dL, no supplementation group).
MEASUREMENTS AND MAIN RESULTS
We identified 4198 patients; median age 70 years, 41% female, 39% invasively ventilated; 2144 (51%) in the supplementation group, of whom 77% received magnesium, and 2054 (49%) in the no supplementation group, of whom 9% received magnesium. Atrial fibrillation or flutter occurred within 24 hours in 355 (16.6%) in the supplementation group…
How strong is the evidence?
Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design. Reported size: 4,198 participants or records.
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