Evidence for Clinical Treatment Decisions Without Randomized Data

Among critically ill patients, serum magnesium levels are commonly checked and repleted. Like many clinical decisions, the rationale for this practice is based on a combination of physiological conjecture and observational data linking lower magnesium levels with worse clinical outcomes. In the absence of better evidence, the 2017 American Heart Association/American College of Cardiology/Heart Rhythm Society guidelines provide a relatively weak recommendation (“it remains quite reasonable…”) without specifying thresholds, doses, or comprehensive indications for repletion for preventing ventricular arrhythmias. Since a major goal of magnesium repletion is to reduce arrythmias, some of which can be lethal, clinicians are reluctant to wait for definitive evidence of benefit.