A pilot study of the pharmacokinetics of continuous magnesium infusion in critically ill patients

Magnesium is vital for numerous biochemical and physiological functions. 1In clinical practice, serum magnesium is most commonly measured as total magnesium, 2 with normal values ranging between 0.7 mmol/L and 1.0 mmol/L. 1 Hypomagnesaemia (< 0.7 mmol/L) is a common finding in critically ill patients, may increase the risk of arrhythmias, and is associated with increased mortality. 2,3Thus, magnesium supplementation in critically ill patients is common. 2ariability in current clinical intravenous magnesium therapy is evident by differences in quantity, frequency, and mode of delivery.0][11] No study, however, has described the pharmacokinetic effects of continuous intravenous magnesium therapy on total serum magnesium levels in critically ill patients receiving mechanical ventilation and vasopressor support.These patients may be at particular risk of arrhythmias, especially atrial fibrillation. 12Moreover, previous small single centre controlled studies have shown that continuous magnesium infusion slows down the ventricular response to atrial fibrillation, 13 increases its conversion to sinus rhythm 13 and prevents its development in cardiac surgery patients. 14ccordingly, we aimed to evaluate the pharmacokinetics of a combined "bolus plus continuous infusion" protocol of intravenous magnesium therapy targeting total serum magnesium levels between 1.5 mmol/L and 2 mmol/L in critically ill, mechanically ventilated, vasopressor-dependent patients.We hypothesised that such intervention would be logistically feasible, provide useful pharmacokinetic data, achieve magnesium target levels, and would not lead to an increase in vasopressor therapy. Methods