• Peter Biesenbach, Johan Mårtensson, Eduardo Osawa, Glenn Eastwood, Salvatore Cutuli, Jessica Fairley, George Matalanis, and Rinaldo Bellomo.
• Department of Intensive Care, Austin Hospital, Heidelberg, Melbourne, Australia; Intensive Care Unit, Warringal Private Hospital, Heidelberg, Victoria, Australia.
• J Crit Care. 2018 Apr 1; 44: 419-423.

BackgroundIntravenous magnesium is routinely administered in intensive care units (ICU) to treat arrhythmias after cardiothoracic surgery. There are no data on the pharmacokinetics of continuous magnesium infusion therapy.ObjectiveTo investigate the pharmacokinetics of continuous magnesium infusion, focusing on serum and urinary magnesium concentration, volume of distribution and half-life.MethodsWe administered a 10 mmol bolus of magnesium-sulfate followed by a continuous infusion of 3 mmol/h for 12 h in twenty cardiac surgery patients. We obtained blood and urine samples prior to magnesium administration and after one, six, and 12 h.ResultsMedian magnesium levels increased from 1.09 (IQR 1.00-1.23) mmol/L to 1.59 (1.45-1.76) mmol/L after 60 min (p < .001), followed by 1.53 (1.48-1.71) and 1.59 (1.48-1.76) mmol/L after 6 and 12 h. Urinary magnesium concentration increased from 9.2 (5.0-13.9) mmol/L to 17 (13.6-21.6) mmol/L after 60 min (p < .001). Cumulative urinary magnesium excretion was 28 mmol (60.9% of the dose given). The volume of distribution was 0.25 (0.22-0.30) L/kg. There were no episodes of severe hypermagnesemia (≥3 mmol/L).ConclusionCombined bolus and continuous magnesium infusion therapy leads to a significant and stable increase in magnesium serum concentration despite increased renal excretion and redistribution.Copyright © 2018. Published by Elsevier Inc.

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