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

Abstract

OBJECTIVE: The pharmacokinetics and haemodynamic effect of continuous magnesium infusion in non-cardiac intensive care unit (ICU) patients are poorly understood. We aimed to measure serum and urine magnesium levels during bolus and continuous infusion in critically ill adults, compare serum levels with those of a control population, and assess its haemodynamic effect. DESIGN: Pharmacokinetic study. SETTING: A single tertiary adult ICU. PARTICIPANTS: Mechanically ventilated adults requiring vasopressor support. INTERVENTION: A 10 mmol bolus of magnesium sulfate followed by 1.5–3 mmol/h infusion for 24 hours. MAIN OUTCOME MEASURES: The primary outcome was the change in total serum magnesium concentration. The main secondary outcome was mean arterial pressure (MAP)-adjusted vasopressor dose. RESULTS: We matched 31 treated patients with 93 controls. Serum total magnesium concentration increased from a median 0.94 mmol/L (interquartile range [IQR], 0.83–1.10 mmol/L) to 1.38 mmol/L (IQR, 1.25–1.69 mmol/L; P < 0.001) and stabilised between a median 1.64 mmol/L (IQR, 1.38–1.88 mmol/L) at 7 hours and 1.77 mmol/L (IQR, 1.53–1.85 mmol/L) at 25 hours. This was significantly greater than in the control group (P < 0.001). The MAP-adjusted vasopressor dose decreased during magnesium infusion (P < 0.001). CONCLUSION: In critically ill patients, a magnesium sulfate bolus followed by continuous infusion achieved moderately elevated levels of total serum magnesium with a decrease in MAP-adjusted vasopressor dose. TRIAL REGISTRATION NUMBER: ACTRN12619000925145.

In This Issue of CCR

“…Magnesium is a frequent therapy in critically ill patients and continuous magnesium infusion may be an option to decrease the incidence and severity of atrial fibrillation in the intensive care unit (ICU); however, the feasibility of such continuous therapy is uncertain. An article by Chan and colleagues 5 shows the safety and feasibility of such magnesium infusion in vasopressor-dependent, ventilated patients to achieve moderate hypermagnesaemia and provides the background for future trials. How should we monitor patients with severe traumatic brain injury in the ICU in 2022?…”