Effects of magnesium sulphate on the pharmacodynamics of rocuronium in patients aged 60 years and older: A randomised trial.

Background: There is little information on the interaction between magnesium sulphate (MgSO4) and rocuronium in elderly patients. With a growing number of older patients who need surgical procedures, it is increasingly important to study this age group.

Objective: To evaluate the effects of MgSO4 administration on the pharmacodynamics of rocuronium in patients aged 60 years or older.

Design: A randomised controlled trial.

Setting: A tertiary care hospital.

Patients: Sixty-four patients, aged 60 years or older, American Society of Anesthesiologists (ASA) physical status classes I to III, scheduled for elective oncological head and neck surgery. Exclusion criteria were severe renal insufficiency (calculated creatinine clearance <30 ml min(-1)), preoperatorive serum magnesium concentration of more than 1.25 mmol l(-1) and patients receiving drugs known to affect neuromuscular function.

Interventions: Patients were randomly allocated to one of two groups: in the magnesium group, patients received MgSO4 30 mg kg(-1) intravenously, for 10 min, and then a continuous intravenous infusion at a rate of 1 g h(-1). The control group received the same volume of physiological saline. Neuromuscular function was evaluated continuously in both groups.

Main Outcome Measures: Total recovery time was the primary outcome. Onset time, clinical duration, recovery index and recovery time were considered as secondary endpoints. Values are given as mean [SD].

Results: Total recovery time from neuromuscular block (NMB) was 113 [36] min in the magnesium group and 101 [39] min in the control group. Clinical duration was 69 [23] min in the magnesium group and 59 [28] min in the control group. Recovery index was 19 [36] min in the magnesium group and 17 [6] min in the control group. Recovery time was 44 [22] min in the magnesium group and 42 [18] min in the control group. There were no statistically significant differences between the groups in any of the recovery indices. In the magnesium group, the mean onset time was 144 [58] s, significantly shorter than the onset time in the group that received physiological saline, which was 187 [90] s (P = 0.03). Group variances were compared using an F test: onset time varied significantly less in the magnesium group (P = 0.02).

Conclusion: In oncology patients of 60 or more years of age, preadministration of MgSO4, with the doses used in this study, significantly reduced the onset time of NMB induced by rocuronium.

Trial Registration: Clinicaltrials.gov identifier: NCT01804205.