Effect of pretreatment with magnesium sulphate on the duration of intense and deep neuromuscular blockade with rocuronium: A randomised controlled trial.

Background: Magnesium sulphate is an important adjuvant drug in multimodal anaesthesia. In combination with rocuronium it can enhance neuromuscular blockade (NMB). Limited data exist concerning the effect of magnesium sulphate on the duration of deep or intense NMB and the period of no response.
Objective(s): To determine the role of magnesium sulphate on the duration of rocuronium-induced deep and intense NMB, and the period of no response to nerve stimulation.
Design: A randomised controlled trial.
Setting: A public tertiary care hospital, Rio de Janeiro, Brazil, from February 2017 to March 2018.
Patients: All patients between 18 and 65 years of age scheduled to undergo elective otorhinolaryngological surgery, with a BMI between 18.5 and 24.9 kg m and an American Society of Anesthesiologists physical status classification of I or II.
Intervention(s): Before induction of anaesthesia 60 patients were pretreated with an intravenous infusion of either 100 ml 0.9% saline (saline group), or 60 mg kg magnesium sulphate (magnesium group). After loss of consciousness, a bolus of rocuronium (0.6 mg kg) was administered. Neuromuscular function was measured by TOF-Watch SX monitor.
Main Outcome Measures: The primary and secondary outcomes were the duration of the period of no response to nerve stimulation and intense and deep NMB, respectively. An additional outcome was the NMB onset time.
Results: Median [IQR] durations of deep NMB were 20.3 [12.0 to 35.4] and 18.3 [11.2 to 26.3] min in the magnesium and saline groups, respectively (P = 0.18). Median durations of intense NMB were 21.7 [0.0 to 32.2] min and 0.0 [0.0 to 6.2] min (P = 0.001) in the magnesium and saline groups, respectively. Median durations of the period of no response were 40.8 [51.4 to 36.0] min and 28.0 [21.9 to 31.6] min (P = 0.0001) in the magnesium and saline groups, respectively.
Conclusion: Magnesium sulphate increased both the duration of intense NMB and the period of no response. The duration of deep NMB was similar in the magnesium sulphate group and saline group.
Trial Registration: ClinicalTrials.gov identifier: NCT02989272.