Preoperative effects of magnesium sulfate on hemodynamics and muscle relaxation

Abstract

Background/Aim: Although there are many studies on the effects of magnesium sulfate in the literature, there is no publication on the effects of low doses of magnesium sulfate, as we administered in our study. This prospective randomized study aimed to reveal that the use of low-dose magnesium sulfate (MgSO 4) shortens the onset time and prolongs the block duration of neuromuscular blockers (NMBs) without changing the hemodynamics in patients monitored using the train-of-four (TOF) ratio. Methods: This is a prospective randomized study. A total of 60 cases aged between 18–65 years with American Society of Anesthesiologists classifications I–II who were scheduled for elective open cholecystectomy were randomly divided into 3 groups. Notably, 15 minutes before the anesthesia induction, 25 mg/kg MgSO 4 in intravenous 0.9% saline (total volume, 100 mL) was administered to the MgSO 4 group (MS group), 0.03 mg/kg midazolam was administered to the midazolam group (MD group), and the same volume of 0.9% saline solution was administered to the control group (PSS group). Nervemuscle conduction monitoring was performed using TOF-Watch® SX (Organon, Ireland) and anesthesia depth was monitored with a BIS® monitor (A-2000; Aspect Medical Systems, USA). Results: NMB onset times were 83.95 (26.8), 111.15 (28.12), and 163.7 (34.16) seconds (P=0.001) in the MS, MD, and PSS groups, respectively. The times until additional rocuronium requirement after the intubation dose were 60.1 (4.19), 50.8 (4.99), and 38.25 (7.27) minutes in the MS, MD, and PSS groups, respectively, which was significantly longer in the MS group compared to the other groups (P<0.001). The recovery time to TOF of 0.9 and time to T1 height of >95% was longer in the MS group than in the other groups. No difference was found between the groups in terms of hemodynamic data. Conclusion: Low-dose MgSO 4 administration before rocuronium injection significantly reduces neuromuscular agent consumption without altering hemodynamics and causing a residual neuromuscular block.