Magnesium Sulfate, Fentanyl, and Their Combination for Attenuating Hemodynamic Responses to Laryngoscopy and Tracheal Intubation: A Randomized, Double-Blind, Active-Controlled Trial

Abstract

Background: Laryngoscopy and endotracheal intubation may elicit a sympathoadrenal response characterized by transient increases in arterial pressure and heart rate (HR), which may be clinically relevant in older patients. This study aimed to compare magnesium sulfate, fentanyl, and their combination for attenuating hemodynamic responses to laryngoscopy and endotracheal intubation in patients aged 50 years and older. Materials and Methods: This prospective, randomized, double-blind, active-controlled trial included patients aged ≥50 years with American Society of Anesthesiologists physical status I–III undergoing elective surgery under general anesthesia. Patients were randomized to receive magnesium sulfate 30 mg/kg (Group M), fentanyl 2 µg/kg (Group F), or magnesium sulfate 30 mg/kg plus fentanyl 2 µg/kg (Group MF), administered intravenously over 10 minutes before induction. The primary outcome was mean arterial pressure (MAP) at 1 minute after intubation. Secondary outcomes included MAP and HR at other predefined time points, bispectral index (BIS), end-tidal desflurane concentration, train-of-four (TOF) responses, and rescue medication requirements. Results: Ninety patients were randomized, and 76 were included in the final analysis (Group M, n=25; Group F, n=25; Group MF, n=26). Baseline characteristics were comparable among the groups. MAP changed significantly over time, with a significant group-by-time interaction (both p<0.001); post-intubation MAP values were higher in Group M than in the fentanyl-containing groups. HR increased significantly from baseline immediately after intubation in Group M, whereas no corresponding post-intubation increase was observed in Groups F or MF. However, between-group HR differences were significant only after induction (p=0.003), with no significant differences at post-intubation time points. Time to TOF count 0 was comparable among groups, whereas recovery to TOF counts 1 and 2 was significantly prolonged in Group MF compared with Group F (both p<0.05). End-tidal desflurane concentrations did not differ among groups. BIS differed at 5 and 15 minutes after intubation but not at the remaining time points. Nitroglycerin requirement was significantly higher in Group M than in Group MF (p=0.019). Conclusion: In patients aged 50 years and older, fentanyl-containing regimens were associated with lower post-intubation MAP values than magnesium sulfate 30 mg/kg alone. Post-intubation between-group HR differences were not significant. Adding magnesium sulfate to fentanyl provided no clear additional hemodynamic benefit but delayed early neuromuscular recovery. Magnesium sulfate 30 mg/kg may be insufficient as a sole agent for attenuating the acute hemodynamic response to laryngoscopy and endotracheal intubation in this population.