ObjectivesThe primary concern in functional endoscopic sinus surgery (FESS) is maintaining a clear and unobstructed surgical field. Achieving this objective necessitates controlled hypotension, which can aid in the surgical dissection process and reduce the overall duration of the operation. This study aims to evaluate the efficacy of a sole bolus injection of intravenous magnesium sulfate in FESS. The outcomes measured include blood loss, surgical field grading, the additional intraoperative requirement of fentanyl, stress attenuation during laryngoscopy and endotracheal intubation, and extubation time.MethodsIn this prospective, double-blinded, randomized control trial (CTRI/2021/04/033052), 50 patients scheduled for FESS were randomly divided into two groups: Group M received 50 mg/kg MgSO4in 100 ml normal saline, and Group N received 100 ml plain normal saline 15 min before induction. The study assessed total blood loss, measured by blood collected from the surgical field and weighing gauze. The surgical field grading was assessed by a six-point Fromme and Boezaart scale. We also observed stress attenuation during laryngoscopy and endotracheal intubation, additional intraoperative fentanyl requirements, and time taken for extubation. The sample size was estimated using the G power calculator 3.1.9.2 (http://www.gpower.hhu.de/). Data were entered in Microsoft Excel (Microsoft Corporation, Redmond, WA) and analyzed using Statistical Package for Social Sciences version 20.0 (IBM Corp., Armonk, NY).ResultsThe demographic data and duration of the surgery were comparable in both groups. The total blood loss in Group M was 100.40 ml ±60.71 ml, which is lower than Group N (133.80 ml ±59.7 ml) with a p-value of 0.016. In addition, the surgical field grading was also better in Group M. The total vecuronium consumption was significantly lower in Group M, which was (7.23±0.84 mg); in Group N, it was (10.64±1.74 mg) with a p-value of 0.0001, respectively. The dosage of additional fentanyl in Group N was 38.46 mcg ± 8.99 mcg, more than in Group M (33.64 mcg ± 11.20 mcg). The time required for extubation was similar in both groups. The duration of the surgery was significantly more significant in Group M (150.0 ±31.36) than in Group N (205.0 ±32.79), with a p-value of 0.0001, respectively.Furthermore, the mean arterial pressure after induction, at 2 min and 4 min after laryngoscopy, was less in Group M, with p=0.001, p=0.003, and p<0.0001, respectively, when compared with Group N. The heart rate after induction, at 2 min and 4 min after laryngoscopy, was also less in Group M, with p=0.016, p=0.003, and p=0.003, respectively, when compared with Group N.The Ramsay Sedation Score was higher in Group M than in Group N's fourth, eighth, and sixteenth hour, with p=0.001, p=0.021, and p=0.001, respectively, in the postoperative period. The sedation score was statistically insignificant after that. No complications were encountered during the study.ConclusionWe conclude that a single bolus dose of MgSO4reduced surgical blood loss more effectively than in the control group. The surgical field grading was also better in Group M, as was the stress attenuation during laryngoscopy and endotracheal intubation. The intraoperative fentanyl requirement was not statistically significant. The time for extubation was similar between the groups. No other adverse effects were encountered during the study.