Phentolamine versus Magnesium Sulphate for Controlled Hypotension in Patients During Lumbar Spine Fixation Surgery under General Anesthesia

Background: Controlled hypotension is commonly employed to minimize blood loss and improve the quality of the surgical field. This study aimed to evaluate the effectiveness of phentolamine versus magnesium sulphate in achieving controlled hypotension during lumbar spine fixation surgery under general anesthesia. Methods: In this prospective, randomized, double-blind clinical trial, sixty-two adult patients (ASA I–II) undergoing elective lumbar spine fixation at Zagazig University Hospitals were included. At random, the patients were split into two equal groups: While Group P received an infusion of phentolamine, Group M received an infusion of magnesium sulphate. Results: Both groups achieved and maintained the target MAP (60–65 mmHg) intraoperatively with no significant differences. In the early postoperative period (up to 60 min), MAP was significantly lower in the phentolamine group (p < 0.05). Heart rate was significantly higher in the phentolamine group during the first two intraoperative hours and throughout the first two postoperative hours (p < 0.05). No significant differences were found between the groups in surgical field quality, surgeon satisfaction, intraoperative blood loss, transfusion requirements, hemoglobin or hematocrit changes, PACU discharge time, Ramsay sedation scores, or the incidence of intra- and postoperative adverse events. Conclusion: Both phentolamine (0.1-2 mg/min) and magnesium sulphate (40mg/kg loading then maintainence 15mg/kg/hr) are effective and safe agents for controlled hypotension during lumbar spine fixation surgery, providing comparable surgical field quality and blood conservation. Magnesium sulphate was associated with greater heart rate stability intra- and postoperatively, whereas phentolamine produced lower MAP in the early postoperative period.