Efficacy and Safety of Preemptive Magnesium Sulfate Infusion during Pheochromocytoma and Paraganglioma Resection: A Randomized, Double-blind, Placebo-controlled Trial

BACKGROUND: Hemodynamic instability frequently occurs in patients undergoing pheochromocytoma and paraganglioma (PPGL) resection. Magnesium sulfate has demonstrated efficacy in mitigating perioperative hemodynamic fluctuations. However, prospective clinical data confirming the safe and effective improvement of intraoperative hemodynamics by magnesium sulfate in PPGL patients are lacking. METHODS: This single-center, double-blind trial enrolled 92 patients who were scheduled for PPGL resection. The patients were randomly assigned to receive either magnesium sulfate (a loading dose of 50 mg · kg -1 followed by a continuous infusion of 15 mg · kg -1 · h -1 ) or placebo (normal saline) with administration initiated 30 min before surgery and discontinued upon complete tumor resection. The primary efficacy outcome was a composite measure of intraoperative hemodynamic instability, defined as the cumulative time outside the blood pressure and heart rate target ranges ( i.e. , systolic arterial pressure greater than 160 mmHg, mean arterial pressure less than 60 mmHg, and heart rate greater than 100 beats/min), expressed as a percentage of total anesthesia duration. RESULTS: A total of 88 patients were included in the modified intention-to-treat analysis. The cumulative time outside the blood pressure and heart rate target range was 4.3% (interquartile range, 2.4 to 9.6%) in the magnesium sulfate group compared to 8.3% (5.2 to 14.8%) in the placebo group ( P = 0.003). Compared with the placebo group, intraoperative maximum systolic arterial pressure (185 [170 to 197] mmHg vs. 196 [185 to 215] mmHg; P < 0.001), proportion of patients requiring phentolamine (66% vs. 89%; P = 0.011), and phentolamine dose (3 [0 to 7] mg vs. 9 [2 to 15] mg; P = 0.011) were all lower in the magnesium sulfate group. In the magnesium sulfate group, the magnesium sulfate concentration peaked at 1.82 (1.47 to 2.14) mmol l -1 upon completion of the loading dose infusion. No significant differences were observed in safety outcomes between groups. CONCLUSIONS: Preemptive magnesium sulfate infusion effectively reduced intraoperative hemodynamic instability in patients undergoing PPGL resection. The intervention regimen used in the trial was safe.