Mannitol vs placebo for brain relaxation in cerebellopontine angle tumor surgeries: A randomized controlled trial

Mannitol is widely used for intraoperative brain relaxation, but its benefit in posterior fossa lesions is still debatable. Hence, we aimed to compare mannitol with placebo for brain relaxation score (BRS) in cerebellopontine angle (CPA) tumor surgeries in the supine position and assess secondary outcomes including serum electrolytes, osmolality, hemodynamic parameters, complications, and postoperative acute kidney injury (AKI) and hospital stay.

This single-center, double-blind, randomized controlled trial was initiated after institute review board approval and Clinical Trial registration. Patients undergoing CPA tumor resection in the supine position were randomly assigned to mannitol (Group-M, received 1 g/kg of mannitol) or placebo group (Group-P, received 0.9 % saline). BRS was assessed after dura opening, and serum electrolytes and osmolarity were measured at baseline and postoperatively.

Sixty-three patients were analyzed, 33 in group-M and 30 in group-P. The BRS was comparable between group-M [2 (1.5-3)] and group-P [2 (2-3)], P = 0.721. Intraoperatively, serum sodium was significantly lower [139.7 (3.5) vs. 142 (3.6), P = 0.011], serum potassium was higher [3.8 (0.6) vs. 3.4 (0.43), P = 0.003], systolic blood pressure was lower [114 (9.9) vs. 121 (9.7), P = 0.007], and urine output was higher [1162 (488.6) vs. 737 (395.9), P < 0.001] in group-M compared to group-P, respectively.

Brain relaxation during posterior fossa surgery is essential for optimizing surgical access and reducing complications. The current study suggests that mannitol may not significantly provide brain relaxation in patients undergoing CPA tumor resection in the supine position. However, further research is needed to establish definitive conclusions regarding its use in posterior fossa surgeries.