Effect of Pregabalin on Optic Nerve Sheath Diameter in Craniotomy Patients.

This study is a prospective, randomized, double‐blind, placebo‐controlled trial. It willbe conducted in the operating rooms and neurosurgical intensive care unit at the studyhospital. The study population consists of adult patients aged eighteen to sixty‐fiveyears who are scheduled for elective supratentorial craniotomy to remove a brain tumor.Participants will be randomly assigned in a one‐to‐one ratio to receive either pregabalin150 mg or an identical placebo capsule. The study drug will be administered orally on theevening before surgery and again ninety minutes before anesthesia induction on the day ofsurgery. Neither the participants nor the treating physicians or outcome assessors willknow which group the participant belongs to.The primary outcome of the study is the optic nerve sheath diameter measured byultrasound at the pre‐induction time point, which is ninety minutes after the second doseof the study drug. An optic nerve sheath diameter greater than 5.5 millimeters isconsidered indicative of elevated intracranial pressure. Secondary outcomes include opticnerve sheath diameter at baseline, upon intensive care unit arrival, and twenty‐fourhours after surgery; the incidence of elevated optic nerve sheath diameter at each timepoint; postoperative pain scores; total opioid consumption in the first twenty‐fourhours; time to first pain medication request; the incidence of postoperative delirium;quality of recovery scores; preoperative anxiety levels; and any adverse events such assedation, dizziness, nausea, or vomiting.The sample size is one hundred participants, with fifty participants in each group. Thiscalculation was based on an expected difference of 0.3 millimeters in optic nerve sheathdiameter between groups, a standard deviation of 0.5 millimeters, an alpha level of 0.05,a power of eighty percent, and an anticipated ten percent dropout rate.Anesthesia will be standardized for all participants using sevoflurane for maintenance.Fentanyl will be used for intraoperative pain control, and the total amount given will berecorded. Optic nerve sheath diameter measurements will be performed using ahigh‐frequency linear ultrasound probe placed gently over the closed eyelid. Threemeasurements will be taken from each eye, and the average will be calculated.Statistical analysis will follow the intention‐to‐treat principle, meaning participantswill be analyzed according to the group they were originally assigned to regardless ofwhether they completed the study protocol. Continuous measurements will be compared usingappropriate statistical tests, and a p‐value less than 0.05 will be consideredstatistically significant.Adverse events will be recorded throughout the hospital stay. Participants who developsevere sedation will be withdrawn from the study. The study protocol has been approved bythe institutional review board, and written informed consent will be obtained from allparticipants. The study will be conducted in accordance with the Declaration of Helsinkiand Good Clinical Practice guidelines. Recruitment is currently ongoing, and the study isexpected to take approximately eighteen months to complete.