Effect of Preoperative Pregabalin on Optic Nerve Sheath Diameter as a Surrogate for Intracranial Pressure in Elective Craniotomy Patients.

This study is a prospective, randomized, double-blind, placebo-controlled trial. It will be conducted in the operating rooms and neurosurgical intensive care unit at the study hospital. The study population consists of adult patients aged eighteen to sixty-five years 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 pregabalin 150 mg or an identical placebo capsule. The study drug will be administered orally on the evening before surgery and again ninety minutes before anesthesia induction on the day of surgery. Neither the participants nor the treating physicians or outcome assessors will know which group the participant belongs to.

The primary outcome of the study is the optic nerve sheath diameter measured by ultrasound at the pre-induction time point, which is ninety minutes after the second dose of the study drug. An optic nerve sheath diameter greater than 5.5 millimeters is considered indicative of elevated intracranial pressure. Secondary outcomes include optic nerve sheath diameter at baseline, upon intensive care unit arrival, and twenty-four hours after surgery; the incidence of elevated optic nerve sheath diameter at each time point; postoperative pain scores; total opioid consumption in the first twenty-four hours; time to first pain medication request; the incidence of postoperative delirium; quality of recovery scores; preoperative anxiety levels; and any adverse events such as sedation, dizziness, nausea, or vomiting.

The sample size is one hundred participants, with fifty participants in each group. This calculation was based on an expected difference of 0.3 millimeters in optic nerve sheath diameter 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 be recorded. Optic nerve sheath diameter measurements will be performed using a high-frequency linear ultrasound probe placed gently over the closed eyelid. Three measurements will be taken from each eye, and the average will be calculated.