The Effect of Epidural Anesthesia on Optic Nerve Sheath Diameter Measurements in Total Knee Prosthesis Surgery

Overview

This study investigates the effects of epidural anesthesia on intracranial pressure (ICP) by using ultrasonographic optic nerve sheath diameter (ONSD) measurements as a non-invasive indicator. The study aims to determine if the volume of local anesthetic applied to the epidural space during total knee replacement surgery leads to transient increases in ONSD compared to spinal anesthesia. Participants are randomized into two groups to receive either epidural or spinal anesthesia, and their ONSD measurements are tracked before, during, and after the surgery.

Neuroaxial techniques like spinal or epidural anesthesia are gold standards for lower extremity surgeries. However, injecting local anesthetics into the epidural space can compress the dural sac, potentially causing a cranial displacement of cerebrospinal fluid (CSF) and a subsequent increase in intracranial pressure (ICP). Since the optic nerve is surrounded by CSF, ONSD measurement serves as a reliable non-invasive surrogate for monitoring these pressure changes. In this prospective randomized study, 60 patients (ASA I-III) undergoing total knee prosthesis surgery are assigned to one of two groups: Group 1 (Spinal Anesthesia): Patients receive 15 mg of 0.5% heavy bupivacaine at the L4-L5 level. Group 2 (Epidural Anesthesia): Patients receive 20 cc of 0.25% bupivacaine at the L4-L5 level. ONSD measurements are recorded at four specific time points: before anesthesia (t0), 10 minutes after anesthetic onset (t1), 40 minutes after tourniquet removal (t2), and 24 hours postoperatively (t3). The study also monitors secondary outcomes, including postoperative complications and clinical safety profiles related to ICP changes.