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

Inclusion criteria

aged 18-75 years with ASA I-III risk group who were scheduled for total knee replacement and volunteered to participate.

Exclusion criteria

Patients with contraindications to regional anesthesia, hypersensitivity to the drugs used, pregnancy, current or past ocular disease/operation history, orbital trauma, optic nerve pathology, glaucoma history; increased intracranial pressure, pseudotumor cerebri, coagulopathy and local infection; and those who refused to participate were excluded.