Comparison of Increase in the Optic Nerve Sheath Diameter between Epidural Saline and Contrast Medium Injections

Normal saline or contrast medium is one of the widely used injection materials during fluoroscopic guided injections. Optic nerve sheath diameter (ONSD) measurement is a reliable and noninvasive method for intracranial pressure evaluation. The purpose of this study was to compare the increase in ONSD and cerebral oxygen saturation (rSO2) between normal saline and contrast medium when they were injected into the epidural space. Prospective randomized trial. An interventional pain management clinic in South Korea. This study included 42 patients who were scheduled to receive thoracic epidural catheterization for postoperative pain control. Patients were randomly allocated to receive 5 mL normal saline or contrast medium following successful thoracic epidural entry. The ONSD was measured using transorbital sonography at baseline (T0), 10 min (T10), 20 min (T20), and 40 min (T40) after epidural normal saline or contrast medium injection. Both groups demonstrated significant increases in ONSD from T10 to T40 when compared with the baseline. Although both groups showed a significant increase in ONSD compared with the baseline, group saline showed a higher increase in ONSD than group contrast. A significantly higher increase in ONSD in group saline than in group contrast was maintained from T10 to T40 (P = 0.015). We could not determine the returning point of the normalized ONSD value. Thoracic epidural injection of 5 mL normal saline or contrast medium resulted in a significant increase of ONSD compared to baseline; however, the degree of ONSD increase was more attenuated in the contrast group than the saline group.