Perioperative and postoperative effects of hydrostatic pressure applied to the dura mater on central nervous system in unilateral biportal endoscopic spine surgery.

Objectives: To evaluate the changes in optic nerve sheath diameter (ONSD) caused by this pressure applied to the dura mater and postoperative complications.

Methods: The study was conducted between 01.01.2022 and 01.06.2022 at Private Medicabil Hospital. The ONSD was measured 3 mm behind the eyeball using US at 5 time points: T1 (in the supine position after anesthesia induction), T2 (after conversion to the prone position), T3 (in the prone position after applying pressure to the dura mater), T4 (in the prone position after the discontinuation of applying pressure to the dura mater), T5 (after conversion to the supine position). Postoperative complications were recorded.

Results: The ONSD at T3 was higher than those at all time points. For an ONSD value >5.3 mm, the sensitivity, specificity, positive predictive, and negative predictive values were 87.5%, 71.9%, 50.9%, and 94.5%, respectively (Area under the curve 0.830, 95% Confidence Interval: 0.761-0.899, p<0.001) CONCLUSION: We think that the hydrostatic pressure applied to the dura mater in unilateral biportal endoscopic (UBE) surgeries causes changes in the ONSD sheath diameter and that monitoring ONSD with peroperative USG can reduce the possible complications in order to reduce the effects of this pressure on the central nervous system.