Intracranial Pressure Evaluation in Swine During Full-Endoscopic Lumbar Spine Surgery.

Background: Neurological complications during full-endoscopic spine surgery (FESS) might be attributed to intracranial pressure (ICP) increase due to continuous saline infusion (CSI). Understanding CSI and ICP correlation might modify irrigation pump usage. This study aimed to evaluate invasive ICP during interlaminar FESS; correlate ICP with irrigation pump parameters (IPPs); evaluate ICP during saline outflow occlusion, commonly used to control bleeding and improve the surgeon's view; and, after durotomy, simulate accidental dural tear.
Methods: Five swine were monitored, submitted to total intravenous anesthesia, and positioned ventrally. A parenchymal catheter was installed through a skull burr for ICP monitoring. Lumbar interlaminar FESS was performed until exposure of neural structures. CSI was used within progressively higher IPPs (A [60 mm Hg, 350 mL/minute] to D [150 mm Hg, 700 mL/minute]), and ICP was documented. During each IPP, different situations were grouped: intact dura with open channels (A1-D1) or occlusion test (A2-D2); dural tear with open channels (Ax1-Dx1) or occlusion test (Ax2-Dx2). ICP <20 mm Hg was defined as safe.
Results: Basal average ICP was 8.1 mm Hg. Adjustment in total intravenous anesthesia or suspension of tests was necessary due to critical ICP or animal discomfort. It was safe to operate with all IPPs with opened drainage channels (A1-D1) even with dural tear (Ax1-Dx1). Several occlusion tests (A2-D2, Ax2-Dx2) caused ICP increase (e.g., 86.1 mm Hg) influenced by anesthetic state and hemodynamics.
Conclusions: During FESS, CSI might critically raise ICP. Keeping drainage channels open, with ideal anesthetic state, ICP remains safe even with high IPPs, despite dural tear. Drainage occlusions can quickly raise ICP, being even more severe with higher IPPs. Total intravenous anesthesia may protect from ICP increase and may allow longer drainage occlusion or higher IPPs.
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