Bispectral Index Monitoring in Endoscopic Lumbar Spine Surgery: Retrospective Analysis of Central Nervous System Complications

Background

Unilateral biportal endoscopic (UBE) spinal surgery involves two separate portals for viewing and working. If the outflow of irrigation fluid between portals is blocked, it can result in increased cerebrospinal fluid pressure, potentially leading to elevated intracranial pressure and related neurological complications. This sudden increase in intracranial pressure may cause transient cerebral hypoperfusion, manifesting as an isoelectric pattern on bispectral index (BIS) monitoring. This study aimed to investigate the use of BIS monitoring as an early indicator of increased intracranial pressure.

Methods

BIS monitoring was conducted on patients undergoing UBE surgery to noninvasively detect sudden increases in intracranial pressure. Cases with a follow-up period of less than twelve months were excluded. Intraoperative BIS values of the patients and postoperative neurological complications were retrospectively evaluated.

Results

As of May 2023, BIS monitoring started to be conducted on all patients undergoing UBE surgery in our clinic. Between May and December 2023, 182 levels of endoscopic spinal surgery were performed on 111 patients. The isoelectric BIS pattern was observed intraoperatively in six of these patients. Among them, 1 patient experienced left retinal vein hemorrhage due to increased intracranial pressure. No neurological complications were observed in the remaining five patients.

Conclusions

BIS monitoring is a noninvasive technique that can indicate cerebral hypoperfusion due to sudden increases in intracranial pressure. Thus, BIS monitoring should be considered a valuable tool in the management of patients undergoing UBE spine surgery, aiding in the early detection and appropriate treatment of central nervous system complications.