# Noninvasive intracranial pressure profile in 31 patients submitted to fullendoscopic spine surgery

## TL;DR

This study examines how intracranial pressure changes during spine surgery using noninvasive monitoring and finds unexpected decreases despite fluid infusion.

## Contribution

The study introduces noninvasive ICP monitoring during spine surgery and reveals anesthesia's potential protective role against ICP increases.

## Key findings

- Noninvasive ICP parameters decreased during surgery despite saline irrigation.
- Anesthesia may have a protective effect against ICP increases.
- Fluid parameters did not significantly affect ICP waveform changes.

## Abstract

Full-endoscopic spine surgery (FESS) is associated with specific complications, possibly linked to increased intracranial pressure (ICP) resulting from continuous saline infusion into the epidural space. This study aimed to assess the impact of saline irrigation and its correlation with noninvasively obtained ICP waveform changes.

Patients undergoing FESS between January 2019 and November 2020 were included. Noninvasive ICP (n-ICP) monitoring utilized an extracranial strain sensor generating ICP waveforms, from which parameters P2/P1 ratio and time to peak (TTP) values were derived and correlated to irrigation and vital parameters. Documentation occurred at specific surgical intervals (M0–preoperatively; M1 to M4–intraoperatively; M5–postoperatively). Mixed-model analysis of variance and multiple comparisons tests were applied, with M0 as the baseline.

Among 31 enrolled patients, three experienced headaches unrelated to increased ICP at M5. The P2/P1 ratio and TTP decreased during surgery (p < 0.001 and p < 0.004, respectively). Compared to baseline, P2/P1 ratio and vital parameters remained significantly lower at M5. No significant differences were observed for fluid parameters throughout surgery.

This study demonstrated a decline in the n-ICP parameters after anesthetic induction despite the anticipated increase in ICP due to constant epidural irrigation. The n-ICP parameters behaved independently of fluid parameters, suggesting a potential protective effect of anesthesia.