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

Abstract

Purpose: 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.

Methods: 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.

Results: 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.

Conclusions: 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.

Figure 1. The intracranial pressure waveform.

Figure 2. Devices used for noninvasive intracranial pressure (ICP) monitoring (BrainCare). (a) Thick black arrow: extensometer (sensor) used for measuring ICP, in contact with the individual’s scalp. Thin arrow: signal amplitude controller. (b) Star: acrylic band on the patient’s skull, with attached extensometer. (c) Infographic demonstrating the curve of intracranial pressure obtained in real-time during the surgical procedure, based on cranial pulsations detected by the sensor (enlarged figure).

Figure 3. Graphics generated by Brain4Care Analytics in two distinct moments in the same individual (n = 17). (a) Report generated in the preoperative period. At the top, continuous record of cranial box pulsations depicted by the solid blue line, measured in Volts on the vertical axis. This continuous data is condensed into curves, representing 3-min intervals, as seen below. (b) A second report details the “closed channel” phase from the 26th to the 28th min, highlighting observable changes in the curve pattern. The P2/P1 ratio and TTP values are displayed at the bottom of each curve for both instances.

Figure 4. Flowchart illustrating the data collection time points, shown in the gray squares.

Figure 5. Graphics representing the variation of P2/P1, TTP, MBP and HR.