ANALYSIS OF THE COUPLING BETWEEN CSF FLOW AND GREY MATTER BOLD SIGNAL DURING LIDOCAINE ADMINISTRATION IN HEALTHY ADULTS

CSF bulk flow in the brain is mediated by brain hemodynamics and has been linked to the brain´s waste-clearance process, i.e., glymphatic system. Brain clearance mechanisms are essential for maintaining neural homeostasis, and their disruption is linked to neuropsychiatric diseases, such as delirium. Factors such as sleep have been shown to influence global brain hemodynamics and improve the coupling between global grey matter (gGM) BOLD and CSF signals, a measure of macroscopic CSF flow in relation to global oxygen fluctuations in fMRI. The effects of anesthetics on glymphatic function in humans remain poorly understood; only one study reported a decrease in coupling with sevoflurane. Although lidocaine is usually used as a local anesthetic, its intravenous usage has been suggested to be protective against postoperative delirium; therefore, investigating its influence on brain fluid dynamics is relevant. We retrospectively analyzed resting-state fMRI data from 11 participants during baseline, and during intravenous lidocaine administration, participants remained fully responsive. gGM and CSF time series were extracted for coupling and power spectral analysis. Vitals were also compared. Results demonstrated a significant increase in CSF-gGM coupling with lidocaine (p=0.017), yet spectral power analysis and vitals did not reveal significant changes across conditions (p>0.05). Findings suggest that lidocaine enhances the temporal coordination of brain fluid hemodynamics, which may be associated with increased glymphatic-like flow; however, the mechanisms remain unclear. This study lays the groundwork for uncovering unconventional anesthetics and for motivating new studies to understand their effects on brain clearance mechanisms.