Occipital Monitoring of PSI During Frontal Tumor Resection: A Feasibility Study

Frontal patient state index (PSI) monitoring is impractical during frontal lobe tumor resection due to surgical field interference. No validated alternative monitoring positions exist currently. This study evaluated the agreement between standard frontal and experimental occipital PSI monitoring. A SEDline sedation monitor was used to record frontal and occipital PSI values in 16 patients who underwent frontal lobe tumor resection. PSI data was collected at 2-s intervals starting from sensor attachment to headframe fixation. Agreement was assessed using the Bland-Altman analysis and intraclass correlation coefficient (ICC). Subgroup analyses evaluated the impact of American Society of Anesthesiologists (ASA) classification (I/II/III) and tumor laterality. A Passing-Bablok regression established predictive equations between frontal and occipital PSI at seven critical time points. Frontal and occipital PSI trends showed high temporal synchrony (P = 0.08) with a strong positive correlation (R2 = 0.805, P < 0.001). Bland-Altman analysis demonstrated excellent agreement (mean log-transformed difference: -0.02; 95% LoA: -0.82 to 0.80). The ICC of all data was 0.82 (95% CI: 0.816-0.830, P < 0.001). Neither ASA classification (P = 0.368) nor tumor laterality (P = 0.382) significantly affected frontal-occipital PSI differences. A Passing-Bablok regression equation was derived to predict frontal PSI from occipital measurements:ePSI=0.37×(zPSI)1.28. Occipital PSI demonstrates excellent agreement with frontal PSI during frontal tumor resection, offering a viable alternative to obstructed frontal monitoring.