Abstract: Objective To investigate the predictive value of combining intraoperative cerebral oxygen saturation (rSO₂) with preoperative serum levels of phosphorylated neurofilament heavy chain (pNF-H) and brain-derived neurotrophic factor (BDNF) for postoperative delirium (POD) in the elderly patients with colorectal cancer (CRC). Methods From February 2022 to February 2025, A total of 225 elderly CRC patients undergoing radical surgery at Linyi Central Hospital were enrolled. They were divided into POD and non-POD groups based on the occurrence of POD. Intraoperative rSO₂ was continuously monitored at different time points, and the rSO₂ fluctuation rate was calculated. Preoperative serum levels of pNF-H and BDNF were measured using enzyme-linked immunosorbent assay. Logistic regression analysis was performed to identify risk factors influencing POD. The predictive value of individual and combined indicators for POD was evaluated using receiver operating characteristic (ROC) curves. Results The POD group exhibited significantly higher levels of surgical duration, serum levels of prostaglandin E2 (PGE2), S100 calcium-binding protein β (S100β), and pNF-H compared to the non-POD group, while serum BDNF levels were lower (P<0.05). The rSO₂ fluctuation rate was significantly higher in the POD group than that in the non-POD group(P<0.05). Multivariate logistic regression analysis indicated that surgical duration, PGE2, S100β protein, rSO₂ fluctuation rate, pNF-H, and BDNF were independent factors influencing POD (P<0.05). The area under the ROC curve (AUC) for predicting POD using the combination of rSO₂ fluctuation rate, serum pNF-H, and BDNF was 0.907, significantly higher than the AUC of rSO₂ fluctuation rate alone (AUC=0.805, Z=2.892, P=0.003), pNF-H alone (AUC=0.767, Z=4.141, P<0.001), and BDNF alone (AUC=0.784, Z=2.834, P=0.005). Conclusions The combination of serum pNF-H and BDNF levels with intraoperative rSO₂ fluctuation rate demonstrates high predictive value for the occurrence of POD in elderly CRC patients, which may aid in the early identification and intervention for high-risk individuals.

Key words: colorectal cancer, cerebral oxygen saturation, phosphorylated neurofilament heavy chain, brain-derived neurotrophic factor, postoperative delirium