Preoperative hypoxic biomarkers and postoperative delirium in patients with obstructive sleep apnea

Postoperative delirium (POD) in patients with obstructive sleep apnea (OSA) is associated with increased mortality and healthcare costs. In this study, we investigated the association of OSA risk, serum biomarkers for central nervous ischemia (S100B and NSE), and POD.

After research ethics approval, patients completed the STOP BANG assessment before undergoing elective surgery. Blood was drawn for S100B and NSE measurement, and cognitive performance was tested using the Montreal Cognitive Assessment (MoCA) at study admission and postoperatively at discharge. Delirium assessment was performed using the Nursing Delirium Screening Scale (NuDESC) and the Confusion Assessment Method (CAM).

One hundred twenty-four enrolled patients were separated into three OSA-risk groups based on STOP BANG score testing (low risk, n = 22; intermediate risk, n = 67; high risk, n = 35). Preoperative NSE values increased with OSA risk (NSE in ng/ml; mean [range]; low risk: 15.6 [9.2-44.3]; intermediate risk: 21.8 [7.6-114.1]; high risk: 29.2 [10.1-151]; p = 0.039). Postoperative MoCA and NuDESC assessments were not different between the OSA-risk groups. We found a decreasing incidence for POD with increasing OSA risk (positive CAM: low risk: 18.1%, intermediate risk: 12.0%; high risk: 11.5%, p = 0.043). However, this was no longer detectable in a complete case analysis. In patients with POD, postoperative ischemic biomarker values were not different between OSA-risk groups.

We found a trend of decreasing POD incidence with increasing OSA risk, which was not robust in a complete case analysis. Our results possibly support the phenomenon of hypoxic preconditioning.