Plasma biomarkers and delirium in critically ill patients after cardiac surgery: A prospective observational cohort study

•In 318 patients who were included, 93 (29.2%) developed delirium.•Levels of IL-6, TNF-α, sTNFR-1, and sTNFR-2 were higher in patients with delirium.•Plasma levels of sTNFR-1 may be an indicator of delirium after cardiac surgery. Delirium is common in postoperative critically ill patients and may affect by intraoperative events. Biomarkers are vital indicators in the development and prediction of delirium. This study aimed to investigate the associations between various plasma biomarkers and delirium. We performed a prospective cohort study on cardiac surgery patients. Delirium assessment was performed twice daily using the confusion assessment method for the intensive care unit (ICU), and the Richmond Agitation Sedation Scale was used to assess the depth of sedation and agitation. Blood samples were collected on the day after ICU admission, and the concentrations of cortisol, interleukin (IL)-1β, IL-6, tumor necrosis factor α, soluble tumor necrosis factor receptor-1 (sTNFR-1), and sTNFR-2 were measured. Delirium in the ICU was noted in 93 (29.2%, 95% CI 24.2–34.3) out of 318 patients (mean age 52 years, SD 12.0). The longer duration of cardiopulmonary bypass, aortic clamping and surgery, and higher plasma, erythrocytes, and platelet transfusion requirements were among the significant differences in intraoperative events between patients with and without delirium. Median levels of IL-6 (p = 0.017), TNF-α (p = 0.048), sTNFR-1 (p