Perioperative total tau as a biomarker of postoperative delirium after major cardiac surgery: A prospective cohort study

Background: Postoperative delirium is a frequent and serious complication in older adults undergoing cardiac surgery with cardiopulmonary bypass (CPB). Identifying blood-based biomarkers of neuronal injury could facilitate early risk stratification. Total tau (t-tau), a microtubule-associated protein released during axonal damage, may serve as a candidate marker. Methods: In this prospective cohort study, 89 adults aged ≥60 years undergoing elective cardiac surgery with CPB were evaluated. Plasma t-tau levels were measured preoperatively and on postop D1 and D3. Cognitive and functional outcomes were assessed. Results: Delirium was diagnosed in 53% of patients on Postop D1 and 42% on postop D3. T-tau increased significantly from baseline (median 1.46 pg/mL) to postop D1 (3.13 pg/mL; P < 0.001), declining on postop D3 (1.89 pg/mL; P < 0.001 vs baseline). Patients with delirium had significantly higher t-tau levels postoperatively and greater t-tau changes from baseline. Postop D1 t-tau independently predicted postop D3 delirium (OR 4.16, 95% CI 2.39–7.23; P < 0.001). Receiver operating characteristic analysis showed excellent diagnostic performance, with an AUC of 0.905 for postop D1 tau levels in predicting postoperative delirium on postop D3. Conclusion: Dynamic elevations in t-tau may predict postoperative delirium and neurocognitive decline after cardiac surgery with CPB. Therefore, t-tau may represent a promising candidate biomarker requiring external validation for risk stratification and monitoring of early postoperative delirium in older surgical patients.