Association between perioperative changes in blood d-amino acid oxidase levels and delayed neurocognitive recovery after cardiac surgery: a prospective observational study

Introduction: Delayed neurocognitive recovery is prevalent among patients undergoing cardiac surgery. Identifying biomarkers may facilitate its early detection and risk stratification. This study evaluated perioperative changes in blood D-amino acid oxidase (DAAO), D-serine, and serine racemase in relation to delayed neurocognitive recovery. Methods: Thirty-seven patients undergoing cardiac surgery completed neurocognitive testing before surgery and 1 week postoperatively. Combined Z -scores were calculated based on changes from baseline. Blood samples were collected before surgery and on postoperative days 1, 2, and 7. Serum levels of DAAO, D-serine, and serine racemase were measured using enzyme-linked immunosorbent assays. Correlations between combined Z -scores and changes in biomarker levels from baseline to each time point were assessed. Results: Delayed neurocognitive recovery occurred in 16 of 37 patients (43.2%). Combined Z -scores showed significant negative correlations with changes in DAAO from baseline to postoperative day 2 ( r = −0.431, P = 0.008) and day 7 ( r = −0.348, P = 0.035), but not with changes in D-serine or serine racemase. Although the combined Z -scores were significantly lower in patients with delayed neurocognitive recovery than those without [−3.9 (2.0) vs. −0.1 (1.7), P < 0.001], no significant between-group differences were observed in biomarker changes. Conclusions: Perioperative increases in blood DAAO levels are inversely associated with postoperative neurocognitive function after cardiac surgery, whereas changes in D-serine and serine racemase show no significant association. These findings should be interpreted cautiously, given the exploratory nature of the study. While these biomarkers did not differentiate patients with and without delayed neurocognitive recovery, changes in DAAO levels may be associated with delayed neurocognitive recovery, and further studies are required to validate these findings.