Natriuretic Peptides as a Predictor for Delirium After Cardiac Surgery: A Prospective Observational Study

Background/Objectives: Subsequent to surgical procedures under cardiopulmonary bypass, at least one third of the patients experience delirium. Among others, the disruption of the blood-brain barrier results from the release of natriuretic peptides during surgery. Furthermore, natriuretic peptides increase the effect of dopamine agonists, which is a key element in the pathomechanism of delirium. The primary endpoint of this study was the adjusted mean difference in natriuretic peptide concentration before surgery between patients with and without delirium. The secondary endpoints were the differences in cognitive performance and quality of life, and physical performance. Methods: Single center observational study. Setting in the Cardiac surgery and intensive care at a German tertiary medical center. Eighty patients for elective cardiac surgery under cardiopulmonary bypass for valve replacement or coronary artery bypass grafting. Preoperative NT-pro C-type natriuretic peptide (CNP) was determined. After surgery, delirium was assessed five times daily using the confusion assessment method for intensive care until 72 h after surgery and before hospital discharge. Data on quality of life and physical performance were also collected. Results: Overall, 28/80 (35%) patients developed delirium. Patients with delirium showed an increased concentration of NT-proCNP preoperatively (p = 0.016) compared to those who did not experience delirium. Patients with delirium during hospitalization reported deterioration in their physical role function (p = 0.036), vitality (p = 0.004), and social function (p = 0.008) before surgery. Conclusions: Increased NT-proCNP before surgery is associated with the occurrence of delirium. A relevant reduction in cognitive and physical performance and quality of life may be a new risk factor for delirium.