Preoperative cardiac function parameters as valuable predictors for nurses to recognise delirium after cardiac surgery: A prospective cohort study

Delirium is a common postoperative complication after cardiac surgery. The relationship between delirium and cardiac function has not been fully elucidated.

The aim of this study was to identify the association between preoperative cardiac function and delirium among patients after cardiac surgery.

We prospectively recruited 635 cardiac surgery patients with a planned cardiac intensive care unit admission. Postoperative delirium was diagnosed using the confusion assessment method for the intensive care unit. Preoperative cardiac function was assessed using N-terminal prohormone of brain natriuretic peptide (NT-proBNP), New York Heart Association functional classification and left ventricular ejection fraction.

Delirium developed in 73 patients (11.5%) during intensive care unit stay. NT-proBNP level (odds ratio (OR) 1.24, 95% confidence interval (CI) 1.01–1.52) and New York Heart Association functional classification (OR 2.34, 95% CI 1.27–4.31) were both independently associated with the occurrence of delirium after adjusting for various confounders. The OR of delirium increased with increasing NT-proBNP levels after the turning point of 7.8 (log-transformed pg/ml). The adjusted regression coefficients were 1.19 (95% CI 0.95–1.49, P=0.134) for NT-proBNP less than 7.8 (log-transformed pg/ml) and 2.78 (95% CI 1.09–7.12, P=0.033) for NT-proBNP greater than 7.8 (log-transformed pg/ml). No association was found between left ventricular ejection fraction and postoperative delirium.

Preoperative cardiac function parameters including NT-proBNP and New York Heart Association functional classification can predict the incidence of delirium following cardiac surgery. We suggest incorporating an early determination of preoperative cardiac function as a readily available risk assessment for delirium prior to cardiac surgery.