Delirium definition influences prediction of functional survival in patients one-year postcardiac surgery.

Background: Delirium after cardiac surgery is associated with prolonged intensive care unit (ICU) and hospital length of stay and elevated rates of mortality. The Society of Thoracic Surgery National Database (STS-ND) includes delirium in routine data collection but restricts its definition to hyperactive symptoms. The objective is to determine whether the Confusion Assessment Method for ICU (CAM-ICU), which includes hypo- and hyperactive symptoms, is associated with improved prediction of poor 1-year functional survival following cardiac surgery.

Methods: Clinical and administrative databases were used to determine the influence of postoperative delirium on 1-year poor functional survival, defined as being institutionalized or deceased at 1 year. Patients experiencing postoperative delirium using the STS-ND definition (2007-2009) were compared with patients with delirium identified by the CAM-ICU (2010-2012). A propensity score match was undertaken, and multivariable Cox proportional hazards regression models were generated to determine risk of poor 1-year functional survival.

Results: There were 2756 and 2236 patients in the STS-ND and CAM-ICU cohorts, respectively. Propensity matching resulted in a cohort of 1835 patients (82.1% matched). The overall rate of delirium in the matched study population was 7.6% in the STS-ND cohort and 13.0% in the CAM-ICU cohort (P < .001). Delirium in the CAM-ICU cohort was independently associated with poor 1-year functional survival (hazard ratio, 2.58; 95% confidence interval, 1.20-5.54; P = .02); delirium in the STS-ND cohort was not associated with poor 1-year functional survival (hazard ratio, 0.92; 95% confidence interval, 0.49-1.71; P = .79).

Conclusions: A systematic screening tool identifies postoperative delirium with improved prediction of poor 1-year functional survival following cardiac surgery.