Impaired executive function is associated with delirium after coronary artery bypass graft surgery

OBJECTIVES: To determine the extent to which preoperative performance on tests of executive function and memory was associated with delirium after coronary artery bypass graft (CABG) surgery. DESIGN: Prospective observational cohort study. SETTING: Two academic medical centers and one Department of Veterans Affairs medical center in Massachusetts. PARTICIPANTS: Eighty subjects without preoperative delirium undergoing CABG or CABG-valve surgery completed baseline neuropsychological assessments with validated measures of memory and executive function. MEASUREMENTS: Beginning on postoperative Day 2, a battery to diagnose delirium was administered daily. Confirmatory factor analysis (CFA) was used to define two cognitive domain composites (memory and executive function). The loading pattern of neuropsychological measures onto the latent cognitive domains was determined a priori. Poisson regression was used to model the association between neuropsychological performance and cognitive domain composite scores and risk of postoperative delirium. The association was expressed as the difference between impaired (0.5 standard deviations (SDs) below mean) and nonimpaired (0.5 SDs above mean) performers. RESULTS: Forty subjects (50%) developed delirium. Measures of memory function were not significantly related to delirium. Of the executive function measures, verbal fluency, category fluency, Hopkins Verbal Learning Test learning, and backward recounting of days and months were significantly related to delirium. Preoperative mental status was a strong predictor of postoperative delirium. After controlling for age, sex, education, medical comorbidity, mental status, and the other cognitive domain, CFA cognitive domain composites suggest that risk for delirium is specific for executive functioning impairment (relative risk (RR) = 2.77, 95% confidence interval (CI) = 1.12-6.87) but not for memory impairment (RR = 0.49, 95% CI = 0.19-1.25). CONCLUSION: Worse preoperative performance in executive function was independently associated with greater risk of developing delirium after CABG.