Delirium as a predictor of sepsis in post-coronary artery bypass grafting patients: a retrospective cohort study

INTRODUCTION Delirium is the most common neurological complication following cardiac surgery. Much research has focused on potential causes of delirium; however, the sequelae of delirium have not been well investigated. The objective of this study was to investigate the relationship between delirium and sepsis post coronary artery bypass grafting (CABG) and to determine if delirium is a predictor of sepsis. METHODS Peri-operative data were collected prospectively on all patients. Subjects were identified as having agitated delirium if they experienced a short-term mental disturbance marked by confusion, illusions and cerebral excitement. Patient characteristics were compared between those who became delirious and those who did not. The primary outcome of interest was post-operative sepsis. The association of delirium with sepsis was assessed by logistic regression, adjusting for differences in age, acuity, and co-morbidities. RESULTS Among 14,301 patients, 981 became delirious and 227 developed sepsis post-operatively. Rates of delirium increased over the years of the study from 4.8 to 8.0% (P = 0.0003). A total of 70 patients of the 227 with sepsis, were delirious. In 30.8% of patients delirium preceded the development of overt sepsis by at least 48 hours. Multivariate analysis identified several factors associated with sepsis, (receiver operating characteristic (ROC) 79.3%): delirium (odds ratio (OR) 2.3, 95% confidence interval (CI) 1.6 to 3.4), emergent surgery (OR 3.3, CI 2.2 to 5.1), age (OR 1.2, CI 1.0 to 1.3), pre-operative length of stay (LOS) more than seven days (OR 1.6, CI 1.1 to 2.3), pre-operative renal insufficiency (OR 1.9, CI 1.2 to 2.9) and complex coronary disease (OR 3.1, CI 1.8 to 5.3). CONCLUSIONS These data demonstrate an association between delirium and post-operative sepsis in the CABG population. Delirium emerged as an independent predictor of sepsis, along with traditional risk factors including age, pre-operative renal failure and peripheral vascular disease. Given the advancing age and increasing rates of delirium in the CABG population, the prevention and management of delirium need to be addressed.