Delirium after coronary artery bypass graft surgery and late mortality

Abstract

Objective: Delirium is common after cardiac surgery, although under-recognized, and its long-term consequences are likely underestimated. The primary goal of this study was to determine whether patients with delirium after coronary artery bypass graft (CABG) surgery have higher long-term out-of-hospital mortality when compared with CABG patients without delirium.

Methods: We studied 5,034 consecutive patients undergoing CABG surgery at a single institution from 1997 to 2007. Presence or absence of neurologic complications, including delirium, was assessed prospectively. Survival analysis was performed to determine the role of delirium in the hazard of death, including a propensity score to adjust for potential confounders. These analyses were repeated to determine the association between postoperative stroke and long-term mortality.

Results: Individuals with delirium had an increased hazard of death (adjusted hazard ratio [HR], 1.65; 95% confidence interval [CI], 1.38-1.97) up to 10 years postoperatively, after adjustment for perioperative and vascular risk factors. Patients with postoperative stroke had a HR of 2.34 (95% CI, 1.87-2.92). The effect of delirium on subsequent mortality was the strongest among those without a prior stroke (HR 1.83 vs HR 1.11 [with a prior stroke] [p-interaction = 0.02]) or who were younger (HR 2.42 [<65 years old] vs HR 1.49 [>/=65 years old] [p-interaction = 0.04]).

Interpretation: Delirium after cardiac surgery is a strong independent predictor of mortality up to 10 years postoperatively, especially in younger individuals and in those without prior stroke. Future studies are needed to determine the impact of delirium prevention and/or treatment in long-term patient mortality.

Figure 1

Kaplan-Meier curve for individuals without (solid upper line) and with (dashed, lower line) postoperative delirium. The unadjusted graph (upper) is displayed, with numbers at risk, as well as the same graph adjusted for age (lower; centered at median age of 65 years old, median cardiopulmonary bypass time, and for male without risk factors). The log-rank p<0.0001 for the differences between each pair of curves.

Figure 2

Kaplan-Meier curves for individuals without (solid upper line) and with (dashed, lower line) postoperative stroke. The unadjusted graph (upper) is displayed, as well as the same graph adjusted for propensity score (centered at age 65, median cardiopulmonary bypass time, and for male without risk factors). The log-rank p<0.0001 for comparison between the pair of curves.