NEJM: Delirium post-CABG leads to drop in cognitive function

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Developing delirium post-CABG can lead to a decreased cognitive function in patients and a prolonged period of impairment after hospital discharge, according to a study published July 5 in the New England Journal of Medicine. The researchers said that delirium patients could benefit from further intervention and customized rehabilitation after hospital discharge.

“Cognitive impairment is common after cardiac surgery, and prevention efforts have not always been successful,” Jane S. Saczynski, PhD, of the University of Massachusetts Medical School in Worcester, and colleagues wrote. “Although a large proportion of patients return to their preoperative level of cognitive function within three months, many do not.”

Saczynski et al set out to understand whether patients with postoperative delirium would have a drop in cognitive function post-surgery and slower rates of cognitive recovery the following year.

To do so, the researchers screened patients 60 years or older who were to undergo CABG at two medical centers and one VA hospital; 225 patients were enrolled. Patients underwent interviews conducted by trained interviewers and the researchers evaluated demographic characteristics, behavioral factors, coexisting conditions and cognitive function.

Of the study cohort, one-quarter of patients were women and most were white and non-Hispanic. The mean age was 73 years and the median follow-up period was 363 days.

The authors reported that delirium developed in 46 percent of patients. In 65 percent of these patients, delirium lasted one to two days. In 35 percent of patients, delirium lasted three or more days. The researchers reported that patients with delirium were older, less educated, more likely to be women and less likely to be white. Additionally, these patients were more likely to have a history of smoking or transient ischemic attack.

Patients who developed delirium saw lower preoperative mean Mini–Mental State Examination (MMSE) scores compared with those who did not develop delirium, 25.8 vs. 26.9, respectively. Patients with delirium also saw greater drops in cognitive function two days post-surgery when compared with those without delirium, 7.7 points vs. 2.1. Delirium patients also had lower postoperative cognitive function at one month and one year.

Lastly, the authors reported that patients with delirium were less likely than those without it to return to their preoperative baseline level at six months, 40 percent vs. 24 percent, respectively.

“These findings suggest that delirium, which was once thought of as a short-term, transient cognitive disorder, may have longer-term observed effects on cognitive function in patients who have undergone cardiac surgery,” the authors wrote. “Our findings are of clinical significance, since the risk of delirium among patients undergoing cardiac surgery can be predicted preoperatively, and delirium is potentially preventable.”

The authors added that cognitive screening at hospital discharge could help identify high-risk patients who may require close monitoring post-CABG or tailored transition care that could help enhance clinical outcomes.

“Identifying patients at high risk for delirium and promoting the development of interventions to prevent delirium in patients undergoing cardiac surgery may reduce the rate of long-term cognitive impairment in this population,” the authors concluded.