Postoperative delirium associated with long-term cognitive impairment

Delirium after cardiac surgery occurred in nearly half of elderly patients and was associated with lower cognitive function postoperatively, a new study found.

Researchers enrolled 225 patients 60 years of age or older who were planning to undergo coronary artery bypass grafting or valve replacement at two academic medical centers and one Veterans Administration hospital. Patients were assessed with the Mini-Mental State Examination (MMSE) preoperatively; daily during hospitalization beginning on postoperative day 2; and at one, six and 12 months after surgery.

Results appeared in the July 5 New England Journal of Medicine.

Postoperative delirium developed in 103 patients (46%), with delirium lasting one to two days in 65% and three or more days in 35%. Those who developed postoperative delirium were more likely to be older, less educated, female, and nonwhite and to have a history of stroke or transient ischemic attack, a higher average score on the Charlson comorbidity index, and a lower level of preoperative cognitive function.

Among all patients, there was a significant decline in cognitive function—4.6 points on the MMSE—from baseline to postoperative day 2 (P<0.001), followed by average increases of 1 point on the MMSE each day on days 3 to 5 (P<0.001). Improvement slowed considerably from day 6 to day 183, and then stabilized from day 184 to day 365. A higher percentage of patients with delirium than those without delirium had not returned to their preoperative baseline level at six months (40% vs. 24%, P=0.01), but the difference was not significant at 12 months (31% vs. 20%, P=0.055).

“In patients with postoperative delirium, cognitive screening at hospital discharge may identify high-risk patients who require close monitoring after discharge or tailored transitional care in order to enhance functional and clinical outcomes,” the authors noted.