Patients who are admitted to a medical or surgical intensive care unit (ICU) have a high risk for long-term cognitive impairment, according to a study in the October 3 New England Journal of Medicine.
At 12 months postdischarge, 24% of ICU patients had a score on the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) that was similar to that for patients with mild Alzheimer’s disease, while 34% had an RBANS score comparable to that of patients with moderate traumatic brain injury (TBI), reported Pratik P. Pandharipande, MD, Professor in the Department of Anesthesiology, Division of Critical Care, Vanderbilt University School of Medicine in Nashville, and colleagues. The researchers also found that a longer period of delirium in the hospital was associated with worse global cognition and executive function scores at three and 12 months.
Dr. Pandharipande’s group included 821 ICU patients with respiratory failure or shock (cardiogenic or septic). These patients were evaluated for delirium, and their global cognition and executive function was assessed with the RBANS and the Trail Making Test, Part B, at three and 12 months after discharge. Fifty-one participants (6%) had cognitive impairment at baseline, and 606 patients (74%) developed delirium (median duration of four days) during their hospital stay.
At three months after discharge, 252 patients (31%) had died, and an additional 59 patients died within the 12-month follow-up. A total of 448 surviving patients underwent cognitive testing after discharge at three months, and 382 surviving patients were tested at 12 months postdischarge.
Participants had a mean RBANS score of 79 at three months and 80 at 12 months. At three months, 40% of patients had a global cognition score that was 1.5 SD below the age-adjusted population mean, which was a similar score to that of patients with moderate TBI. In addition, 26% had a score that was 2 SD below the population mean, which was a score similar to that of patients with mild Alzheimer’s disease. The cognitive deficits continued in both older and younger patients throughout the 12-month follow-up. “A longer duration of delirium was independently associated with worse global cognition at three and 12 months and worse executive function at three and 12 months,” stated Dr. Pandharipande. “Use of sedative or analgesic medications was not consistently associated with cognitive impairment at three and 12 months.
“The significant association between benzodiazepines and executive function at three months should be interpreted cautiously, owing to multiple testing and the nonsignificant associations between benzodiazepines and global cognition scores at 12 months,” Dr. Pandharipande said. “However, the lack of a consistent association should not be taken to suggest that large doses of sedatives are safe, given studies showing that oversedation is associated with adverse outcomes.”
Because delirium is linked to long-term cognitive impairment, the researchers suggested that interventions aimed at reducing delirium may lessen the degree of brain injury that is associated with critical illness.
“Although the judicious use of sedative agents and routine monitoring for delirium—recommended components of care for all patients in the ICU—are increasingly applied, only a few interventions (eg, early mobilization and sleep protocols) have been shown to reduce the risk of delirium among patients in the ICU, and it is not known whether any preventive or treatment strategies can reduce the risk of long-term cognitive impairment after critical illness,” Dr. Pandharipande said.
—Colby Stong
Editor