SAN DIEGO – Subsyndromal delirium was present in 86% of critically ill patients, results from a large observational study demonstrated. In addition, the duration of delirium was associated with increased odds of institutionalization, an association that was modified by the duration of delirium.
"In patients with less delirium, the effect of subsyndromal delirium on institutionalization was actually stronger," lead author Dr. Nathan E. Brummel said in an interview at an international conference of the American Thoracic Society, where the research was presented. "This identifies a cohort of people who previously were considered to have normal brain function, but it appears that this has long-term implications for their lives.
Dr. Nathan E. Brummel
"Screening for delirium should occur not only in the ICU but on the wards as well. Patients who have delirium or delirium symptoms may benefit from measures used to prevent and treat this syndrome, such as the Hospital Elder Life Program, routine mobilization, and frequent reorientation through the use of nursing staff or even family members," he later added. This study data may help clinicians discuss long-term outcomes of critical illness with patients and their family members," he said.
For the study, Dr. Brummel, an instructor in medicine in the division of allergy, pulmonary and critical care medicine at Vanderbilt University Medical Center, Nashville, Tenn., and his associates evaluated 821 medical or surgical ICU patients with respiratory failure and/or shock who were enrolled in the BRAIN-ICU observational cohort study (N. Engl. J. Med. 2013;369:1306-16).
They used the Confusion Assessment Method for the ICU (CAM-ICU) to screen for delirium symptoms twice daily in the ICU and daily thereafter. The researchers considered delirium to be present if the CAM-ICU was positive. If the CAM-ICU was negative, they considered subsyndromal delirium (SSD) to be present if any delirium features were present or if inattention was present with or without other features of delirium.
SSD "is said to be present when a patient exhibits some delirium symptoms but does not meet the full delirium diagnostic criteria," the researchers wrote in their poster. "In patients without critical illness, SSD is associated with institutionalization, mortality, and cognitive decline, but these associations remain unclear in the critically ill."
The researchers tracked discharge location, mortality after hospital discharge and assessed for cognitive impairment at 3 and 12 months follow-up and used multivariate regression to determine the relationship between days of SSD and outcomes.
The mean age of the 821 patients was 61 years and their mean APACHE II score was 25. In all, 702 patients (86%) had SSD that lasted an average of 3 days. The most common SSU pattern based on the CAM-ICU was fluctuation of mental status (which occurred in 50% of assessments) and fluctuation in mental status plus altered level of consciousness (which occurred in 22% of assessments).
Dr. Brummel and his associates also found that the duration of SSD was independently associated with increased odds of institutionalization (odds ratio, 1.90), but SSD did not predict mortality or long-term cognitive impairment at 3 or 12 months. "We don’t yet understand the mechanism behind why subsyndromal delirium and institutionalization are associated," Dr. Brummel said. "It probably relates to an association between SSD and factors that drive institutionalization, such as physical disability and cognitive impairment. Once patients survived the hospital stay, subsyndromal delirium wasn’t associated with an increased risk of mortality. It may be the fact that this less severe form of brain dysfunction in the ICU does not have the same effect as the full syndrome of delirium."
He acknowledged certain limitations of the study, including the fact that the CAM-ICU only measures four features of delirium and that no assessments of cognitive or physical function were conducted at hospital discharge.
The study was supported by the National Institutes of Health, the Vanderbilt Clinical and Translational Scholars Program, and the Veterans Affairs Tennessee Valley Healthcare System Geriatric Research Education and Clinical Centers. Dr. Brummel said that he had no relevant financial conflicts to disclose.