Objective: Delirium, an acute organ dysfunction, is common among critically ill patients leading to significant morbidity and mortality; its epidemiology in a mixed cardiology and cardiac surgery ICU is not well established. We sought to determine the prevalence and risk factors for delirium among cardiac surgery ICU patients.
Design: Prospective observational study.
Setting: Twenty-seven-bed medical-surgical cardiac surgery ICU.
Patients: Two hundred consecutive patients with an expected cardiac surgery ICU length of stay >24 hrs.
Measurements: Baseline demographic data and daily assessments for delirium using the validated and reliable Confusion Assessment Method for the ICU were recorded, and quantitative tracking of delirium risk factors were conducted. Separate analyses studied the role of admission risk factors for occurrence of delirium during the cardiac surgery ICU stay and identified daily occurring risk factors for the development of delirium on a subsequent cardiac surgery ICU day.
Main Results: Prevalence of delirium was 26%, similar among cardiology and cardiac surgical patients. Nearly all (92%) exhibited the hypoactive subtype of delirium. Benzodiazepine use at admission was independently predictive of a three-fold increased risk of delirium (odds ratio 3.1 [1, 9.4], p = 0.04) during the cardiac surgery ICU stay. Of the daily occurring risk factors, patients who received benzodiazepines (2.6 [1.2, 5.7], p = 0.02) or had restraints or devices that precluded mobilization (2.9 [1.3, 6.5], p < 0.01) were more likely to have delirium the following day. Hemodynamic status was not associated with delirium.
Conclusions: Delirium occurred in one in four patients in the cardiac surgery ICU and was predominately hypoactive in subtype. Chemical restraints via use of benzodiazepines or the use of physical restraints/restraining devices predisposed patients to a greater risk of delirium, pointing to areas of quality improvement that would be new to the vast majority of cardiac surgery ICUs.
1 Department of Medicine, Cardiovascular Division, Vanderbilt University Medical Center, Nashville, TN.
2 Department of Anesthesiology, Critical Care Medicine Division, Vanderbilt University Medical Center, Nashville, TN.
3 Division of General Internal Medicine, Pulmonary Critical Care Division and Center for Health Sciences Research, Vanderbilt University Medical Center, Nashville, TN.
4 Department of Biostatistics, Vanderbilt University Medical Center, Nashville, TN.
5 Anesthesia Service, VA Tennessee Valley Health Care System, Nashville, TN.
6 Geriatric Research, Education, and Clinical Center, VA Tennessee Valley Health Care System, Nashville, TN.
*See also p. 660.
Dr. Wagner has received honoraria from ImaCor. Dr. Wagner has received honoraria from ImaCor. Ms. Boehm has received honoraria from Hospira. Dr. Ely has received a grant from Aspect Medical Systems and honoraria from Pfizer, Eli Lilly, GlaxoSmithKline, and Hospira. Dr. Shintani has received funding from the National Institutes of Health. Dr. Ely is supported by the VA Clinical Science Research and Development (VA Merit Review Award) and the National Institutes of Health (AG027472). Dr. Pandharipande has received honoraria from Hospira and Orion Pharma. Dr. Pandharipande is supported by a VA Career Development Award (CSRD). The remaining authors have not disclosed any potential conflicts of interest.
Address requests for reprints to: John A. McPherson, MD, Vanderbilt University Medical Center, 1215 21st Ave., South, MCE, 5th Floor South Tower, Nashville, TN 37205. E-mail: firstname.lastname@example.org