The impact of delirium on the survival of mechanically ventilated patients* Shu-Min Lin, MD; Chien-Ying Liu, MD; Chun-Hua Wang, MD; Horng-Chyuan Lin, MD; Chien-Da Huang, MD; Pei-Yao Huang, MD; Yueh-Fu Fang, MD; Meng-Heng Shieh, MD; Han-Pin Kuo, MD, PhD D elirium, defined as an acute change in mental status or a fluctuating course, impaired attention, and disorganized thinking, is associated with underlying illnesses such as medical problems or drug use or withdrawal (1–3). It is not a disease itself but a marker of acute cere- bral insufficiency affecting the brain in many ways. Delirium is recognized as a sign of brain failure (4) and is associated with poor outcome in hospitalized pa- tients, including longer hospital stay (5) and higher mortality rate (6, 7). A previ- ous study has reported that preventive intervention strategies targeting risk fac- tors could reduce the incidence and du- ration of delirium in older hospitalized patients (8). However, delirium is com- monly unrecognized or overlooked by physicians during their practice, espe- cially for those patients in critical condi- tion or receiving mechanical ventilation. A delay in recognition or ignorance of the development of delirium in those patients may lead to poor outcome and an in- crease in medical cost. Patients in the intensive care unit (ICU) are extraordinarily vulnerable to the development of delirium because of multiple system illness and comorbidi- ties, use of sedative medications, and en- vironmental factors in the ICU. Although many studies have investigated the inci- dence, risk factors, and treatment of de- lirium, few of them included patients in ICU (9 –11). The Diagnostic and Statisti- cal Manual of Mental Disorders, Fourth Edition (DSM-IV), is the most popular tool used in medical research and therapy to evaluate the development of delirium (3, 5). It requires verbal communication between the professional psychiatrists and patients. However, this is not appli- cable in mechanically ventilated patients who are not verbally communicable due to endotracheal intubation. The Confusion Assessment Method for the Intensive Care Unit (CAM-ICU), based on the Confusion Assessment Method (12), is a new method for the detection of delirium in the ICU. It consists of four categories of nonverbal assessment items and has been validated in evaluation of delirium in critically ill (13) and mechan- ically ventilated patients (14). This newly developed tool was also documented to be easily accessible by medical staff without formal psychiatric training and can reli- ably detect delirium in mechanically ven- tilated patients with a high degree of sen- sitivity and specificity. Using the CAM- ICU, Ely et al. (13, 14) disclosed that 87% of ICU patients and 83% of mechanically ventilated patients were delirious at some time during their stay. In addition, devel- opment of delirium in patients receiving mechanical ventilation at some point during the ICU stay was an independent predictor of higher 6-month mortality and longer hospital stay (6). In this report, we conducted a pro- spective study of mechanically ventilated subjects admitted to the ICU to deter- mine whether the CAM-ICU test charac- *See also p. 2352. From the Department of Thoracic Medicine II, Chang Gung Memorial Hospital, Taipei, Taiwan. Supported, in part, by NSC-92-2314-B-182A-158, National Science Council, Taiwan, R.O.C. Copyright © 2004 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins DOI: 10.1097/01.CCM.0000145587.16421.BB Objectives: To revalidate a means of assessing delirium in intensive care unit patients and to investigate the independent effect of delirium on the mortality of mechanically ventilated patients. Design: A prospective cohort study. Setting: A 37-bed medical intensive care unit of a tertiary care hospital. Patients: Subjects were 102 of 131 consecutive mechanically ventilated patients. Measurements: All the enrolled patients were assessed for delirium using the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU). Mortality rate were compared between pa- tients with or without delirium, and the predictors of death were investigated. Results: The two CAM-ICU assessors’ sensitivities in diagnos- ing delirium compared with reference standard were 91% and 95%, whereas their specificities were both 98%. They also dem- onstrated high interrater reliability with kappa statistics of 0.91. Delirium was present in 22 of 102 (22%) patients in the first 5 days. The delirious patients had higher intensive care unit mor- tality rate than nondelirious patients (63.6% vs. 32.5%, respec- tively), with a hazard ratio of 2.57 (95% confidence interval, 1.56 – 8.15). In multivariate analysis, delirium (odds ratio, 13.0; 95% confidence interval, 2.69 – 62.91), shock (odds ratio, 12.91; 95% confidence interval, 2.93–56.92), and illness severity (odds ratio, 9.61; 95% confidence interval, 2.24 – 41.18) were indepen- dent predictors of mortality. Conclusions: This study confirms previous work showing that delirium is an independent predictor for increased mortality among mechanically ventilated patients. (Crit Care Med 2004; 32:2254 –2259) KEY WORDS: delirium; mechanical ventilation; respiratory failure; Confusion Assessment Method for the Intensive Care Unit 2254 Crit Care Med 2004 Vol. 32, No. 11