Evaluation of delirium in critically ill patients: Validation of the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU)

Objective: To develop and validate an instrument for use in the intensive c are unit to accurately diagnose delirium in critically ill patients who are often nonverbal because of mechanical ventilation. Design: Prospective cohort study. Setting: The adult medical and coronary intensive care units of a tertiary care, university-based medical center. Patients: Thirty-eight patients admi tted to the intensive care units. Measurements and Main Results: We designed and tested a modified version of the Confusion Assessment Method for use in intensive care unit patients an d called it the CAM-ICU. Daily ratings from intensive care unit admission t o hospital discharge by two study nurses and an intensivist who used the CA M-ICU were compared against the reference standard, a delirium expert who u sed delirium criteria from the Diagnostic and Statistical Manual of Mental Disorders (fourth edition). A total of 293 daily, paired evaluations were c ompleted, with reference standard diagnoses of delirium in 42% and coma in 27% of all observations. To include only interactive patient evaluations an d avoid repeat-observer bias for patients studied on multiple days, we used only the first-alert or lethargic com parison evaluation in each patient. Thirty-three of 38 patients (87%) developed delirium during their intensive care unit stay, mean duration of 4.2 +/- 1.7 days. Excluding evaluations o f comatose patients because of lack of characteristic delirium features, th e two critical care study nurses and intensivist demonstrated high interrat er reliability for their CAM-ICU ratings with kappa statistics of 0.84, 0.7 9, and 0.95, respectively (p < .001). The two nurses' and intensivist's sen sitivities when using the CAM-ICU compared with the reference standard were 95%, 96%, and 100%, respectively, whereas their specificities were 93%, 93 %, and 89%, respectively. Conclusions: The CAM-ICU demonstrated excellent reliability and validity wh en used by nurses and physicians to identify delirium in intensive care uni t patients. The CAM-ICU may be a useful instrument for both clinical and re search purposes to monitor delirium in this challenging patient population.