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

Crit Care Med. 2001 Jul;29(7):1370-9. doi: 10.1097/00003246-200107000-00012.

Abstract

Objective: To develop and validate an instrument for use in the intensive care 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 admitted 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 and called it the CAM-ICU. Daily ratings from intensive care unit admission to hospital discharge by two study nurses and an intensivist who used the CAM-ICU were compared against the reference standard, a delirium expert who used delirium criteria from the Diagnostic and Statistical Manual of Mental Disorders (fourth edition). A total of 293 daily, paired evaluations were completed, with reference standard diagnoses of delirium in 42% and coma in 27% of all observations. To include only interactive patient evaluations and avoid repeat-observer bias for patients studied on multiple days, we used only the first-alert or lethargic comparison 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 of comatose patients because of lack of characteristic delirium features, the two critical care study nurses and intensivist demonstrated high interrater reliability for their CAM-ICU ratings with kappa statistics of 0.84, 0.79, and 0.95, respectively (p <.001). The two nurses' and intensivist's sensitivities 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 when used by nurses and physicians to identify delirium in intensive care unit patients. The CAM-ICU may be a useful instrument for both clinical and research purposes to monitor delirium in this challenging patient population.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aged
  • Delirium / diagnosis*
  • Delirium / etiology
  • Dementia / complications
  • Female
  • Humans
  • Intensive Care Units*
  • Male
  • Middle Aged
  • Neuropsychological Tests*
  • Observer Variation
  • Prospective Studies
  • Reference Standards
  • Reproducibility of Results
  • Respiration, Artificial*
  • Sensitivity and Specificity