No Method Is Perfect for Detecting Delirium In ICU Patients, but Some Methods Are Better Than Others

Abstract & Commentary

By Richard J. Wall, MD, MPH, Pulmonary Critical Care & Sleep Disorders Medicine, Southlake Clinic, Valley Medical Center, Renton, WA, is Associate Editor for Critical Care Alert.

Dr. Wall reports no financial relationship to this field of study.

Synopsis: This study compared two popular tools for assessing delirium in ICU patients (CAM-ICU and ICDSC), and it showed that physicians often under-diagnose delirium in ICU patients.

Source: van Eijk MM, et al. Comparison of delirium assessment tools in a mixed intensive care unit. Crit Care Med 2009;37:1881-1885.

Delirium is a common and serious disorder in ICU patients, with up to 87% incidence in some ICU populations. Studies have shown that delirium is associated with higher costs and complication rates, namely increased ventilator days and longer hospital stays. Several tools are now available that permit ICU clinicians to easily screen for delirium. Two of the most popular tools are the Confusion Assessment Method for the ICU (CAM-ICU) and the Intensive Care Delirium Screening Checklist (ICDSC). Both tools have been validated using the Diagnostic and Statistical Manual of Mental Health Disorders, 4th edition.

In the current study, the authors rigorously compared the CAM-ICU and ICDSC against each other in a mixed ICU population. The study was conducted in a 32-bed teaching ICU in the Netherlands, with adult medical, surgical, neurologic, neurosurgery, and cardiothoracic patients. The two tools were also compared against a "gold standard" neuropsychiatric assessment, which was performed by an expert trained in delirium diagnosis.

A total of 126 patients were evaluated (mean age, 62 years; 72% male). As a whole, the study population was moderately ill (mean APACHE, 21). The overall prevalence of delirium was 34% (43/126), with delirious patients older and sicker. Among patients with delirium, the majority (69%) had hypoactive delirium.

Neither tool was especially sensitive for detecting delirium. The CAM-ICU had a sensitivity of 64% and the ICDSC had a sensitivity of 43%. However, the CAM-ICU and ICDSC both had decent specificity for delirium diagnosis (88% and 95%, respectively). Among neurologic patients with another cerebral disorder (e.g., stroke), the CAM-ICU was much more sensitive than was the ICDSC (sensitivity 80% vs 31%, respectively). However, ICDSC specificity was higher in this neurologic subpopulation (93% vs 84%, respectively).

When ICU physicians were asked whether they thought a patient was delirious, their sensitivity for detecting delirium was only 29%. Intensivist attendings and fellows fared slightly better than residents, but their sensitivity was still only 63% (i.e., they missed 37% of delirium cases).

Commentary

A few quick questions: Do you routinely measure delirium in your ICU patients? If so, do you know which measurement tool(s) you use? Do you regularly discuss delirium assessment with staff on multidisciplinary rounds?

I imagine many clinicians still answer "no" to these questions. Despite the persistent and energetic efforts of researchers, the saga of delirium testing in ICU patients has been an uphill battle. Dr. Wes Ely, one of the CAM-ICU developers, often tells the story about how his first grant proposal for studying this subject was flatly rejected because the reviewers thought it was an irrelevant topic. Moreover, when he searched the literature for a well-validated delirium instrument that he could use in ventilated patients, he found the following sentence in the Methods section of nearly every delirium study: "Mechanically ventilated patients were excluded."

In less than a decade, the pendulum has swung. Several validated instruments are now available for assessing delirium in mechanically ventilated patients. These instruments are easy to use at the bedside and freely available. A growing body of research has clearly demonstrated the relevance of the topic. Delirium in mechanically ventilated patients is associated with higher 6-month mortality, increased length of stay, and higher cost of care.

The ICDSC is an 8-item scoring checklist based on observations made during routine patient care.1 No patient cooperation is required. Raters complete a checklist based on observations from the previous 24 hours. Items are scored 1 (present) or 0 (absent), for a maximum of 8 points. A score ³ 4 indicates delirium is present.

The CAM-ICU is another well-validated tool that is easy to administer.2 Patients must be rousable on the ventilator. It performs well even among patients with dementia, the elderly, and those with high severity of illness. It takes less than 2 minutes to complete and requires minimal training.

Although past studies compared the CAM-ICU and ICDSC against each other, this is the first comparison in a mixed ICU with a large neurologic population. In neurologic patients, the CAM-ICU was clearly more sensitive, a useful finding. However, what I find most startling is the low sensitivity of ICU physicians in detecting delirium. Even ICU attendings and fellows missed 37% of cases. I believe this emphasizes the need for use of a standard screening tool for assessing delirium on a daily basis. We already know that clinician skills for assessing extubation readiness are shoddy — hence, the utility of the daily spontaneous breathing trial. Similarly, clinician skills for assessing delirium are imperfect. Every ICU should also use a simple tool for screening (and hopefully reducing) delirium.

References

  1. Bergeron N, et al. Intensive Care Delirium Screening Checklist: Evaluation of a new screening tool. Intensive Care Med 2001;27:859-864.
  2. Ely EW, et al. Delirium in mechanically ventilated patients: Validity and reliability of the confusion assessment method for the intensive care unit (CAM-ICU). JAMA 2001;286:2703-2710.