The Confusion Assessment Method for the Intensive Care Unit (CAM-ICU) was originally developed and validated for mechanically ventilated and ICU patients. Given its brevity and ease of use, its use has been explored for non-ICU settings.
A patient must be positive for both Features 1 and 2, and either Feature 3 or 4 to be CAM-ICU–positive.
Like the CAM, altered mental status or fluctuating course (Feature 1) is determined by proxy interview or observation.
To test for inattention (Feature 2), the CAM-ICU incorporates the Vigilance A task, where the rater provides a series of 10 letters (“SAVEAHAART”) and the patient squeezes the rater’s hand every time they hear the letter “A”.
To test for disorganized thinking (Feature 3), it asks the patient 4 simple yes/no questions (eg, “Will a stone float on water?”) and a simple command (eg, “Hold up this many fingers…” [Rater holds up 2 fingers] “Now do the same thing with the other hand” [Do not demonstrate]).
Altered level of consciousness (Feature 4) is determined by the Richmond Agitation Sedation Scale (RASS). For the RASS, a score other than 0 (normal and alert) is indicative of an altered level of consciousness.
The CAM-ICU has limited validation data outside the ICU, especially in the ED. In general, the CAM-ICU is thought to have poorer sensitivity, but higher specificity than the bCAM. Based upon its likelihood ratios, a negative CAM-ICU will moderately reduce the likelihood of delirium, while a positive CAM-ICU will moderately to strongly increase the likelihood of delirium.
Of note, the CAM-ICU’s sensitivities are markedly lower in medical oncology, older postoperative, and hospitalized patients. The reasons for these discrepancies are unclear and require additional research. Additional validation studies are also needed to fully characterize the CAM-ICU’s diagnostic accuracy in older ED patients.
Additional details of the CAM-ICU, including the instruction manual and videos, can be seen at www.icudelirium.org.
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CAM-ICU, Confusion Assessment Method for the Intensive Care Unit
ED, emergency department