Because of the morbidity associated with delirium, all patients, especially older patients should be screened for delirium, at least, daily and more frequently if they are high risk. An algorithm for the diagnosis of delirium, the Confusion Assessment Method (CAM), which is based on Diagnostic and Statistical Manual of Mental Disorders (DSM)-IIIR criteria15
, has been demonstrated to be reliable, sensitive, and specific for diagnosis of delirium compared to expert clinician examination.16,17
The algorithm for the CAM is displayed in . Briefly, the criteria are a combination of Feature 1 (acute onset and fluctuating course), Feature 2 (inattention), and either Feature 3 (disorganized thinking) or Feature 4 (abnormal level of consciousness).
Figure 1 The Algorithm of the Confusion Assessment Method (CAM). The diagnosis of delirium is made with the presence of Feature 1 AND Feature 2 AND either Feature 3 OR Feature 4. Examples of assessments applicable in the postoperative period are included below (more ...)
There are important elements of the CAM, which need to be clarified. First, attention is best assessed when formal testing (digit span, months of the year backward, serial 7s, etc) is combined with interviewer observations18
. Importantly, orientation items have low sensitivity for inattention and delirium and should not be considered the standard assessment for attention.19
Additionally, there are two variants of delirium that are characterized as the hyperactive (agitated) variant and the hypoactive (quiet) variant of delirium. The hyperactive variant, which accounts for only about 25% of cases, is rarely missed, because the patient disrupts the flow of care20
. The more common hypoactive variant is often missed because the patient is neither disruptive nor threatening21
. For example, a patient with hypoactive delirium would briefly wake when addressed and may comply with some requests, but then quickly falls back to sleep. Several studies have found that the hypoactive variant is detected less frequently and carries a higher mortality, presumably from the delay in diagnosis.21-23
Thus, the CAM is a useful algorithm for diagnosis of delirium, but requires additional assessment of attention and observation.
The CAM-ICU operationalizes the CAM by adding objective assessments for attention, consciousness, and thought.24
The CAM-ICU has been validated in nonverbal ICU patients.24
The advantages of the CAM-ICU are that it can be performed by trained nurses or physicians; can be repeated over time to detect fluctuation and changes; and has been associated with ICU outcomes including mortality25
, length of stay26
, and cost27
. The key elements of the CAM-ICU are the Richmond Agitation and Sedation Scale, a validated measure of consciousness28
, the Attention Screening Exam29
, and 5 thought questions. This information is used to complete the CAM algorithm for delirium.