Confusion Assessment Method for Monitoring Delirium (CAM-ICU)

The CAM-ICU Explained

The CAM‐ICU was developed from the longer Confusion Assessment Method (CAM) tool and is recognized for its quick administration and for the fact that it can be administered in patients undergoing invasive mechanical ventilation and orotracheal intubation because it does not require any communication with the patient. This tool is also widely used in research and clinical settings.

The 2018 clinical practice guidelines for Pain, Agitation, Delirium, Immobility, and Sleep Disruption (PADIS) recommend that all adult patients admitted to intensive care units be regularly assessed for delirium. This can be accomplished by administering the five items of the CAM-ICU.

The CAM-ICU consists in a staged approach. The first stage evaluated level of consciousness and helps the tool administrator decide whether assessment can progress at that particular stage or the patient must be re-evaluated later.

The second stage evaluates four cardinal criteria (in terms of presence/absence) to establish whether delirium is present:

1. Acute Onset or Fluctuating Course
2. Inattention
3. Altered Level of Consciousness
4. Disorganized Thinking

The patient is CAM-ICU positive (delirium present) if:

• Richmond Agitation Sedation Scale ≥ -3, AND
• Acute onset change in mental status or fluctuating course in mental status, AND
• >2 errors in letters attention test, AND
• Either RASS is not 0, OR combined number of errors to questions and commands >1

The original study by Inouye et al. set out to develop and validate a standardized tool for confusion assessment that could be used by nonpsychiatric clinicians in intensive care settings. An expert panel was drawn to develop the CAM, which consists of nine operationalized criteria from the Diagnostic and Statistical Manual of Mental Disorders (DSM-III-R).

The CAM algorithm for diagnosis of delirium required the presence of both the first and the second criteria and of either the third or the fourth criterion.

The CAM was later modified for use in ICU units, with up to 100% sensitivity and 93% specificity for the diagnosis of delirium.

Active surveillance for delirium and timely diagnosis are crucial in the management of critically ill patients and so the CAM-ICU can be confidently used for its sensitive, specific, reliable results.

Delirium assessment is often complicated by the level of sedation of the patient, difficulties in communication due to intubation and the variation in staff training.

It is considered that delirium (whose incidence increases with age – 1/3 of older patients displaying delirium during hospitalization) is associated with a variety of adverse and deleterious outcomes, such as:

• Increased length of hospital stay;
• Increased rate of hospital re-admission;
• Increased mortality up to 12 months after hospital discharge;
• Persisting cognitive impairments at three and 12 months of follow‐up.

References

Original reference

Inouye SK, van Dyck CH, Alessi CA, Balkin S, Siegal AP, Horwitz RI. Clarifying confusion: the confusion assessment method. A new method for detection of delirium. Ann Intern Med. 1990; 113(12):941-948.

Validation

Ely EW, Margolin R, Francis J, et al. Evaluation of delirium in critically ill patients: validation of the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU). Crit Care Med. 2001; 29(7):1370-1379.

Other references

Ely EW, Inouye SK, Bernard GR, 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(21):2703-2710.

Devlin JW, Skrobik Y, Gélinas C, et al. Clinical Practice Guidelines for the Prevention and Management of Pain, Agitation/Sedation, Delirium, Immobility, and Sleep Disruption in Adult Patients in the ICU. Crit Care Med. 2018; 46(9):e825-e873.

Miranda F, Arevalo‐Rodriguez I, Díaz G, Gonzalez F, Plana MN, Zamora J, Quinn TJ, Seron P. Confusion Assessment Method for the intensive care unit (CAM‐ICU) for the diagnosis of delirium in adults in critical care settings. Cochrane Database Syst Rev. 2018; 2018(9):CD013126.