Written and maintained by CASRAI Editorial Board
Last updated
The Confusion Assessment Method for the ICU (CAM-ICU) is the standard bedside instrument for screening mechanically ventilated and non-verbal intensive care patients for delirium, using a four-feature algorithm that produces a positive/negative result in a couple of minutes. This page covers the four-feature algorithm and scoring rule, the Attention Screening Exam, the CAM-ICU-7 severity score, and how CAM-ICU relates to the Richmond Agitation-Sedation Scale (RASS), which must be checked first before CAM-ICU can be validly administered.
What CAM-ICU is, and where it came from
The original Confusion Assessment Method (CAM) was developed by Sharon Inouye and colleagues as a bedside delirium-detection instrument for general medical patients (Inouye SK et al., “Clarifying Confusion: The Confusion Assessment Method. A New Method for Detection of Delirium,” Annals of Internal Medicine 113(12):941–948, 1990). Because the original CAM depends on verbal responses the original CAM assumes a patient can give, it does not work for mechanically ventilated ICU patients who cannot speak. Wes Ely and colleagues at Vanderbilt adapted it into the CAM-ICU, validating the ICU-specific version against psychiatrist-rendered DSM diagnoses (Ely EW et al., “Evaluation of Delirium in Critically Ill Patients: Validation of the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU),” Critical Care Medicine 29(7):1370–1379, 2001). CAM-ICU now sits, alongside RASS, at the center of the Society of Critical Care Medicine’s PADIS guidelines and the ABCDEF liberation bundle for routine ICU delirium monitoring.
Step 1: check RASS first
CAM-ICU cannot be validly administered to a patient who is too sedated to attend to simple commands, so the protocol requires checking the patient’s current RASS score before attempting it. CAM-ICU should only be attempted when RASS is -3 or higher (that is, -3, -2, -1, 0, or a positive score). If RASS is -4 or -5 — deep sedation or unarousable — the correct step is to document the patient as unable to be assessed at that time and re-check RASS later, not to force a CAM-ICU result on a patient who cannot follow the test’s commands in the first place. See CASRAI’s RASS Scale guide for the full 10-point scale and assessment procedure.
The four features
CAM-ICU screens for four features. A patient is CAM-ICU positive (delirious) if Feature 1 AND Feature 2 are both present, plus at least one of Feature 3 or Feature 4.
| Feature | What it tests, and how |
|---|---|
| 1. Acute onset or fluctuating course | Is there an acute change in mental status from the patient’s baseline, or has the patient’s mental status (RASS, GCS, or prior delirium assessment) fluctuated over the past 24 hours? Assessed from nursing/family report and the chart, not a bedside test. |
| 2. Inattention | Tested with the Attention Screening Exam (ASE) — see below. More than two errors on the letters test indicates inattention. |
| 3. Altered level of consciousness | Any current RASS score other than 0 (i.e. not fully alert and calm) automatically satisfies this feature. If RASS is 0, this feature is scored absent and Feature 4 is tested instead. |
| 4. Disorganized thinking | Only tested if RASS is 0 (Feature 3 not already positive). Uses four simple yes/no questions plus a two-step command; more than one combined error indicates disorganized thinking. |
The Attention Screening Exam (Feature 2)
The standard letters version of the ASE reads the patient a fixed 10-letter sequence — “S-A-V-E-A-H-A-A-R-T” — in a normal tone, roughly one letter per second, instructing the patient beforehand to squeeze the examiner’s hand whenever they hear the letter “A.” An error is either a missed squeeze on an “A” or a squeeze on a non-“A” letter; more than two errors across the 10 letters indicates inattention (Feature 2 positive). Institutions that use a picture-based ASE instead (for patients who cannot reliably respond to an auditory task, such as those who are hard of hearing) follow the same error-count logic against a set of picture cards rather than letters.
Feature 4 in practice: the questions and command
When Feature 4 needs to be tested (RASS is 0), the standard version asks four simple yes/no questions with an obvious correct answer — for example, whether a stone floats on water, whether there are fish in the sea, whether one pound weighs more than two pounds, and whether a hammer can be used to pound a nail — followed by a two-step command such as asking the patient to hold up a given number of fingers, then repeat the action with the other hand without being shown again. More than one combined error across the questions and command indicates disorganized thinking.
CAM-ICU-7: the severity score
Beyond the binary positive/negative result, a validated severity score called CAM-ICU-7 sums points across the four CAM-ICU features plus the RASS score itself, producing a 0–7 scale (Khan BA et al., “The CAM-ICU-7 Delirium Severity Scale,” Critical Care Medicine 45(5):851–857, 2017, PMC5392153). Commonly reported bands categorize a score of 0–2 as no delirium, 3–5 as mild-to-moderate delirium, and 6–7 as severe delirium, giving units a way to track delirium severity and trend over time rather than only a positive/negative call at each check.
CAM-ICU vs. the Intensive Care Delirium Screening Checklist (ICDSC)
CAM-ICU is not the only validated ICU delirium instrument. The Intensive Care Delirium Screening Checklist (ICDSC) is an alternative eight-item checklist that a bedside clinician completes based on observations gathered across an entire nursing shift, rather than an acute point-in-time test administered in a couple of minutes. Both are endorsed in the SCCM PADIS guidelines; the practical difference for a unit choosing between them is workflow — CAM-ICU is a discrete, repeatable bedside test tied to a specific RASS check, while the ICDSC is a running checklist scored from accumulated shift observations. Units should pick one instrument and use it consistently, since scores from the two tools are not interchangeable on the same flowsheet.
Documentation and practical use
Because delirium can wax and wane rapidly, CAM-ICU is typically checked at least once per nursing shift (more often if agitation or a mental-status change is suspected), alongside RASS, as part of routine ICU monitoring under the ABCDEF bundle. What a chart audit or quality review looks for is not just whether a CAM-ICU result was recorded, but whether a positive result triggered the expected response — a search for reversible causes, a review of sedating medications, and application of non-pharmacologic delirium-prevention measures — rather than being charted and left without follow-up.
Frequently asked questions
What does a positive CAM-ICU mean?
A CAM-ICU positive result means the patient has screened positive for delirium: Feature 1 (acute onset or fluctuating course) and Feature 2 (inattention) are both present, plus at least one of Feature 3 (altered consciousness) or Feature 4 (disorganized thinking).
Why does CAM-ICU require checking RASS first?
CAM-ICU depends on the patient being able to attend to simple commands, which a patient at RASS -4 or -5 (deep sedation or unarousable) cannot reliably do. CAM-ICU should only be attempted at RASS -3 or higher; below that, the correct step is to document the patient as unable to be assessed and re-check later.
What is the Attention Screening Exam?
A short test for Feature 2 (inattention) in which the examiner reads the patient a fixed 10-letter sequence (S-A-V-E-A-H-A-A-R-T) and the patient squeezes the examiner’s hand whenever they hear the letter “A.” More than two errors indicates inattention.
What is CAM-ICU-7?
A validated 0–7 delirium severity score derived from the CAM-ICU features and the RASS score, used to track delirium severity and trend over time rather than only a positive/negative result. Commonly reported bands are 0–2 (no delirium), 3–5 (mild-to-moderate), and 6–7 (severe).
Is CAM-ICU the same as the ICDSC?
No. CAM-ICU is a discrete point-in-time bedside test tied to a RASS check; the Intensive Care Delirium Screening Checklist (ICDSC) is an eight-item checklist scored from observations across an entire nursing shift. Both are validated and guideline-endorsed, but scores are not interchangeable, so a unit should use one consistently.
RASS Scale covers the full sedation-agitation scale CAM-ICU depends on. Back to the CASRAI Patient Safety hub for surveillance definitions, root cause analysis, credentialing, and the rest of the hospital patient-safety and infection-prevention library.
