CAM-ICU Calculator — Confusion Assessment Method for the ICU
Work through the CAM-ICU delirium assessment: RASS, acute change or fluctuation, inattention (letters test), altered consciousness and disorganised thinking — with motor subtype.
How it works
Step 1: RASS −4 or −5 → unable to assess. Step 2: CAM-ICU positive = Feature 1 (acute change or fluctuation) AND Feature 2 (inattention: > 2 errors on 10 letters) AND either Feature 3 (RASS ≠ 0) or Feature 4 (disorganised thinking: > 1 error on 4 questions + command). Motor subtype: RASS > 0 hyperactive, RASS ≤ 0 hypoactive.
The Confusion Assessment Method for the ICU (Ely et al., JAMA 2001) adapts the CAM so that delirium can be detected in critically ill and ventilated patients who cannot speak. It is a two-step process: first sedation depth is measured with the RASS, then the four CAM features are tested. In validation it showed 93–100% sensitivity and 89–100% specificity against expert psychiatric diagnosis. Hypoactive delirium is the most common and the most often missed, which is why routine screening at least once per shift is recommended by the PADIS guideline.
Worked example
A ventilated patient is drowsy (RASS −1), was alert this morning (acute change = Feature 1 positive), makes 4 errors on the letters test (Feature 2 positive) and is not alert and calm (RASS ≠ 0, Feature 3 positive): CAM-ICU positive — delirium present, hypoactive subtype.
Sources: Ely EW et al. Delirium in mechanically ventilated patients: validity and reliability of the CAM-ICU. JAMA 2001 · Sessler CN et al. The Richmond Agitation-Sedation Scale. Am J Respir Crit Care Med 2002 · ICU Delirium and Cognitive Impairment Study Group — CAM-ICU training manual
Frequently asked questions
Why must RASS be −3 or lighter?
At RASS −4 or −5 the patient cannot respond to voice, so content of consciousness cannot be tested. Record “unable to assess” and repeat the assessment once sedation is lighter.
How is the letters attention test scored?
Read S-A-V-E-A-H-A-A-R-T at one letter per second; the patient squeezes your hand on every A. Missing an A or squeezing on another letter is an error; more than 2 errors means Feature 2 is positive.
What is hypoactive delirium?
Delirium in a patient who is quiet, drowsy or withdrawn (RASS 0 or below). It is more common than the agitated, hyperactive form and is easily missed without screening.
How often should CAM-ICU be done?
Most ICUs screen at least once per nursing shift and whenever mental status changes, as recommended by the SCCM PADIS guideline.
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Clinical decision tool for education and for use by trained clinicians alongside clinical judgement — not a diagnosis and not a substitute for medical assessment. Scores validated in specific populations may not apply to every patient.