Critical Care
RASS (Sedation–Agitation)
Richmond Agitation–Sedation Scale.
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Background
The Richmond Agitation–Sedation Scale (RASS) is a 10-point scale used to assess the level of sedation or agitation in critically ill, often ventilated, patients. It runs from +4 (combative) through 0 (alert and calm) to −5 (unarousable), with the intermediate levels graded by the response to voice and then physical stimulation. The assessment is quick and structured: observe the patient, then if needed speak and finally touch, recording the best response. It underpins goal-directed sedation and is a prerequisite for delirium screening tools such as the CAM-ICU.
Interpreting the result
A RASS of 0 is alert and calm and is usually the goal; +1 to +2 indicates restlessness or agitation and +3 to +4 marks dangerous agitation; −1 to −3 represents light-to-moderate sedation while −4 to −5 is deep sedation or an unarousable state. For most ventilated patients a target of 0 to −2 balances comfort and arousability. Deeper sedation (−4 or −5) is associated with longer ventilation, more delirium and worse outcomes, so sedation should be reassessed regularly against a set target.
Advice
A common target for ventilated patients is 0 to −2. Deep sedation (−4/−5) is linked to worse outcomes; reassess sedation regularly.
Worked example
A ventilated patient opens their eyes and makes eye contact for less than ten seconds when spoken to: this is RASS −2 (light sedation). If the target is 0 to −2, sedation is at goal and need not be deepened.
Pearls / pitfalls
- Assess in sequence — observe, then voice, then physical stimulation — and record the best response to avoid over-sedating.
- A valid RASS is required before a CAM-ICU delirium assessment; a deeply sedated patient (−4/−5) cannot be assessed for delirium.
- Targeting a lighter level of sedation and using daily sedation interruption are linked to better outcomes than routine deep sedation.
- Neuromuscular blockade invalidates RASS, since the patient cannot move; depth of sedation must then be judged by other means.
Evidence & validation
Developed and validated by Sessler and colleagues with strong inter-rater reliability, RASS is endorsed within the Society of Critical Care Medicine PADIS guidelines and is the recommended sedation scale in many intensive-care sedation and delirium-prevention bundles.
Frequently asked questions
What is the target RASS for a ventilated patient?
For most ventilated patients a target of 0 to −2 is used, keeping them calm but rousable. Deeper sedation is reserved for specific indications and is associated with worse outcomes.
How is RASS assessed?
Observe the patient first; if not alert and calm, speak to them and grade the eye-contact response; if there is no response to voice, apply physical stimulation. Record the best response on the −5 to +4 scale.
Why does RASS matter for delirium screening?
Delirium tools such as the CAM-ICU require a RASS of −3 or above. A patient sedated to −4 or −5 cannot be assessed, so RASS is the gateway step before delirium screening.
What does a negative RASS mean?
Negative scores indicate sedation, from −1 (drowsy) to −5 (unarousable). The more negative the value, the deeper the sedation and the less the patient responds to voice and then touch.
Can RASS be used in a paralysed patient?
No. Neuromuscular blockade prevents the movement and eye-opening the scale relies on, so RASS is not valid and sedation depth must be judged by other clinical means.
References
- Sessler CN, Gosnell MS, Grap MJ, et al. The Richmond Agitation–Sedation Scale: validity and reliability in adult intensive care unit patients. Am J Respir Crit Care Med. 2002;166(10):1338–1344.
- 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 (PADIS). Crit Care Med. 2018.
About the creator
Sessler CN et al.
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