RASS

Overview

The Richmond Agitation-Sedation Scale (RASS) measures a patient's level of agitation or sedation in the ICU on a single 10-level scale from +4 (combative) to −5 (unarousable), with 0 meaning alert and calm. Positive values describe agitation, negative values sedation. In the derivation study, inter-rater reliability among two physicians, two nurses and one pharmacist was excellent (r = 0.956; κ = 0.73) and held across medical, surgical, cardiac surgery, coronary and neuroscience ICUs; RASS correlated highly with a visual analogue scale of sedation (r = 0.93) ^[1].

A subsequent prospective cohort study in medical and coronary ICUs (275 ventilated patients for validity testing) confirmed excellent inter-rater reliability (weighted κ = 0.91). RASS was the first sedation scale validated for detecting changes in sedation status over consecutive ICU days, and it correlated with the administered doses of sedatives and analgesics ^[2]. The 2013 SCCM PAD guidelines recommend RASS and the Sedation-Agitation Scale (SAS) among the available sedation scales ^[3], and the two are regarded as the most validated and reliable sedation scales in ICU use ^[4].

RASS is routinely paired with delirium screening tools such as the CAM-ICU, which was validated for mechanically ventilated patients ^[5] and includes an altered level of consciousness as one of its four features ^[3].

Scale

Score	Level	Description
+4	Combative	Overtly combative or violent; immediate danger to staff
+3	Very agitated	Pulls on or removes tube(s) or catheter(s), or aggressive behaviour towards staff
+2	Agitated	Frequent non-purposeful movement or patient–ventilator dyssynchrony
+1	Restless	Anxious or apprehensive, but movements not aggressive or vigorous
0	Alert and calm	—
−1	Drowsy	Not fully alert, but sustained awakening (eye opening / eye contact) to voice (> 10 s)
−2	Light sedation	Briefly awakens with eye contact to voice (< 10 s)
−3	Moderate sedation	Movement or eye opening to voice, but no eye contact
−4	Deep sedation	No response to voice, but movement or eye opening to physical stimulation
−5	Unarousable	No response to voice or physical stimulation

Assessment Procedure

1. Observe the patient. If alert and calm, score 0. If the patient is restless, agitated, or combative, score +1 to +4.
2. If not alert, call the patient by name and ask them to open their eyes and look at you (repeat once if needed). Sustained awakening with eye contact (> 10 s): −1. Brief awakening with eye contact (< 10 s): −2. Any movement to voice but no eye contact: −3.
3. If there is no response to voice, stimulate physically by shaking the shoulder and/or rubbing the sternum. Any movement to physical stimulation: −4. No response: −5.

The assessment relies on the duration of eye contact after verbal stimulation and takes less than 20 seconds to perform ^[3].

Interpretation & Sedation Targets

The SCCM PADIS 2018 guideline makes a conditional recommendation for light rather than deep sedation in critically ill, mechanically ventilated adults ^[6][4]. There is, however, no defined RASS cutoff for light sedation, which limits comparison between studies ^[4]: studies have, for example, defined light sedation as RASS −2 to 0 ^[3] and a large trial comparing dexmedetomidine with usual sedation (3,912 patients) targeted RASS −2 to +1 ^[7]. The target should therefore be set individually for each patient.

RASS	Meaning	Consider
+1 to +4	Agitation	Pain (assessed with BPS or CPOT) and hyperactive delirium, which presents in the positive RASS range [3]
0 to −2	Alert to lightly sedated	Range used as light sedation in studies [3]
−3	Moderate sedation	Counted as deep sedation in outcome studies [8] — reassess whether intended
−4 to −5	Coma range [3]	Reassess whether intended; delirium screening is limited (e.g. ICDSC items 1–4 cannot be completed) [3]

Deep sedation is not harmless: in a multicentre cohort from 25 Australian and New Zealand hospitals, early deep sedation (RASS −3 to −5 in the first 48 hours) independently predicted delayed extubation and higher hospital and 180-day mortality ^[8].

ABCDEF Bundle

Sedation monitoring with RASS is part of the C component ("Choice of analgesia and sedation") of the ICU Liberation ABCDEF Bundle, an evidence-based guide for coordinating ICU patient care ^[3]:

• A — Assess, prevent, and manage pain
• B — Both spontaneous awakening and spontaneous breathing trials
• C — Choice of analgesia and sedation
• D — Delirium (e.g. CAM-ICU / ICDSC)
• E — Early mobility
• F — Family engagement

Scientific Validity & Limitations

RASS and the SAS ^[9] are considered the two most validated and reliable ICU sedation scales ^[4]. RASS correlated with both the Ramsay scale (r = −0.78) and the SAS (r = 0.78) in its derivation study ^[1], and RASS and Ramsay both showed excellent inter-rater reliability (weighted κ 0.91 and 0.94), superior to the Glasgow Coma Scale (0.64) ^[2]. Unlike the Ramsay scale, which has a single agitation category, RASS grades agitation in four levels ^[3][9].

Known limitations:

• Requires a motor or eye response: every level is defined by the patient's movement, eye opening or eye contact, so RASS cannot grade sedation depth in patients under neuromuscular blockade.
• Not a pain or delirium measure: RASS describes arousal only. Pain should be assessed separately (BPS and CPOT are the most valid behavioural pain scales for patients unable to communicate), and delirium with CAM-ICU or ICDSC ^[3].
• No agreed definition of light sedation: studies use different RASS cutoffs, which limits comparison of sedation targets and outcomes across studies ^[4].
• Inter-rater agreement is high, not perfect: κ ranged from 0.64 to 0.82 across patient subgroups in the derivation study ^[1], and each score is a single bedside observation of a state that can change over time.

Literature

1. Sessler CN, Gosnell MS, Grap MJ, Brophy GM, O'Neal PV, Keane KA, Tesoro EP, Elswick RK. 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. doi:10.1164/rccm.2107138
2. Ely EW, Truman B, Shintani A, et al. Monitoring sedation status over time in ICU patients: reliability and validity of the Richmond Agitation-Sedation Scale (RASS). JAMA. 2003;289(22):2983–2991. doi:10.1001/jama.289.22.2983
3. Marra A, Ely EW, Pandharipande PP, Patel MB. The ABCDEF Bundle in Critical Care. Crit Care Clin. 2017;33(2):225–243. doi:10.1016/j.ccc.2016.12.005
4. Boncyk C, Nahrwold DA, Hughes CG. Targeting light versus deep sedation for patients receiving mechanical ventilation. J Emerg Crit Care Med. 2018;2:79. doi:10.21037/jeccm.2018.10.03
5. 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. doi:10.1001/jama.286.21.2703
6. 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. doi:10.1097/CCM.0000000000003299
7. Stollings JL, Kotfis K, Chanques G, Pun BT, Pandharipande PP, Ely EW. Delirium in critical illness: clinical manifestations, outcomes, and management. Intensive Care Med. 2021;47(10):1089–1103. doi:10.1007/s00134-021-06503-1
8. Shehabi Y, Bellomo R, Reade MC, et al. Early intensive care sedation predicts long-term mortality in ventilated critically ill patients. Am J Respir Crit Care Med. 2012;186(8):724–731. doi:10.1164/rccm.201203-0522OC
9. Riker RR, Picard JT, Fraser GL. Prospective evaluation of the Sedation-Agitation Scale for adult critically ill patients. Crit Care Med. 1999;27(7):1325–1329. doi:10.1097/00003246-199907000-00022