Richmond Agitation-Sedation Scale (RASS)
The Richmond Agitation-Sedation Scale (RASS) is a validated 10-point scale ranging from +4 (combative) to -5 (unarousable) that is the preferred tool for assessing sedation depth and agitation in adult ICU patients 1.
Scale Structure and Scoring
The RASS uses a 10-level scoring system that captures both agitation and sedation states 1:
Agitation Levels (Positive Scores)
- +4: Combative - overtly combative or violent; immediate danger to staff
- +3: Very agitated - pulls or removes tubes or catheters; aggressive
- +2: Agitated - frequent non-purposeful movement or patient-ventilator dyssynchrony
- +1: Restless - anxious or apprehensive but movements not aggressive or vigorous
Calm State
- 0: Alert and calm
Sedation Levels (Negative Scores)
- -1: Drowsy - not fully alert, but has sustained (≥10 seconds) awakening with eye contact to voice
- -2: Light sedation - briefly (less than 10 seconds) awakens with eye contact to voice
- -3: Moderate sedation - any movement (but no eye contact) to voice
- -4: Deep sedation - no response to voice, but any movement to physical stimulation
- -5: Unarousable - no response to voice or physical stimulation
Clinical Application
Assess sedation at least 4 times per shift and as needed 1. The guidelines establish clear definitions for sedation depth based on RASS scores 1:
- Agitated: RASS +1 to +4
- Awake and calm: RASS 0
- Lightly sedated: RASS -1 to -2
- Deeply sedated: RASS -3 to -5
Target Sedation Goals
The recommended target for most mechanically ventilated ICU patients is RASS -2 to 0 (light sedation to awake and calm) 1, 2. This target allows patients to purposefully follow commands without agitation and is associated with improved outcomes including shorter duration of mechanical ventilation and reduced ICU length of stay 1.
Management Algorithm Based on RASS
If under-sedated (RASS >0): First assess and treat pain, then consider sedatives as needed. Non-benzodiazepines are preferred unless alcohol or benzodiazepine withdrawal is suspected 1.
If over-sedated (RASS <-2): Hold sedatives until patient reaches target range, then restart at 50% of previous dose 1.
Evidence for Validity and Reliability
The RASS demonstrates excellent inter-rater reliability with weighted kappa values of 0.73-0.95 across multiple studies 1, 3. The scale has been validated in diverse ICU populations including medical, surgical, cardiac surgery, coronary, and neuroscience ICUs, in both mechanically ventilated and non-ventilated patients 1, 3.
The RASS is superior to older scales like the Ramsay Sedation Scale, showing stronger inter-rater agreement (weighted κ = 0.879 vs 0.449) and better internal consistency 4. The 2013 PAD Guidelines specifically identified RASS (along with SAS) as having the most robust psychometric properties among all available sedation scales 1.
Important Clinical Caveats
RASS is a subjective clinical assessment and may not accurately reflect objective sedation depth. Studies show substantial variability in objective measures (like bispectral index) within the same RASS category 5, 6. For example, patients scored as RASS -5 can have BIS values ranging from near 0 (burst suppression) to over 80 (near awake states) 6.
For patients receiving neuromuscular blocking agents, brain function monitoring should be used as the primary sedation assessment tool, as RASS cannot be assessed in paralyzed patients 1.
Documentation compliance is often suboptimal in clinical practice. Audits show only 33% of required hourly RASS assessments are documented despite 75% accuracy when performed 7. This emphasizes the need for systematic implementation and staff education.
The RASS has been successfully validated in pediatric populations 8 and translated into multiple languages including Swedish 9, demonstrating its broad applicability across different clinical settings and cultures.