What does the Richmond Agitation-Sedation Scale measure?

The RASS is a validated ordinal scale grading a patient's level of arousal and agitation, from combative through calm and alert to deep sedation and unarousable, allowing sedation to be titrated to a defined target.

Why assess sedation level before screening for delirium?

Delirium screening tools such as the CAM-ICU require a minimum level of arousal; assessing sedation depth first establishes whether the patient is responsive enough to be evaluated for delirium.

Assessment of Consciousness and Sedation Scales

Reliable bedside measurement of arousal, sedation depth and delirium underpins safe critical care: it lets clinicians titrate sedatives to a defined target rather than guessing, and it enables systematic detection of delirium. Validated instruments such as the Richmond Agitation-Sedation Scale (RASS) and the CAM-ICU made this assessment reproducible across observers.

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Definition

Consciousness and sedation assessment in critical care is the structured evaluation of a patient's arousal and agitation using validated ordinal scales (such as the RASS), used to set and monitor a sedation target and to anchor delirium screening.

Scope

This topic covers the standardised tools used to assess level of consciousness, agitation and sedation depth in critically ill patients, and how they connect to delirium screening and to targeted, light-sedation strategies. It is a reference overview of the assessment instruments, not a guide to setting sedation targets for an individual patient.

Key concepts

Level of arousal and agitation
Richmond Agitation-Sedation Scale (RASS)
Sedation-Agitation Scale (SAS)
Targeted (goal-directed) sedation
Sequential assessment: sedation level before delirium screening
Inter-rater reliability and validity
Link to daily awakening and light-sedation strategies

Clinical relevance

Using a validated, reproducible scale to target sedation supports the light-sedation strategies associated with shorter ventilation and less delirium, and a defined arousal level is the entry point for delirium screening. This entry summarises the assessment tools and their evidence base for orientation; it is not a basis for setting an individual patient's sedation target.

Evidence & guidelines

The Richmond Agitation-Sedation Scale (Sessler et al., 2002) is a widely validated tool for grading sedation and agitation, and the CAM-ICU (Ely et al., 2001) builds on a defined arousal level to screen for delirium. The 2018 PADIS guidelines (Devlin et al.) recommend assessing sedation depth and delirium with validated tools and titrating sedation to light targets where feasible.

History

Early ICU sedation was managed subjectively, with limited reproducibility between clinicians. The development and validation of ordinal sedation scales (such as the SAS and, in 2002, the RASS) and of structured delirium instruments (CAM-ICU, 2001) established reproducible bedside assessment, which became the foundation for goal-directed, light-sedation protocols in the 2013 and 2018 SCCM guidelines.

Key figures

Curtis Sessler
E. Wesley Ely
Richard Riker
John Devlin

Seminal works

sessler-2002-rass
ely-2001-camicu
devlin-2018

Frequently asked questions

What does the Richmond Agitation-Sedation Scale measure?: The RASS is a validated ordinal scale grading a patient's level of arousal and agitation, from combative through calm and alert to deep sedation and unarousable, allowing sedation to be titrated to a defined target.
Why assess sedation level before screening for delirium?: Delirium screening tools such as the CAM-ICU require a minimum level of arousal; assessing sedation depth first establishes whether the patient is responsive enough to be evaluated for delirium.