Monitoring Sedation Status Over Time in ICU Patients: Reliability and Validity of the Richmond Agitation-Sedation Scale (RASS)
2003
ContextGoal-directed delivery of sedative and analgesic medications is recommended
as standard care in intensive care units (ICUs) because of the impact these
medications have on ventilator weaning and ICU length of stay, but few of
the available sedation scales have been appropriately tested for reliability
and validity.ObjectiveTo test the reliability and validity of the Richmond Agitation-Sedation
Scale (RASS).DesignProspective cohort study.SettingAdult medical and coronary ICUs of a university-based medical center.ParticipantsThirty-eight medical ICU patients enrolled for reliability testing (46%
receiving mechanical ventilation) from July 21, 1999, to September 7, 1999,
and an independent cohort of 275 patients receiving mechanical ventilation
were enrolled for validity testing from February 1, 2000, to May 3, 2001.Main Outcome MeasuresInterrater reliability of the RASS, Glasgow Coma Scale (GCS), and Ramsay
Scale (RS); validity of the RASS correlated with reference standard ratings,
assessments of content of consciousness, GCS scores, doses of sedatives and
analgesics, and bispectral electroencephalography.ResultsIn 290-paired observations by nurses, results of both the RASS and RS
demonstrated excellent interrater reliability (weighted κ, 0.91 and
0.94, respectively), which were both superior to the GCS (weighted κ,
0.64; P<.001 for both comparisons). Criterion
validity was tested in 411-paired observations in the first 96 patients of
the validation cohort, in whom the RASS showed significant differences between
levels of consciousness (P<.001 for all) and correctly
identified fluctuations within patients over time (P<.001).
In addition, 5 methods were used to test the construct validity of the RASS,
including correlation with an attention screening examination (r = 0.78, P<.001), GCS scores (r = 0.91, P<.001), quantity of different
psychoactive medication dosages 8 hours prior to assessment (eg, lorazepam: r = − 0.31, P<.001),
successful extubation (P = .07), and bispectral electroencephalography
(r = 0.63, P<.001). Face
validity was demonstrated via a survey of 26 critical care nurses, which the
results showed that 92% agreed or strongly agreed with the RASS scoring scheme,
and 81% agreed or strongly agreed that the instrument provided a consensus
for goal-directed delivery of medications.ConclusionsThe RASS demonstrated excellent interrater reliability and criterion,
construct, and face validity. This is the first sedation scale to be validated
for its ability to detect changes in sedation status over consecutive days
of ICU care, against constructs of level of consciousness and delirium, and
correlated with the administered dose of sedative and analgesic medications.
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