Ely EW, Truman B, Shintani A, Thomason JWW, Wheeler AP, Gordon S, Francis J, Speroff T, Gautam S, Margolin R, Sessler CN, Dittus RS, Bernard GR. Monitoring Sedation Status Over Time in ICU PatientsReliability and Validity of the Richmond Agitation-Sedation Scale (RASS). JAMA. 2003;289(22):2983-2991. doi:10.1001/jama.289.22.2983
Author Affiliations: Department of Medicine, Division of Allergy, Pulmonary, and Critical Care Medicine (Drs Ely, Thomason, Wheeler, and Bernard, and Ms Truman), and Geriatric Psychiatry and Neuroscience (Drs Gordon and Margolin), Center for Health Services Research (Drs Ely, Shintani, Dittus, Gordon, Speroff, and Ms Truman) of Vanderbilt University School of Medicine, Nashville, Tenn; Geriatric Research Education and Clinical Center of the Veterans Administration Tennessee Valley Healthcare System, Nashville (Drs Ely, Gordon, Speroff, and Dittus); Department of Preventive Medicine, Division of Biostatistics (Dr Gautam), Division of Quality and Data Management (Dr Francis), St Vincent Hospital Health System, Indianapolis, Ind; Department of Internal Medicine, Virginia Commonwealth University, Richmond (Dr Sessler).
Caring for the Critically Ill Patient Section Editor: Deborah J. Cook, MD, Consulting Editor, JAMA.
Context Goal-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
Objective To test the reliability and validity of the Richmond Agitation-Sedation
Design Prospective cohort study.
Setting Adult medical and coronary ICUs of a university-based medical center.
Participants Thirty-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 Measures Interrater 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.
Results In 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.
Conclusions The 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.
Increased scrutiny has recently been placed on appropriate titration
of sedative and analgesic medications in critically ill patients, especially
those being treated with mechanical ventilation.1- 5 Patient
comfort should be a primary goal in the intensive care unit (ICU), including
adequate pain control,6,7 anxiolysis,
and prevention and treatment of delirium.8 However,
achieving an appropriate balance of sedation and analgesia is challenging.9- 11 Without rational and
agreed on target levels of sedation, different members of the health care
team will have disparate treatment goals,12- 14 increasing
the chance for iatrogenic complications and potentially impeding recovery.
The clinical practice guidelines of the Society of Critical Care Medicine
emphasize the need for goal-directed delivery of psychoactive medications.8,15 Although the Ramsay Scale (RS)16 was not originally intended for use as a clinical
monitoring tool, it has been used for decades in both clinical practice and
research. Still, most patients are not monitored with any scale to guide delivery
of sedative medications. Objective, goal-directed sedation therapy is now
the recommended standard to avoid oversedation and to promote earlier extubation.2,8,14,17- 19 As
pointed out by others,1,20- 22 very
few of the available sedation scales have been appropriately tested for reliability
and validity. Even among available instruments that have been tested for reliability
and validity,23- 26 none
discretely separates verbal from physical stimulation (ie, the potency of
the stimulus) in generating scores at pivotal levels of sedation. Two recent
systematic reviews concluded that goal-directed sedative and analgesic administration
would be enhanced if such instruments were shown to detect variations in level
of consciousness over time and according to delivery of psychoactive drugs.1,26 Other investigators observed cardiac
surgery patients over time, yet the duration of monitoring was only 6 hours,
the sample size was small (only 14 patients followed up to extubation), and
correlations with drug doses were not published.27
The Richmond Agitation-Sedation Scale (RASS)28,29 was
developed by a multidisciplinary team at Virginia Commonwealth University
in Richmond. It is a 10-point scale that can be rated briefly using 3 clearly
defined steps and that has discrete criteria for levels of sedation and agitation.
A unique feature of the RASS is that it uses the duration of eye contact following
verbal stimulation as the principal means of titrating sedation. Hence, this
scale's validation could be linked to both arousal and content of thought—the
2 components of consciousness.30 We determined
that the duration of eye contact could be easily measured with minimal training,
allowing reproducibility and increased acceptability of the instrument by
bedside physicians, nurses, and researchers alike. The RASS has been demonstrated
to have excellent interrater reliability in a broad range of adult medical
and surgical ICU patients and to have excellent validity when compared with
a visual analogue scale and selected sedation scales.29
The current investigation was designed to extend the reliability and
validity testing of the RASS in novel ways to include assessment of sedation
over time, correlation of the RASS with independent neuropsychiatric experts'
measures of level of consciousness and formally measured content of consciousness
(ie, inattention and delirium), doses of sedative and analgesic medications,
and objective measurement of brain function using bispectral array electroencephalography.
This investigation was conducted in the adult medical and coronary ICUs
at Vanderbilt University Medical Center, a 641-bed tertiary-care, academic
medical center. The institutional review board approved the study, and written
informed consent was obtained from the patients or proxies. Reliability and
validity testing was performed in 2 phases. We enrolled patients into the
reliability testing cohort from July 21, 1999, to September 7, 1999, and into
the validity testing cohort from February 1, 2000, to May 3, 2001.
While none of the data in this report have been previously published,
other data from this cohort of patients have been published as would be expected
from prospective cohort investigations that have the capacity to address different
issues. Specifically, the 38 patients from the RASS reliability testing cohort
were those reported in the first Confusion Assessment Method for the Intensive
Care Unit (CAM-ICU) study,31 and 96 of the
patients from this RASS validity testing were those reported in the second
CAM-ICU study cohort.32
Patients receiving and not receiving mechanical ventilation were screened
during reliability testing to ensure reliability in verbal and nonverbal patients.
Any adult admitted to the ICU who did not meet the following a priori exclusion
criteria was eligible for enrollment: a history of severe dementia, psychosis,
or neurologic disease (n = 12); patient or family refusal to participate (n
= 8); and admission to the ICU after the predefined cap of 10 study patients
per day (because of research staffing limitations) had been reached (n = 18).
Consecutive patients receiving mechanical ventilation were enrolled into the
validity testing cohort (and followed up until ICU discharge), because the
primary challenge and use for sedation scales in the ICU are for patients
who are nonverbal and are intubated. Patients were excluded if they had a
history of psychosis or neurologic disease (n = 16), were non–English-speaking
or deaf (n = 5), were extubated or had died before nurses' screen (n = 15),
were previously enrolled in reliability cohort (n = 5), or because of patient
or family refusal to participate (n = 9).
During this investigation, no protocol to guide analgesia, sedation,
or neuromuscular blockade existed in our ICU, and no objective target levels
of sedation were routinely identified according to disease state or ventilator
settings. All doses of narcotics, benzodiazepines, propofol, and neuromuscular
blocking agents were recorded prospectively in 8-hour intervals throughout
the investigation. Administered narcotics were either morphine or fentanyl.
Administered benzodiazepines were either lorazepam or midazolam (the midazolam
dose was converted to lorazepam equivalents by dividing by 3 to achieve equipotent
dose33). If neuromuscular blocking agents had
been given within 8 hours of RASS assessment, patient observations were excluded
from our pharmacological analyses.
Prior to this investigation, raters had no experience with the RASS.
Sessler et al29 from the Virginia Commonwealth
University provided a 1-page handout with the RASS description and the Procedure
for RASS assessment (Table 1)
to the investigators. No other formal training was received or required. All
raters performed the RASS using the same sequence of 3 steps as outlined in Table 1. If the patients were alert or
agitated prior to stimulation, they were scored 0 to + 4 accordingly. If patients
were not spontaneously alert, they were then called by name to look at the
rater, with the duration of eye contact measured, at which time a positive
response was scored accordingly as −1 to −3. If the patients did
not respond to verbal stimulation, they were then physically stimulated (ie,
shoulder shake and/or sternal rub) and scored according to their response
as –4 or –5. If calm and not alert prior to verbal and physical
stimulation, patients were then rated as −1 to −5 (as standardized
in Table 1) even if they became
agitated on stimulation. Assessments required less than 20 seconds.
Two critical care study nurses, an intensivist, and a neuropsychiatric
expert performed daily, independent RASS ratings during each patient's ICU
stay. Interrater reliability assessments were conducted in the afternoon,
and none of the raters had access to the others' scores at any time. The study
nurses performed simultaneous ratings (one interacted with and rated the patient
while the other observed and rated the same patient), while the intensivists
and neuropsychiatric experts performed their independent RASS ratings within
4 hours of the nurses' ratings. In addition, both nurses performed independent
RS16 ratings and Glasgow Coma Scale (GCS)34 ratings for each patient.
Validity, the extent to which the instrument measured what it was intended
to measure, was tested in 3 ways according to standard definitions.35,36Criterion validity, the extent to which a measure relates to a set of externally derived
criteria, was tested on the first 96 patients of the validation cohort by
comparing patients' RASS levels against reference standard evaluations performed
by neuropsychiatric experts (ie, a geriatric psychiatrist and a geriatric
neuropsychologist) who rated patients' levels of consciousness as normal,
delirious, stuporous, or comatose using standardized definitions that did
not incorporate the RASS in any way.31,32,37 The
neuropsychiatric experts were blinded to the study nurses' RASS ratings and
the 2 ratings were performed within 4 hours of one another. To address 2 areas
of sedation monitoring that have not been studied adequately to date,21,26 we analyzed data for patients who
were and were not receiving mechanical ventilation and the ability of the
RASS to identify changes in level of consciousness over time (as rated by
the neuropsychiatric expert).
Construct validity, the extent to which a measure
relates to the other measures that would theoretically support the concept
(or construct) being measured, also should be measured whenever no universally
accepted criterion exists.35,38,39 Thus,
construct validity was tested 5 ways in patients with normal and abnormal
consciousness: (1) RASS scores were compared with abnormalities in the "content
of consciousness" as rated by the nurse using a screening examination for
attention,31 which served as a measure of content
of consciousness since this is the pivotal feature of delirium32;
(2) comparisons were made against ratings of the GCS, a standard instrument
widely used in neurologic monitoring throughout the world; (3) RASS scores
were correlated with the quantity of sedative and analgesic drugs administered
to patients in the 8- and 24-hour periods prior to their assessments; (4)
outcomes of planned extubation were compared with concurrent RASS scores;
and (5) bispectral-XP electroencephalography (BIS-XP EEG) (Aspect Medical
Systems Inc, Newton, Mass) was measured and correlated with RASS scores as
described below. Both the GCS and BIS-XP EEG measurements were recorded at
the same time as the RASS ratings, while the ratings by the neuropsychiatric
experts occurred within 4 hours of the study nurses' ratings. The decision
to extubate was made by the attending physician according to the results of
spontaneous breathing trials with no knowledge of the RASS scores and without
a predetermined neuorologic status. Extubations were considered successful
if the patient remained extubated and did not receive mechanical ventilation
for 48 hours. Detailed reasons for unsuccessful extubation were not recorded.
Face validity, the extent to which an instrument
appears to measure what it is intended to measure, was tested by surveying
critical care nurses about whether or not the RASS was an appropriate and
clinically useful measure of agitation and sedation. The survey included 4
relevant questions each worded 2 different ways and embedded within other
questions regarding patient management. The survey asked nurses to rate the
following 4 statements using a 5-point Likert scale (1 [strongly disagree]
to 5 [strongly agree]): (1) RASS levels for agitation (+1 to + 4) are clinically
relevant and easy to score; (2) it makes sense clinically that the RASS assessment
begins with verbal stimulation (−1 to − 3) and then moves to physical
stimulation (−4 to − 5); (3) use of the RASS improves communication
among the health care team; and (4) use of the RASS provides a team consensus
for target-level sedation.
Bispectral index uses a nonlinear signal processor to measure brain
wave activity in the form of raw electroencephalography (EEG) and to create
a score ranging from 100 (awake) to 0 (no cortical activity). Both raw EEG
and BIS-XP EEG data were recorded using a fronto-temporal montage with disposable
sensors that were connected to a portable EEG monitor (A1050, Aspect Medical
Systems Inc).40,41 As opposed
to earlier versions of the BIS-XP EEG used in other investigations designed
for the anesthetized surgical patients in the operating room,42 this
version has been specifically designed for use in ICU patients who are sedated
and receiving mechanical ventilation to reduce electromyographic interference.43,44 Electrode impedance values were acceptable
if they were no greater than 5 kΩ and if the threshold for acceptable
signal quality index was greater than 80%. Raw EEG data was sampled at 128
samples per second and recorded continuously in real time; processed variables
were downloaded and recorded every 5 seconds. The data sampling rate was 256
times per second with filter settings of 70 Hz for the high frequency (70
Hz) and 2 Hz for the low frequency. The study nurses were blinded to both
the raw EEG and the BIS-XP EEG data. The continuous EEG recording was later
reviewed by a separate investigator blinded to the clinical assessment ratings
to identify the reported baseline value (ie, a stable portion of the tracing
that the EEG would return to after the sensor was attached).
Patients' baseline characteristics were presented using means and SDs
for continuous variables, and frequencies and proportions for dichotomous
variables. Interrater reliability was determined for the RASS, RS, and GCS
by comparing ratings between raters using weighted κ indices and 95%
confidence intervals. For criterion validity, RASS scores were compared with
the neuropsychiatric expert rating using Wilcoxon rank sum tests. As part
of criterion validity, and to account for dependency among observations within
an individual patient, proportional odds regression analysis with generalized
estimating equations was performed to assess the neuropsychiatric expert ratings
vs RASS ratings, and odds ratios were presented. Similar analysis using Wilcoxon
rank sum tests assessed the difference between observations within a level
of consciousness of patients receiving and not receiving mechanical ventilation.
For construct validity testing, the Spearman correlation coefficient (r) was calculated for the associations between RASS scores
and onset of inattention, GCS score, daily dosage of sedative drugs, and BIS-XP
EEG results. Wilcoxon rank sum tests were used to assess significant differences
in GCS scores according to RASS levels, and proportional odds models were
used with the generalized estimating equations to analyze the relationship
over time among the RASS score, GCS score, and daily dosage of sedative drugs.
Statistical analyses were performed using SAS version 8.02 (SAS Institute
Inc, Cary NC) and STATA version 7.0 (STATA Corp, College Station, Tex).
Eighty-six patients were admitted to the medical and coronary ICUs during
the reliability testing phase, of whom 38 (44%) were enrolled. During the
validity testing phase, 325 consecutive patients receiving mechanical ventilation
were admitted to the ICU, of whom 275 (84.6%) were enrolled. Baseline characteristics
from all 313 patients are presented in Table 2. At the time of enrollment, 22 (46%) of the reliability
cohort received mechanical ventilation, while all 275 of the validation cohort
received mechanical ventilation. The 2 cohorts had a high baseline severity
of illness as measured by Acute Physiology and Chronic Health Evaluation II
(APACHE II) scores (mean [SD], 17.1 [8.7] and 25.0 [8.0]), and had a wide
variety of medical diagnoses.
Patients were evaluated on multiple occasions during their ICU stay.
The mean (SD) RASS scores for each rater were as follows: nurse 1, −1.60
(2.16); nurse 2, −1.88 (2.20); intensivist, −1.61 (2.17); and
neuropsychiatric expert, −1.50 (2.25). In 290 paired observations by
nurses, both the RASS and the RS demonstrated excellent interrater reliability
(weighted κ, 0.91 and 0.94, respectively), which were superior to GCS
(weighted κ, 0.64; P<.001 for both comparisons).
Using only the first observation for each patient (n = 38), the weighted κ
values for the RASS, RS, and GCS were unchanged at 0.95, 0.95, and 0.65, respectively.
The interrater reliability of the RASS was very high across nurses, intensivists,
and neuropsychiatric experts (Table 3).
Because reliability testing was expected to be most challenging for patients
receiving mechanical ventilation, we conducted another analysis of interrater
reliability restricted to the 22 patients who were intubated. The weighted κ
for the RASS between the 2 nurse ratings for patients who were intubated was
0.88 (95% confidence interval, 0.78-0.97).
The relative frequency that the validation cohort spent in each major
arousal category for 1833 observations in 275 patients indicated that the
patients who received mechanical ventilation spent about one third of their
time either unarousable or in a deeply sedated state (RASS score, −5
or −4; n = 548 observations), one third in a moderate to light sedation
state (RASS score, −3 to −1; n = 625 observations), and one third
in an alert and calm state (RASS score, 0; n = 619 observations). Spontaneous
agitation (RASS score, + 1 to + 4; n = 41 observations), which was rated prior
to stimulation, was an uncommon state (<5%) found by the study nurses.
Criterion validity was tested in 411 paired observations in the validation
cohort for the first 96 patients with a median of 3 observations per patient.
The results of the RASS showed excellent discrimination between levels of
consciousness as rated using the neuropsychiatric expert reference standard
(P<.001 for all) (Figure 1). Furthermore, as the neuropsychiatric expert raters and
RASS raters independently tracked level of consciousness within patients over
successive days of ICU care, RASS scores continued to correlate with expert
raters' evaluations despite fluctuations in consciousness (P<.001 for all) (Table 4).
When comparing patients over the course of their ICU stay, the reference standard
ratings of abnormal levels of consciousness (ie, delirium, stupor, and coma)
compared similarly with RASS ratings regardless of intubation status: delirium
(−2 median RASS score if intubated vs –2 median RASS score if
extubated, P = .18), stupor (−3 vs –3, P = .92), or coma (−5 vs –5, P = .62) (Figure 1).
Five methods were used to test construct validity: (1) RASS was correlated
with onset of inattention using an attention-screening examination, the pivotal
criterion for delirium (r = 0.78, P<.001). (2) To compare the RASS to the GCS, 1360 paired observations
(among 275 patients with a median of 3 observations per patient) showed excellent
correlation and discrimination (r = 0.91, P<.001) (Figure 2). The
RASS also correlated with the GCS over time (P<.001),
and the odds ratio of having higher RASS scores with greater GCS scores was
1.39 (P <.001). (3) We compared RASS scores with
the cumulative lorazepam, propofol, fentanyl, and morphine dose over the 8-hour
and 24-hour periods prior to RASS assessments (Table 5). As described in the "Methods" section, midazolam dose
was converted into lorazepam equivalents for the purposes of these analyses.
As an example of the dose-response relationship between psychoactive medication
and RASS scores, correlative data for lorazepam equivalents over 8 hours prior
to RASS assessment are shown in Figure 3.
In contrast to the benzodiazepines, correlations between RASS and fentanyl
and morphine were performed and presented as separate analyses because of
significantly different results for these 2 agents (Table 5). (4) Of 185 planned extubations in the 275 validation cohort
patients, 19 (10.3%) patients required reintubation within 48 hours. Of these
planned extubations, 137 had RASS scores available during the shift prior
to extubation, of which 13 (9.5%) were unsuccessful. The median (interquartile
range) RASS score for successful extubation was − 2 (−3 to 0)
and for unsuccessful extubation was − 3 (−3 to − 2) (P = .07). (5) From the validation cohort, a random sampling
of 124 patients was monitored over 321 days in the ICU with the BIS-XP EEG.
The RASS scores correlated with the BIS-XP EEG results over the range of levels
of consciousness (r = 0.64, P<.001
for all) (Figure 4). For patients
in 3 different, clinically relevant states (ie, spontaneously awake and alert
[RASS score, 0], arousable with verbal stimulation [RASS score, –1 to
–3], and arousable only with physical stimulation or not at all [RASS
score, –4 or –5]), the median (interquartile range) EEG values
were 96.8 (90.0-97.6), 69.0 (57.6-87.6), and 57.4 (46.4-66.3), respectively.
Face validity was demonstrated via a survey of 26 bedside critical care
nurses. According to the results of the survey, 77% of the nurses agreed or
strongly agreed that the RASS levels for agitation were clinically relevant
and easy to score. Regarding the construct of the sedation assessment, 92%
agreed or strongly agreed with the "verbal followed by physical stimulation"
scoring scheme, 69% agreed or strongly agreed that the RASS improved communication
among the managing team, and 81% agreed or strongly agreed this instrument
provided a consensus target for goal-directed delivery of sedative and analgesic
This investigation was designed to test a very brief yet structured
approach to assessment of patient sedation in the ICU for reliability and
validity, using a new, broader, and more rigorous set of validation procedures
than those previously studied. The RASS demonstrated strong interrater reliability
and criterion, construct, and face validity. In previous work, Sessler et
al29 demonstrated strong interrater reliability
of RASS between 5 nurse, pharmacist, and physician investigators in 192 consecutive
patients who did or did not receive mechanical ventilation in surgical, neuroscience,
and medical ICUs. The authors further documented strong reliability between
a nurse educator and 27 bedside nurses in more than 100 patient observations.
Building on these data, the present study included the use of neuropsychiatric
experts as reference standard raters of patients' levels of consciousness
to demonstrate criterion validity, 5 methods of confirming construct validity,
and incorporating views of bedside critical care nurses for face validity.
In keeping with the stated priorities of recent critical appraisals
of sedation scales,1,20- 22,26 the
present report shows the RASS to be valid over successive days in individual
patients, to correlate with the administered dose of sedative and analgesic
drugs as well as brain wave activity, and confirms that it is a reliable and
valid measurement for patients who were and were not receiving mechanical
This report and that by Sessler et al29 are
complementary and constitute an evaluation of the RASS in more than 600 patients,
both having avoided selection bias present in other investigations by enrolling
consecutive patients. The large sizes of these 2 investigations, combined
with the strong reliability of the instrument and the scope of our validity
testing, lend strong credibility for the use of the RASS in patient management.
The RASS itself has several important strengths that warrant comment.
Unlike other recently validated instruments,23,25 the
RASS separates verbal from physical stimulation so that the patient's level
of arousal may be graded according to the potency of the stimulus.28 It has been common to consider sedation scales valid
as long as they delineate levels of arousal (considered a surrogate of consciousness).20,23- 25,49Consciousness, however, is classically defined as the combination
of a person's level of arousal plus the content of consciousness (eg, delirium).30 Only recently has the ICU community begun to focus
on delirium as an essential element of patient comfort and outcome.8,50,51 Importantly, a key
feature of delirium is the presence or absence of inattention, which can be
measured in part by the ability of a person to maintain eye contact. Indeed,
this study demonstrated that RASS scores correlated with the onset of inattention
and delirium. These 2 main strengths of the RASS assessment procedure (ie,
completely distinguishing verbal from physical stimulation, and relying heavily
on duration of eye contact) complement the recently developed delirium monitoring
instrument, the CAM-ICU.31,32 Using
such a combined neurologic monitoring schema for patients receiving mechanical
ventilation in future trials may offer a significant advance in our ability
to measure short- and long-term cognitive outcomes of goal-directed delivery
of sedative and analgesic medications or newer pharmacological agents with
procognitive advantages over traditionally used agents in treating delirium.8,52,53
The κ values between nurses' and between physicians' paired assessments
were both 0.91, and the κ values between any nurse and physician pair
ranged from 0.79 to 0.88. While all very high, the subtle differences in these
values likely reflect that time elapsed between the nurse and physician assessments.
The fact that the correlations were high despite elapsed time between the
nurses' and physicians' assessments makes the data even more compelling.
We correlated RASS scores with quantity (ie, dose) of sedative and analgesic
medications and found highly significant yet moderately to low correlation
coefficients. Considering the broad distribution of drug dose variables and
the numerous other covariates affecting consciousness (eg, underlying illness,
electrolytes, hypoxemia, and other pharmacological agents), it would be unrealistic
to expect RASS correlation with actual dose to be any higher. Similar to other
reports on risk factors for delirium,47,54 we
found disparate correlation coefficients between RASS levels and different
drugs. For example, the highly significant correlations between RASS levels
vs lorazepam or fentanyl (both P<.001) contrast
sharply with that of morphine (P = .10). Future investigations
should attempt to determine the relative importance of other covariates contributing
to level of consciousness, such as patients' age, sex, race, disease state,
body mass index, the duration and cumulative drug levels of narcotics and
analgesics over days of ICU care, and pharmacological interindividual variability
based on drug metabolism and transport.
Most available evidence regarding sedatives and analgesics in ICU patients
indicates that it may be less important which drugs are delivered than their
proper titration using goal-directed delivery to optimize patient comfort
while avoiding complications, such as prolonged mechanical ventilation or
example, recent data showed that deeper levels of sedation at the time of
extubation, measured using the RASS, were associated with a higher likelihood
of reintubation.56 Future investigations should
evaluate the usefulness of this tool in single or multicenter clinical trials,
local or national quality-improvement collaboratives,57 and
different management strategies based on goal-directed delivery.
Some patients are sedated but subsequently demonstrate agitation following
stimulation,5,20 which represents
another limitation of this investigation. Since we only recorded a single
RASS score per patient assessment, we do not know the number of times patients
were initially sedated and assigned negative RASS scores, only to become agitated
minutes later. It may be surprising to some that so few patients in this investigation
and that by Sessler et al29 were found in the
vigilant or agitated state, which we believe reflects a recurring theme of
oversedation in critical care.2,10,17 On
the other hand, undersedation and inadequate relief of symptoms could lead
to problems such as unaddressed pain or anxiety,7,58 and
ultimately posttraumatic stress disorder.59- 62 The
fact that the RASS has an expanded set of clinically relevant scores for tracking
both agitation and sedation makes it well suited for future investigators
to help better understand the clinical implications of such crossover states.
While the RASS demonstrated excellent face validity among our nurses,
reports of ongoing large-scale implementation projects using the RASS will
aid in our understanding of how to effect sustained change in the practice
patterns of ICU nurses, therapists, pharmacists, and physicians using such
instruments. Preliminary work in this area has already been reported from
academic settings,63 but should be forthcoming
from community settings as well.
Lastly, as a barometer of brain wave activity, we used BIS-XP EEG monitoring
in a method comparable with that used by other investigators.27,42,44 The
BIS-XP used in this investigation was an advance over that of earlier versions
of BIS42 because of improved screening of an
electromyographic artifact.43,64 However,
the overlapping BIS values at different RASS levels (Figure 4) may be the result of the broad distribution of psychoactive
drugs administered to this cohort and their interindividual effects on brain
wave activity or merely a limitation in this emerging EEG technology.
The RASS, which takes less than 20 seconds to perform and requires minimal
training,29 has been shown to be highly reliable
among multiple types of health care professionals. The RASS has an expanded
set of scores at pivotal levels of sedation that are determined by patients'
response to verbal vs physical stimulation, which will help the clinician
in titrating medications. This extensive body of new data, with a variety
of unique approaches to assess an agitation-sedation scale, expands the usefulness
of such instruments for patient care. In accordance with recent recommendations,
health care professionals should use valid and reliable instruments such as
the RASS to implement sedative and analgesic drug delivery protocols for patients
receiving mechanical ventilation. The driving unmet need for goal-directed
sedation practice has been met—now an instrument has been shown to detect
variations in level of consciousness over time. Taken together, advances in
neurologic assessment provided by the RASS and the CAM-ICU should lead to
better characterization of acute brain dysfunction as an organ failure, reductions
in the random variation with which patients' sedatives are currently managed,
and appropriate interventions aimed at prevention or reversal of acute brain