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Acute Pain Assessment in Sedated Patients in the
Postanesthesia Care Unit
Sherily Pereira-Morales, RNA, PhD1,2,*, Carmen M. Arroyo-Novoa, RN, PhD1, Annette
Wysocki, RN, PhD2, and Lucille Sanzero Eller, RN, PhD3
1Medical Sciences Campus, School of Nursing, University of Puerto Rico, San Juan, Puerto Rico
2College of Nursing, University of Massachusetts-Amherst, Amherst, MA
3School of Nursing, Rutgers University, Newark, NJ
Abstract
Context—Acute postoperative pain remains inadequately assessed and managed. A valid
instrument that assesses acute pain in sedated postanesthesia care unit (PACU) patients is needed.
Objectives—Two behavioral pain assessment instruments, the nonverbal pain scale revised
(NVPS-R) and critical care pain observation tool (CPOT), were used to determine whether these
instruments adequately assess acute pain in the PACU.
Methods—A crossover study design was used. The study was conducted in the Medical Services
Administration at the Puerto Rico Medical Center. Upon PACU arrival, patient sedation levels
were evaluated using the Richmond Agitation Sedation Scale. Acute pain was assessed using the
CPOT (scored, 0 to 8) and the NVPS-R (scored, 0 to 10) at time points 0, 15, 30, 45, 60, 90, and
120 minutes. Descriptive statistics and mixed model regression analysis were used to compare
pain score assessment between instruments.
Results—Clinically significant increases in vital signs and respiratory indicators using the
NVPS-R were not seen in patients with significant pain at time 0, 15, and 120 minutes. The CPOT
vocalization indicator was more frequent in patients with significant pain.
Conclusions—Findings suggest that NVPS-R and CPOT can assess acute pain in sedated
PACU patients. In patients with significant pain, the CPOT vocalization indicator was more
consistent than physiological and respiratory indicators in detecting acute pain. Thus, our data do
not support the exclusive use of vital sign indicators to assess acute pain, suggesting the
superiority of the CPOT for the assessment of acute pain in sedated PACU patients.
Keywords
acute pain assessment; behavioral pain scales; critical care pain observation tool (CPOT);
nonverbal pain scale revised (NVPS-R); postanesthesia care unit (PACU)
*Reprints: Sherily Pereira-Morales, RNA, PhD, P.O. Box 365067, San Juan 00936-5067, Puerto Rico (sherily.pereira@upr.edu).
The authors declare no conflict of interest.
HHS Public Access
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Clin J Pain. Author manuscript.
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Acute pain represents a significant concern for surgical postanesthesia care unit (PACU)
patients during the early postoperative period and remains inadequately assessed and
managed.1 The American Pain Society, the American Society of Regional Anesthesia and
Pain Medicine, and the American Society of Anesthesiologists (ASA) Committee on
Regional Anesthesia reported a gap in the assessment of acute pain in postoperative sedated
patients unable to self-report pain.1 The most commonly used instrument for the assessment
of acute pain is the numeric rating scale, considered the gold standard for pain assessment. It
is designed to evaluate pain intensity in conscious patients who can report their pain.2 The
absence of specific recommendations from professional societies and health institutes for the
use of specific instruments and/or protocols for pain assessment in sedated PACU patients
after general anesthesia, could affect the early assessment and adequate management of
acute postoperative pain.
According to data reported by the Centers for Disease Control and Prevention, 〜100 million
surgical procedures are performed in the United States each year; of these, 40% are in an
inpatient setting.3 Data suggest that 80% of those receiving inpatient surgery experience
pain postoperatively.4
Several studies examined the efficacy of the management of postoperative pain in surgical
inpatients. In 2003, Apfelbaum et al5 published a retrospective study of postoperative pain in
patients who received inpatient or outpatient surgery. Pain reported by participants varied by
whether their surgeries occurred within the last year or within the past 2 to 5 years. Those
with surgeries in the last year reported lower incidences of acute pain overall. Participants
reported an 80% to 84% incidence of acute pain. Of those, 44% to 51% reported moderate
pain, and 38% to 42% reported severe to extreme pain. Similarly, in a recent retrospective
study, 91.8% of those who received inpatient surgery (N=146) experienced pain, with 47%
of these reporting moderate postoperative pain, and 32% of these reporting severe to
extreme pain. In contrast, in a recent prospective study of surgical inpatients (N=441),4
Buvanendran et al6 reported a 66% incidence of pain at discharge, with 54% of participants
reporting moderate pain, and only 12% reporting severe to extreme pain. Despite differences
in methodology, taken together, these studies suggest a gradual decrease in postoperative
pain intensity over time. However, the incidence of acute postoperative pain remains a
significant issue.
Evidence-based recommendations are needed to identify an optimal behavioral pain
instrument for acute pain assessment in postoperative adult patients who cannot self-report
their pain.1 In some instances the assessment of acute pain begins with a subjective scale,
after patients are able to self-report pain. Although patient safety must always be considered
in the use of sedation and analgesia, judicious use in unconscious patients is warranted.
Some studies, including a functional brain imaging study, reported patterns of nervous
system activation in unconscious patients similar to those of conscious controls, suggesting
that pain perception may be intact in unconscious patients, and indicate stimulation of the
pain regions of the brain.7 “The inability to communicate verbally does not negate the
possibility that an individual is experiencing pain and is in need of appropriate pain-
relieving treatment.”8
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The use of behavioral instruments, for the assessment of acute pain in sedated adult patients
unable to self-report is recommended by the Critical Care Medicine Association, the
American Society of Perianesthesia Nurses, the ASA, and the American Pain Society,
among others. Although they have not been examined in sedated PACU patients, behavioral
instruments studied in patients with similar characteristics include the critical care pain
observation tool (CPOT) and the nonverbal pain scale revised (NVPS-R).9–12 The main
differences between the 2 instruments are the presence of the vocalization indicator for the
CPOT and the physiological and respiratory indicators for the NVPS-R. The CPOT is
described as the most psychometrically sound behavioral pain instrument for monitoring
pain in medical, postoperative cardiac, and trauma intensive care unit adult patients who are
unable to self-report.13
Although it is recommended that clinicians use a validated behavioral pain assessment
instrument, there is inadequate evidence to guide recommendations for an optimal
instrument for use in PACU. The purpose of this study was to evaluate and compare pain
scores on 2 behavioral pain assessment instruments, the NVPS-R and CPOT, to determine
whether either of these instruments is superior in adequately assessing the presence of acute
pain in sedated patients in the PACU.
Study aims were: (1) to describe the relationships and change in pain scores over time
obtained using the CPOT and NVPS-R assessment instruments; (2) to assess differences in
pain scores between CPOT and NVPS-R assessment instruments and; (3) to explore the
contribution of vocalization (CPOT) and physiological pain indicators (NVPS-R) in patients
with significant pain.
METHODS
Design
A crossover design was used for this study. The study protocol was approved by the
University of Massachusetts-Amherst Human Research Protection Office (HRPO) (Protocol
#20152603) and University of Puerto Rico Medical Sciences Campus Institutional Review
Board (IRB) (Protocol #A5570115).
Study Participant Recruitment
To generate baseline information that allowed us to explore this topic in-depth in a
prospective study, we used a convenience sample of 40 patients. The information generated
with this study allowed us to formulate information about the functionality of the CPOT and
NVPS-R instrument in a group of Hispanic patients undergoing abdominal, pelvic,
gastrointestinal, or gynecologic surgeries between October 20 and December 2, 2015 at the
Medical Services Administration (ASEM) in the Puerto Rico Medical Center. Patients were
included in the study if they: (1) were adults 21 years or older; (2) were able to give
informed consent; (3) were under general anesthesia during surgery; (4) were unable to self-
report pain using the traditional verbal scale upon arrival in the PACU; (5) were able to
breathe spontaneously, and (6) had a Richmond Agitation Sedation Scale =–4 to –2
(indicating deep sedation [–4], moderate sedation [–3], or light sedation [–2]).14 Patients
were excluded if the surgery was canceled, were under spinal or epidural anesthesia,
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remained verbal after the surgical procedure, or if they had cognitive impairment (ie,
diagnosis of dementia or Alzheimer disease).10
Behavioral Pain Assessment Instruments
Acute pain in sedated patients unable to self-report was assessed using both NVPS-R and
CPOT. The NVPS-R includes 3 behavioral indicators (facial expression, activity, and
guarding), 1 physiological parameter; heart rate (HR) and blood pressure (BP), and 1
respiratory parameter; respiratory rate (RR) and pulse oxygen saturation (SpO2). The CPOT
includes 4 behavioral pain indicators (facial expression, body movements, muscle tension,
and compliance with the ventilator for intubated patients or vocalization for nonintubated
patients). In this study, the vocalization indicator was used because only patients able to
breathe spontaneously were included in the study. For both scales, each category of
indicators is rated by behavioral or physiological severity from 0 to 2 to generate a total
possible score of 10 for NVPS-R11 and a total possible score of 8 for CPOT.12 The presence
of significant acute pain, for both instruments, was defined as a total score of ≥3.10,12
Therefore, those patients with a total score from 0 to 2 were categorized as not having
significant pain.
Demographic and Clinical Data Acquisition
Patient medical records were used to collect demographic and clinical data that included sex,
age, education, ASA physical status classification, surgery category, primary diagnoses, and
preoperative and intraoperative pain medications administered (Table 1).
Study Procedures
Preoperative Data Collection—Data collection began during the preoperative visit, 0 to
7 days before the scheduled surgery. Potential participants, who met inclusion criteria, were
informed of the study purpose, risks, benefits, and confidentiality. Those who agreed to
participate were asked to sign a consent form. Before surgery, sociodemographic
information and vital signs (BP, HR, RR, and SpO2) were obtained from patient medical
records to establish baseline physiological measures.
Postoperative Data Collection—After surgery, when the participant arrived at PACU
(timepoint, 0 min), the baseline level of sedation was measured using the Richmond
Agitation Sedation Scale. If the participant scored between –2 and –4, then both nonverbal
pain scales, NVPS-R11 and CPOT,12 were administered using a randomized order. These
scales were subsequently administered at timepoints 15, 30, 45, 60, 90, and 120 minutes
until the patient was able to self-report in the PACU.
Statistical Analysis
The study cohort was described in terms of their sociodemographics, medical history, type
of surgery, and pain variables using absolute frequencies and proportions (Table 1). For
continuous variables, we used means (±SDs), or medians (interquartile range). Parameters of
normality and homogeneity of variance were obtained. The nature and strength of the
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relationships between CPOT and NVPS-R total pain scores, at time 0 and 120 minutes, were
explored using the Pearson correlations, scatter plots, and linear regression models.
To assess whether there were differences among the change in pain scores over time (at 0,
15, 30, 45, 60, 90, and 120 minutes after arrival in the PACU) between CPOT and NVPS-R
we performed a paired t test analysis. A Bonferroni correction test was performed to adjust
the P-value for the multiple comparison tests. In addition, a violin plot was generated to
depict these results.
A multilevel linear regression model was performed to access the fixed and random effect
that CPOT and NVPS-R have on the mean pain scores of patients across time. For this
model, we evaluated the different pain behavior scores assessment instruments (CPOT,
NVPS-R), and the 7 different timepoints (Table 2).
Additional analyses, using a Kruskal-Wallis test, compared CPOT and NVPS-R in terms of
selected vital sign indicators: HR, mean arterial pressure (MAP), RR, and SpO2 at different
timepoints (Tables 4–6). All the data for this study were stored in REDCap15 and was
analyzed using Stata version 14 (StataCorp LP, College Station, TX).
RESULTS
Initially, 59 patients scheduled for abdominal, pelvic, gynecologic, or gastrointestinal
surgery consented to participate in this study. Of these, a total of 19 patients were excluded
due to chronic cognitive impairment (n=1), canceled surgeries (n=8), use of regional
anesthesia during surgery (n=5), or that they were verbal upon arrival to the PACU (n=5).
Our final convenience sample consisted of 40 patients with a mean age of 49.3±17.1 (Table
1). The majority of participants (72.5%) were female and all participants (100%) were of
Hispanic origin. Most participants had mild systemic disease (67.5%) and did not receive
preoperative pain medication. The surgical categories included in the study were 45%
gynecologic, 37.5% gastrointestinal, and 17.5% abdominal-pelvic surgery. Most of the
participants had a cancer diagnosis (42.5%); of these 25% were gynecologic carcinoma,
15% were colon carcinoma, and 2.5% were ureter carcinoma (Table 1).
A total of 246 assessments were obtained using CPOT and NVPS-R instruments in the 40
patients in this study. The positive linear relationship among the pain total scores at
timepoint 0 when comparing CPOT and NVPS-R (r=0.88; P≤0.05) is shown in Figure 1.
CPOT scores explained 77% of the variance observed in the NVPS-R scores. At the 120-
minute timepoint, CPOT scores explained 80% of the variance in the NVPS-R scores (Fig.
2). Both results were statistically significant (P≤0.05).
To observe changes in pain scores over time, we evaluated the CPOT and NVPS-R total
scores at 6 timepoints (0, 30, 45, 60, 90, and 120 min). In Figure 3 we show, in a violin plot,
the distribution of the median change in scores across different timepoints. After the
Bonferroni correction (whose significant P-value was set to be P≤0.007), we did not find
any significant differences in the change in pain behavior scores obtained by CPOT and
NVPS-R at different timepoints.
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In the multilevel mixed regression model we observed that the overall mean pain score of
sedated patients unable to self-report in the PACU was 〜2.52 (95% confidence interval,
1.99-3.06), after adjusting for pain behavior assessment instruments and the multiple
postoperative time in minutes. There was no statistically significant difference in the mean
pain scores calculated by 2 pain assessment instruments (NVPS-R and CPOT). When we
evaluated pain scores over the follow-up time, there were no statistically significant
differences between the mean pain scores obtained at minutes 15 through 90, and those
obtained at baseline (minute 0). However, the mean pain score was significantly lower at
minute 120, when compared with that at minute 0, with the adjusted difference of (Δadj) of
−0.93 (95% confidence interval, −1.67 to −0.19). The estimated intraclass correlation
coefficient for this model was 0.29; indicating that 〜29% of the variance in pain scores can
be attributed to differences between patients (Table 2).
Role of Vocalization and Physiological Indicators in Pain Assessment
An evaluation was made to explore in-depth indicators that were found to be different
between the 2 pain instruments (ie, vocalization in CPOT and physiological and respiratory
parameters in NVPS-R) (Table 3). Only patients with scores indicating significant pain
(CPOT or NVPS-R≥3) were included. Results showed that CPOT vocalization was
consistently frequent in patients with significant pain (from 74% to 100%), whereas the
frequency of physiological indicators on the NVPS-R varied among timepoints in patients
with significant pain. In addition, changes in the RR on the NVPS-R scale, were hardly
found among patients with significant pain. As shown in Table 3, vocalization was more
frequent at each timepoint when compared with the physiological and respiratory indicators.
These findings do not confirm the original observation that NVPS-R vital signs correlate
with behavioral indicators of pain. And they suggest that medicating based on acute vital
signs alone may be dangerous in the sedated patient.
Ancillary analyses were used to evaluate the relationships between selected vital sign
indicators of the CPOT and NVPS-R. These included HR, MAP, RR, and SpO2. Vital signs
at the 0, 15, and 120-minute timepoints were evaluated using the Kruskal-Wallis test; none
were significantly different (P>0.05). Another evaluation to assess differences among
specific vital signs was made by classifying our patients into 3 groups considered clinically
different (group A CPOT total ≤2 and NVPS-R total ≤2); (group B one of CPOT total ≥3 or
NVPS-R total ≥3); and (group C CPOT total ≥3 and NVPS-R total ≥3) at the 0-minute
(Table 4), 15-minute (Table 5), and 120-minute (Table 6) timepoints. All 3 groups were
similar in terms of their median (IQR).
DISCUSSION
Postoperative patients first become aware of acute pain in the PACU; thus, one of the most
important goals in the postoperative period is pain management. The consequences of severe
postoperative acute pain can contribute to the development of several multisystem effects
that may adversely affect postoperative outcomes. Patients may present with different
physiological stress responses to surgery, and fluid retention initiated by neural stimuli.16
They are at risk for increases in physiological parameters such as HR and BP,17 atelectasis,
18 blood clots, pneumonia, vasoconstriction, decreased tissue oxygen partial pressure,19
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hypermetabolism resulting in hyperglycemia, fluid retention or elimination,16 delayed
wound healing, risk of wound infection,20 reduced mobility, impaired physical function,
disturbed sleep, and immune impairment, among others.21 In the United States, it has been
reported that patients only have 1 in 4 chance of receiving adequate pain relief after surgery.
22
In 2016, the American Pain Society reported that there was insufficient evidence to
recommend specific pain assessment instruments to track responses to postoperative pain
treatments to adjust personalized pain management plans.1 Clinicians must be able to
reliably detect pain, using pain assessment methods adapted for patients unable to self-report
pain. These include patients with diminished levels of consciousness (sedated).9 Behavioral
pain scales have been studied and recommended for pain assessment in patients unable to
self-report pain in contexts similar to PACU. Patients’ behavioral reactions can be used as
surrogate measures of pain, as long as their motor function is intact.10 Therefore, this study
examined, for the first time, the use of 2 behavioral pain assessment instruments, the CPOT
and the NVPS-R, for the assessment of acute pain in sedated PACU patients unable to self-
report. The use of objective measures by nurses and other health care professionals could
reduce the underestimation of pain in postoperative patients, improve postoperative
outcomes, and increase pain relief in the PACU.
Findings of this study provide evidence to support relationships between the CPOT and
NVPS-R in certain behavioral indicators including facial expressions, muscle tension, and
body movements. Pain scores on both instruments, based on behavioral indicators, were
strongly correlated. Other studies with sedated, critical care patients established the
reliability of behavioral pain indicators, which supports the observed correlations between
CPOT and NVPS-R in this study.26,27 However, despite observed associations between total
pain scores on both scales, findings reported here suggest that vital signs, as measured by the
NVPS-R, are not consistent indicators of significant acute pain in sedated PACU patients.
These findings were supported by other authors, who have indicated that changes in vital
signs might not be specific to pain, and physiological indicators lack sensitivity in assessing
acute pain.28,29
In contrast, the finding that the frequency of vocalization, as measured by the CPOT, is a
consistent indicator of significant pain, warrants further investigation. The main differences
observed between the 2 behavioral pain assessment instruments was that the vocalization
indicator of the CPOT, in patients with significant pain, was the most frequent pain indicator
in comparison with the physiological and respiratory indicators of the NVPS-R (Table 6).
This suggests the superiority of the CPOT for the assessment of acute pain in sedated PACU
patients.
There is an absence of studies to support and recommend a specific pain assessment
instrument for sedated patients unable to self-report pain in the PACU. This can lead to
inaccurate assessment and undertreatment of acute pain, and increase the gap in the standard
of care for pain assessment and management. Sedated patients who are accurately assessed
and adequately treated for acute pain in the PACU may have lower rates of postoperative
complications.1,27
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In summary, the results of this clinical study suggest that the vocalization indicator of the
CPOT was superior at assessing acute postoperative pain as compared with the
physiological and respiratory indicators of the NVPS-R. Significant change in the vital sign
and respiratory indicators of the NVPS-R did not occur, even in the presence of significant
pain. And, despite an overall high correlation between total pain scores of the NVPS-R and
CPOT, findings suggest that physiological and respiratory pain indicators of the NVPS-R,
measured over time in sedated patients with acute pain presence, are not consistent in their
results. Identification of valid, reliable instruments will lead to the development of
institutional policies and procedures for effective postoperative pain assessment and
management. Future study of the CPOT, specifically the vocalization indicator, must
continue to define and establish a valid, reliable, and consistent measure to assess acute pain
in sedated PACU patients unable to self-report pain.
The strengths of this study include the randomization used to reduce the bias for order
effect, and the use of 2 tested and validated objective instruments for the assessment of pain
in a previously unstudied population: sedated PACU patients unable to self-report.
Limitations of the study included the progressive attrition of patients throughout the study,
as they could self-report pain they were no longer eligible for the evaluation, the selection of
patients with specific type of surgeries, which limits the generalization of results to other
populations with different characteristics or types of surgeries, and the small sample size.
Finally, female sex could be a potential source of bias, because of the high proportion of
gynecologic procedures, which comprised 45% of the total of surgical procedures in the
study.
Supplementary Material
Refer to Web version on PubMed Central for supplementary material.
Acknowledgments
Supported by the University of Puerto Rico (UPR) Medical Sciences Campus, the Center for Research and
Evidence-Based Practice at the UPR School of Nursing, the Puerto Rico Clinical and Translational Research
Consortium (2U54MD007587) and the Medical Services Administration at the Medical Center of Puerto Rico.
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FIGURE 1.
Scatter plot of CPOT versus NVPS-R total scores at 0-minute timepoint. The size of the dot
visually represents the amount of possible (x, y) pairs in the same coordinate. The bigger the
dot the more cases that reported the same scores on both scales. CPOT indicates critical care
pain observation tool; NVPS-R, nonverbal pain scale revised.
(The size of the dot visually represents the amount of possible (x, y) pairs in the same
coordinate. The bigger the dot the more cases that reported the same scores on both scales).
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FIGURE 2.
Scatter plot of CPOT versus NVPS-R total scores at 120-minute timepoint. The size of the
dot visually represents the amount of possible (x, y) pairs in the same coordinate. The bigger
the dot the more cases that reported the same scores on both scales. CPOT indicates critical
care pain observation tool; NVPS-R, nonverbal pain scale revised.
(The size of the dot visually represents the amount of possible (x,y) pairs in the same
coordinate. The bigger the dot the more cases that reported the same scores on both scales
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FIGURE 3.
Violin plot showing difference in pain score between CPOT and NVPS-R across time. For
the change in pain score behavior through time, P-values were calculated using paired t test
analysis. A Bonferroni correction test was used and the statistical significance value was set
to be (P≤0.007). CPOT indicates critical care pain observation tool; NVPS-R, nonverbal
pain scale revised.
8For the change in pain score behavior through time, P-values were calculated using paired
t-test analysis.
**A Bonferroni correction test was used and the statistical significance value was set to be
(p ≤ 0.007)
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TABLE 1
Characteristics of Study Participants (n=40)
Characteristics Total (n [%])
Variables
Sex
Male 11 (27.5)
Female 29 (72.5)
Age (y)
49.3 (17.1)
22.0-87.0
American Society of Anesthesiologists Physical Status Classification System
(1) Healthy patient 4 (10.0)
(2) Mild systemic disease 27 (67.5)
(3) Severe systemic disease 8 (20.0)
(4) Incapacitating systemic disease 1 (2.5)
Preoperative analgesic/medications treatment
Yes 17 (42.5)
No 23 (57.5)
Preoperative analgesic/medications
Acetaminophen 6.0 (15.0)
Other pain medication 13.0 (32.5)
No medication 23.0 (57.5)
Surgery category
Abdominal-pelvic 7 (17.5)
Gastrointestinal 15 (37.5)
Gynecologic 18 (45)
Primary diagnoses
Uterine myoma 5 (12.5)
Hernia 5 (12.5)
Gynecologic carcinoma 10 (25)
Colon carcinoma 6 (15.0)
Ureter carcinoma 1 (2.5)
Other diagnoses 13 (32.5)
Intraoperative opioids*
Fentanyl 40 (100.0)
Morphine 21 (52.5)
Other 0 (0.0)
*Not mutually exclusive.
Clin J Pain. Author manuscript.
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Pereira-Morales et al. Page 14
TABLE 2
Linear Mixed Regression Model for Predicting the Mean Pain Scores Among Sedated Patients Unable to Self-
Report at Postanesthesia Care Unit
Estimated Coefficient 95% Confidence Interval P
Fixed part
Intercept 2.52 1.99-3.06 ≤0.001*
Pain behavior assessment tool
CPOT 0.00 — —
NVPS −0.15 −0.78 to 0.48 0.637
Postoperative time (min)
0 0.00 — —
15 0.36 −0.28 to 1.00 0.259
30 0.19 −0.45 to 0.84 0.554
45 0.13 −0.51 to 0.77 0.683
60 −0.26 −0.91 to 0.39 0.422
90 −0.61 −1.28 to 0.06 0.069
120 −0.93 −1.67 to −0.19 0.012*
Random effect
Intercept variance 0.83 0.49-1.40 —
Intercept residual 2.02 1.78-2.31 —
CPOT for the groups and minute 0 for the time were considered as reference for this assessment.
No interaction was found between the pain behavior assessment tools and the postoperative time variables.
*Statistically significant P-value (P<0.05).
CPOT indicates critical care pain observation tool; NVPS-R, nonverbal pain scale revised.
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TABLE 3
Patients With Significant Pain that Exhibit CPOT Vocalization, NVPS-R Physiological, and Respiratory Indicators ≥1
CPOT NVPS-R
Timepoints (min) CPOT ≥3 Frequency*Vocalization ≥1 Frequency (n
[%]) NVPS-R≥3 Frequency*Physiological ≥1 Frequency (Blood
Pressure, Heart Rate) (n [%]) Respiratory ≥1 Frequency (SpO2,
Respiratory Rate) (n [%])
0 16 14 (88) 15 5 (33) 2 (13)
15 22 19 (86) 20 5 (25) 0 (0)
30 19 18 (95) 15 7 (47) 2 (13)
45 19 14 (74) 17 4 (24) 2 (12)
60 15 12 (80) 12 3 (25) 0 (0)
90 10 9 (90) 11 6 (55) 3 (27)
120 6 6 (100) 6 4 (67) 0 (0)
*Total patients with significant pain per timepoints using CPOT and NVPS-R.
CPOT indicates critical care pain observation tool; NVPS-R, nonverbal pain scale revised.
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Pereira-Morales et al. Page 16
TABLE 4
Summary Statistics of Vital Signs and Respiratory Indicators by Pain Behavior Groups at Postanesthesia Care
Unit: Time 0
Group A (n=23) Group B (n=3) Group C (n=14) P*
Heart rate (L/min) 0.11
Median (IQR) 77 (17) 99 (12) 82 (30)
Range 60-113 90-102 56-102
MAP (mm Hg) 0.89
Median (IQR) 92.7 (20) 97.7 (67.3) 97.5 (18)
Range 73-117.7 68-135.3 68.7-119
SpO2 (%) 0.21
Median (IQR) 100 (2) 100 (0) 99 (2)
Range 95-100 100-100 92.0-100
RR (r/min) 0.74
Median (IQR) 18 (5) 18 (1) 16.5 (8)
Range 9-28 18-19 9-36
Group A, both CPOT and NVPS-R total pain scores were ≤2; group B, CPOT or NVPS-R total pain scores (but not both) were ≥3; group C, both
CPOT and NVPS-R total pain scores were ≥3.
*A Kruskal-Wallis test was performed to assess association between vital signs and pain behavior groups.
CPOT indicates critical care pain observation tool; MAP, mean arterial pressure; NVPS-R, nonverbal pain scale revised; RR, respiratory rate.
Clin J Pain. Author manuscript.
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Pereira-Morales et al. Page 17
TABLE 5
Summary Statistics of Vital Signs and Respiratory Indicators by Pain Behavior Groups at Postanesthesia Care
Unit: Time 15
Group A (n=23) Group B (n=3) Group C (n=14) P*
Heart rate (L/min) 0.14
Median (IQR) 75 (15) 91 (9) 82 (28)
Range 56-92 80-94 59-120
MAP (mm Hg) 0.69
Median (IQR) 94 (13.3) 99.3 (50) 95.5 (23)
Range 73-111 85-123 67.3-122.7
SpO2 (%) 0.30
Median (IQR) 100 (1) 100 (0) 99.5 (2)
Range 96-100 100-100 83-100
RR (r/min)
Median (IQR) 17 (5) 16 (4) 17 (8) 0.99
Range 11-26 14-20 10-25
Group A, both CPOT and NVPS-R total pain scores were ≤2; group B, CPOT or NVPS-R total pain scores (but not both) were ≥3; group C, both
CPOT and NVPS-R total pain scores were ≥3.
*A Kruskal-Wallis test was performed to assess association between vital signs and pain behavior groups.
CPOT indicates critical care pain observation tool; MAP, mean arterial pressure; NVPS-R, nonverbal pain scale revised; RR, respiratory rate.
Clin J Pain. Author manuscript.
Author Manuscript Author Manuscript Author Manuscript Author Manuscript
Pereira-Morales et al. Page 18
TABLE 6
Summary Statistics of Vital Signs and Respiratory Indicators by Pain Behavior Groups at Postanesthesia Care
Unit: Time 120
Group A (n=23) Group B (n=3) Group C (n=14) P*
Heart rate (L/min) 0.85
Median (IQR) 76 (16.5) 84.5 (40) 75 (15)
Range 53-110 58-115 66-88
MAP (mm Hg) 0.32
Median (IQR) 95.3 (13) 104.7 (13.3) 100 (25.8)
Range 69.7-112.7 97.3-112 66.3-109.3
SpO2 (%) 0.44
Median (IQR) 100 (0.5) 100 (0) 99.5 (4.5)
Range 98-100 100-100 92-100
RR (r/min) 0.16
Median (IQR) 17.5 (6) 13.5 (6.5) 18 (4)
Range 8-27 10-18 18-26
Group A, both CPOT and NVPS-R total pain scores were ≤2; group B, CPOT or NVPS-R total pain scores (but not both) were ≥3; group C, both
CPOT and NVPS-R total pain scores were ≥3.
*A Kruskal-Wallis test was performed to assess association between vital signs and pain behavior groups.
CPOT indicates critical care pain observation tool; MAP, mean arterial pressure; NVPS-R, nonverbal pain scale revised; RR, respiratory rate.
Clin J Pain. Author manuscript.
