550441 research-article2014
CNU0010.1177/1474515114550441CNU550441 European Journal of Cardiovascular NursingBjørnnes et al.
EUROPEAN SOCIETY OF CARDIOLOGY ®
Original Paper
Pain characteristics and analgesic intake before and following cardiac surgery
European Journal of Cardiovascular Nursing 1–8 © The European Society of Cardiology 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/1474515114550441 cnu.sagepub.com
Ann Kristin Bjørnnes1, Tone Rustøen1,2, Irene Lie3, Judy Watt-Watson4 and Marit Leegaard5
Abstract Background: Cardiac surgery is a common intervention that involves several pain-sensitive structures, and intense postoperative pain is a predictor of persistent pain. Aims: To describe pain characteristics (i.e. intensity, location, interference, relief) and analgesic intake preoperatively and across postoperative days 1 to 4 after cardiac surgery, and to explore associations between postoperative pain and demographic and clinical characteristics. Methods: Four hundred and sixteen patients (24% women) undergoing elective coronary artery bypass grafting and/or valve surgery were enrolled in a randomized controlled trial. Data were collected using standardized measures including the Brief Pain Inventory-short form. A linear mixed model analysis estimated the impact of sex, age, body mass index, analgesic intake and preoperative pain on postoperative worst pain ratings in the previous 24 hours from postoperative days 1 to 4 prior to discharge Results: Thirty-eight per cent of the cardiac surgery patients reported preoperative pain. Postoperative worst pain remained in the moderate to severe range for the majority of patients across day 1 (85%) to day 4 (57%), mainly around the chest incision area for the majority (70%). Mean oral morphine intake was 17 mg/24 h (day 1: 27mg; day 4: 10mg). Lower age, female sex, preoperative pain and analgesic intake had a statistically significant association with higher postoperative worst pain ratings. Conclusion: Study findings demonstrated a high prevalence of moderate to severe pain after cardiac surgery and insufficient analgesic administration. Results indicated that patients were discharged from hospital with unrelieved pain and a potential risk for further postoperative complications. Keywords Cardiac surgery, postoperative pain, pain management, analgesic intake Received 23 May 2014; revised 17 August 2014; revised manuscript accepted 18 August 2014
Introduction Cardiac surgery is painful as it involves opening the sternum. This creates several pain-sensitive areas related to tissue injury and inflammation not merely at the site of surgical incision but also at sites that involve prolonged sternal retraction and use of chest and mediastinal tubes.1 Uncontrolled acute pain after the surgery is reported to result in slower rehabilitation,2,3 a higher long term morbidity risk for the patients4,5 and persistent non-anginal pain for up to two years afterwards.6 Inadequate pain management and resulting postoperative pain have been a challenge for more than 40 years7,8 and continue to be a relevant concern.3,9,10 Studies1 have
1Department
of Research and Development, Division of Emergencies and Critical Care, Oslo University Hospital, Ullevål, Norway 2Institute of Health and Society, University of Oslo, Norway 3Department of Cardiothoracic Surgery, Oslo University Hospital, Ullevål, Norway 4Lawrence S Bloomberg Faculty of Nursing, Senior Fellow, Massey College University of Toronto, Canada 5Oslo and Akershus University College of Applied Sciences, Faculty of Health Sciences, Institute of Nursing, Norway Corresponding author: Ann Kristin Bjørnnes, Division of Emergencies and Critical Care, Oslo University Hospital, Ullevål P.O Box 4956 Nydalen, Oslo 0424, Norway. Email: [email protected]
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European Journal of Cardiovascular Nursing
reported high prevalence of moderate to severe acute pain after cardiac surgery from severe pain at rest for 49% on postoperative day 4 to moderate pain at movement across the first week after surgery.4,12,13 Watt-Watson et al.4 investigated associations between pain characteristics and analgesic consumption. They found that 69–80% of the 406 participants reported moderate to severe pain on movement across the first five days after cardiac surgery, although nurses administered only 3% of the prescribed analgesics. In a recent observational study of 1247 cardiac surgical patients followed for two years, more than 65% rated their worst pain on movement as moderate to severe across the week after surgery, which continued for two years for 10% of the sample.6 Preoperative pain, anxiety, female sex and lower age1416 are reported to be the most significant predictive factors for postoperative pain intensity and are also found to be predictors for inadequate analgesic consumption.17 However, female sex has been found to be an inconsistent predictor.17 Health related characteristics such as higher body mass index and comorbidities also have been associated with more severe postoperative pain, but the evidence is inconclusive.3,8,18 In a Canadian study6 of cardiac surgical patients, predictors of long term pain included the intensity of pain and related interference in the first postoperative week, pre-existing persistent pain and greater preoperative anxiety. Analgesic use was inadequate, with the total dose in morphine mg equivalents being 98.5±63 during the first week after surgery. Further studies of these factors are required to assess their connection with postoperative pain in cardiac surgery patients in Europe. The majority of the published studies on postoperative pain after cardiac surgery have been long term studies with limited data about analgesic consumption. Pain in the acute postoperative period has usually been measured over one or two days, and regarded as a primary predictor for long term pain.5,6,19,20 In view of the importance of pain management after cardiac surgery and the fact that no large study in Europe has assessed postoperative pain characteristics and analgesic consumption, the purposes of this study are to: a) describe pain prevalence, pain intensity, pain location and analgesic consumption preoperatively and across four days after cardiac surgery and b) explore associations between postoperative pain intensity and patients’ demographic and clinical characteristics.
Methods The present study is part of a randomized controlled trial with the primary aim of evaluating the effect of an educational intervention given after discharge from cardiac surgery to enhance patients’ pain management (Clinical Trials gov Identifier: NCTO1976403). The consenting patients were randomly assigned to an intervention or control group, with 208 patients in each group, when participation
in the study was confirmed. Both patients and nurses were blinded to group assignment until discharge from hospital. Since the intervention was given after discharge, the study intervention had no effect on patients’ pain intensity scores and analgesic intake during hospitalization. The study conforms with the principles outlined in the Declaration of Helsinki.21 The institutional clinical research panel and the Regional Committee for Medical Research Ethics, Health Region South-East, Norway approved the study
Participants and procedure The study was conducted at two separately located departments of cardiothoracic surgery in Oslo University Hospital. Department 1 serves east Norway, and department 2 serves south Norway. In 2012 1968 coronary artery bypass grafting (CABG) and 1572 valve surgeries were performed in Norway.22 During a period of 18 months (March 2012 to September 2013) eligible patients over 18 years old, able to read, write and speak Norwegian and scheduled for elective, uncomplicated CABG and /or valve surgery were consecutively invited to participate in the study. Patients were excluded if they spent more than 12 hours in the intensive care unit after surgery. When time for surgery was confirmed, eligible patients received written information about the study together with standard pre-operative information from Patients’ Coordinators. Patients willing to participate were given the consent form and the baseline questionnaires to complete at home, between approximately two weeks and one day before surgery. When admitted for surgery, consenting patients gave the questionnaire with the signed consent form to designated nurses. Postoperatively, patients were asked to complete a short questionnaire about pain characteristics daily from day 1 to day 4. These times were chosen as patients undergoing CABG were usually discharged to local hospitals on day 3 and patients undergoing valve surgery were discharged on day 4.
Data collection Demographic and clinical characteristics. At baseline participants completed the Demographic Questionnaire including information about age, sex, ethnicity, civil status, cohabitation, education level and income. Data about comorbidities were collected with the Self-administered Comorbidity Questionnaire (SCQ-16).23 The SCQ-16 included 15 common comorbidities and one optional condition. Patients were asked to indicate whether they had the comorbid condition (yes/no); if they received treatment for it (yes/no); and if it limited their activities (yes/ no). The total score ranged from 0 to 48 when the one optimal item was used. A higher score indicated a more severe comorbidity profile. Information about body mass index
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Bjørnnes et al. (BMI) was collected from the medical records after discharge from hospital. Pain characteristics and analgesic intake. Items from the Brief Pain Inventory short form (BPI-SF)24 were used to assess pain intensity, locations, relief and interference. The reliability and validity of BPI-SF have been well established in the general25 as well as in the cardiac population.26,27 The BPI consists of four numerical rating scales (NRSs) of pain intensity (i.e. worst pain, least pain, average pain and pain now). Each NRS scale has 11 points ranging from 0 (no pain) to 10 (pain as bad as you can imagine). Scores of 4–6 on the NRS were considered as moderate and 7–10 on the NRS as severe.28 The BPI-SF also included a subscale of seven 11-point NRSs (0=no interference, 10=interferes completely) to rate pain-related interference in everyday activities. In this study five out of the seven NRSs were used: general activity, mood, walking ability, relationship with other people and sleep. The BPI-SF assessed patients’ pain locations using a body outline diagram. The diagram was scored by using a modified version of the procedures described by Puntillo;29 the body diagram was divided into a template of 45 different areas marked by the patients. Marked areas were counted and summed and scores ranged from 0 to 45, with higher scores indicating a higher number of painful sites. Further, one NRS (0=no relief, 100= complete relief) measured the degree of pain relief obtained from pain treatments or medications in the previous 24 hours. At baseline, patients were asked to rate only their worst and average pain on movement in the previous 24 hours. In addition, they were asked one general question about presence of pain the prior week. If they answered yes, the participants were asked about duration and frequency of the pain and use of analgesic medications prior to the surgery. After surgery, patients completed all NRSs from the BPI-SF to rate their pain intensity at rest and the body diagram for pain sites on a daily basis before 13:00 hours across postoperative days 1 to 4. Postoperative analgesic intake, both around-the-clock and as needed, was examined on a 24 hour basis, starting at 06:00 hours on the first postoperative day. Only charts from complete hospital days were included. Information about analgesic intake was collected from the electronic medical records after discharge from hospital. Standard procedures at hospital were to administer parenteral and oral ketobemidone, oral oxycodone and paracetamol with codeine to patients for postoperative pain relief. Doses were converted into oral morphine equivalents and summed to obtain an index of daily opioid intake.30,31 Ketobemidone is the most common drug for treating postoperative pain in Norway and is considered equivalent to morphine with comparable morphine equivalents.32
Figure 1. Flow chart of patient assessment.
Statistical analysis Stata 13SE Statistical Data Analysis statistical program (StataCorp, College Station, TX) was used for analyses. Descriptive statistics were used to present demographic and clinical characteristics of the sample. Continuous variables are presented as mean ± standard deviation (SD). Categorical variables are shown as the percentage of the sample. Student’s t-test or Man–Whitney U-test were used for comparison between continuous variables. Cross tabulation with chi-square analyses or Fisher’s exact test was used to test for differences between categorical variables. All tests were two-tailed and associations were considered significant if p < 0.05. General linear mixed models were used to assess worst pain intensity scores across postoperative days 1 to 4. Linear mixed models use all available measurements; patients with only one occasion of the longitudinal outcome measurements were included in data analysis.33 The model was selected by using the Akaike Information Criteria (AIC) as recommended.33 The variance–covariance structure with the smallest AIC was selected. The final model assessed worst pain intensity postoperatively as dependent factor, time (day), age, sex, BMI, preoperative worst pain intensity and postoperative analgesic intake as fixed factors and subjects and time (day) as random factors with unstructured covariance.
Results A total of 525 patients were assessed for eligibility with a response rate of 79% (Figure 1). Exclusion included 45
Downloaded from cnu.sagepub.com at U.A.E University on November 15, 2015
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European Journal of Cardiovascular Nursing
(11%) out of 416 participating patients, mainly due to complications related to surgery with a prolonged stay at the intensive care unit.
Demographic characteristics At the time of surgery, the mean age of the sample was 66 ±10 years (range 32–88 years); 50% were between 60 and 75 years old and 24% were women. Only five participants reported their ethnicity to be different from European (Table 1). The majority (73%) were married and living with a partner, and most had secondary education or higher (84%).
Clinical characteristics and comorbidities Most patients had either valve or CABG surgery, the latter involving internal mammary artery grafts with additional saphenous grafts (Table 2). Mean total SCQ-16 score was 3.5± 2.8 with a range of 0–16. Comorbidities with ≥ 5% prevalence are shown in Table 2. Hypertension was the most common (51%) in addition to back/neck problems, osteoarthritis and diabetes mellitus. Fifty-two per cent reported to have ≥ 2 comorbidities, and 34% reported limitations in their activities due to their comorbid condition.
Preoperative pain characteristics When asked about pain during the prior week 38% reported having pain before surgery (Table 3) that for 11% had lasted more than one year (mean 11±10 years). Although the means for worst pain (3.1±2.4) and average pain (2.9±2.0) were in the mild range, pain interfered with usual activities, particularly with general activity (3.4±2.8).
Postoperative pain characteristics As outlined in Table 4, postoperative worst pain remained in the moderate to severe range for the majority of patients across all four days after surgery: 85% (day 1) to 57% (day 4). For the total sample, the mean score for worst pain on day 1 was 6.0 ±2.3 with 85% reporting scores in the moderate–severe range (NRS≥4/10). Younger patients (≤ 60 years, n=91) reported moderate (35%) or severe (61%) worst pain on day 1 that remained in the moderate–severe range (NRS≥4/10) across days 1 to 4. Older patients (≥ 80 years, n=34) reported less pain on average (mean 4.5±2.4), although 62% reported worst pain >3 on day 1. At the time of discharge on day 3 or 4, almost one-half of patients reported average pain in the moderate–severe range (42%, 43% respectively). About a quarter (21–24%) reported the presence of moderate–severe pain at the time of the interview. The sternotomy area was identified as a location for pain by approximately 70% of the patients across days 1 to
Table 1. Demographic characteristics of the total sample at baseline (N=371). Demographic characteristics
Age, mean±SD, years Income (100 000 Kr)a, mean±SD 5.1±4.0 Female sex, n (%) European ethnicity, n (%) Education levelb, n (%) Primary education Secondary education Higher education Marital statusb, n (%) Single Married/Cohabitant Divorced/Widowed
66 ±10 89 (24) 366 (99) 58 (16) 159 (45) 136 (39) 24 (7) 260 (73) 71 (20)
Descriptive data are given as frequencies (%) and means ±SD. aMissing, 73 participants did not answer. bMissing, 16 participants did not answer.
Table 2. Clinical characteristics of the total sample at baseline (N=371). Clinical characteristics
Type of surgery, n (%) CABG Heart valve CABG and valve Comorbiditiesa,b, n (%) Hypertension Back/neck problem Osteoarthritis Diabetes mellitus Headache Depression SCQ-16b total score, mean±SD Number of comorbiditiesb, mean±SD BMI (kg/m²), mean±SD
164 (44) 163 (44) 44 (12) 176 (51) 97 (28) 63 (18) 56 (16) 25 (7) 18 (5) 3.5±2.8 1.8±1.4 27.0±4.1
Descriptive data are given as frequencies (%) and means ± SD. aMissing, 16 participants did not answer. bThe Self-administered Comorbidity Questionnaire. CABG: coronary artery bypass grafting; BMI: body mass index
4. In addition, osteoarticular pain was common as shoulders (29%), upper back (23%) and the lumbar region (14%) were frequently marked out as locations for pain with a mean of 5±2.6 pain sites, and with no significant differences related to sex or preoperative pain.
Analgesic intake Twenty per cent of patients reported using pain medication before surgery. The most common drugs were paracetamol and paracetamol with codeine. After surgery, the majority (92% to 51%) received on average one to almost three
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Bjørnnes et al. Table 3. Characteristics of preoperative pain in the total sample at baseline (N=371). Preoperative pain characteristics Pain last week, yes, n (%) Pain duration > 1 year, n (%) Frequency pain ≥ 1–2 times/day, n (%) Pain intensity, mean±SD Worst pain Average pain Number of pain sites, mean±SD Pain interference, mean±SD General activity Mood Walking ability Relations with other people Sleep
141 (38) 39 (11) 63 (17) 3.1±2.4 2.9±2.0 4.4±4.0 3.4±2.8 2.6±2.4 2.7±2.9 1.7±2.3 2.5±2.6
Descriptive data are given as frequencies (%) and means ±SD.
Table 4. Total sample percentage distribution scores in the moderate to severe range for pain across postoperative days 1 to 4. Measure (NRS 0–10) Day 1
Day 2
(n=330)a
(n=282)a (n=209)b (n=67)b
39 46 85
45 33 78
42 26 68
33 24 57
15 2 17
10 2 12
5 1 6
6 2 8
48 14 62
46 6 52
37 5 42
38 5 43
34 13 47
24 5 29
17 4 21
22 2 24
Worst pain, % Moderate, 4–6 Severe, 7–10 Total Least pain, % Moderate, 4–6 Severe, 7–10 Total Average pain, % Moderate, 4–6 Severe, 7–10 Total Pain right now, % Moderate, 4–6 Severe, 7–10 Total
Day 3
Day 4
aMissing
due to logistic reasons (nurses forgot to hand out questionnaires). bMissing due to discharge to other hospitals. NRS: numerical rating scale
doses of morphine per 24 h during their hospital stay (see Table 5). Additionally 4 g of paracetamol were given to 98% of the patients each day during hospitalization. Sedatives, such as sleeping pills, were given to 14% on day 1, 15% on day 2, 35% on day 3 and to 38% of the patients still hospitalized on day 4. In the majority of medical records, only paracetamol was prescribed for pain relief. Stronger analgesics were rarely prescribed, were only to be given ‘as required’ and were minimally administered.
Table 5. Postoperative opioid analgesic administration. Postoperative day
% patients
Morphine dose/24 h
1, n=371 2, n=365a 3, n=191a 4, n=94a
92% 85% 69% 51%
27±19 mg 20±18 mg 12±14 mg 10±13 mg
Descriptive data are given as frequencies (%) and means ±SD. aMissing due to discharge to other hospitals.
Table 6. Linear mixed model; estimates for postoperative worst pain ratings. Factors
Postoperative daya 2 3 4 Female sex Ageb (years) 60–70 70–80 ≥ 80 Preoperative worst pain Analgesic intake BMI (kg/m²)
Coefficient
95% confidence interval
p value
–0.5 –0.8 –1.4 0.6
[–0.7, –0.2] [–1.2, –0.4] [–2.1, –0.6] [0.1, 1.1]
CNU0010.1177/1474515114550441CNU550441 European Journal of Cardiovascular NursingBjørnnes et al.
EUROPEAN SOCIETY OF CARDIOLOGY ®
Original Paper
Pain characteristics and analgesic intake before and following cardiac surgery
European Journal of Cardiovascular Nursing 1–8 © The European Society of Cardiology 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/1474515114550441 cnu.sagepub.com
Ann Kristin Bjørnnes1, Tone Rustøen1,2, Irene Lie3, Judy Watt-Watson4 and Marit Leegaard5
Abstract Background: Cardiac surgery is a common intervention that involves several pain-sensitive structures, and intense postoperative pain is a predictor of persistent pain. Aims: To describe pain characteristics (i.e. intensity, location, interference, relief) and analgesic intake preoperatively and across postoperative days 1 to 4 after cardiac surgery, and to explore associations between postoperative pain and demographic and clinical characteristics. Methods: Four hundred and sixteen patients (24% women) undergoing elective coronary artery bypass grafting and/or valve surgery were enrolled in a randomized controlled trial. Data were collected using standardized measures including the Brief Pain Inventory-short form. A linear mixed model analysis estimated the impact of sex, age, body mass index, analgesic intake and preoperative pain on postoperative worst pain ratings in the previous 24 hours from postoperative days 1 to 4 prior to discharge Results: Thirty-eight per cent of the cardiac surgery patients reported preoperative pain. Postoperative worst pain remained in the moderate to severe range for the majority of patients across day 1 (85%) to day 4 (57%), mainly around the chest incision area for the majority (70%). Mean oral morphine intake was 17 mg/24 h (day 1: 27mg; day 4: 10mg). Lower age, female sex, preoperative pain and analgesic intake had a statistically significant association with higher postoperative worst pain ratings. Conclusion: Study findings demonstrated a high prevalence of moderate to severe pain after cardiac surgery and insufficient analgesic administration. Results indicated that patients were discharged from hospital with unrelieved pain and a potential risk for further postoperative complications. Keywords Cardiac surgery, postoperative pain, pain management, analgesic intake Received 23 May 2014; revised 17 August 2014; revised manuscript accepted 18 August 2014
Introduction Cardiac surgery is painful as it involves opening the sternum. This creates several pain-sensitive areas related to tissue injury and inflammation not merely at the site of surgical incision but also at sites that involve prolonged sternal retraction and use of chest and mediastinal tubes.1 Uncontrolled acute pain after the surgery is reported to result in slower rehabilitation,2,3 a higher long term morbidity risk for the patients4,5 and persistent non-anginal pain for up to two years afterwards.6 Inadequate pain management and resulting postoperative pain have been a challenge for more than 40 years7,8 and continue to be a relevant concern.3,9,10 Studies1 have
1Department
of Research and Development, Division of Emergencies and Critical Care, Oslo University Hospital, Ullevål, Norway 2Institute of Health and Society, University of Oslo, Norway 3Department of Cardiothoracic Surgery, Oslo University Hospital, Ullevål, Norway 4Lawrence S Bloomberg Faculty of Nursing, Senior Fellow, Massey College University of Toronto, Canada 5Oslo and Akershus University College of Applied Sciences, Faculty of Health Sciences, Institute of Nursing, Norway Corresponding author: Ann Kristin Bjørnnes, Division of Emergencies and Critical Care, Oslo University Hospital, Ullevål P.O Box 4956 Nydalen, Oslo 0424, Norway. Email: [email protected]
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reported high prevalence of moderate to severe acute pain after cardiac surgery from severe pain at rest for 49% on postoperative day 4 to moderate pain at movement across the first week after surgery.4,12,13 Watt-Watson et al.4 investigated associations between pain characteristics and analgesic consumption. They found that 69–80% of the 406 participants reported moderate to severe pain on movement across the first five days after cardiac surgery, although nurses administered only 3% of the prescribed analgesics. In a recent observational study of 1247 cardiac surgical patients followed for two years, more than 65% rated their worst pain on movement as moderate to severe across the week after surgery, which continued for two years for 10% of the sample.6 Preoperative pain, anxiety, female sex and lower age1416 are reported to be the most significant predictive factors for postoperative pain intensity and are also found to be predictors for inadequate analgesic consumption.17 However, female sex has been found to be an inconsistent predictor.17 Health related characteristics such as higher body mass index and comorbidities also have been associated with more severe postoperative pain, but the evidence is inconclusive.3,8,18 In a Canadian study6 of cardiac surgical patients, predictors of long term pain included the intensity of pain and related interference in the first postoperative week, pre-existing persistent pain and greater preoperative anxiety. Analgesic use was inadequate, with the total dose in morphine mg equivalents being 98.5±63 during the first week after surgery. Further studies of these factors are required to assess their connection with postoperative pain in cardiac surgery patients in Europe. The majority of the published studies on postoperative pain after cardiac surgery have been long term studies with limited data about analgesic consumption. Pain in the acute postoperative period has usually been measured over one or two days, and regarded as a primary predictor for long term pain.5,6,19,20 In view of the importance of pain management after cardiac surgery and the fact that no large study in Europe has assessed postoperative pain characteristics and analgesic consumption, the purposes of this study are to: a) describe pain prevalence, pain intensity, pain location and analgesic consumption preoperatively and across four days after cardiac surgery and b) explore associations between postoperative pain intensity and patients’ demographic and clinical characteristics.
Methods The present study is part of a randomized controlled trial with the primary aim of evaluating the effect of an educational intervention given after discharge from cardiac surgery to enhance patients’ pain management (Clinical Trials gov Identifier: NCTO1976403). The consenting patients were randomly assigned to an intervention or control group, with 208 patients in each group, when participation
in the study was confirmed. Both patients and nurses were blinded to group assignment until discharge from hospital. Since the intervention was given after discharge, the study intervention had no effect on patients’ pain intensity scores and analgesic intake during hospitalization. The study conforms with the principles outlined in the Declaration of Helsinki.21 The institutional clinical research panel and the Regional Committee for Medical Research Ethics, Health Region South-East, Norway approved the study
Participants and procedure The study was conducted at two separately located departments of cardiothoracic surgery in Oslo University Hospital. Department 1 serves east Norway, and department 2 serves south Norway. In 2012 1968 coronary artery bypass grafting (CABG) and 1572 valve surgeries were performed in Norway.22 During a period of 18 months (March 2012 to September 2013) eligible patients over 18 years old, able to read, write and speak Norwegian and scheduled for elective, uncomplicated CABG and /or valve surgery were consecutively invited to participate in the study. Patients were excluded if they spent more than 12 hours in the intensive care unit after surgery. When time for surgery was confirmed, eligible patients received written information about the study together with standard pre-operative information from Patients’ Coordinators. Patients willing to participate were given the consent form and the baseline questionnaires to complete at home, between approximately two weeks and one day before surgery. When admitted for surgery, consenting patients gave the questionnaire with the signed consent form to designated nurses. Postoperatively, patients were asked to complete a short questionnaire about pain characteristics daily from day 1 to day 4. These times were chosen as patients undergoing CABG were usually discharged to local hospitals on day 3 and patients undergoing valve surgery were discharged on day 4.
Data collection Demographic and clinical characteristics. At baseline participants completed the Demographic Questionnaire including information about age, sex, ethnicity, civil status, cohabitation, education level and income. Data about comorbidities were collected with the Self-administered Comorbidity Questionnaire (SCQ-16).23 The SCQ-16 included 15 common comorbidities and one optional condition. Patients were asked to indicate whether they had the comorbid condition (yes/no); if they received treatment for it (yes/no); and if it limited their activities (yes/ no). The total score ranged from 0 to 48 when the one optimal item was used. A higher score indicated a more severe comorbidity profile. Information about body mass index
Downloaded from cnu.sagepub.com at U.A.E University on November 15, 2015
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Bjørnnes et al. (BMI) was collected from the medical records after discharge from hospital. Pain characteristics and analgesic intake. Items from the Brief Pain Inventory short form (BPI-SF)24 were used to assess pain intensity, locations, relief and interference. The reliability and validity of BPI-SF have been well established in the general25 as well as in the cardiac population.26,27 The BPI consists of four numerical rating scales (NRSs) of pain intensity (i.e. worst pain, least pain, average pain and pain now). Each NRS scale has 11 points ranging from 0 (no pain) to 10 (pain as bad as you can imagine). Scores of 4–6 on the NRS were considered as moderate and 7–10 on the NRS as severe.28 The BPI-SF also included a subscale of seven 11-point NRSs (0=no interference, 10=interferes completely) to rate pain-related interference in everyday activities. In this study five out of the seven NRSs were used: general activity, mood, walking ability, relationship with other people and sleep. The BPI-SF assessed patients’ pain locations using a body outline diagram. The diagram was scored by using a modified version of the procedures described by Puntillo;29 the body diagram was divided into a template of 45 different areas marked by the patients. Marked areas were counted and summed and scores ranged from 0 to 45, with higher scores indicating a higher number of painful sites. Further, one NRS (0=no relief, 100= complete relief) measured the degree of pain relief obtained from pain treatments or medications in the previous 24 hours. At baseline, patients were asked to rate only their worst and average pain on movement in the previous 24 hours. In addition, they were asked one general question about presence of pain the prior week. If they answered yes, the participants were asked about duration and frequency of the pain and use of analgesic medications prior to the surgery. After surgery, patients completed all NRSs from the BPI-SF to rate their pain intensity at rest and the body diagram for pain sites on a daily basis before 13:00 hours across postoperative days 1 to 4. Postoperative analgesic intake, both around-the-clock and as needed, was examined on a 24 hour basis, starting at 06:00 hours on the first postoperative day. Only charts from complete hospital days were included. Information about analgesic intake was collected from the electronic medical records after discharge from hospital. Standard procedures at hospital were to administer parenteral and oral ketobemidone, oral oxycodone and paracetamol with codeine to patients for postoperative pain relief. Doses were converted into oral morphine equivalents and summed to obtain an index of daily opioid intake.30,31 Ketobemidone is the most common drug for treating postoperative pain in Norway and is considered equivalent to morphine with comparable morphine equivalents.32
Figure 1. Flow chart of patient assessment.
Statistical analysis Stata 13SE Statistical Data Analysis statistical program (StataCorp, College Station, TX) was used for analyses. Descriptive statistics were used to present demographic and clinical characteristics of the sample. Continuous variables are presented as mean ± standard deviation (SD). Categorical variables are shown as the percentage of the sample. Student’s t-test or Man–Whitney U-test were used for comparison between continuous variables. Cross tabulation with chi-square analyses or Fisher’s exact test was used to test for differences between categorical variables. All tests were two-tailed and associations were considered significant if p < 0.05. General linear mixed models were used to assess worst pain intensity scores across postoperative days 1 to 4. Linear mixed models use all available measurements; patients with only one occasion of the longitudinal outcome measurements were included in data analysis.33 The model was selected by using the Akaike Information Criteria (AIC) as recommended.33 The variance–covariance structure with the smallest AIC was selected. The final model assessed worst pain intensity postoperatively as dependent factor, time (day), age, sex, BMI, preoperative worst pain intensity and postoperative analgesic intake as fixed factors and subjects and time (day) as random factors with unstructured covariance.
Results A total of 525 patients were assessed for eligibility with a response rate of 79% (Figure 1). Exclusion included 45
Downloaded from cnu.sagepub.com at U.A.E University on November 15, 2015
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European Journal of Cardiovascular Nursing
(11%) out of 416 participating patients, mainly due to complications related to surgery with a prolonged stay at the intensive care unit.
Demographic characteristics At the time of surgery, the mean age of the sample was 66 ±10 years (range 32–88 years); 50% were between 60 and 75 years old and 24% were women. Only five participants reported their ethnicity to be different from European (Table 1). The majority (73%) were married and living with a partner, and most had secondary education or higher (84%).
Clinical characteristics and comorbidities Most patients had either valve or CABG surgery, the latter involving internal mammary artery grafts with additional saphenous grafts (Table 2). Mean total SCQ-16 score was 3.5± 2.8 with a range of 0–16. Comorbidities with ≥ 5% prevalence are shown in Table 2. Hypertension was the most common (51%) in addition to back/neck problems, osteoarthritis and diabetes mellitus. Fifty-two per cent reported to have ≥ 2 comorbidities, and 34% reported limitations in their activities due to their comorbid condition.
Preoperative pain characteristics When asked about pain during the prior week 38% reported having pain before surgery (Table 3) that for 11% had lasted more than one year (mean 11±10 years). Although the means for worst pain (3.1±2.4) and average pain (2.9±2.0) were in the mild range, pain interfered with usual activities, particularly with general activity (3.4±2.8).
Postoperative pain characteristics As outlined in Table 4, postoperative worst pain remained in the moderate to severe range for the majority of patients across all four days after surgery: 85% (day 1) to 57% (day 4). For the total sample, the mean score for worst pain on day 1 was 6.0 ±2.3 with 85% reporting scores in the moderate–severe range (NRS≥4/10). Younger patients (≤ 60 years, n=91) reported moderate (35%) or severe (61%) worst pain on day 1 that remained in the moderate–severe range (NRS≥4/10) across days 1 to 4. Older patients (≥ 80 years, n=34) reported less pain on average (mean 4.5±2.4), although 62% reported worst pain >3 on day 1. At the time of discharge on day 3 or 4, almost one-half of patients reported average pain in the moderate–severe range (42%, 43% respectively). About a quarter (21–24%) reported the presence of moderate–severe pain at the time of the interview. The sternotomy area was identified as a location for pain by approximately 70% of the patients across days 1 to
Table 1. Demographic characteristics of the total sample at baseline (N=371). Demographic characteristics
Age, mean±SD, years Income (100 000 Kr)a, mean±SD 5.1±4.0 Female sex, n (%) European ethnicity, n (%) Education levelb, n (%) Primary education Secondary education Higher education Marital statusb, n (%) Single Married/Cohabitant Divorced/Widowed
66 ±10 89 (24) 366 (99) 58 (16) 159 (45) 136 (39) 24 (7) 260 (73) 71 (20)
Descriptive data are given as frequencies (%) and means ±SD. aMissing, 73 participants did not answer. bMissing, 16 participants did not answer.
Table 2. Clinical characteristics of the total sample at baseline (N=371). Clinical characteristics
Type of surgery, n (%) CABG Heart valve CABG and valve Comorbiditiesa,b, n (%) Hypertension Back/neck problem Osteoarthritis Diabetes mellitus Headache Depression SCQ-16b total score, mean±SD Number of comorbiditiesb, mean±SD BMI (kg/m²), mean±SD
164 (44) 163 (44) 44 (12) 176 (51) 97 (28) 63 (18) 56 (16) 25 (7) 18 (5) 3.5±2.8 1.8±1.4 27.0±4.1
Descriptive data are given as frequencies (%) and means ± SD. aMissing, 16 participants did not answer. bThe Self-administered Comorbidity Questionnaire. CABG: coronary artery bypass grafting; BMI: body mass index
4. In addition, osteoarticular pain was common as shoulders (29%), upper back (23%) and the lumbar region (14%) were frequently marked out as locations for pain with a mean of 5±2.6 pain sites, and with no significant differences related to sex or preoperative pain.
Analgesic intake Twenty per cent of patients reported using pain medication before surgery. The most common drugs were paracetamol and paracetamol with codeine. After surgery, the majority (92% to 51%) received on average one to almost three
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Bjørnnes et al. Table 3. Characteristics of preoperative pain in the total sample at baseline (N=371). Preoperative pain characteristics Pain last week, yes, n (%) Pain duration > 1 year, n (%) Frequency pain ≥ 1–2 times/day, n (%) Pain intensity, mean±SD Worst pain Average pain Number of pain sites, mean±SD Pain interference, mean±SD General activity Mood Walking ability Relations with other people Sleep
141 (38) 39 (11) 63 (17) 3.1±2.4 2.9±2.0 4.4±4.0 3.4±2.8 2.6±2.4 2.7±2.9 1.7±2.3 2.5±2.6
Descriptive data are given as frequencies (%) and means ±SD.
Table 4. Total sample percentage distribution scores in the moderate to severe range for pain across postoperative days 1 to 4. Measure (NRS 0–10) Day 1
Day 2
(n=330)a
(n=282)a (n=209)b (n=67)b
39 46 85
45 33 78
42 26 68
33 24 57
15 2 17
10 2 12
5 1 6
6 2 8
48 14 62
46 6 52
37 5 42
38 5 43
34 13 47
24 5 29
17 4 21
22 2 24
Worst pain, % Moderate, 4–6 Severe, 7–10 Total Least pain, % Moderate, 4–6 Severe, 7–10 Total Average pain, % Moderate, 4–6 Severe, 7–10 Total Pain right now, % Moderate, 4–6 Severe, 7–10 Total
Day 3
Day 4
aMissing
due to logistic reasons (nurses forgot to hand out questionnaires). bMissing due to discharge to other hospitals. NRS: numerical rating scale
doses of morphine per 24 h during their hospital stay (see Table 5). Additionally 4 g of paracetamol were given to 98% of the patients each day during hospitalization. Sedatives, such as sleeping pills, were given to 14% on day 1, 15% on day 2, 35% on day 3 and to 38% of the patients still hospitalized on day 4. In the majority of medical records, only paracetamol was prescribed for pain relief. Stronger analgesics were rarely prescribed, were only to be given ‘as required’ and were minimally administered.
Table 5. Postoperative opioid analgesic administration. Postoperative day
% patients
Morphine dose/24 h
1, n=371 2, n=365a 3, n=191a 4, n=94a
92% 85% 69% 51%
27±19 mg 20±18 mg 12±14 mg 10±13 mg
Descriptive data are given as frequencies (%) and means ±SD. aMissing due to discharge to other hospitals.
Table 6. Linear mixed model; estimates for postoperative worst pain ratings. Factors
Postoperative daya 2 3 4 Female sex Ageb (years) 60–70 70–80 ≥ 80 Preoperative worst pain Analgesic intake BMI (kg/m²)
Coefficient
95% confidence interval
p value
–0.5 –0.8 –1.4 0.6
[–0.7, –0.2] [–1.2, –0.4] [–2.1, –0.6] [0.1, 1.1]
