Integrative acupoint stimulation to alleviate postoperative pain and morphine-related side effects: A sham-controlled study

International Journal of Nursing Studies 51 (2014) 370–378

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Integrative acupoint stimulation to alleviate postoperative pain and morphine-related side effects: A sham-controlled study Yu-Chu Chung a,1, Mei-Yung Tsou b,2, Hsing-Hsia Chen c,3, Jaung-Geng Lin d,4, Mei-Ling Yeh e,* a

School of Nursing, Yuanpei University, No. 306, Yuanpei Street, Hsinchu 30015, Taiwan, ROC Physician of Anesthesiology Department, Veterans General Hospital, Taipei, No. 201, Shih-Pai Road, Section 2, PeiTou 112, Taipei, Taiwan, ROC c Department of Applied Mathematics, Chung-Yuan Christian University, No. 200, Chung Pei Road, Chung Li City 32023, Taiwan, ROC d School of Chinese Medicine, China Medical University, No. 91, Hsueh-Shih Road, Taichung 40402, Taiwan, ROC e School of Nursing, National Taipei University of Nursing and Health Sciences, No. 365, Minte Road, Taipei, Taiwan, ROC b

A R T I C L E I N F O

A B S T R A C T

Article history: Received 12 January 2013 Received in revised form 6 June 2013 Accepted 11 June 2013

Background: Although it can be reduced, postoperative pain remains a problem. Acupressure with electric stimulation may be more effective for postoperative pain management than acupressure alone. Objectives: This study aimed to evaluate the effects of integrative acupoint stimulation (IAS) on the relief of postoperative pain and on the reduction of morphine-related side effects. Design: A single-blinded, sham-controlled study with three groups. Setting: An orthopedic ward in a 2900-bed teaching medical center. Participants: Forty-five subjects in each of three groups. Methods: Each subject received a multimedia course on patient-controlled analgesia (PCA) before surgery to learn about the use of narcotic analgesics and the operation of the PCA device. Treatment was as follows: (1) for the IAS group, auricular acupressure combined with transcutaneous electric acupoint stimulation (TEAS) at the true acupoint; (2) for the sham group, acupoint stimulation in the same manner but at a sham acupoint or without embedding seeds and pressure; (3) for the control group, no IAS intervention. Results: Pain scores were significantly lower in the IAS group than the other two groups at 2 h and 4 h after returning to the ward, and 24 h after surgery. The analgesic requirement during the 72 h after surgery and the overall incidence of morphine-related side effects were significantly lower in the IAS group. Conclusion: The study demonstrates that combined auricular acupressure and TEAS decreased postoperative pain, the use of equianalgesic morphine, and morphine-related side effects. IAS provides better analgesia when used in conjunction with PCA after lumbar spine surgery and can be regarded as a component of multimodal analgesia. ß 2013 Elsevier Ltd. All rights reserved.

Keywords: Auricular acupressure Transcutaneuos electric acupoint stimulation (TEAS) Postoperative pain Morphine-related side effects Sham-controlled study

* Corresponding author. Tel.: +886 2 28227101x3317. E-mail addresses: [email protected] (Y.-C. Chung), [email protected] (M.-Y. Tsou), [email protected] (H.-H. Chen), [email protected] (J.-G. Lin), [email protected] (M.-L. Yeh). 1 Tel.: +886 3 5381183x7504. 2 Tel.: +886 2 28757101. 3 Tel.: +886 3 456 3126. 4 Tel.: +886 4 252053366x3311. 0020-7489/$ – see front matter ß 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijnurstu.2013.06.007

Y.-C. Chung et al. / International Journal of Nursing Studies 51 (2014) 370–378

What is already known about the topic?  Clinical pain management practices are well established, but 50–60% of the lumbar spine surgical patients experience moderate pain.  With PCA, patients may decrease their pain but in the process cause postoperative nausea and vomiting.  Pain beliefs and pain attitudes of patients could interfere with postoperative pain management, such as misconceptions about the use of analgesics. What this paper adds  Auricular acupressure combined with TEAS tends to decrease pain intensity over the first 72 h after lumbar spine surgery, especially during the 4–7 h period just after surgery when pain is at its peak.  Auricular acupressure combined with TEAS helps reduce postoperative analgesic requirements and morphinerelated side effects.  Postoperative analgesic requirement is reduced by IAS, but the high incidence of morphine-related side effects needs to improve. 1. Introduction Postoperative pain continues to be a concern because treatment of pain is not optimal (Benhamou et al., 2008; Sommer et al., 2009). There are well-established procedures for clinical pain management, but more than half of lumbar spine surgery patients experience moderate pain at rest (Sommer et al., 2009). Postoperative pain contributes to emotional distress, and prolonged hospitalization (Kwekkeboom and Gretarsdottir, 2006). Up to 5% of individuals undergoing surgery will develop severe persisting pain leading to chronic physical disability and psychosocial distress (Poleshuck and Green, 2008). Reduction of postoperative pain is therefore essential. Patient-controlled analgesia (PCA), a patient-oriented approach, is widely used to administer opioids for postoperative pain management. PCA provides better pain control and greater patient satisfaction than ‘asneeded’ analgesia according to a Cochrane systematic review of 55 randomized controlled trials (RCTs) (Hudcova et al., 2006). However, pain in patients with access to PCA is moderate during first 24 h after spinal surgery (Yeh et al., 2010b). With PCA, postoperative nausea and vomiting (PONV) is the most common complication (Wang et al., 2009a; Yeh et al., 2009). A systematic review showed the incidence of PONV without antiemetics ranged from 54% to 87% (Tramer and Walder, 1999). With antiemetics, the incidence of PONV decreased to 20–48% (Huh et al., 2010; Warren and King, 2007). However, use of antiemetic therapy for PONV, though it is effective, has risks (Golembiewski et al., 2005). Non-pharmacologic postoperative pain management interventions and their PONV side effects are of considerable concern. Evidence shows that auricular acupressure combined with transcutaneous acupoint electric stimulation (TAES), a noninvasive method of acupoint stimulation, relieves

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pain. According to principles of Chinese medicine, the acupoints on the ear and meridian are closely tied to the internal organs (Yeh et al., 2004a,b). Stimulation of the acupoint rectifies qi, stabilizes the body, strengthens bodily functions, and cures disease (Yeh et al., 2011a). In TAES, the acupoint is stimulated intermittently with alternating low- and high-frequency (called dense-anddispersed) electrical current. Different frequencies of TAES cause the release of different opioid peptides with analgesic effects. Low frequency stimulation (e.g., 2 Hz) induces analgesia by release of b-endorphin, enkephalin, and orphanin, whereas high frequency stimulation (typically 80–100 Hz) induces analgesia by release of dynorphin (Lin and Chen, 2008; White et al., 2008). TAES stimulates the large myelinated (Ab) fibers that inhibit the transmission of nociceptive stimuli and thereby stimulates the release of g-aminobutyric acid (GABA, which relieves pain) according to the gate control theory of pain (Melzack and Wall, 1965). TAES produces an obvious decrease in PCA opioid consumption after lumbar spine surgery (Yeh et al., 2010a). According to a systematic review of the literature on the effect of auricular acupuncture on postoperative pain, the effects were positive in eight of nine randomized controlled trials. However, these studies had methodological problems including small sample size and inadequate control of nonspecific effects or blinding (Usichenko et al., 2008). Although a meta-analysis of 17 auriculotherapy studies showed pain reduction, it was suggested that further large, well-designed trials would be necessary to obtain a more accurate estimate of this effect (Asher et al., 2010). It has also been suggested that auriculotherapy can be used to minimize the morphine-related side effects of PCA pain treatment (Yeh et al., 2011b). For lumbar spine surgery, the average operating time is 200–270 min (Yeh et al., 2010a,b), that is a major surgical procedure. Patients using self-controlled analgesia still felt moderate intensity postoperative pain 72 h after surgery and adding auricular acupressure did not relieve pain efficiently (Yeh et al., 2010b). In contrast, TAES had analgesic effects when used alone (Yeh et al., 2010a) or combined with acupuncture (White et al., 2008). The effect of acupressure alone was insufficient. Studies are needed to determine the adjuvant effects of auricular acupressure combined with TAES on pain in lumbar spine surgical patients with access to PCA. There are many obstacles to postoperative pain management. Patients’ reluctance to report pain and to use analgesics is major barriers to the control of pain. This is caused by inadequate preoperative instruction (Clarke et al., 1996), beliefs concerning pain (Tzeng et al., 2006), and misconceptions (Yeh and Chung, 2009), and taking the drugs will lead to addiction (Yeh et al., 2007). Some studies identified the preoperative determinants of severe postoperative pain, including young age (Gagliese et al., 2008), female (Gagliese et al., 2008), preoperative narcotic use (Lynch et al., 1997), moderate to severe preoperative pain (Sommer et al., 2009), preoperative anxiety and depression (Caumo et al., 2002), chronic sleeping difficulty (Mamie et al., 2004), and catastrophizing (Sommer et al., 2009).

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2. Purpose statements This study aimed to examine the effects of integrative acupoint stimulation on reducing postoperative pain, analgesic consumption, and incidence of morphine-related side effects during first 72 h after spinal surgery. There were significant differences in pain intensity, analgesic requirement, and incidence of morphine-related side effects were hypothesized among three groups. 3. Methods 3.1. Research design and participants This was a single-blinded, sham-controlled study with three groups. The placebo effect was evaluated in a sham acupoint stimulation group. The subjects and medical staff were blind to treatment assignment. The integrative acupoint stimulation (IAS) group received auricular acupressure combined with transcutaneous electric acupoint stimulation (TEAS) at the true acupoints; the sham group received acupoint stimulation in the same manner but at sham acupoints or without embedding seeds and pressure; and the control group received none of the above interventions. To avoid contamination of the intervention, enrollment and data collection for the control group was completed first and was followed by enrollment and data collection for the other two groups. Computer-generated randomization was used to allocate subjects to the IAS group or sham group. To conceal the allocation, randomization was carried out using sequentially numbered, opaque, sealed envelopes. Each subject received multimedia lessons on PCA. All subjects with a pathological diagnosis of spinal stenosis, spondylolisthesis, and herniated intervertebral disk and who had similar neurological deficit cause low back pain, numbness or tingling, and underwent lumbar spine surgery with decompression or stabilization procedure (Harvey, 2005), were consecutively recruited from an orthopedic ward in our 2909-bed medical center in Taiwan. Inclusion criteria were: age 18 years or older, general anesthesia, American Sociological Association (ASA) class III, consent to PCA, and return to the ward directly from the anesthesia recovery room. Exclusion criteria were: use of antiemetics or morphine before surgery, usage of a pacemaker, history of arrhythmia or epilepsy, opiate dependence, clinically significant cardiovascular diseases, abnormally shaped earlobes, and abnormally shaped cutaneous lesions at the application sites. Based on the primary outcome of morphine consumption with a medium effect size (f = 0.25) and 80% power at 5% level of significance using repeated-measures 3 times (Cohen, 1988), our calculation indicated that 108 subjects would be minimally required. With an estimated follow-up loss of 25%, 135 subjects overall (45 in each group) were thought to be necessary. Fig. 1 shows the flow chart of the research protocol and allocation of participants of this study. 3.2. Interventions The PCA device containing 100 mg of morphine and 2 mg of droperidol per 100 mL of solution was connected to

the patient’s intravenous line in the anesthesia recovery room, and pain medication was continuously administered for 72 h. The loading dose was 2.0–3.2 mg, basal infusion rate was 0.40–0.75 mg h 1, bolus dose was 0.7–1.0 mg, lockout interval between each PCA dose was 6 min, and maximal dosage in 4 h was 8–10 mg. To prevent PCA abuse, all subjects received printed booklets and multimedia instruction on how to use the PCA device the evening before surgery. The multimedia videodisk with printed booklet was divided into four main sections: introduction to PCA, clinical conditions, nursing guide, and frequently asked questions (FAQs) about clinical conditions or situations related to pain (Yeh et al., 2004a,b). Each section contained a word description, pictures, figures, films, sound, etc. The entire program lasted about 20 min. Our previous study showed that PCA multimedia presentations with printed booklets led to significant improvement in pain cognition and analgesia quality (Yeh et al., 2007). The PCA multimedia presentation with printed booklets was given to each participant individually, and the content was discussed one-on-one until the patient was confident they could use the PCA device accurately. Auricular acupressure was applied to five common auricular acupoints, including the shenmen (TF4), lumbosacral vertebrae (AH10), kidney (CW8), subcortex (AT5), and stomach (CO4). Pressure to the shenmen raises endorphin levels in the body and thus reduces pain (Yeh et al., 2004a,b). The lumbosacral vertebrae is the most commonly stimulated point in clients with low back pain and is used to reduce lumbosacral pain (Suen et al., 2007). Stimulation of the kidney acupoint strengthens the lumbar spine (Suen et al., 2007), and stimulation of the subcortex and stomach acupoints normalize qi energy flow and harmonize the stomach (Chou and Chou, 2008). For the IAS group, a seedembedding method with Wangbuliuxingzi seeds (Beijing, China) was used to prolong stimulation at the auricular acupoint. Seeds were placed unilaterally by applying an adhesive patch (0.5 cm  0.5 cm) onto the acupoints. Pressure was applied by thumb and index finger for 3 min per acupoint, for a total session duration of 15 min (5 points  3 min). The intervention consisted of ten 15-min sessions, including 1 session at 1 h after returning to the ward, 1 session at 3 h after returning to the ward, 4 sessions (9AM, 1PM, 5PM, and 9PM) on Day 1 after surgery, and 4 sessions (9AM, 1PM, 5PM, and 9PM) on Day 2 after surgery. The presence of the de qi sensation was used to establish the efficacy of auricular acupressure and TAES (Han, 2004). In addition, TAES was delivered to the Weizhong (BL40) and Yanglingquan (GB34) acupoints (Lin, 2010) using a Transcutaneous Electrical Muscle/ Nerve Stimulator (GP8016M, Sanidad Tens/Ems, FDA510K: K021430) with two pairs of disposable electrode-pads (3 cm  3 cm). The dense-and-dispersed mode of stimulation was used at a current of 4–7 mA, depending on subject’s tolerance (Chen et al., 2005; Yeh et al., 2010a), with pulse duration of 0.25 ms for 20 min at 1 and 3 h after returning to the ward. The sham group was treated in the same manner, except that acupressure was applied at the true auricular acupoints without embedding seeds and TAES was applied to sham acupoints that were 2 cm from the true acupoints and not on any meridians (Wang and

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Assessed for eligibility (n=177)

Enrollment (n=135)

Written and verbal consent Random assignment (n=90)

Preoperative day: PCA education for three groups

IAS group (n=45)

Sham group (n=45)

Control group (n=45)

1. Demography 2. STAI-state 3. TDQ

1hr after returning to the ward: AA+TAES

IAS group (n=40)

Sham group (n=42)

Control group (n=45)

3hr after returning to the ward: AA+TAES

IAS group (n=40)

Sham group (n=42)

Control group (n=45)

Pain intensity: 1. 1 h after returning to the ward but before treatment 2. 2 h and 4 h after returning to the ward

Day1 after surgery: AA (qid)

IAS group (n=40)

Sham group (n=42)

Control group (n=45)

Day2 after surgery: AA (qid)

IAS group (n=40)

Sham group (n=42)

Control group (n=45)

24 h, 48 h, 72 h after surgery: 1. Pain intensity 2. Consumption of opioid 3. Side effect of morphine

Fig. 1. The flow of research design, participants’ recruitment, intervention and assessment. IAS, integrative acupoint stimulation; AA, Auricular acupressure; TAES, Transcutaneuos acupoint electric stimulation; STAI, state-trait anxiety inventory; TQD, Taiwanese depression questionnaire.

Trannier, 2000; Yeh et al., 2010a) with current less 1 mA. Subjects in the control group received no acupoint stimulation. Interventions were provided by a research nurse with academic credits in relevant subjects and verified by two traditional Chinese medicine (TCM) physicians. 3.3. Measurement Demographic and intraoperative data were collected. Preoperative pain intensity was assessed on a visual analog scale (VAS), ranging from 0 (no pain) to 10 (extreme pain). Preoperative anxiety was measured using the State Anxiety Inventory (STAI) (Spielberger et al., 1983), which reflects emotional state as intensity of environmental stimuli changes. Each of the 20 items were scored on a 4point Likert scale, from 1 (not at all) to 4 (very much), and an overall score between 20 and 80 was computed, with 20–39 being low, 40–59 moderate, and 60–80 high. Cronbach’s a was 0.70. The Taiwanese depression questionnaire (TDQ) is a culturally specific depression instrument and has satisfactory reliability and validity (Lee et al., 2000). The test consists of 18 items scored on a 4-point scale ranging from 0 to 3 on the basis of physical and emotional feelings. An overall score ranges from 0 to 54,

with the higher score indicating greater severity. A cut-off score of 19 had good predictive value, sensitivity of 0.89, and specificity of 0.92 (Lee et al., 2000). Cronbach’s a was 0.90. Postoperative pain was assessed on a visual analog scale (VAS), ranging from 0 (no pain) to 10 (extreme pain). The outcomes were evaluated at 1 h after returning to the ward (pretest; before the first session), 2 h after returning to the ward (post test 1; 30 min after the first session), 4 h after returning to the ward (post test 2; 30 min after the second session), and 24 h (post test 3), 48 h (post test 4), and 72 h (post test 5) after surgery. Analgesics including morphine from the PCA device, oral analgesic medication, and other analgesics were given for 72 h. The equianalgesic usage was calculated from a conversion chart for opioid analgesics (Donnelly et al., 2002). Morphine-related side effects included dizziness, nausea/vomiting, itching, sedation, and hypotension. Respiratory depression was defined as SpO2 < 90% and respiratory rate < 10 breaths min 1 (Behera et al., 2008). Sedation was evaluated on a 5-point scale (0 = awake; 1 = drowsy; 2 = asleep but easily aroused; 3 = asleep but difficult to arouse; 4 = coma), and a score > 2 was defined as sedated (Lee et al., 2008). Hypotension was defined as a more than 20% drop in systolic blood pressure from the preoperative level or as < 90 mmHg during the

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study period (Behera et al., 2008). Morphine-related side effects were rated 0 = absent or 1 = present. Adverse events were assessed. The outcome measures were evaluated at 24 h, 24–48 h, and 48–72 h after surgery.

determine which one appear to fit best. For a selected model, the best correlation structure was the one with the lowest value of QIC (quasi-likelihood estimation) (Norusˇis, 2007).

3.4. Procedures and data analysis

4. Results

Ethical approvals were obtained from the institutional review board of our hospital. Informed consent was obtained from all participants after they received a full explanation of the study. They were told that all data will remain confidential at all times and were free to withdraw at any time during the study without affecting their care. Data were analyzed using IBM SPSS 20.0 for Windows. Demographic data and medical history data were analyzed using descriptive statistics. To verify the homogeneity between groups, the chi-square test was used for categorical data, whereas one-way analysis of variance (ANOVA) was used for continuous data. The ANOVA test must meet the assumptions of independence, normailty and variance homogeneity. Postoperative pain scores at repeated measurements violated the assumption of normal distribution. Therefore, the differences in effects of outcomes among the groups were analyzed with generalized estimating equations (GEE). We compared several different correlation structures for the same data to

Of the 177 patients who were eligible, 135 signed the informed consent form and were included, and 127 completed the study (79 female and 48 male; mean age 57.97  13.78 [range, 19–82]). Eight withdrew (7 refusing IAS, and 1 because of fever). Table 1 presents the demographic and intraoperative characteristics. The three groups had similar characteristics (p > 0.05). Fig. 2 shows the pain VAS scores over time for the three groups. Before acupoint stimulation, the VAS scores at pretest were not significantly different among the groups (F(2, 124) = 1.56; p = 0.21). There were significantly different at post test 1 (F(2, 124) = 24.23; p < 0.001), post test 2 (F(2, 124) = 27.98; p < 0.001), post test 3 (F(2, 124) = 4.32; p = 0.02), post test 4 (F(2, 124) = 3.34; p = 0.04), and post test 5 (F(2, 124) = 5.25; p = 0.006) among three groups. Table 2 shows parameter estimates and their standard errors for a model with an auto-regressive order 1 autocorrelation and model-based estimates of variance in GEE models. After adjusting for age and gender, relationships among the VAS

Table 1 Homogeneity of the demographics and intraoperative parameters among groups. Variables

Age (mean  SD) Gender (n, %) Female Male Body mass index (mean  SD) Chronic sleep disturbance (n, %) No Yes Postoperative pain expectation (n, %) No to mild Moderate to severe Diagnosis (n, %) Vertebral formen stenosis Spondylolith Herniation intervertebral disk Anesthesia history (n, %) 0 1 2 Preoperative pain (mean  SD) Preoperative depression (mean  SD) Preoperative anxiety (mean  SD) American society of anesthesiologists (n, %) I II III Anesthesia duration (mean  SD) Operation duration (min, mean  SD) Intravenous fluid (mL, mean  SD) Blood loss (mL, mean  SD) Number of drainage (n, %) 1 2 In recovery room (min, mean  SD) a

Fisher’s exact test.

F or x2 (p)

IAS group

Sham group

Control group

(n = 40)

(n = 42)

(n = 45)

60.25  13.42

59.79  12.61

54.24  14.63

F = 2.62 (0.08)

30 (75.0) 10 (25.0) 25.70  4.36

26 (61.9) 16 (38.1) 26.70  3.92

22 (51.1) 22 (48.9) 26.23  4.97

x2 = 5.14 (0.08)

21 (52.5) 19 (47.5)

25 (59.5) 17 (40.5)

24 (53.3) 21 (46.7)

x2 = 0.50 (0.78)

9 (22.5) 31 (77.5)

9 (21.4) 33 (78.6)

9 (20.0) 36 (80.0)

x2 = .08 (0.96)

28 (70.0) 9 (22.5) 3 (7.5)

23 (54.8) 14 (33.3) 5 (11.9)

37 (82.2) 5 (11.1) 3 (6.7)

x2 = 8.04 (0.09)a

11 (27.5) 20 (50.0) 9 (22.5) 4.23  2.43 15.00  10.88 44.60  7.28

19 (45.2) 17 (40.5) 6 (14.3) 4.16  1.80 15.81  11.66 44.71  5.72

21 (46.7) 15 (33.3) 9 (20.0) 4.11  1.81 12.53  9.78 43.29  9.14

F = 4.46 (0.34)

6 (15.0) 28 (70.0) 6 (15.0) 260.75  60.06 212.90  65.17 2902.50  837.5 477.00  309.19

5 (11.9) 31 (73.8) 6 (14.3) 275.60  81.92 231.71  74.39 2983.45  1019.37 598.68  328.69

11 (24.4) 30 (66.7) 4 (8.9) 259.93  81.12 215.00  80.06 2796.80  897.21 469.33  300.00

37 (92.5) 3 (7.5) 169.15  40.31

38 (90.5) 4 (9.5) 160.60  33.45

43 (95.6) 2 (4.4) 161.76  40.93

F = 0.51 (0.60)

F = 0.04 (0.96) F = 1.93 (0.15) F = 0.47 (0.63) x2 = 3.08 (0.56)

F = 0.54 (0.58) F = 0.82 (0.44) F = 0.45 (0.64) F = 2.14 (0.12) x2 = 0.87(0.69)a

F = 0.59 (0.56)

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Fig. 2. Change in pain intensity change over time. ***p < 0.001; **p < 0.01; *p < 0.05; Sheff post hoc: post test 2 (IAS < sham; IAS < control); post test 3 (IAS < sham; IAS < control); post test 4 (nil); post test 5 (IAS < sham); pretest: 1 h after returning the ward but before the 1st session; post test 1: 2 h after returning to the ward (30 min after 1st session); post test 2 (30 min after 2nd session): 4 h after returning to the ward. Post test 3: 24 h after surgery; post test 4: 48 h after surgery; post test 5: 72 h after surgery.

scores, and time, group, and time-group interaction were explored. The time effect was significant in post test 1 (p < 0.001), post test 2 (p < 0.001), post test 3 (p < 0.001), post test 4 (p < 0.001), and post test 5 (p < 0.001), compared to pretest. Trend differences (interactions between time and group) were significant decrease in VAS scores for the IAS group at post test 1 (p < 0.001), post test 2 (p < 0.001), and post test 3 (p = 0.047), indicating time-dependent growth effects. Fig. 3 shows that equianalgesic morphine consumption decreased over time in all three groups. The three groups differed significantly at 24 h (F(2, 124) = 8.79, p < 0.001) and 24–48 h (F(2, 124) = 4.97, p = 0.008), but not at 48–72 h (F(2, 124) = 2.86, p = 0.06), after surgery. The overall equianalgesic morphine consumption was 69.16  25.62 mg for the IAS group, 84.36  28.93 mg for the sham group, and

Table 2 Results of generalized estimating equations in pain. Parameters Intercept IAS groupa Sham groupa Post test 1b Post test 2b Post test 3b Post test 4b Post test 5b IAS  post test 1c IAS  post test 2c IAS  post test 3c IAS  post test 4c IAS  post test 5c Sham  post test 1c Sham  post test 2c Sham  post test 3c Sham  post test 4c Sham  post test 5c

Estimate 7.75 0.15 0.62 0.06 0.14 2.54 3.93 4.68 2.74 3.83 0.99 0.50 0.78 0.38 0.25 0.08 0.06 0.08

SE

p

0.51 0.40 0.39 0.25 0.31 0.34 0.40 0.37 0.36 0.46 0.50 0.52 0.54 0.36 0.44 0.49 0.52 0.53

<0.001 0.72 0.12 0.81 0.64 <0.001 <0.001 <0.001 <0.001 <0.001 0.047 0.34 0.15 0.29 0.58 0.88 0.92 0.88

N = 127, adjusted: age and gender. a Reference group: control group. b Reference group: pretest. c Reference group: control group  pretest, : interaction.

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Fig. 3. Trends in equianalgesic morphine consumption over time. ***p < 0.001; **p < 0.01.

94.16  29.89 mg for the control group, with a significant difference among the three groups (F(2, 124) = 8.34, p = 0.001) and between the IAS and control groups (p = 0.001 in the Scheffe post hoc test). Table 3 shows the parameter estimates and their standard errors for a model with an independent working correlation structure and model-based estimates of variance in GEE models. After adjusting for age and gender, relationships among the equianalgesic morphine consumption, and time, group, and time-group interaction were explored. The model showed significant between-group differences over time in equianalgesic morphine consumption for the IAS group (p < 0.001) and sham group (p = 0.03), respectively, compared to the control group. After surgery, the time effect was significant during 24–48 h (p < 0.001) and 48–72 h (p < 0.001), compared to 24 h. Trend differences (interactions between time and group) were also significant decrease in equianalgesic morphine consumption at 48–72 h versus the 24 h (p = 0.04) for the IAS group, and at 48–72 h versus the 24 h (p = 0.04) for the sham group. The number of morphine-related side effects ranged from 0 to 4, with a mean of 1.59  1.22. The incidence of morphine-related side effects was 62.5%, 85.7%, and 68.9% for the IAS, sham, and control groups, respectively, with a significant between-group difference (x2 = 5.97, df = 2, p = 0.048). The overall incidence was 72.4%; the most frequent was dizziness (45.7%), followed by nausea/vomiting (39.4%), sedation (35.4%), itching (33.1%), and hypotension (5.5%). Table 4 presents the morphine-related side effects, with a significant between-group difference in sedation (p = 0.004) and hypotension (p = 0.01) during the first 24 h after surgery, and in dizziness (p = 0.007) between 24 h and 48 h. 5. Discussion Adjuvant use of auricular acupressure combined with TEAS reduced postoperative pain, analgesic requirements, and morphine-related side effects in lumbar spine surgical patients postoperatively. IAS tended to decrease pain over the first 72 h after surgery, especially during the 4–7-h period of peak pain. There is no similar study currently available. Postoperative pain intensity was severe in the first hour after returning to the ward from the anesthesia recovery room. In general, patients stay in the anesthesia recovery room about 3 h, and pain intensity peaks at 4–7 h postoperatively (Minville et al., 2008; Wang et al., 2009b).

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Table 3 Generalized estimating equation model in equianalgesic morphine consumption. Parameters

Estimate

Intercept IAS groupa Sham groupa 24–48 h after surgeryb 48–72 h after surgeryb IAS group  24–48 h after surgeryc IAS group  48–72 h after surgeryc Sham group  24–48 h after surgeryc Sham group  48–72 h after surgeryc

41.82 9.04 5.36 8.36 14.82 2.67 7.35 3.65 7.23

SE

p

2.98 2.50 2.45 2.40 2.40 3.49 3.49 3.45 3.45

<0.001 <0.001 0.03 <0.001 <0.001 0.45 0.04 0.29 0.04

N = 127; adjusted: age and gender. a Reference group: the control group. b Reference group: 24 h after surgery. c Reference group: control group  24 h after surgery, : interaction.

IAS had a true, not placebo, pain-lowering effect during the ward period. Similarly, Yeh et al. (2010a) reported that TEAS reduces pain in the first few hours after surgery. Chao et al. (2007) showed that electrical stimulation reduced pain in the first stage of labor. Some studies also report that acupoint stimulation reduces pain from abdominal surgery (El-Rakshy et al., 2009), inguinal hernia repair (Dias et al., 2010), and cardiac surgery (Coura et al., 2011), but not nasal septoplasty (Sahmeddini et al., 2010). Increased pain may be caused by insufficient stimulation as previously mentioned. Clinical studies normally suggest a 20–30-min period of electrical stimulation for pain reduction (Chao et al., 2007; Coura et al., 2011; Dias et al., 2010). In addition to reducing pain, IAS also decreased overall analgesic consumption in the first postoperative 72 h. This is consistent with findings in other studies (Chen et al., 1998; Usichenko et al., 2005, 2007; Wang et al., 1997; Yeh

Table 4 Postoperative morphine-related side effects. Variables

Sham group

Control group

(n = 40)

(n = 42)

(n = 45)

Yes (%)

Yes (%)

Yes (%)

(38%) (38%) (18%)

17 (40%) 18 (43%) 9 (21%)

16 (36%) 6 (13%) 5 (11%)

(33%) (10%) (8%)

15 (36%) 12 (29%) 9 (21%)

8 (18%) 6 (13%) 5 (11%)

3.94 (0.14) 5.71 (0.06) 3.74 (0.15)

(25%) (18%) (5%)

6 (14%) 12 (29%) 5 (12%)

7 (16%) 11 (24%) 3 (7%)

1.89 (0.41) 1.42 (0.49) 1.49 (0.48)

(13%) (3%) (0%)

19 (45%) 7 (17%) 2 (5%)

17 (38%) 3 (7%) 1 (2%)

11.01 (0.004) 5.55 (0.07)a 1.78 (0.53)a

(0%) (0%) (0%) (63%)

6 1 1 36

1 0 0 31

Dizziness 15 0–24 h 24–48 h 15 48–72 h 7 Nausea/vomiting 0–24 h 13 24–48 h 4 48–72 h 3 Itching 0–24 h 10 24–48 h 7 48–72 h 2 Sedation 0–24 h 5 24–48 h 1 48–72 h 0 Hypotension 0–24 h 0 24–48 h 0 48–72 h 0 Overall 25 a

x2 (p)

IAS group

Fisher’s exact test.

(14%) (2%) (2%) (86%)

(2%) (0%) (0%) (69%)

0.23 (0.90) 10.17 (0.007) 1.72 (0.42)

7.72 1.85 1.85 5.97

(0.01)a (0.65)a (0.64)a (0.048)

et al., 2010a). These studies also gave participants the same preoperative education with multimedia instruction or printed booklets or both to ensure they understood PCA and used the PCA device correctly. TEAS alone decreased morphine consumption after lower abdominal surgery in 39% of such patients (Chen et al., 1998) and decreased the PCA opioid requirement in 30–35% of such patients, 90– 95% of whom assessed their postoperative pain relief as adequate (Wang et al., 1997). Auricular acupuncture or electric acupuncture also decreased analgesic consumption after total hip arthroplasty (Usichenko et al., 2005) and ambulatory knee surgery (Usichenko et al., 2007). Adequate preoperative patient education influences patients’ pain beliefs and pain attitudes that could interfere with postoperative pain management such as taking inadequate analgesic dose. All participants in this study received preoperative education with multimedia instruction and printed booklets, which was sure the consistent baseline for a comparison of the analgesic consumption. However, participants in the sham and control groups did not receive their analgesic dose enough. On the other hand, if given enough opioids to control pain, patients may overmedicate, increasing the risks of oversedation and respiratory depression (Wang et al., 2009a). In conclusion, auricular acupressure combined with TAES added to the analgesic effect and effectively decreased analgesic requirements, without causing adverse events, after lumbar spine surgery in patients given access to PCA during this period. PCA morphine has numerous side effects. In our study, the IAS group (compared with the sham group) used less morphine, which lowered the incidence of morphinerelated side effects during the 72-h postoperative period. The side effects in descending order of frequency were dizziness, nausea/vomiting, sedation, itching, and hypotension. The most common side effects in other studies were vomiting/nausea, followed by dizziness (Chen et al., 1998; Wang et al., 2009a). Applying auricular acupressure to the subcortex and stomach acupoints that normalize qi energy flow and harmonize the stomach may be like adding antiemetics to PCA. IAS somehow had a therapeutic effect on nausea/vomiting. It is worth mentioning that for the IAS, sham, and control groups, PCA morphine consumption was respectively 50.30 mg, 60.22 mg, and 70.31 mg, and the total amount of droperidol consumption was respectively 2.51 mg, 3.01 mg, and 3.52 mg. Compared to the IAS group, the control group remarkably used more antiemetic thereby potentially lowering the relative frequency of nausea and vomiting. Decrease in the incidence of nausea and vomiting was a true effect of IAS. In addition, the highest incidence of dizziness in this study occurred between 24 h and 48 h postoperatively. Dizziness caused physical discomfort, and led to avoidance of getting out of bed; the first time out of bed occurred on average 85.62 h postoperatively. It will be necessary to provide interventions that alleviate morphine-related dizziness in future studies. The sham group, compared to the other two groups, had the highest incidence of dizziness, nausea/vomiting, and sedation 24–48 h postoperatively. Sensory stimulation via acupuncture has the potential to produce placebo effects

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(Lin et al., 2002). In this study, no attempt was made to influence participants’ expectations regarding the effectiveness of acupoint stimulation. To evaluate the true effect of acupoint stimulation, this study added two control groups, a PCA-only group and PCA with sham group. Tables 2 and 3 show that there was no obvious placebo effect. IAS was obviously superior to the control intervention in reducing postoperative pain and morphine consumption, and significantly more morphine was consumed in the sham group than the control group. This is in agreement with other studies (Chen et al., 1998; Lin et al., 2002). IAS therefore has an adjuvant effect on postoperative pain and morphine consumption after lumbar spine surgery in patients given PCA. 6. Limitations and recommendations This study has several limitations. First, a randomized controlled trial plus non-randomized cohort was used; therefore, a selection bias exists. Second, the sample from one hospital may not be generalizable. Third, findings do not distinguish between acute pain and chronic pain. Future investigations should examine multiple sites. Exploring the effects of IAS without PCA after lumbar spine surgery is also suggested. 7. Conclusion This study examines pain intensity, amount of analgesic use, and morphine-related side effects in the first three postoperative days in order to provide a more complete assessment of postoperative pain management. IAS used as an adjunct to PCA after lumbar spine surgery reduced pain, postoperative equianalgesic morphine requirements, and morphine-related side effects. It is not associated with any of the complications of needle acupuncture. IAS is a practical and safe method of producing analgesia, and can be used for multimodal analgesia. Conflict of interest None of the authors has any potential conflicting interest in this study. Funding No funding. Ethical approval Ethical approval was obtained from the Institute of Review Board in the study hospital; written informed consent was signed by and obtained from all participants. All participants were provided written and verbal information about the study, and made aware that data collected by the researcher were remained confidential; they would be free to withdraw. References Asher, G.N., Jonas, D.E., Coeytaux, R.C., Reilly, A.C., Loh, Y.L., MotsingerReif, A.A., et al., 2010. Auriculotherapy for pain management: a

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