Evidence-Based Complementary and Alternative Medicine
Volume 2015 (2015), Article ID 657809, 28 pages
http://dx.doi.org/10.1155/2015/657809

Review Article

Acupuncture-Point Stimulation for Postoperative Pain Control: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Xian-Liang Liu,1,2,3 Jing-Yu Tan,⁴ Alex Molassiotis,⁴ Lorna K. P. Suen,⁴ and Yan Shi¹

¹10th People’s Hospital of Tongji University, 301 Yanchang Road, Shanghai 200072, China
²School of Nursing, Midwifery and Paramedicine, Australian Catholic University, 1100 Nudgee Road, Banyo, Brisbane, QLD 4014, Australia
³School of Nursing, Jinggangshan University, 28 Xueyuan Road, Ji’an 343009, China
⁴School of Nursing, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong

Received 3 April 2015; Revised 19 August 2015; Accepted 3 September 2015

Academic Editor: George David Baxter

Copyright © 2015 Xian-Liang Liu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

The purpose of this study was to evaluate the effectiveness of Acupuncture-point stimulation (APS) in postoperative pain control compared with sham/placebo acupuncture or standard treatments (usual care or no treatment). Only randomized controlled trials (RCTs) were included. Meta-analysis results indicated that APS interventions improved VAS scores significantly and also reduced total morphine consumption. No serious APS-related adverse effects (AEs) were reported. There is Level I evidence for the effectiveness of body points plaster therapy and Level II evidence for body points electroacupuncture (EA), body points acupressure, body points APS for abdominal surgery patients, auricular points seed embedding, manual auricular acupuncture, and auricular EA. We obtained Level III evidence for body points APS in patients who underwent cardiac surgery and cesarean section and for auricular-point stimulation in patients who underwent abdominal surgery. There is insufficient evidence to conclude that APS is an effective postoperative pain therapy in surgical patients, although the evidence does support the conclusion that APS can reduce analgesic requirements without AEs. The best level of evidence was not adequate in most subgroups. Some limitations of this study may have affected the results, possibly leading to an overestimation of APS effects.

1. Introduction

Nearly 86% of surgery patients experience moderate to severe postoperative pain [1]. Depending on surgery type, as many as half of these patients go on to experience chronic postoperative pain [2]. Unsatisfactory pain control can limit patients’ physical activities, prolong recovery time, and contribute to poor quality of life [3, 4]. Pain may also increase postoperative complications, such as postoperative morbidity, and may extend the length of hospitalization, increasing health care costs [5, 6].

Administration of standard analgesics, which are considered generally safe and effective, remains the primary approach to postoperative pain management [7]. However, systemic analgesic administration can induce some adverse effects (AEs), such as nausea, vomiting, depressive symptoms, pruritus, urinary retention, gastrointestinal motility, and ileus [8, 9]. AEs can impair physical and psychological wellbeing and, more seriously, may result in significant morbidity or even mortality [8–10]. To achieve better postoperative pain relief and reduce the requirement for analgesic medication, various nonpharmacological approaches, including educational intervention, relaxation, and acupuncture-point stimulation (APS), have been employed. APS has been lauded as a promising alternative method for achieving postoperative pain relief [11, 12].

APS is a widely used component of traditional Chinese medicine (TCM) together with full-body and auricular approaches [11]. In addition to the most popular methods of manual acupuncture and acupressure, APS can be achieved using modalities such as electrical acupuncture (EA) or laser stimulation and acupoint massage [12]. According to TCM philosophy, the stimulation of target acupoints along meridians produces positive effects by rebalancing qi circulation in the body [13]. However, the existence of the qi meridian system, as described in TCM, has never been demonstrated scientifically [13]. Nevertheless, the management of various forms of pain remains a key purported benefit of APS [14, 15].

Many animal experiments and clinical studies have examined the therapeutic effects of APS [16]. Early studies showed that APS provided postoperative pain relief in comparison with control groups [17, 18]. Recently, several small trials [3, 19] demonstrated that APS can relieve pain and reduce analgesic requirements associated with hysterectomy and inguinal surgery. However, Sakurai et al. [20] failed to identify any significant change in pain intensity or morphine requirement in surgical patients undergoing acupressure. A prior systematic review found that acupuncture and related techniques aided postoperative pain control, but the quality of evidence was low due to the quality and quantity of included trials, and no subgroup analysis according to acupuncture type was performed [21]. The results of another systematic review conducted by Usichenko et al. [22] suggested that auricular acupuncture was a promising method of postoperative pain reduction, but the heterogeneity of primary studies precluded data synthesis and the evidence was insufficient to draw a definitive conclusion about the treatment’s effectiveness. Following the 2008 publication of these reviews, several clinical trials were conducted to evaluate the efficacy of APS for postoperative pain management, generating new evidence on this topic [23–25].

The present systematic review and meta-analysis was conducted to evaluate the effectiveness of APS for pain control following surgical procedures. Therefore, in this study, current evidence generated by randomized controlled trials (RCTs) on the use of APS interventions for postoperative pain management was reviewed and analyzed. Data from patients receiving APS were compared with those from control groups receiving sham/placebo acupuncture, usual care, or no treatment. Compared with the previous literature, this systematic review and meta-analysis incorporates new evidence not previously synthesized and distinguishes between multiple types of APS for postoperative pain control.

2. Methods

2.1. Study Selection

As summarized in Figure 1, we performed a literature search to identify RCTs examining APS interventions in surgical patients with postoperative pain. We searched PubMed, Embase, PsycINFO, Allied and Complementary Medicine, Thomson Reuters Web of Science, ScienceDirect, China National Knowledge Infrastructure, Chinese Biological Medical Literature databases, the Cochrane Central Register of Controlled Trials, and the Cumulative Index to Nursing and Allied Health Literature from inception through 31 May 2014 (search strategies are described in Appendix). Additional relevant articles were identified by screening the reference lists of eligible studies and previous systematic reviews and by performing a manual search for articles published in the last 3 years in eight core TCM journals: Journal of Beijing University of Traditional Chinese Medicine, Journal of Nanjing University of Traditional Chinese Medicine (Natural Sciences), Chinese Journal of Traditional Chinese Medicine and Pharmacy, Chinese Journal of Information on Traditional Chinese Medicine, Chinese Journal of Basic Medicine in Traditional Chinese Medicine, Chinese Journal of Integrated Traditional and Western Medicine, Journal of Traditional Chinese Medicine, and Journal of Integrative Medicine. We also used PubMed’s “related articles” function to identify additional potentially relevant studies. The electronic search had no language restriction. In the case that there were multiple publications from the same RCT, overlapping results were extracted from one publication.

Figure 1: Flow chart of the study selection process. CINAHL, Cumulative Index to Nursing and Allied Health Literature; AMED, Allied and Complementary Medicine Database; CBMdisc, Chinese Biological Medical Literature Database; CNKI, China National Knowledge Infrastructure.

Two reviewers assessed all potentially relevant articles independently. Disagreements regarding study selection were resolved by discussion, with strict adherence to the inclusion criteria. Studies were selected for inclusion based on the following criteria: (1) RCT; (2) adult (age ≥ 18 years) participants with pain following any surgical procedure; (3) APS intervention (including full-body or auricular manual acupuncture or EA, acupressure, seed embedding, and plaster therapy) conducted by an acupuncturist, TCM practitioner, or other health care providers with qualification and/or training in acupuncture therapy; (4) control group receiving standard treatment (e.g., active pain control approach normally provided to surgical patients, including analgesia medication, nursing guidance, and other usual cares), sham/placebo APS (faked APS intervention), or no treatment (provision of usual postoperative care not involving active analgesic interventions); (5) primary outcome of pain intensity, measured by a valid self-reported instrument such as a visual analog scale (VAS), numerical rating scale (NRS), or verbal reporting; and (6) secondary outcomes of analgesic consumption and APS-related AEs (i.e., any adverse events resulting from APS intervention, minor (e.g., needling site pain), intermediate (e.g., bleeding and hematoma), or serious (pneumothorax and cardiac tamponade)).

In the study selection process, acupuncture was defined as the stimulation of specific acupuncture points along the skin of the body by using thin needles, with or without the application of heat, pressure, or laser light to these same points [12]. EA is similar to acupuncture but involves the use of devices (e.g., a wristwatch-like device and surface electrodes attached to a transcutaneous electrical nerve stimulation device) on acupoint [14]. Seed embedding was defined as an auricular acupressure process involving the embedding of magnetic beads or other seeds within skin-colored adhesive tape, which is placed on the auricular acupoints and retained in situ for several days [6]. In this systematic review, plaster therapy mainly referred to the use of capsicum plaster as an alternative to acupuncture [23].

2.2. Quality Assessment

Two reviewers conducted independent assessments of the methodological quality and risk of bias of each RCT using Cochrane Collaboration’s risk of bias tool [26]. This tool provides for the assessment of seven domains: sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective outcome reporting, and “other issues.” Items were scored as showing low, high, or unclear risk of bias [26]. All disagreements on scoring were resolved by discussion. When a sufficient number of studies were available and a meaningful assessment of publication bias could be carried out, a funnel plot was constructed.

Adequate allocation concealment and blinding of outcome assessors were designated as key domains for this assessment, where key domains are not only more likely to influence bias magnitude and direction but also more likely to impact study results. Domain-based evaluation was employed as described in the Cochrane Handbook for Systematic Reviews of Interventions 5.0.2 (updated September 2009). The overall risk of bias was categorized as follows. An overall low risk of bias (plausible bias unlikely to alter the results) was identified when all key domains were assessed as having a low risk of bias. An overall unclear risk of bias (plausible bias that raises some doubt about the results) was identified when one or more key domains were assessed as having an unclear risk of bias. An overall high risk of bias (plausible bias that seriously weakens confidence in the results) was identified when one or more key domains were assessed as having a high risk of bias. Small studies have been shown to overestimate treatment effects and to be at increased risk of bias, allowing critical criteria such as blinding to be compromised. Studies were considered to be at low risk of bias if they had at least 200 participants, at unknown risk if they had 50 to 200 participants, and at high risk if they had fewer than 50 participants.

2.3. Data Extraction and Management

Two reviewers independently extracted the following data from included studies using a predefined form: authors, study design, setting, population and participant demographics, intervention characteristics (e.g., acupuncture type, acupoints used, and treatment duration), comparators, outcome measures and instruments, follow-up, and some numeric data (mainly the results of pain intensity and analgesic consumption). We contacted RCT authors by email to obtain data necessary for effect size estimation when such data were missing from publications (e.g., due to aggregated data reporting). When authors did not reply, outcome data presented only in figures and/or graphs were extracted when possible; these data were included in the analysis only when the two reviewers independently obtained the same results.

When a study reported multiple group comparisons (e.g., high electrical stimulation versus low electrical stimulation or usual care and preoperative acupuncture versus postoperative acupuncture or usual care), only data from the treatment group that received the more intensive and comprehensive postoperative intervention were included in the analysis. These data were compared with those from the control group.

2.4. Subgroup Analysis

When data were sufficient, subgroup analyses of different types of APS, surgery, and control groups were conducted. Analyses of APS type compared the use of acupoints on the body (EA, manual acupuncture, acupressure, and plaster therapy) and/or auricular points (EA, manual acupuncture, and seed embedding). A subgroup analysis of EA studies compared the use of different devices (e.g., a wristwatch-like device and surface electrodes attached to a transcutaneous electrical nerve stimulation device). Analyses of control group types compared APS with standard treatment (usual care and no treatment) or placebo/sham therapies. On the basis of whether body acupoints, auricular points, or integrative acupoints were stimulated, we also undertook subgroup analyses of surgery types, including abdominal, knee, oral, and cardiac surgeries.

2.5. Statistical Analysis

Meta-analysis was performed using Review Manager software (ver. 5.1; available from http://www.cochrane.org/). For continuous outcomes, mean differences with 95% confidence intervals (CIs) were calculated as appropriate. When the same continuous outcome was assessed using different instruments, the standardized mean difference was calculated. For dichotomous outcomes, effect size variables, such as the relative risk (RR), were calculated. In the presence of significant heterogeneity ( test, ), random-effects model was used. Otherwise, fixed-effects model was applied. Descriptive analysis was used when data could not be converted or pooled.

Potential sources of heterogeneity in the outcomes examined are differences in the tool used to measure pain, population differences (e.g., surgery type, age, and sex), and differences in the comparator used (e.g., sham/placebo acupuncture, usual care, and no treatment). We assessed heterogeneity using the statistic, which describes the percentage of total variation across trials (low, 0–40%; moderate, 30–60%; substantial, 50–90%; considerable, 75–100%; Chapter 9: Analysing Data and Undertaking Meta-Analyses; The Cochrane Collaboration 2011, available from http://www.cochrane-handbook.org/). To assess which RCTs affected the overall results, sensitivity analyses were performed for the entire sample and subgroups with significant heterogeneity. If heterogeneity was considerable, even with the random-effects model, best evidence synthesis was also used. The evidence was synthesized based on each subgroup. We employed a qualitative modified approach to grading of evidence, as summarized in Table 1.

Table 1: Qualitative modified approach to grading of evidence.

Level
Description

I
Evidence obtained from multiple relevant high quality randomized controlled trials

II
Evidence obtained from at least one relevant high quality randomized controlled trial or multiple relevant moderate or low quality randomized controlled trials

III
Evidence obtained from at least one relevant moderate or low quality randomized controlled trial with multiple relevant observational studies, or
evidence obtained from at least one relevant high quality nonrandomized trial or observational study with multiple moderate or low quality observational studies

IV
Evidence obtained from multiple moderate or low quality relevant observational studies

V
Opinion or consensus of large group of clinicians and/or scientists

Source: [27].

3. Results

3.1. Characteristics of Included Trials

The database search yielded 3,203 publications. Manual searching of the reference lists and journals resulted in the retrieval of 10 additional citations. A total of 121 full-text articles were reviewed. After application of the inclusion criteria, 59 RCTs [3, 6, 14, 19, 20, 23–25, 28–78] conducted between 1986 and 2014 were included in the review (Figure 1; Tables 2–4). Nine publications were in Chinese, and the remaining 50 publications were in English. The included studies were conducted in mainland China, Hong Kong, Taiwan, the United States, Germany, Austria, South Korea, Japan, Iran, the United Kingdom, Brazil, Sweden, Singapore, Italy, and Turkey. Sixteen of these RCTs had three arms and three trials had four arms.

Table 2: Characteristics of RCTs examining body acupoint stimulation included in the meta-analysis.

First author, year, setting
Study design
Participants (n), age (years)
Surgery type
APS type
Intervention (acupoints, parameters)
Follow-up
Main outcomes

Intervention group
Sham/control group

An, 
2013, 
China 
[28]
Double-blind
RCT,
three groups
Randomized = 120
Completed = 120 
EA: 40, 40.7 (12.1) 
TEAS: 40, 42.7 (10.9) 
Control: 40, 39.1 (10.9)
Supratentorial tumor resection
EA
EA/TEAS groups: LI4/TE5, BL63/LV3, ST36/GB40  
Duration: throughout operation
Standard treatment
NR
VAS, recovery time, AE, PCA

Yin, 
2013, 
China 
[29]
RCT
Randomized = 60
Completed = 60 
Intervention: 30, 35.1 (8.6) 
Control: 30, 36.7 (10.3)
Gynecological laparoscopic surgery
EA
ST36 and ST34 
Duration: 30 min
General anesthesia
NR
VAS, PONV, exhaust defecation

Taghavi, 
2013, 
Iran 
[3]
Randomized, double-blind, placebo-
controlled study
Randomized = 90, 25 (5) 
Completed = 90 
Intervention: 45 
Placebo: 45
Inguinal surgeries
EA
LI4 and SD36 
Duration: 20 min sessions 30 min preoperatively, 1 and 2 h postoperatively
No electrical excitement through needles
NR
VAS, PCA, vital signs, side effects

Zhang, 
2013, 
China 
[30]
RCT
Randomized = 80
Completed = 80 
Intervention: 40 (19–64) 
Control: 40 (20–65)
Hemorrhoidectomy
EA
BL30 
Duration: 30 min, twice a day
50 mg tramadol hydrochloride
NR
VAS, edema score, analgesics requirement, AE

Lan, 
2012, 
China 
[31]
RCT
Randomized = 68
Completed = 60 
Intervention: 30, 76 (6) 
Sham: 30, 75 (5)
Total knee arthroplasty
EA
Bilateral P6, L14; ST36, and GB31  
Duration: 30 min before incision; 2, 4, 20, and 44 h postoperatively
Stimulation 30 min before incision at 0 mA
NR
Analgesics, VAS, RSS, AE

Chen, 
2012, 
China 
[32]
RCT
Randomized = 70
Completed = 70 
Intervention: 35, 67.4 (5.1) 
Control: 35, 65.6 (5.1)
Total knee arthroplasty
EA
SP10, ST34, ST35, EX-LE4, GB34 
Duration: 30 min daily for 1-2 postoperative weeks, twice a week in postoperative weeks 3–12
Routine rehabilitation therapy
12 weeks post-op
HSS, ROM, VAS, MMT

Coura, 
2011, 
Brazil 
[33]
Prospective, randomized, controlled study
Randomized = 22
Completed = 22 
Intervention: 13, 56.2 (11.8) 
Control: 9, 62.5 (10.8)
Cardiac surgery
EA
LI4–LI11, LR3–ST36, and PC6–TE5 acupoints 
Duration: 30 min
LI4–LI11, LR3–ST36 acupoints; device turned off but connected, 30 min
NR
Analgesics/boluses required, VAS, hospitalization length

Yeh, 
2011, 
Taiwan 
[34]
Single-blind, randomized, placebo-
controlled trial
Randomized = 90
Completed = 90 
Intervention: 30, 60.7 (12.0) 
Sham: 30, 57.2 (15.7) 
Control: 30, 63.2 (14.0)
Spinal surgery
EA
BL40, GB34, HT7, P6s 
Duration: 20 min, 3 and 4 h postoperatively
Sham: same acupoints, not meridian acupoints 
Control: no AES intervention
NR
VAS, BPI, opiate requirement

Deng, 
2010, 
China 
[35]
RCT
Randomized = 60
Completed = 60 
Intervention: 30, 50.2 (11.0) 
Control: 30, 50.1 (8.5)
Gastrectomy, proctocolectomy
EA
LI4, PC8, ST25, and BL25 acupoints 
Duration: 30 min
Simple general anesthesia
NR
VAS, satisfaction, somnus score, PCA, BP, HR, SpO₂, PONV

Sahmeddini, 
2010, 
Iran 
[36]
Randomized, double-blind
study
Randomized = 90
Completed = 90 
Intervention: 45, 27 (11) 
Control: 45, 29 (10)
Septoplasty
EA
LI4, LI11, HT7, HC6 acupoints 
Duration: 5 min prior to start of surgery
EA system pasted over hand without needle and stimulation.
NR
VAS, pulse rate, arterial pressure, AE

Colak, 
2010, 
Turkey 
[37]
RCT
Randomized = 30
Completed = 30 
Intervention: 15, 52.3 (8.1) 
Control: 15, 51.5 (8.5)
Coronary surgery
EA
LI4, LI11, ST36, PC6, LIV3 
Duration: 20 min after a 24 h rest interval and then daily for the first 7 postoperative days
Pharmacological analgesia
NR
VAS, analgesic intake, pulmonary function, postoperative complications

Larson, 
2010, 
USA 
[38]
Single-blind
RCT
Randomized = 122
Completed = 122 
Intervention: 61 
Control: 61
Outpatient plastic surgery
EA
P6 
Duration: NR
Standardized pharmacological treatment
NR
Nausea, vomiting, pain, medications required, hospitalization length

El-Rakshy, 
2009, 
UK 
[39]
Randomized, double-blind, comparative
study
Randomized = 107
Completed = 102 
Intervention: 58 
Control: 44
Abdominal hysterectomy, laparoscopic cholecystectomy
EA
Bilateral CV2, GV4, BL32, BL23, LI4, PC6; LR3, SP6, L14, PC6 
Duration: during operation
Morphine sulfate via PCA
NR
Morphine requirement, pain, nausea, vomiting

He, 
2007, 
China 
[40]
RCT
Randomized = 60
Completed = 60 
Intervention: 30, 57.65 (6.67) 
Control: 30, 58.07 (7.02)
Radical surgery for intestinal cancer
EA
“E pang 3 line” and “Ding pang 1 line” acupoints 
Duration: from 20 min preoperatively to end of operation
Epidural analgesia at end of operation
NR
VAS, BCS, gastrointestinal function

Wong, 
2006, 
Hong Kong 
[14]
Randomized, double-blind, placebo-
controlled trial
Randomized = 27
Completed = 25 
Intervention: 13, 64.6 (8.0) 
Sham: 12, 64.5 (8.5)
Thoracotomy
EA
LI4, GB34, GB36, TE8 acupoints 
Duration: two 30 min sessions a day for the first 7 postoperative days
Same acupoints, mimic prick sensation without piercing skin
NR
Peak flow rate, chest drain, VAS, PCA, complications

Gilbertson, 
2003, 
USA 
[41]
RCT
Randomized = 40
Completed = 40 
Intervention: 20, 43 (9.195) 
Sham: 20, 47.81 (6.765)
Arthroscopic acromioplasty
EA
Acupoints chosen with primary expectation of localized benefit to the operated shoulder 
Duration: postoperative days 3–8 and then three times per week for 1 month (12 sessions)
Similar to true acupoints and needles, connected but not functioning, blinking red light
4 mos.
UCLA, VAS,
analgesic use, SF-36,
ROM

Lin, 
2002, 
Taiwan 
[42]
RCT, four
groups
Randomized = 100
Completed = 100 
M/F = 0/100 
Control: 25, 39 (8) 
Sham: 25, 41 (12) 
LF EA: 25, 38 (7) 
HF EA: 25, 42 (13)
Lower abdominal surgery
EA
ST36 acupoint 
Duration: 20 min before anesthesia induction
Control group: no stimulation 
Sham group: needle insertion but no electrical stimulation
NR
VAS, analgesic, PCA demand, HR, BP, SpO₂, opioid-related AE

Sim, 
2002, 
Singapore 
[43]
RCT, three
groups
Randomized = 90
Completed = 90 
Control: 30, 47 (6) 
Preoperative EA: 30, 46 (5) 
Postoperative EA: 30, 45 (4)
Gynecological lower abdominal surgery
EA
ST36 and PC6 acupoints 
Duration: 45 min
Control group: 45 min placebo EA
NR
VAS, morphine requirement, AE, satisfaction

Chen, 
1998, 
USA 
[44]
RCT
Randomized = 100
Completed = 100 
Sham TENS: 25, 45 (12) 
No TENS: 25, 44 (13) 
Dermatomal TENS: 25, 44 (13) 
Acupoint TENS: 25, 43 (13)
Total abdominal hysterectomy, myomectomy
EA
Dermatomal TENS: dermatomal levels corresponding to incision.
Acupoint TENS: ST36 
Duration: every 2-3 h while awake, at bedtime, on waking in morning
Sham: no electrical stimulation 
No TENS: shoulder electrical stimulation (nonacupoint)
NR
VAS, PCA demand, analgesic, recovery time, AE

Wang, 
1997, 
USA 
[45]
Prospective, randomized, sham-controlled, single-blind
study
Randomized = 101
Completed = 101 
PCA only: 26, 44 (10) 
Sham TAES: 25, 44 (9) 
LF TAES: 25, 45 (9) 
HF TAES: 25, 43 (8)
Lower abdominal surgery
EA
LI4 acupoint 
Duration: every 2 h for 30 min while awake
PCA only 
Sham TAES
NR
Hospitalization length, VAS, analgesia required, PCA need, AE, recovery time

Masuda, 
1986, 
Japan 
[46]
Controlled study
Randomized = 24
Completed = 24 
Intervention: 11, 48 (13) 
Control: 13, 49 (10)
Eye surgery
EA
“Gohkoku” (Hoku) and “Shikoh” (Chikkou) acupoints 
Duration: from 30 min before surgery until end of operation
Usual neuroleptanesthesia without acupuncture
NR
Pain, anesthetics required, swelling circulatory,

Kim, 
2009, 
Korea 
[23]
Double-blind, placebo- and sham-controlled study
Randomized = 84
Completed = 84 
Intervention: 28, 27.7 (9.1) 
Sham: 28, 28.6 (8.1) 
Control: 28, 29.2 (9.3)
Orthognathic surgery
Plaster therapy
Bilateral LI4 acupoints 
Duration: 30 min before anesthesia induction in first operation, 8 h/day for 3 postoperative days
Sham: inactive tape 
Control: inactive tape at bilateral LI4 points and deltoid regions
NR
VAS, PCA, AE, PONV, satisfaction score

Kim, 
2006, 
Korea 
[47]
Double-blind, placebo- and sham-controlled study
Randomized = 90
Completed = 90 
Intervention: 30, 41.5 (9.7) 
Sham: 30, 43.2 (10.7) 
Control: 30, 42.0 (9.2)
Abdominal hysterectomy
Plaster therapy
ST36 acupoint 
Duration: 30 min preoperatively, 8 h/day for 3 postoperative days
Sham: plaster on sham acupoints 
Control: inactive tape without plaster
NR
PCA, VAS, PONV, urinary retention, AE, satisfaction

Park, 
2004, 
Korea 
[49]
Randomized, double-blind, sham-controlled study
Randomized = 150
Completed = 150 
Intervention: 50, 43.8 (32–39) 
Sham: 50, 44.9 (33–61) 
Control: 50, 42.6 (32–47)
Total abdominal hysterectomy
Plaster therapy
K-A20 acupoint 
Duration: 8 h beginning 30 min before anesthesia induction
Sham: placebo tape at K-A20; PAS placed on the lateral thighs as in Group K  
Placebo: placebo 
tape placed at K-A20 and on lateral thighs as in Group K.
NR
Sore throat, PONV, fentanyl dose, AE

Adib-Hajbaghery, 
2013, 
Iran 
[51]
Single-blind
RCT
Randomized = 70
Completed = 70 
Intervention: 35, 26.89 (9.59) 
Control: 35, 31.17 (14.79)
Appendectomy
Acupressure
LE7 acupoint 
Duration: 7 h
Sham point opposite LE7
NR
VAS, nausea, vomiting

Chen, 
2005, 
Taiwan 
[48]
RCT
Randomized = 104
Completed = 104 
Intervention: 52, 32.69 (4.09) 
Control: 52, 32.27 (4.74)
Cesarean section (CS)
Acupressure
P6 acupoint 
Duration: 20 min per arm before and within 24 h after CS
Postoperative nursing
NR
DDQ, RINV, VASA, STAI, VAS

Sakurai, 
2003, 
Austria 
[20]
RCT
Randomized = 53
Completed = 53 
Intervention: 23, 43 (16) 
Control: 30, 49 (14)
Abdominal surgery
Acupressure
Nei guan, Zusanli, Sanyinjiao, and Gongsun acupoints 
Duration: NR
Standard anesthesia monitoring
NR
VAS, PONV, side effects, antiemetic requirement

Felhendler, 
1996, 
Sweden 
[50]
RCT
Randomized = 40
Completed = 40 
Intervention: 20, 32 (22–44) 
Control: 20, 35 (29–45)
Knee arthroscopy
Acupressure
ST1, ST45, SP1, SP21, SP4, BL1, BL67, KI1, KI27, KI4, GB1, GB44, LR1, LR14, LR5
Duration: 30 min after waking from anesthesia
15 nonacupoints, no active stimulation
NR
VAS, cardiovascular measurements

Maimer, 
2013, 
Germany 
[52]
Prospective, randomized, controlled, observer-blinded clinical trial
Randomized = 100
Completed = 100 
Control acupuncture: 33, 65 (10) 
Classic Chinese acupuncture: 34, 68 (11) 
Control: 33, 66 (10)
Heart surgery
Manual acupuncture
Control acupuncture: LI4, SI6, BL60, EX1, GV20, GB8, ST8  
Classic acupuncture: P6, ST34, SP10, ST44, K3R, LIV2  
Duration: needle stimulation by rotation for ~5 s at insertion, after 10 min, before removal after 20 min
Standard treatment with no additional acupuncture
NR
PPR, FVC

Langenbach, 
2012, 
Germany 
[53]
Patient-blind
RCT,
three groups
Randomized = 50
Completed = 50 
Intervention: 17, 62 (15) 
Sham: 16, 48 (17) 
Control: 17, 57 (16)
Stapled hemorrhoidopexy
Manual acupuncture
DU2, DU20, BI30, BI57, MA44, PE6 
Duration: 20–30 min at 4 pm on day of surgery, mornings, and afternoons of postoperative days 1 and 2
Sham: needles placed away from meridians 
Control: analgesic drug regimen
NR
NRS, analgesics, cardiovascular parameters, complications

Marra, 
2011, 
Italy 
[54]
Pilot RCT
Randomized = 42
Completed = 42 
Intervention: 21, >18 
Control: 21, >18
Mediolateral episiotomy
Manual acupuncture
Lower 1 acupoint according to wrist-ankle acupuncture, right ankle 
Duration: needle left in place from discharge on day 2 or 3 after delivery, removed by midwife
Standard treatment without acupuncture
NR
Oral analgesics, perineal pain, acupuncture acceptability, AE

Wu, 
2009, 
China 
[55]
RCT, three
groups
Randomized = 60
Completed = 60 
PCA only: 20, 30.8 (3.2) 
PCA + acupuncture: 20, 31.0 (4.2) 
PCA + EA: 20, 30.1 (4.1)
CS
Manual acupuncture, EA
SP6 
Duration: 30 min, prior to PCA
No special treatment, PCA machine applied
NR
VAS, PCA demand, AE

Sertel, 
2009, 
Germany 
[56]
Single-blind, randomized, prospective bicenter study
Randomized = 123
Completed = 123 
Verum acupuncture: 41, 29.51 (16–58) 
Control acupuncture: 41, 26.6 (16–50) 
Medication: 41, 28.21 (16–58)
Tonsillectomy
Manual acupuncture
S34, S44, PC5 
Duration: 20 min
Control acupuncture: nonspecific points away from meridians 
Medication: standard pain medication
NR
VAS, AE

Tsang, 
2007, 
Hong Kong 
[57]
Prospective patient- and assessor-
blinded RCT
Randomized = 36
Completed = 30 
Intervention group: 15, 70.6 (5.8) 
Sham group: 15, 66.1 (7.5)
Bilateral total knee arthroplasty
Manual acupuncture
ST32, ST33, GB31, GB35, GB34, ST36 
Duration: 20 min, with needle manipulation every 5 min to achieve numbness
No needle manipulation, no inducement of or inquiry about numbness, tingling, or heaviness
NR
VAS, analgesics, ROM, timed up-and-go test

Kotani, 
2001, 
Japan 
[58]
RCT
Upper abdominal surgery 
Randomized = 107
Completed = 98 
Intervention group: 50, 52 (15) 
Control group: 48, 55 (14) 
Lower abdominal surgery 
Randomized = 84
Completed = 77 
Intervention group: 39, 55 (10) 
Control group: 38, 55 (11)
Abdominal surgery
Manual acupuncture
Upper abdominal surgery: bilateral BL18–BL24 
Lower abdominal surgery: bilateral BL20–BL26 
Duration: NR
Needles positioned at acupoints but not inserted into intradermal space
NR
VRS, analgesics, analgesic-related effects, PONV,
plasma cortisol level, epinephrine requirement

Gupta, 
1999, 
UK 
[59]
Prospective, double-blind, randomized controlled
study
Randomized = 42
Completed = 42 
Intervention group: 21, 40.1 (19.4) 
Control group: 21, 47.4 (19.6)
Elective single-knee arthroscopy
Manual acupuncture
SP9, SP10, ST34, ST36s 
Duration: 15 min, with manual stimulation for 5 s by 180° needle rotation every 5 min, and just before needle removal
Standard treatment
NR
VAS, analgesic requirement

Lao, 
1999, 
USA 
[60]
Randomized, double-blind, placebo-
controlled trial
Randomized = 39
Completed = 39 
Intervention group: 19, 18–34 
Control group: 20, 18–34
Oral surgery
Manual acupuncture
LI4, ST6, ST7, SJ17 
Duration: 20 min, with manual manipulation for 20–30 s immediately after insertion, at midpoint, and at end of treatment
Identical to intervention treatment but no needle insertion into skin
7 days
Medication consumption, pain, psychological impact, AE

Lao, 
1995, 
USA 
[61]
Randomized, single-blind, placebo-
controlled trial
Randomized = 22, (18–40) 
Completed = 19 
Intervention group: 11 
Placebo acupuncture group: 8
Oral surgery
Manual acupuncture
LI4, ST6, ST7, SJ17s 
Duration: 20 min, with manual acupuncture on initially and at midpoint of treatment
Tapping next to acupoints to produce discernible sensation
7 days
Pain, medication consumption, AE, local discomfort

RCT, randomized controlled trial; APS, acupoint stimulation; EA, electroacupuncture; LF, low frequency; HF, high frequency; TEAS, transcutaneous electrical acupoint stimulation; NR, not reported; VAS, visual analog scale; PCA, patient-controlled analgesia; TAES, transcutaneous acupoint electrical stimulation; PONV, postoperative nausea and vomiting; RSS, Ramsay Sedation Scale; TENS, transcutaneous electrical nerve stimulation; HSS, New York Hospital for Special Surgery score; ROM, range of motion; MMT, manual muscle test; AES, acupoint electrical stimulation; AE, adverse effects/side effects; BPI, Brief Pain Inventory; BP, blood pressure; HR, heart rate; BCS, Bruggemann Comfort Scale; SF-36, Short Form 36; CS, cesarean section; PPR, percentile pain reduction; FVC, forced vital capacity; NRS, numerical rating scale; VRS, verbal rating scale; DDQ, Demographic Data Questionnaire; RINV, Rhodes Index of Nausea and Vomiting; VASA, Visual Analog Scale for Anxiety; STAI, State-Trait Anxiety Inventory.

Table 3: Characteristics of RCTs examining auricular acupoint stimulation included in the meta-analysis.

First author, year, setting
Study design
Participants (), age (years)
Surgery type
APS type
Intervention
Follow-up
Main 
outcomes

Intervention group
Sham/control group

Zhang, 2013, China [62]
RCT
Randomized = 120
Completed = 120 
Intervention group: 60, 35 (7) 
Placebo group: 60, 34 (8)
Gynecological laparoscopy
Seed
embedding
TF4, CO4, and AH6A auricular points 
Duration: pressed for 5 min preoperatively and 1, 5, 9, and 23 h postoperatively
No sticking or pressing of vaccaria seeds
NR
PONV, VAS, tropisetron and morphine usage rates, adverse effects

He, 2013,
China [24]
Prospective, randomized, sham-controlled trial
Randomized = 90
Completed = 90 
Intervention group: 45, 61.58 (6.66) 
Control group: 45, 65.62 (6.10)
Total knee arthroplasty
Seed
embedding
Site-knee joint, Shen Men, subcortex, and sympathesis auricular points 
Duration: pressed for 3 min four times per day until 7 days postoperatively
Sham acupuncture at four nonacupoints on helix ipsilateral to surgical site
3 months after operation
VAS, analgesic, analgesic-related adverse effects, HSS, ROM

Chang, 2012, Taiwan [6]
Double-blind
RCT
Randomized = 62
Completed = 62 
Intervention group: 31, 71.23 (7.09) 
Sham group: 31, 70.74 (8.09)
Total knee arthroplasty
Seed
embedding
TF4 and AT4 auricular points 
Duration: pressed for 3 min three times per day (9 am, 1 pm, and 5 pm)
Regular care
NR
VAS, SF-MPQ, analgesic dosage, ROM

Kong, 2012,
China [64]
RCT
Randomized = 60
Completed = 60 
Intervention group: 30, 39.02 (11.19) 
Control group: 30, 38.17 (13.02)
Calcaneal fracture surgery
Seed
embedding
Shen Men, thalamus lung, liver, kidney, and knee joint auricular points 
Duration: 10–15 min five times per day
Standard treatment (PCIA)
NR
VAS, analgesic, adverse reactions, urinary retention

Yeh, 2010,
Taiwan [65]
Single-blind
RCT
Randomized = 94
Completed = 74 
Intervention group: 36, 58.8 (13.6) 
Control group: 38, 55.1 (16.1)
Lumbar spinal surgery
Seed
embedding
TF4, AT3, AH9, CO4, CO3, and CO18 auricular points 
Duration: 3 minutes per point, four times per day until 72 h postoperatively
Standard treatment with no acupressure
NR
APSPOQ, pain intensity, analgesic dose, PONV, satisfaction

Tsang, 2011,
Hong Kong 
[19]
Patient- and assessor-blinded RCT
Randomized = 48
Completed = 48 
Intervention group: 16, 45.31 (2.68) 
Sham group: 16, 45.88 (3.91) 
Control group: 17, 44.63 (4.92)
Hysterectomy
EA
Uterus, abdomen, sympathetic, Shen Men, and subcortex auricular points 
Duration: several hours postoperatively
Sham TENS group: 90 s stimulation at 1 Hz 
Control group: 20 min bed rest
NR
VAS, PEFR

Kager, 2009, Austria [66]
Double-blind, randomized study
Randomized = 33
Completed = 33 
Intervention group: 16, 30.78 (7.19) 
Placebo: 17, 30.92 (7.78)
Tonsillectomy
EA
Point 55 (entrance of the spirit, Shen Men), point 29 (occiput, pillow, Zhen), and point 73 (BIAN TAO Ti 1) 
Duration: 3 h application, 3 h pause for 96 h
Placement of acupuncture needles without stimulation, removed after 96 h
NR
VAS, NRS, oral analgesia, PONV

Michalek-Sauberer, 2007, Austria [67]
Prospective, randomized, double-blind, placebo-
controlled study
Randomized = 149
Completed = 119 
AA + AE group: 60, 27 (18–35) 
AA group: 41, 24 (20–35) 
Sham AE group: 41, 26 (19–35)
Unilateral mandibular third molar extraction
EA
AA points 1 (tooth), 55 (Shen Men), and 84 (mouth) 
Duration: 30 min prior to procedure, 3 h stimulation with 3 h pause
Sham AE with metal plates instead of needles, no electrical stimulation
NR
VAS, acetaminophen requirement, patient satisfaction

Sator-Katzenschlager, 2006,
Austria [69]
Prospective, randomized, double-blind, controlled study
Randomized = 94
Completed = 93 
EA group: 32, 33.3 (1.7) 
A group: 32, 34.2 (1.1) 
Control group: 30, 33.9 (1.9)
IVF treatment
EA
Auricular points 57 (uterus), 55 (Shen Men), and 29 (cushion) 
Duration: 30 min preoperatively until 1 h postoperatively
Adhesive tape over whole ear
NR
Side effects, satisfaction, IVF outcome data

Wang, 2012,
China [63]
RCT
Randomized = 60
Completed = 60 
Intervention group: 31, 60.19 (6.33) 
Control group: 29, 60.10 (6.10)
Total knee arthroplasty
Manual
auriculotherapy
Shen Men, thalamus lung, and knee joint auricular points 
Duration: the night before surgery until the end of their surgeries.
Sham needle embedding at nonacupoints
NR
VAS, PONV, dizziness, drowsiness, PCA

Usichenko,
2007,
Germany [68]
Prospective, patient- and evaluator-blinded, controlled study
Randomized = 120
Completed = 120 
Intervention group: 61, 42.0 (14.6) 
Control group: 59, 43.8 (12.6)
Ambulatory knee surgery
Manual
auriculotherapy
Knee joint, Shen Men, and lung auricular points 
Duration: preoperatively until first morning postoperatively
Invasive needle control at three nonacupoints of helix ipsilateral to surgical site
NR
VAS, analgesia, discharge time, nighttime sleep quality, adverse events

Usichenko,
2005,
Germany 
[70, 71]
Prospective, patient- and evaluator-blinded, controlled pilot study
Randomized = 20
Completed = 18 
Intervention group: 10, 33 (13) 
Control group: 8, 45 (15)
Ambulatory knee surgery
Manual
auriculotherapy
Knee joint, Shen Men, and lung auricular points 
Duration: 5 min each before tracheal intubation, during most painful phase of surgery, and before extubation
Invasive needle control at nonacupoints of helix ipsilateral to surgical site
NR
VAS, analgesia requirement, discharge time, night sleep,
adverse events

Usichenko,
2005,
Germany
[70, 71]
Prospective randomized patient-, anesthesiologist-, evaluator-, and analyst-blinded, sham-controlled study
Randomized = 61
Completed = 54 
Intervention group: 29, 68 (10) 
Control group: 25, 66 (11)
Total hip arthroplasty
Manual
auriculotherapy
Hip joint, Shen Men, lung, and thalamus auricular points 
Duration: AA needle retention up to 3 days postoperatively
Nonacupoints of helix ipsilateral to surgical site
NR
PCA demand, VAS, analgesia-related side effects

Li, 1994,
China [72]
Double-blind, randomized study
Randomized = 48, 48.64 (11.35) 
Completed = 48 
Chinese herb group: 16 
Auricular acupoint group: 16 
Epidural morphine group: 16
Surgery for liver cancer
Manual
auriculotherapy
Chinese herb group: Astragalus L., Angelica L., Ophiopogon J., Corydalis, and Rhizome Pinelliae (10 mL, w/v = 1 g/mL) 
Duration: orally three times a day 
Auricular acupoint group: heart, lung, and Shen Men acupoints 
Duration: three times a day, 24 h postoperatively
Epidural morphine group: 2 mg epidural morphine before peritoneum suturing
NR
VAS, pethidine requirement, leucine
enkephalin level

RCT, randomized controlled trial; APS, acupoint stimulation; NR, not reported; PONV, postoperative nausea and vomiting; VAS, visual analog scale; HSS, New York Hospital for Special Surgery score; ROM, range of motion; PCA, patient-controlled analgesia; SF-MPQ, Short-Form McGill Pain Questionnaire; PEFR, peak expiratory flow rate; APSPOQ, American Pain Society Patient Outcome Questionnaire; TENS, transcutaneous electrical nerve stimulation; NRS, numerical rating scale; AA/A, auricular acupuncture; AE/EA, auricular electroacupuncture; IVF, in vitro fertilization.

Table 4: Characteristics of RCTs examining integrative acupoint stimulation included in the meta-analysis.

First author, year, setting
Study design
Participants (n), age (years)
Surgery type
APS type
Intervention
Follow-up
Main outcomes

Intervention group
Sham/control group

Chung, 2014, Taiwan [24]
Single-blind, sham-controlled study, three groups
Enrolled = 135
Completed = 127 
Intervention group: 40, 60.25 (13.42) 
Sham group: 42, 59.79 (12.61) 
Control group: 45, 54.24 (14.63)
Lumbar spinal surgery
AA + EA
TF4, AH10, CW8, AT5, CO4; BL40 and GB34 acupoints 
Duration:
AA: ten 15 min sessions (1 and 3 h after returning to ward, four each on postoperative days 1 and 2) 
TAES: 20 min 1 and 3 h after returning to ward
Sham group: sham acupressure and sham TAES 
Control group: no acupoint stimulation
NR
VAS, morphine consumption, morphine-related side effects

Dias, 2010, Brazil [73]
Single-blind RCT
Randomized = 33
Completed = 33 
Intervention group: 16, 47 (14) 
Control group: 17, 43.1 (10)
Inguinal hernia repair
EA
Acupoints on limbs and ear (heart and Shen Men) 
Duration: 5 min at 3 Hz in continuous mode, increased incrementally to 5, 10, 20, 50, 100, 160, and finally 240 Hz after 30 min
Sham TENS at same sites
2 weeks
Anesthetics requirement, VAS, HR, BP, edema, adverse events

Pfister, 2010, USA [74]
Prospective, open-label RCT
Randomized = 70
Completed = 58 
Intervention group: 28, 61 
Control group: 30, 57
Neck dissection
Manual acupuncture
LI4, SP6, GV20, Luo Zhen, and auricular Shen Men acupoints 
Duration: 30 min once a week for 4 weeks
Usual care
NR
NRS, medication use, adverse events

Deng, 2008, USA [75]
Randomized, sham-controlled, subject-blinded trial
Randomized = 162
Completed = 106 
Intervention group: 52, 65 
Sham group: 54, 63
Thoracotomy
Manual acupuncture
BL12–BL19, Wei Guan Xia Shu, ST36, and bilateral auricular Shen Men acupoints 
Duration: 4 weeks
Dummy studs placed in back
3 months postoperatively
BPI, medication use, MQS, NRS

Mehling, 2007, USA [76]
RCT
Randomized = 138
Completed = 138 
Intervention group: 93, 55.9 (1.9) 
Control group: 45, 59.2 (1.7)
Cancer-related surgery
Massage + EA
Acupressure-type foot massage, large intestine 4, spleen 6, and auricular acupoints 
Duration: 10–30 min massage, depending on participants’ clinical needs and conditions; 20 min acupuncture
Usual care, offered 30 min massage
NR
NRS, nausea, vomiting, POMS-SF, health care cost

Tavares, 2007, Brazil [77]
RCT
Randomized = 24, 20.42 (1.44) 
Completed = 24 
Intervention group: 12 
Control group: 12
Mandibular third molar surgery
EA
IG4, F3, E44, VB39, TA21, B60, Shen Men, and ponto total acupoints 
Duration: needles rotation every 10 min at beginning of procedure, after 10 min of treatment, and at end of procedure
No acupoint stimulation
NR
VAS, analgesic dose

Ekblom, 1991, Sweden [78]
RCT
Randomized = 110
Completed = 110 
PRE-ACU group: 25 
POST-ACU group: 25 
Age, groups 1 and 2: 29.9 (18–50) 
Control group: 60, 30.2 (18–55)
Mandibular third molar extraction
Manual acupuncture
ST6, ST7, S119, and LI4 acupoints ipsilateral to extraction site; SJ5 contralateral 
Duration: 20 min
No acupuncture
1 week postoperatively
VAS, tension and stress, analgesic consumption, wound healing

RCT, randomized controlled trial; APS, acupoint stimulation; AA, auricular acupuncture; EA, electroacupuncture; TAES, transcutaneous acupoint electrical stimulation; NR, not reported; VAS, visual analog scale; TENS, transcutaneous electrical nerve stimulation; BP, blood pressure; HR, heart rate; NRS, numerical rating scale; BPI, Brief Pain Inventory; MQS, Medication Quantification Scale; POMS-SF, Mood States Short Form; PRE-ACU, preoperative acupuncture; POST-ACU, postoperative acupuncture.

RCTs included in the analysis involved a total of 4,578 randomized patients, 4,402 of whom completed the respective studies (APS groups, ; control groups, ; 96.16% completion rate). The average sample size was 73 (range, 18–150). Standardized anesthetic and postoperative analgesia regimens were used in all studies. Follow-up duration ranged widely from 7 days [60, 61] to 4 months [41]. Twenty-one RCTs stated that an intention-to-treat analysis was used.

Five types of APS were used: low- and/or high-intensity EA, manual needle acupuncture, seed embedding, acupressure, and plaster therapy. Preoperative and postoperative APS were used in two RCTs, and sham/placebo control was used in 36 studies. Chinese herbs were used as a control in a single study.

Acupuncture points on the body and/or auricular points were stimulated. Commonly used body points included Hegu (LI4), Sanyinjiao (SP6), Zusanli (ST36), and Nei guan (P6); commonly used auricular points included Shen Men (TF4), Stomach (CO4), and Lung (CO14).

3.2. Methodological Quality and Risk of Bias of Included Trials

The methodological quality of included studies is characterized in Figures 2 and 3. Eighteen (30.5%) publications specifically stated that the outcome assessor was blinded and 23 (38.98%) studies used adequate allocation concealment together with full methodological description. Twelve (20.33%) studies were rated highly in both of these domains and were deemed to be at low risk of overall bias. Forty-two studies (71.19%) were deemed to be at unclear risk of overall bias. Finally, five studies (8.5%) were deemed to be at high overall risk of bias. Allocation concealment was not reported or was described poorly in 24 (40.67%) studies. According to the number of participants, no studies were considered to be at low risk of bias (≥200 participants), 42 studies (71.19%) were at unknown risk of bias (50–200 participants), and 17 studies (28.81%) were at high risk of bias (<50 participants). Visual inspection of funnel plots revealed some substantial asymmetry in comparisons (Figure 4).

Figure 2: Methodological quality of included studies. Each methodological quality item was qualitatively assessed and is presented as a percentage across all included studies.

Figure 3: Risk of bias in the included studies. Each bias item was qualitatively assessed.

Figure 4: Funnel plot.

3.3. Meta-Analysis and Descriptive Analysis of Outcomes

3.3.1. Postoperative Pain

The results of the meta-analysis are reported in Table 5. The RCTs evaluated the efficacy of APS for postoperative pain relief by using VAS scores (), NRS scores () [53, 66, 74–76], Brief Pain Inventory (BPI) scores () [34, 75], and a four-point scale and pain-free time to evaluate postoperative pain () [58, 60, 61]. Two of the five RCTs [53, 74] that used NRS scores reported a significant difference between groups, but these data could not be included in the meta-analysis due to clinical and statistical heterogeneity. One of two RCTs [34, 75] that used BPI scores reported a significant difference between the intervention and control groups, but these data could not be included in the meta-analysis due to different data modes. Three trials [58, 60, 61] using a four-point scale reported that the intervention reduced pain intensity, but one of these studies [58] reported that total or partial pain relief did not differ significantly between the groups. Two trials [60, 61] reported that the APS intervention increased the duration of postoperative pain-free status compared with that of the control groups.

Table 5: Summary of meta-analysis results.

Group
Outcome
Number of trials
Number of participants
Statistical method
Effect size

Heterogeneity

Overall effects (AM)

    I versus ST
VAS
20
1227
Std. MD (IV, random, 95% CI)
−1.05 (−1.44, −0.67)
<0.00001
P < 0.00001; = 89%

    I versus S/P
VAS
23
1284
Std. MD (IV, random, 95% CI)
−0.72 (−1.03, −0.41)
<0.00001
P < 0.00001; = 85%

Body points (AM)
VAS
24
1370
Std. MD (IV, random, 95% CI)
−0.97 (−1.32, −0.62)
<0.00001
P < 0.00001; = 89%

    I versus ST
VAS
14
893
Std. MD (IV, random, 95% CI)
−1.08 (−1.54, −0.61)
<0.00001
P < 0.00001; = 90%

    I versus S/P
VAS
14
693
Std. MD (IV, random, 95% CI)
−0.86 (−1.28, −0.45)
<0.0001
P < 0.00001; = 84%

Body points (EA)
VAS
17
928
Std. MD (IV, random, 95% CI)
−0.71 (−1.02, −0.40)
<0.00001
P < 0.00001; = 80%

    I versus ST
VAS
10
591
Std. MD (IV, random, 95% CI)
−0.68 (−1.04, −0.32)
0.0002
P < 0.00001; = 78%

    I versus S/P
VAS
9
417
Std. MD (IV, random, 95% CI)
−0.67 (−1.13, −0.22)
0.004
P < 0.00001; = 80%

Body points (EA)-NIN
VAS
8
463
Std. MD (IV, random, 95% CI)
−0.66 (−1.10, −0.22)
0.003
P < 0.00001; = 80%

Body points (EA)-IN
VAS
10
545
Std. MD (IV, random, 95% CI)
−0.67 (−1.11, −0.24)
0.002
P < 0.00001; = 83%

Body points (M)
VAS
3
152
Std. MD (IV, random, 95% CI)
−1.55 (−3.91, 0.81)
0.20
P < 0.00001; = 97%

    I versus ST
VAS
2
122
Std. MD (IV, random, 95% CI)
−2.43 (−5.49, 0.46)
0.12
P < 0.00001; = 97%

Body points (A)
VAS
3
214
MD (IV, random, 95% CI)
−1.44 (−2.56, −0.33)
0.01
P < 0.00001; = 92%

Body points (Pla) I versus ST
VAS
2
116
MD (IV, random, 95% CI)
−10.85 (−15.59, −6.12)
<0.00001
P = 0.09; = 66%

Body points for AS
VAS
8
471
Std. MD (IV, random, 95% CI)
−0.67 (−1.06, −0.29)
0.0006
P = 0.0001; = 76%

Body points for KS
VAS
4
200
Std. MD (IV, random, 95% CI)
−0.90 (−2.14, 0.34)
0.16
P < 0.00001; = 94%

Body points for CaS
VAS
2
52
Std. MD (IV, random, 95% CI)
−0.94 (−1.52, −0.36)
0.002
P = 0.98; = 0%

Body points for CeS
VAS
2
144
Std. MD (IV, random, 95% CI)
−0.81 (−1.15, −0.47)
<0.00001
P = 0.83; = 0%

    I versus S/P
VAS
2
116
MD (IV, random, 95% CI)
−8.38 (−12.10, −4.65)
<0.0001
P = 0.13; = 56%

Auricular points (AM)
VAS
12
784
Std. MD (IV, random, 95% CI)
−0.66 (−1.06, −0.25)
0.001
P < 0.00001; = 86%

    I versus ST
VAS
4
225
Std. MD (IV, random, 95% CI)
−1.23 (−2.44, −0.03)
0.04
P < 0.00001; = 92%

    I versus S/P
VAS
9
591
Std. MD (IV, random, 95% CI)
−0.56 (−1.05, −0.07)
0.02
P < 0.00001; = 87%

Auricular points (EM)
VAS
5
404
Std. MD (IV, random, 95% CI)
−0.77 (−1.42, −0.12)
0.02
P < 0.00001; = 90%

Auricular points (M)
VAS
4
252
Std. MD (IV, random, 95% CI)
−0.16 (−0.62, 0.30)
0.49
P = 0.04; = 64%

Auricular points (EA)
VAS
3
128
Std. MD (IV, random, 95% CI)
−1.11 (−1.60, −0.61)
<0.0001
P = 0.19; = 40%

Auricular points for KS
VAS
5
350
Std. MD (IV, random, 95% CI)
−0.27 (−0.68, 0.14)
0.20
P = 0.009; = 70%

Auricular points for AS
VAS
2
138
Std. MD (IV, random, 95% CI)
−1.19 (−2.12, −0.26)
0.01
P = 0.07; = 70%

Integrative points
VAS/NRS
6
444
Std. MD (IV, random, 95% CI)
−0.61 (−1.14, −0.07)
0.03
P < 0.0001; = 84%

Integrative points for OS
VAS
2
109
Std. MD (IV, random, 95% CI)
−1.87 (−5.69, 1.94)
0.34
P < 0.00001; = 96%

Analgesic requirement
TMC
6
399
MD (IV, random, 95% CI)
−4.99 (−7.51, −2.47)
0.0001
P < 0.00001; = 94%

    I versus S/P
TMC
2
132
MD (IV, random, 95% CI)
−15.20 (−21.24, −9.16)
<0.00001
P = 1; = 0%

AM, all modalities; VAS, visual analog scale; NRS, numerical rating scale; I, intervention group; ST, standard treatment control group; S/P, sham/placebo control group; EA, electroacupuncture; NIN, noninvasive; IN, invasive; M, manual acupuncture; A, acupressure; Pla, plaster; EM, seed embedding; TMC: total morphine consumption; Std. MD, Std. mean difference; MD, mean difference; AS, abdominal surgery; KS, knee surgery; CaS, cardiac surgery; CeS, cesarean section; OS: oral surgery.

test.

Thirty-eight RCTs used body points for stimulation. Subgroup analyses according to control treatment and meta-analysis of 20 RCTs indicated that APS interventions improved VAS scores significantly in comparison with standard treatment and sham/placebo control (both ; Table 5). Similarly, pooled results from 24 trials showed that body APS significantly improved VAS scores in comparison with all control groups (), and subgroup analyses revealed similar improvement compared with standard treatment () and sham/placebo control (; Table 5). The evidence for body points APS reducing postoperative pain intensity in surgery patients was determined to be of Level I quality based on six overall high quality RCTs [14, 23, 47, 49, 52, 58]. A meta-analysis of pooled results and subgroup analyses of body EA, as well as invasive and noninvasive forms of this treatment, yielded similar results (Table 5). The evidence for body points EA reducing postoperative pain intensity in surgery patients was determined to be of Level II quality based on one overall high quality RCT [14]. High-frequency EA was found to be more effective than low-frequency EA [42, 45]. Pooled results from three RCTs examining acupressure [48, 50, 51] showed a significant difference in VAS scores between intervention and control groups (; Table 5), although a fourth study [20] not included in the meta-analysis showed no such difference. The evidence for body points acupressure reducing postoperative pain intensity in surgery patients was determined to be of Level II quality based on three moderate quality RCTs [20, 48, 50] and one low quality RCT [51]. Synthesis of data from two RCTs [23, 47] examining plaster therapy showed a significant reduction in pain intensity compared with standard treatment () and sham controls (; Table 5), and one other study [49] examining this treatment obtained similar results. The evidence for body points plaster therapy reducing postoperative pain intensity in surgery patients was determined to be of Level I quality based on three overall high quality RCTs [23, 47, 49].

In contrast, meta-analysis including three studies [55–57] revealed no significant effect of manual acupuncture on VAS score. Four [55, 57, 59, 60] of 10 RCTs examining manual acupuncture reported no difference in pain score between the intervention and control groups, whereas the remaining six studies found that this treatment reduced postoperative pain intensity ().

Twelve RCTs used body point stimulation for patients with abdominal surgery. The pooled results from eight trials [29, 35, 40, 42, 43, 45, 47, 51] showed that body APS significantly improved VAS scores in these patients (). The evidence for body points APS reducing postoperative pain intensity in patients who had undergone abdominal surgery was determined to be of Level II quality based on one overall high quality RCT [47]. Five [31, 32, 50, 57, 59] RCTs used body point stimulation for patients with knee surgery. Pooled results from four trials [31, 32, 50, 57] showed that body APS did not significantly improve VAS scores for these patients (). Each of two RCTs used body point stimulation for patients with oral surgery [60, 61], cardiac surgery [33, 37], hemorrhoid operation [30, 53], or cesarean section [48, 55]. Pooled results from two trials showed that body APS significantly improved VAS scores for patients undergoing cardiac surgery [33, 37] () or cesarean section [48, 55] (). The evidence for body points APS reducing pain intensity in patients who underwent cardiac surgery and cesarean section surgery was determined to be of Level III quality based on two moderate quality RCTs [33, 37]. Other studies could not be included in the meta-analyses due to insufficient data and the different types of surgery.

Fourteen [6, 19, 24, 62–72] RCTs used auricular points for stimulation. Data synthesis from 12 studies showed significantly lower VAS scores in intervention groups than in all types of control group (), and similar results were obtained in comparison with standard treatment () and sham/placebo control () groups (Table 5). The evidence for auricular points APS reducing postoperative pain intensity was determined to be of Level I quality based on six overall high quality RCTs [6, 24, 68, 69, 71]. Meta-analysis of data from five studies [6, 24, 62, 64, 65] examining seed embedding also showed a significant effect on VAS score in comparison with all control groups (; Table 5). The evidence for auricular points seed embedding reducing postoperative pain intensity was determined to be of Level II quality based on two overall high quality RCTs [6, 24]. Two studies [6, 65] of this auricular APS technique found a gradual reduction in pain, but no significant difference, according to VAS and Short-Form McGill Pain Questionnaire scores. One study [63] of manual auricular acupuncture data reported a significant difference in VAS score, and another study [72] showed a positive trend toward less pain in the intervention group, but meta-analysis of data from four studies [63, 68, 70, 71] showed that this auricular APS type was not associated with significant pain reduction. The evidence for manual auricular acupuncture reducing postoperative pain intensity in surgery patients was determined to be of Level II quality based on two overall high quality RCTs [68, 71]. Meta-analysis of auricular EA data from three studies [19, 66, 69] showed a significant reduction in VAS scores (including those reflecting pain at rest and on huffing and coughing; ), although two of the four RCTs examining this treatment found no significant difference due to low pain intensity in intervention groups. The evidence for auricular EA reducing postoperative pain intensity in surgery patients was determined to be of Level II quality based on one overall high quality RCT [69].

Five [6, 24, 63, 68, 70] RCTs used auricular point stimulation for patients with knee surgery. Pooled results from five trials [6, 24, 63, 68, 70] showed that auricular point APS did not significantly improve VAS scores for these patients (). Two [19, 62] RCTs used auricular point stimulation for patients with abdominal surgery. Pooled results from both trials [19, 62] showed that auricular point APS significantly improved VAS scores for these patients (). The evidence for auricular point stimulation reducing postoperative pain intensity in abdominal surgery patients was determined to be of Level III quality based on two moderate quality RCTs [19, 62].

Seven RCTs [25, 73–78] used integrative APS (combined stimulation of body and auricular points) and evaluated postoperative pain relief using VAS () and NRS () scores. This meta-analysis showed a significant effect of integrative APS on pain intensity based on pooled VAS and NRS scores (; Table 5) [73–78]. The evidence for integrative APS reducing postoperative pain in surgery patients was determined to be of Level II quality based on five moderate quality [25, 73, 76–78] and two low quality [74, 75] RCTs. Two [77, 78] RCTs used integrative APS for patients with oral surgery. Pooled results from both trials [77, 78] showed that integrative APS did not significantly improve the VAS scores for these patients ().

3.3.2. Analgesic Requirement

Forty-three RCTs measured analgesic use, and most studies documented a lesser analgesic requirement in APS intervention groups than in control groups. Meta-analysis of data from six RCTs [3, 25, 34, 42, 43, 55] showed a significant reduction in total morphine consumption in intervention groups compared to the control groups (). Similar results were obtained in the comparison of intervention and sham/placebo control groups (; Table 5). In addition, Lin et al. [42] reported that the morphine requirement after high-frequency EA was decreased by 31% compared with that after low-frequency EA. The evidence for APS reducing analgesic requirement in surgery patients was determined to be of Level I quality based on multiple overall high quality RCTs.

3.3.3. AEs

No serious AEs were associated with APS, and patients were reported to tolerate the intervention well in the 21 RCTs that reported on this outcome. Reported minor AEs included temporary increased pain [74], localized pain or discomfort at insertion sites [60, 71], minor bruising or bleeding [74], constitutional symptoms [74], and a mild burning sensation with erythema [23, 47, 49]. Michalek-Sauberer et al. [67] stated that 38% of patients reported minimal side effects of acupuncture, most commonly fatigue (16%) and ear pain (10%).

3.4. Sensitivity and Heterogeneity

Given the detection of obvious heterogeneity () in meta-analyses, we conducted a sensitivity analysis to remove studies with a greater risk of bias. The results are presented in Table 6. values were decreased substantially by the removal of such trials in most comparisons.

Table 6: Sensitivity analysis results.

Presensitivity analysis
statistical method
Heterogeneity
Sensitivity analysis
Number of trials
(patient )
Postsensitivity analysis
statistical method
Heterogeneity

Effects of interventions, all body modalities versus standard treatment control (VAS)

Random, −1.08 (−1.54, −0.61)
P < 0.00001; 
= 90%
Remove Kim et al. 2009 [23] and Sertel et al. 2009 [56]
12 (755)
Random, −0.74 (−1.05, −0.43)
P < 0.00001; 
= 76%

Effects of invasive body electroacupuncture versus all controls (VAS)

Random, −0.67 (−1.11, −0.24)
P < 0.00001; 
= 83%
Remove Gilbertson et al. 2003 [41]
9 (505)
Random, −0.47 (−0.79, −0.15)
P = 0.002; 
= 68%

Effects of body electroacupuncture versus standard treatment (VAS)

Random, −0.68 (−1.04, −0.32)
P < 0.00001; 
= 78%
Remove Deng et al. 2010 [35] and Chen et al. 2012 [32]
8 (461)
Fixed, −0.38 (−0.57, −0.20)
P = 0.33; 
= 13%

Effects of body electroacupuncture versus sham/placebo control (VAS)

Random, −0.67 (−1.13, −0.22)
P < 0.00001; 
= 80%
Remove Gilbertson et al. 2003 [41]
8 (377)
Fixed, −0.42 (−0.62, −0.21)
P = 0.08; 
= 44%

Effects of body acupressure versus standard treatment (VAS)

Random, −1.44 (−2.56, −0.33)
P < 0.00001; 
= 92%
Remove Adib-Hajbaghery and Etri 2013 [51]
2 (144)
Fixed, −1.93 (−2.33, −1.53)
P = 0.75; 
= 0%

Overall effects of auricular interventions, all modalities versus sham/placebo control (VAS)

Random, −0.56 (−1.05, −0.07)
P < 0.00001; 
= 87%
Remove Zhang 2013 [62] and Sator-Katzenschlager et al. 2006 [69]
7 (409)
Random, −0.23 (−0.54, 0.09)
P = 0.04; 
= 55%

Effects of auricular manual acupuncture versus sham/placebo control (VAS)

Random, −0.16 (−0.62, 0.30)
P = 0.04; 
= 64%
Remove Usichenko et al. 2007 [68]
3 (132)
Fixed, −0.34 (−0.69, 0.00)
P = 0.25; 
= 27%

Overall effects of integrative interventions versus all controls (VAS and NRS)

Random, −0.61 (−1.14, −0.07)
P < 0.0001; 
= 84%
Remove Tavares et al. 2007 [77]
5 (420)
Fixed, −0.29 (−0.49, −0.09)
P = 0.12; 
= 46%

4. Discussion

In this review, it was determined that there is insufficient evidence thus far to conclude that APS is an effective nonpharmacological approach to the reduction of postoperative pain intensity for surgery patients, although the evidence did show a reduced analgesic requirement with no significant adverse effects in surgery patients. The results may have been affected by some limitations of this study, such as the wide variability of interventions and participants, absence of follow-up evaluation in most included trials, and the often mediocre methodological quality of the included studies. These factors contributed to the high heterogeneity of the data, which limits the strength of the evidence. No studies were considered to be at low risk of bias (≥200 participants) based on the number of participants. These factors may have led to overestimations of APS efficacy.

Given the intensity of surgical trauma, postoperative pain is inevitable and it is deemed to be a serious problem. If this pain is not managed effectively, it can contribute to several clinical risks and affect patients’ physical and psychological wellbeing; potential effects include emotional distress, infection, increased myocardial oxygen consumption, and prolonged hospitalization. Associated pathological changes can harm organs and lead to abnormal function [31, 33]. Reduction of postoperative pain is therefore essential.

Our meta-analysis of overall effects from 39 trials showed that interventions involving stimulation of body or auricular points significantly reduced postoperative pain, as measured by VAS scores. Data from studies using integrative APS or manual acupuncture showed uncertain outcomes or no significant change. In one of these studies, Deng et al. [75] suggested that these results may be due to the insufficient strength of APS to produce analgesic effects.

Among body APS studies, the largest subgroup analyzed, all intervention types except manual acupuncture significantly reduced postoperative pain. The precise analgesic mechanism of body APS remains unclear. However, it has been found to facilitate central nervous system release of met-enkephalin and dynorphins into the spinal fluid, causing synergistic pain relief with exogenous opioid medication and production of pain-producing substances, such as potassium and lactic acid [31, 34, 39, 79]. The finding that high-frequency EA at body points was more effective than low-frequency EA may be due to differences in opioid peptide release [33].

Similarly, auricular APS therapies were found to significantly reduce postoperative pain, with the exception of manual acupuncture. The most commonly used auricular point is Shen Men, which generates analgesic, sedative, and anti-inflammatory effects [6]. It also increases endorphin secretion and serotonin production, thereby suppressing the transmission of pain messages and thus pain perception [80]. The results for integrative (auricular and body) APS are less clear; this treatment was found to significantly reduce NRS and VAS scores. Thus, the existing evidence neither supports nor refutes the effectiveness of integrative APS for postoperative pain control.

We also undertook subgroup analyses of surgery types, including abdominal, knee, oral, cesarean, and cardiac surgeries. The meta-analysis results showed that body point acupuncture stimulation and auricular therapy had no significant change on VAS scores for patients undergoing knee surgery. The same trend was observed for patients receiving integrative acupoint stimulation and undergoing oral surgery. Short-term APS stimulation may have been insufficient to reduce patients’ pain intensity after knee or oral surgery, or the postoperative rehabilitation program may have affected the results of APS interventions [57]. Rigorously designed large-scale RCTs are needed to identify the effects of APS for these kinds of patients.

This analysis also showed that APS significantly reduces patients’ postoperative analgesic requirement. Given the dose-response relationship between analgesics and related adverse effects [81], any nonpharmacological method that reduces the use of analgesic medication is likely to be beneficial. Lin et al.’s [42] finding of reduced morphine requirement after high-frequency EA compared with that after low-frequency EA demonstrates the existence of a dose-response relationship in this treatment as well. However, analgesic requirements are controlled by the health care staff and directly affected by the surgery type and patient’s economic condition. Thus, analgesic medication use is not a particularly reliable indicator for the effects of APS.

No APS study reported the occurrence of a serious adverse event, although some minor (mild and transient) side effects were reported. To prevent such effects, APS should be carried out by experienced, well-trained health care professionals who understand the theories underlying this therapy and take necessary precautions.

APS may produce strong placebo effects; for example, sham acupuncture did not affect analgesic-related side effects but did exert a moderate pain-relieving effect [42]. The use of sham/placebo control groups, as in 36 of the examined RCTs, enables clear distinction between true and placebo effects. This meta-analysis showed that the true effects of APS were much stronger than placebo effects. Short-term APS and placebo interventions have shown similar effects, but long-term APS treatment causes beneficial changes in specific brain areas [82].

A small sample size can distort the results of meta-analyses, by overestimating treatment effects, probably due to methodological weaknesses [83]. In our review, no studies were considered to be at low risk of bias (≥200 participants) on the basis of sample size. Forty-two studies (71.19%) were at an unknown risk of bias (50–200 participants), and 17 studies (28.81%) were at a high risk of bias (<50 participants).

In this review, statistical heterogeneity was considerable, even with use of the random-effects model. The best level of evidence was not found for most forms of APS, suggesting that there is, thus far, insufficient evidence to conclude that APS is an effective method for reducing pain intensity in postoperative patients. Within the available body of evidence, there is Level I evidence supporting the effectiveness of body points plaster therapy. Additionally, there is Level II evidence supporting the use of body points EA, body points acupressure, and body points APS in abdominal surgery patients specifically, as well as Level II evidence supporting the use of auricular points seed embedding, manual auricular acupuncture, and auricular EA in surgery patients. Meanwhile, there is only Level III evidence for the use of body points APS in patients who have undergone cardiac surgery and a cesarean section and Level III evidence for the use of auricular point stimulation for pain reduction after abdominal surgery. The main reason that better levels of evidence were not achieved was the methodological quality of the included studies, with only 13 (22.03%) studies meeting at least five of the seven Cochrane review criteria and only 12 (20.33%) studies that were rated highly in key domains being considered at low risk of overall bias.

Two systematic reviews [21, 22] with objectives similar to those of the present study were published in 2008, but overall they produced low quality evidence due to the insufficient quality of included trials. A number of the clinical trials included in the present analysis also had some methodological problems that may have affected their efficacy results. However, we examined all types of APS, with combined and separate analyses of body, auricular, and integrative APS. Rigorously designed large-scale RCTs are needed to identify an optimal standard APS program.

4.1. Study Limitations

Some limitations of this study may have affected the results. For example, the wide variability in APS and surgery types, populations, intervention durations, and timing of outcome measurement may be the main factors underlying the observed heterogeneity, which limits the strength of the study results. The small samples and absence of follow-up evaluation in most included trials may have led to overestimation of the effects of APS. Methods of randomization, blinding, and allocation concealment were not reported or were poorly described in some trials, making quality assessment difficult. In addition, visual inspection of the funnel plots revealed some substantial asymmetry in comparisons; thus, the possibility of publication bias (i.e., preference for publication of significant over nonsignificant results) cannot be excluded. In addition, the end-points of included studies varied. End-points in Gilbertson et al. [41] and Chen et al. [32] were 4 and 3 months, respectively. When removing these two studies, the values were decreased markedly (Table 6). Therefore, the end-points of included studies have important biases in this review. Future studies of APS should be designed rigorously to ensure a high level of methodological quality.

4.2. Implications for Practice and Research

The major advantages of APS are related to its clinical safety, favorable effects in postoperative pain relief, and low complication rate following surgery [58]. Clinical nurses and other health care providers should thus be encouraged to learn and implement this simple, convenient, and economical method of postoperative pain control in routine clinical care [34].

Our findings have implications for research on the precise mechanism of APS in postoperative pain relief. Optimal acupoint selection, session duration, stimulation intensity, and application frequency have not been established. A standardized APS program for postoperative pain management should be designed using an evidence-based method. Because available evidence for integrative APS and manual acupuncture is inconclusive, further studies should focus on further assessing the effects of these treatments on postoperative pain control. Moreover, the best APS type for the reduction or elimination of long-term opioid use and the long-term effects of APS therapies remain unknown. Thus, large-scale multicenter RCTs with long-term follow-up periods should be conducted to verify the short- and long-term effects of APS on postoperative pain control. Furthermore, more attention should be paid to the economic effects of APS in health care systems.

In conclusion, this study indicates that, thus far, there is still insufficient evidence to conclude that APS is an effective method for controlling postoperative pain in surgery patients, although the evidence does suggest that APS can reduce patients’ analgesic requirement with no significant adverse effects. The best level of evidence was not adequate in most subgroups. Some limitations of this study may have affected the results, leading to an overestimation of the effects of APS. Rigorously designed large-scale RCTs are needed to identify the effects of APS.

Appendix

A. Searching Strategies

A.1. PubMed

#1“acupuncture”[MeSH Terms] OR “acupuncture therapy”[MeSH Terms] OR “acupuncture analgesia”[MeSH Terms] OR “acupuncture points”[MeSH Terms] OR “acupressure”[MeSH Terms] OR “auriculotherapy”[MeSH Terms] OR “acupuncture, ear”[MeSH Terms]#2((((((((((((((acupunctur[Title/Abstract]) OR acupoin[Title/Abstract]) OR acupressur[Title/Abstract]) OR auriculotherap[Title/Abstract]) OR (auricu[Title/Abstract] AND poin[Title/Abstract])) OR (ear[Title/Abstract] AND poin[Title/Abstract])) OR (auricu[Title/Abstract] AND acupoin[Title/Abstract])) OR (ear[Title/Abstract] AND acupoin[Title/Abstract])) OR (auricu[Title/Abstract] AND plaster[Title/Abstract])) OR (massag[Title/Abstract] AND ear[Title/Abstract])) OR (ear[Title/Abstract] AND plaster[Title/Abstract])) OR (massag[Title/Abstract] AND auricu[Title/Abstract])) OR (magnetic[Title/Abstract] AND ear[Title/Abstract])) OR (magnetic[Title/Abstract] AND auricu[Title/Abstract])) OR otopoin[Title/Abstract] OR vaccaria[Title/Abstract]#3#1 OR #2#4“perioperative period”[MeSH Terms] OR “postoperative period”[MeSH Terms] OR “preoperative period”[MeSH Terms] OR “intraoperative period”[MeSH Terms]#5(((((perioperati[Title/Abstract]) OR surger[Title/Abstract]) OR preoperati[Title/Abstract]) OR intraoperati) OR postoperati[Title/Abstract]) OR operati#6#4 OR #5#7((((pain[Title/Abstract]) OR ache[Title/Abstract])) OR (“pain”[MeSH Terms] OR “acute pain”[MeSH Terms] OR “pain management”[MeSH Terms] OR “chronic pain”[MeSH Terms]) OR “analgesia”[MeSH Terms])#8#3 AND #6 AND #7#9((((((((“randomized controlled trial”[Publication Type]) OR “controlled clinical trial”[Publication Type]) OR “ramdomized”[Title/Abstract]) OR “ramdomised”[Title/Abstract]) OR “placebo”[Title/Abstract]) OR “sham”[Title/Abstract]) OR “randomly”[Title/Abstract]) OR “trial”[Title/Abstract]) OR “groups”[Title/Abstract]#10(animals[MeSH Terms] NOT (humans[MeSH Terms] AND animals[MeSH Terms]))#11#9 NOT #10#12#8 AND #11

A.2. Embase

#1‘acupuncture’/exp#2‘acupuncture analgesia’/exp#3‘acupressure’/exp#4acupunctur:ab,ti OR acupoin:ab,ti OR acupressur:ab,ti OR auriculotherap:ab,ti OR (auricu NEAR/3 acupunctur):ab,ti OR (auricu NEAR/3 acupressur):ab,ti OR (auricu NEAR/3 poin):ab,ti OR ‘auricular plaster’:ab,ti OR (ear NEAR/3 plaster):ab,ti OR (ear NEAR/3 poin):ab,ti OR (ear NEAR/3 acupoint):ab,ti OR otopoin:ab,ti OR earhole:ab,ti OR (vaccaria NEAR/15 ear):ab,ti OR (vaccaria NEAR/15 auricu):ab,ti OR (massag NEAR/3 auricu):ab,ti OR (massag NEAR/3 ear):ab,ti OR (cowherb NEAR/15 ear):ab,ti OR (cowherb NEAR/15 auricu):ab,ti OR (seed NEAR/15 auricu):ab,ti OR (seed NEAR/15 ear):ab,ti OR (magnetic NEAR/15 ear):ab,ti OR (magnetic NEAR/15 auricu):ab,ti OR erxue:ab,ti#5#1 OR #2 OR #3 OR #4#6‘perioperative period’/exp#7‘postoperative period’/exp#8‘preoperative period’/exp#9‘intraoperative period’/exp#10‘surgery’/exp#11‘perioperative period’:ab,ti OR operative:ab,ti OR surgery:ab,ti OR (peri NEAR/3 operative):ab,ti OR (post NEAR/5 operative):ab,ti OR (pre NEAR/5 operative):ab,ti OR (intra NEAR/5 operative):ab,ti#12#6 OR #7 OR #8 OR #9 OR #10 OR #11#13‘pain’/exp#14‘analgesia’/exp#15pain:ab,ti OR analgesia:ab,ti OR ache:ab,ti OR (pain NEAR/3 management):ab,ti OR (pain NEAR/3 control):ab,ti#16#13 OR #14 OR #15#17#5 AND #12 AND #16#18‘controlled clinical trial’/exp OR ‘single blind procedure’/exp OR ‘double-blind procedure’/exp OR ‘crossover procedure’/exp#19random:ab,ti OR crossover:ab,ti OR (cross NEAR/3 over):ab,ti OR placebo:ab,ti OR (doubl NEAR/3 blind):ab,ti OR (doubl NEAR/3 mask):ab,ti OR (singl NEAR/3 blind):ab,ti OR (singl NEAR/3 mask):ab,ti OR (trebl NEAR/3 blind):ab,ti OR (trebl NEAR/3 mask):ab,ti OR (tripl NEAR/3 blind):ab,ti OR (tripl NEAR/3 mask):ab,ti OR assign:ab,ti OR allocat:ab,ti OR volunteer:ab,ti#20#18 OR #19#21‘animal’/exp OR ‘nonhuman’/exp OR ‘animal experiment’/exp#22‘human’/exp#23#21 AND #22#24#21 NOT #23#25#20 NOT #24#26#17 AND #25

A.3. Cochrane Central Register of Controlled Trials (CENTRAL)

#1MeSH descriptor: [Acupuncture] explode all trees#2MeSH descriptor: [Auriculotherapy] explode all trees#3MeSH descriptor: [Acupressure] explode all trees#4MeSH descriptor: [Acupuncture Analgesia] explode all trees#5MeSH descriptor: [Acupuncture, Ear] explode all trees#6acupunctur or acupressur or acupoin or auriculotherap or (auricu near/3 poin) or (ear near/3 poin) or (ear near/3 plaster) or (auricu near/3 plaster) or (ear near/3 acupoint) or otopoint or earhole or (vaccaria near/15 ear) or (vaccaria near/15 auricu) or (cowherb near/15 ear) or (cowherb near/15 auricu) or (magnetic near/15 ear) or (magnetic near/15 auricu) or (massag near/3 ear) or (massag near/3 auricu) or erxue:ti,ab,kw (Word variations have been searched)#7#1 OR #2 OR #3 OR #4 OR #5 OR #6#8MeSH descriptor: [General Surgery] explode all trees#9perioperative period or operati or surger or (peri near/5 operati) or (post near/5 operati) or (pre near/5 operati) or (intra near/5 operati):ti,ab,kw (Word variations have been searched)#10#8 OR #9#11MeSH descriptor: [Pain] explode all trees#12MeSH descriptor: [Analgesia] explode all trees#13pain or analgesia or ache or (pain near/3 management) OR (pain near/3 control):ti,ab,kw (Word variations have been searched)#14#11 OR #12 OR #13#15#7 AND #10 AND #14#16#15 in Trials

A.4. Cumulative Index to Nursing and Allied Health Literature (CINAHL)

#1MM Acupuncture OR MM Auriculotherapy OR MM Acupuncture, Ear OR MM acupressure OR MM acupuncture analgesia OR MM acupuncture points#2TI acupunctur OR acupoin OR acupressur OR auriculotherap OR (auricu N3 acupunctur) OR (ear N3 poin) OR (ear N3 plaster) OR (auricu N3 plaster) OR (ear N5 acupoint) OR otopoint OR earhole OR (vaccaria N15 ear) OR (vaccaria N15 auricu) OR (magnetic N15 ear) OR (magne N15 auricu) OR (massa N3 ear) OR (massag N3 auricu)#3AB acupunctur OR acupoin OR acupressur OR auriculotherap OR (auricu N3 acupunctur) OR (ear N3 poin) OR (ear N3 plaster) OR (auricu N3 plaster) OR (ear N5 acupoint) OR otopoint OR earhole OR (vaccaria N15 ear) OR (vaccaria N15 auricu) OR (magnetic N15 ear) OR (magne N15 auricu) OR (massag N3 ear) OR (massag N3 auricu)#4#1 OR #2 OR #3#5MM perioperative period OR MM postoperative period OR MM preoperative period OR MM intraoperative period#6TI perioperati OR surger OR preoperati OR intraoperati OR postoperati OR operati OR (peri N5 operati) OR (post N5 operati) OR (pre N5 operati) OR (intra N5 operati)#7AB perioperati OR surger OR preoperati OR intraoperati OR postoperati OR operati OR (peri N5 operati) OR (post N5 operati) OR (pre N5 operati) OR (intra N5 operati)#8#5 OR #6 OR #7#9MM Pain OR MM Analgesia#10TI pain OR ache OR analgesia OR (pain N5 management) OR (pian N5 contral)#11AB pai OR ach OR analgesia OR (pain N5 management) OR (pian N5 contra)#12#9 OR #10 OR #11#13#4 AND #8 AND #12

A.5. PsycINFO

#1MJSUB.EXACT.EXPLODE(“Acupuncture”)#2TI(acupunctur OR acupressur OR acupoin OR auriculotherap OR auricu NEAR/3 acupunctur OR auricu NEAR/3 poin OR ear NEAR/3 plaster OR auricu NEAR/3 plaster OR ear NEAR/3 poin OR ear NEAR/3 acupoint OR otopoint OR earhole OR vaccaria NEAR/15 ear OR vaccaria NEAR/15 auricu OR cowherb NEAR/15 ear OR cowherb NEAR/15 auricu OR magne NEAR/15 ear OR magne NEAR/15 auricu OR massag NEAR/3 ear OR erxue OR massag NEAR/3 auricu)#3AB(acupunctur OR acupressur OR acupoin OR auriculotherap OR auricu NEAR/3 acupunctur OR auricu NEAR/3 poin OR ear NEAR/3 plaster OR auricu NEAR/3 plaster OR ear NEAR/3 poin OR ear NEAR/3 acupoint OR otopoint OR earhole OR vaccaria NEAR/15 ear OR vaccaria NEAR/15 auricu OR cowherb NEAR/15 ear OR cowherb NEAR/15 auricu OR magne NEAR/15 ear OR magne NEAR/15 auricu OR massag NEAR/3 ear OR erxue OR massag NEAR/3 auricu)#4#1 OR #2 OR #3#5MJSUB.EXACT.EXPLODE(“surgery”)#6TI(perioperati OR surger OR preoperati OR intraoperati OR postoperati OR operati)#7AB(perioperati OR surger OR preoperati OR intraoperati OR postoperati OR operati)#8#5 OR #6 OR #7#9MJSUB.EXACT.EXPLODE(“pain”)#10TI(pain OR ache OR analgesia)#11AB(pain OR ache OR analgesia)#12#9 OR #10 OR #11#13#4 AND #8 AND #12#14TI(random OR crossover OR cross NEAR/3 over OR placebo OR double NEAR/3 blind OR double NEAR/3 mask OR single NEAR/3 blind OR single NEAR/3 mask OR treble NEAR/3 blind OR treble NEAR/3 mask OR triple NEAR/3 blind OR triple NEAR/3 mask OR assign OR allocate OR volunteer)#15AB(random OR crossover OR cross NEAR/3 over OR placebo OR double NEAR/3 blind OR double NEAR/3 mask OR single NEAR/3 blind OR single NEAR/3 mask OR treble NEAR/3 blind OR treble NEAR/3 mask OR triple NEAR/3 blindOR triple NEAR/3 mask OR assign OR allocate OR volunteer)#16#14 OR #15#17#13 AND #16

A.6. Allied and Complementary Medicine (AMED)

#1exp acupuncture/#2exp acupressure/#3exp Ear acupuncture/#4(“acupunctur” or “acupoin” or “acupressur” or “auriculotherap” or “ear adj3 acupressur” or “auricu adj3 acupressur” or “ear adj3 plaster” or “ear adj3 acupoint” or “otopoin” or “earhole” or “vaccaria adj15 ear” or “vaccaria adj15 auricu” or “massag adj3 auricu” or “massag adj3 ear” or “cowherb adj15 auricu” or “seed adj15 auricu” or “seed adj15 ear” or “magnetic adj15 auricu” or “erxue”).ti.#5(“acupunctur” or “acupoin” or “acupressur” or “auriculotherap” or “ear adj3 acupressur” or “auricu adj3 acupressur” or “ear adj3 plaster” or “ear adj3 acupoint” or “otopoin” or “earhole” or “vaccaria adj15 ear” or “vaccaria adj15 auricu” or “massag adj3 auricu” or “massag adj3 ear” or “cowherb adj15 auricu” or “seed adj15 auricu” or “seed adj15 ear” or “magnetic adj15 auricu” or “erxue”).ab.#6#1 OR #2 OR #3 OR #4 OR #5#7exp surgery/#8(“perioperative period” or “postoperative period” or “preoperative period” or “intraoperative period” or “perioperati” or “surger” or “preoperati” or “intraoperati” or “postoperati” or “operati”).ti.#9(“perioperative period” or “postoperative period” or “preoperative period” or “intraoperative period” or “perioperati” or “surger” or “preoperati” or “intraoperati” or “postoperati” or “operati”).ab.#10#7 OR #8 OR #9#11exp pain/#12(“pain” or “ache” or “pain adj3 management” or “pain adj3 control” or “analgesia”).ti.#13(“pain” or “ache” or “pain adj3 management” or “pain adj3 control” or “analgesia”).ab.#14#11 OR #12 OR #13#15#6 AND #10 AND #14#16exp Random allocation/ or exp Clinical trials/ or exp Randomized controlled trials/ or exp Placebos/#17(“random” or “crossover” or “cross adj3 over” or “placebo” or “doubl adj3 blind” or “doubl adj3 mask” or “singl adj3 blind” or “singl adj3 mask” or “trebl adj3 blind” or “trebl adj3 mask” or “tripl adj3 blind” or “allocat” or “ volunteer” or “tripl adj3 mask” or “assign”).ti.#18(“random” or “crossover” or “cross adj3 over” or “placebo” or “doubl adj3 blind” or “doubl adj3 mask” or “singl adj3 blind” or “singl adj3 mask” or “trebl adj3 blind” or “trebl adj3 mask” or “tripl adj3 blind” or “allocat” or “volunteer” or “tripl adj3 mask” or “assign”).ab.#19#16 OR #17 OR #18#20#15 AND #19

A.7. Thomson Reuters Web of Science

#1TS = (acupunctur OR acupoin OR acupressur OR auriculotherap OR (auricu NEAR/3 acupunctur) OR (auricu NEAR/3 poin) OR (ear NEAR/3 plaster) OR (auricu NEAR/3 plaster) OR (ear NEAR/3 poin) OR (auricu NEAR/3 acupoint) OR (ear NEAR/3 acupoint) OR otopoint OR (vaccaria NEAR/15 ear) OR (vaccaria NEAR/15 auricu) OR (cowherb NEAR/15 auricu) OR (magnetic NEAR/15 ear) OR (magnetic NEAR/15 auricu) OR (massag NEAR/3 ear) OR (massag NEAR/3 auricu) OR erxue) Indexes = SCI-EXPANDED, SSCI, A&HCI, CPCI-S, CPCI-SSH Timespan = All years#2TS = (perioperative period OR postoperative period OR preoperative period OR intraoperative period OR perioperati OR surger OR preoperati OR intraoperati OR postoperati OR operati OR (peri NEAR/3 operati) OR (post NEAR/3 operati) OR (pre NEAR/3 operati) OR intra NEAR/3 operati) Indexes = SCI-EXPANDED, SSCI, A&HCI, CPCI-S, CPCI-SSH Timespan = All years#3TS = ((acute NEAR/3 pain) OR (chronic NEAR/3 pain) OR (pain NEAR/3 management) OR (pain NEAR/3 control) OR pain OR ache OR analgesia) Indexes = SCI-EXPANDED, SSCI, A&HCI, CPCI-S, CPCI-SSH Timespan = All years#4#1 AND #2 AND #3

A.8. ScienceDirect

#1TITLE-ABSTR-KEY(acupuncture OR acupoint OR acupressure OR auriculotherapy OR (ear W/5 acupressur) OR (auricu W/5 acupressur) OR (auricu W/5 poin) OR (vaccaria W/5 auricu) OR (cowherb W/5 auricu) OR (magnetic W/5 auricu) OR (massag W/5 auricu) OR erxue) [All Sources(- All Sciences -)]#2TITLE-ABSTR-KEY(perioperative period OR postoperative period OR preoperative period OR intraoperative period OR perioperati OR surger OR preoperati OR intraoperati OR postoperati OR operati)[All Sources(- All Sciences -)]#3TITLE-ABSTR-KEY(pain OR ache OR acute pain OR chronic pain OR (pain W/5 management) OR (pain W/5 control) OR analgesia) [All Sources(- All Sciences -)]#4#1 AND #2 AND #3

Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

Authors’ Contribution

Each author’s contributions to the paper are detailed as follows: Xian-Liang Liu participated in study conception and design, literature searching and sorting, data extraction, analysis and interpretation of data, and paper writing and revising. Jing-Yu Tan participated in study conception and design, literature searching and sorting, data extraction, and revising the paper. Alexander Molassiotis participated in study conception and design and in revising the paper. Lorna K. P. Suen participated in study conception and design and in revising the paper. Yan Shi participated in data analysis and interpretation of data and in revising the paper.

Acknowledgments

The authors would like to thank the authors of the original articles who provided additional unpublished data. This study was supported by the Tin Ka Ping Education Fund for Visiting Scholars from the Chinese Mainland of the School of Nursing, The Hong Kong Polytechnic University.

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