Half of the included studies measured and recorded the results of PONV after non-needle acupoint stimulation. Seven trials (N = 475)[14,16–19,23,24] reported that non-needle acupoint stimulation might more effectively reduce PONV, compared with the control (RR: 0.56, 95% CI: 0.43–0.72, N = 475, and I 2 = 0%; Fig. 3).
3.6.1 Nausea within PO6H
Nausea within PO6H in non-needle acupoint stimulation groups was compared with that in the control groups. Data from 3 studies[16,18,27] indicated that nausea during this period (N = 185) had an evidence of significant difference (RR: 0.46, 95% CI: 0.29–0.72, N = 185, and I 2 = 0%; Fig. 4A). This result indicated that non-needle acupoint stimulation could reduce nausea within PO6H compared with that in the control group.
3.6.2 Nausea within PO12H
There was a significant difference about the results of nausea within PO12H. The combination of these 3 trials[16,27] revealed that non-needle acupoint stimulation might more favorably reduce nausea within PO12H (RR: 0.40, 95% CI: 0.22–0.73, N = 119, and I 2 = 0%; Fig. 4B).
3.6.3 Nausea within PO24H
The analysis of data obtained from five studies[16,18,21,22,27] indicated heterogeneity with respect to nausea within PO24H (P < .05, I 2 = 49%). The decreasing change in non-needle acupoint stimulation group was statistically significant (RR: 0.61, 95% CI: 0.42–0.88, N = 399, and I 2 = 49%; Fig. 4C). In this result, there were 2 kinds of non-needle acupoint stimulation, but only 1 trial performed acupressure. So, when the trial by Majholm was excluded, the heterogeneity decreased to 0% (RR: 0.52, 95% CI: 0.39–0.70, N = 291, and I 2 = 0%, Fig. 4C). The remained trials revealed that, compared with control intervention, transcutaneous electrical acupoint stimulation could reduce nausea within PO24H compared with that in the control group.
3.6.4 Nausea within PO48H
Three of the included studies[16,22,27] measured nausea within PO48H of the participants (N = 226) after non-needle acupoint stimulation. There was a significant difference in nausea within PO48H (RR: 0.56, 95% CI: 0.40–0.77, N = 225, and I 2 = 0%; Fig. 4D). This result indicated that nausea within PO48H could be improved by non-needle acupoint stimulation.
3.6.5 Nausea in the recovery room
Two studies[21,26] were pooled and analyzed for the results of nausea in the recovery room. There was not a significant difference of nausea between non-needle acupoint stimulation and the control intervention in the recovery room (RR: 0.57, 95% CI: 0.30–1.05, N = 176, I 2 = 0%, P > .05; Fig. 4E).
3.6.6 VRS of nausea within PO2H
Three studies[15,16,25] measured nausea by using VRS in PO2H. With no statistical significance, this result revealed that non-needle acupoint stimulation could not relieve nausea within PO2H (MD:−0.47, 95% CI: −0.97–0.03, N = 169, and I 2 = 0%, P > .05; Fig. 4F).
3.7.1 Vomiting within PO6H
There were 3 studies[16,18,27] recorded vomiting within PO6H after non-needle acupoint stimulation. Data obtained from these studies revealed that vomiting in PO6H (N = 186) had no statistical significance (P > .05). This result indicated that non-needle acupoint stimulation could not reduce vomiting within PO6H compared with that in the control group (RR: 0.48, 95% CI: 0.23–1.02, N = 185, and I 2 = 0%; Fig. 5A).
3.7.2 Vomiting within PO12H
The analysis of data obtained from 2 studies[16,27] indicated low significant heterogeneity and no statistical significance with respect to vomiting within PO12H (P > .05, I 2 = 22%). There was no evidence of significant difference in vomiting within PO12H (RR: 0.35, 95% CI: 0.10–1.2, N = 119; Fig. 5B).
3.7.3 Vomiting within PO24H
There were 7 trials[15,16,18,20–22,27] focus on results of vomiting within PO24H after non-needle acupoint stimulation. The combination of these data had an evidence of significant difference and revealed that non-needle acupoint stimulation might more favorably reduce vomiting within PO24H (RR: 0.60, 95% CI: 0.44–0.81, N = 537, and I 2 = 0%; Fig. 5C).
3.7.4 Vomiting within PO48H
Three studies[16,22,27] were pooled and analyzed for the results of vomiting within PO48H. Data from these studies had a negligible statistically heterogeneity (P < .05, I2 = 3%). There was a significant difference of vomiting between non-needle acupoint stimulation and the control intervention during postoperative 48 hours (RR: 0.57, 95% CI: 0.35–0.92, N = 225; Fig. 5D). This result indicates that non-needle acupoint stimulation might improve vomiting within PO48H.
3.7.5 Vomiting in the recovery room
Two of the included studies[21,26] recorded vomiting of the participants (N = 175) in the recovery room. The results of non-needle acupoint stimulation groups were compared with that of the control groups (Fig. 5E). There was no evidence of significant difference in vomiting in PO12H (RR: 0.35, 95% CI: 0.10–1.2, N = 120, I 2 = 0%, P > .05; Fig. 5E).
3.7.6 Use of rescue antiemetic
The analysis of data obtained from 5 studies[14,15,18,20,21] indicated a statistical significance with respect to use of rescue antiemetic within PO24H. This result showed that non-needle acupoint stimulation had a positive effect on reducing use of rescue antiemetic within PO24H compared with that in the control group (RR: 0.60, 95% CI: 0.44–0.83, N = 112, and I 2 = 0%; Fig. 6).
3.8 Adverse events
Only 2 study reported adverse events in the intervention or control group. Majholm and Møller reported 77 patients with wrist and hand side effects such as redness, swelling, tenderness, and paresthesias that were caused by the wristbands.
Despite the fact that the curative effect of antiemetic on PONV has been widely proved, the avoidless side-effect remains a challenge to both surgeons and nurses. There are reports that the female patients undergoing different kinds of breast surgery have a stronger tendency to suffer from PONV. Facing these problems, various methods from clinical to nursing aspects such as surgery methods changing from mastectomy to modified radical mastectomy and from usual care to comfortable nursing have been applied to minimize the incidence of nausea and vomiting after breast surgery. However, the safe and effective method still remains unknown.
Acupoint stimulation is a complex, ritualistic somatosensory intervention with multiple components. Acupuncture is an original and important method of acupoint stimulation. Along with the development of TCM, more and more researchers apply acupoint stimulation to settle complications after treatment. Because of the particularity of acupuncture, reliance on skilled acupuncturist becomes the crucial part of treatment as well as limits the dissemination and generalization. The problem has been resolved, since instrumented replacements of acupuncture like transcutaneous electrical acupoint stimulation and acupressure are widely used to reduce postoperative complications. Particularly, studies about nausea and vomiting with satisfactory curative effects can often be found.
According to TCM constitutional theory, most of patients undergoing breast surgery have Qi-stagnation constitution or Qi-deficiency constitution. And patients with PONV often have Qi-deficiency constitution. By stimulating acupoints, meridian and collaterals could be activated to tonify and promote Qi. Neiguan, for example, is an important acupoint of pericardium meridian, which has an effect on regulating Qi and decreasing inverse. Additionally, stimulating Laogong, Waiguan, Zusanli, Hegu or Quchi could also be used for reducing PONV by activating different meridians. Therefore, theoretically, acupoint stimulation may prevent nausea and vomiting after breast surgery. In response to this, some clinical researches have been done to explore practical effects.[14–27] Unfortunately, conclusions from these researches are not the same. Comprehensive summary and analysis become more urgent.
Through rigorous reviewing and screening, we finally collected 14 trials to complete a meta-analysis to explore the result whether acupoint stimulation could have effect on reducing PONV after the breast surgery or not. In this review, unclear risk of bias was found in most of the included trails. Description of blind method and allocation concealment were the main reason that was prone to prevent the analysis of a subjective outcome. Jadad scale was applied to assess all selected trials, a high-quality study should have the Jadad score equal to or more than 3. All of included studies had the Jadad score no less than 2. There were nine trials with Jadad score 2. Combining particularity of acupoint stimulation and elaborative evaluation, reviewers found that design and implementation of these trials were reasonable and reliable. Therefore, these trials with Jadad score 2 were also included. These enrolling criteria allowed us a moderate quality analysis.
Methods of evaluating nausea and vomiting mainly include frequency, VRS of nausea, and use of rescue antiemetic. Here, the included outcomes were within PO48H. According to the results of analysis, nausea could be reduced by acupoint stimulation in the early phase after breast surgery (0-12H). However, acupoint stimulation had no reducing effect on vomiting at the same time. Nausea was often treated as the early symptom of vomiting. From the data of included studies, the frequency of vomiting in the early phase was less than other phases. This reasonably explained why pooled analysis did not support the effectiveness of acupoint stimulation for reducing vomiting. PO24H was thought to be the medium phase in this study. Frequency of PONV, frequency of nausea, and frequency of vomiting were selected to assess the curative effect of acupoint stimulation in the early and medium phases (0-24H). Analysis results kept consistency showing that acupoint stimulation was able to markedly reduce the occurrence of nausea and vomiting. In this period, frequency of nausea and vomiting increased. Although there was the difference of included patients, those research results about other kinds of surgery still supported our viewpoint. Analyzing the outcome of nausea within PO24H, we only found heterogeneity appearing in this result. Then, according to the classification of non-needle acupoint stimulation, a subgroup analysis was completed and showed no heterogeneity. Between electrical stimulation and acupressure, there may be some differences such as operation, curative effect and so on. This explained the reason of the existence of heterogeneity. Within PO48H, the possibility of nausea and vomiting continues to increase for postoperative patients. The pooled analysis of 2 outcomes including nausea and vomiting suggested the effect of non-needle acupoint stimulation on reducing nausea and vomiting after breast surgery continue until PO48H. In addition, adverse events were reported in only 1 included study, which adopted wristbands to stimulating acupoint. However, these commercialized wristbands caused redness, swelling, tenderness and paresthesias. The occurrence of adverse events was related to tight wearing.
In terms of the choice of non-needle acupoint stimulation, electrical stimulation was more popular. The most common acupoint is PC6 that was selected in all the included studies. This was in line with trends in research that often recommended PC6 as the acupoint to prevent nausea and vomiting. Acupoint selection could be either bilateral or unilateral. Meanwhile, other acupoints also could be chose to play a synergistic role of reducing nausea and vomiting. Working time was generally specified as from 30 minutes before induction of anaesthesia to the end of surgery. When electrical stimulation was selected, working electric current was different among various instruments. Without the need of professional acupuncturist, non-needle acupoint stimulation has been gradually popularized in clinical nursing practice and revealed the potential of replacing antiemetic. Moreover, there was an inevitable question that the use of acupressure is often limited to wristband structures that cause uncomfortable or tight feelings. The presentation of adverse events may lead to reduce the usage of acupoint stimulation by wristband. Therefore, transcutaneous electrical acupoint stimulation seems safer than acupressure by wristband acupressure.
Most of studies that were included in this review had unclear risk of bias, recruited a small number of patients, and provided sparse data on most of our pre-established outcomes of interest. So, the pooling results in these meta-analyses were affected. Heterogeneity existed in the aspects of type of surgery, duration of surgery and anesthesia. From the viewpoint of gastrointestinal stimulation and nervous stimulation, laparoscopic abdominal surgery, gynecological surgery, and procedures involving the ear, nose and throat were easier to induce PONV. However, the difference of increasing PONV among different breast surgeries could not be ignored. Duration of surgery always had effect on incidence of PONV. Here, due to the selection of different breast surgery, the duration of surgery varied greatly from study to study. Anesthetic agents were also related to PONV. The use of anesthetic inhalation agents like nitrous oxide has long been associated with an increase in the risk of PONV. On the contrary, total intravenous anesthetic using propofol has been found to reduce PONV. Therefore, heterogeneity in anesthetic agents was obvious in the included studies. Furthermore, there were only 2 studies about acupressure. Others selected electroacupuncture as the therapeutic method for PONV. For reducing PONV of breast surgery, the different between acupressure and electroacupuncture was no conclusion. But heterogeneity in acupoint stimulation methods could not be ignored, too.
To some extent, this had an effect on the final result of meta-analysis. The main methodological limitations of these included studies were the lack of description of allocation concealment, blinding of participants, and outcome assessors; which were due to the characteristic of non-needle acupoint stimulation. Due to the different publication standard, risk of bias in English trials was lower than that in Chinese trials. In addition, the inclusion criteria of patients in different studies was inconsistent, especially in age, history of nausea and vomiting, type of breast disease and surgery, the duration of surgery and use of anesthetic drug. Further studies with more consistent measurements and more standard data records would help to more accurately confirm the final conclusion.
The results of this meta-analysis of fourteen relatively studies showed that non-needle acupoint stimulation was an effective method for reducing nausea and vomiting of female patients after breast surgery. Because of the limited number and quality of included studies, this conclusion could not be considered a conclusive statement. As one of the most commonly used non-pharmaceutical therapy, acupoint stimulation was especially suitable for solving PONV by nurses. It could be recommended in patients undergoing breast surgery with moderate-high risk for PONV or drugs contraindications. The routine operation was application of transcutaneous acupoint electrical stimulation on PC6 from 30 minutes before induction of anesthesia to the end of surgery. The comparison among various methods and different stimulating acupoints will be a meaningful topic for future studies. Although the quantity of Chinese studies about acupoint stimulation mounted up, more well-designed studies should be carried out.
Conceived and designed this meta-analysis: STY, SMZ and SR. Performed this meta-analysis: SR, DW and LCL. Analyzed the data: SMZ and SR. Contributed to software analysis and review of the paper: SR, DW, LCL, LYN, GY, SXH, STY and SMZ. Wrote the paper: SR and SMZ. Revised the paper: LY
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Keywords:Copyright © 2019 The Authors. Published by Wolters Kluwer Health, Inc. All rights reserved.
acupoint; breast; meta-analysis; nausea; non-needling stimulation; PONV; vomiting