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Original Articles: Adult Cardiac

Efficacy of Acupuncture in Prevention of Postoperative Nausea in Cardiac Surgery Patients

^a Mayo Medical School, Mayo Clinic College of Medicine, Rochester, Minnesota
^b Division of General Internal Medicine, Mayo Clinic College of Medicine, Rochester, Minnesota
^c Department of Surgery, Mayo Clinic College of Medicine, Rochester, Minnesota
^d Division of Biostatistics, Mayo Clinic College of Medicine, Rochester, Minnesota
^e Division of Cardiovascular Surgery, Mayo Clinic College of Medicine, Rochester, Minnesota

Accepted for publication April 27, 2009.

^_* Address correspondence to Dr Vincent, Division of General Internal Medicine, Mayo Clinic, 200 First St SW, Rochester, MN 55905 (Email: vincent.ann{at}mayo.edu).

	Abstract

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Background: Coronary artery bypass graft and cardiac valve surgeries are frequently performed in medical facilities in the United States, and postoperative nausea (PON) is a prevalent problem in this patient population. The purpose of this study was to evaluate the efficacy of a single preoperative acupuncture treatment in the prevention of PON in patients undergoing coronary artery bypass graft or cardiac valve surgery, or both.

Methods: Ninety participants presenting for coronary artery bypass graft or cardiac valve surgery, or both, were recruited for this study. Patients were randomly assigned to receive either one preoperative acupuncture and standard postoperative care (acupuncture group) or solely standard postoperative care (control group). Acupuncture was performed 0.5 to 3 hours before surgery. The PON incidence and severity on postoperative day (POD) 2 and POD 3 were measured with validated nausea tools.

Results: The acupuncture group had a significantly lower incidence of nausea compared with the control group (POD 2, odds ratio [OR], 0.38; p = 0.05; and POD 3, OR, 0.26; p = 0.01). The acupuncture group also had a significantly lower score of nausea severity than the control group (POD 2, OR, 0.29; p = 0.01; and POD 3, OR, 0.25; p = 0.01). No adverse effects due to acupuncture treatment were reported. Antiemetics, pain medications, and anesthetics administered intraoperatively did not differ between the two groups and did not influence study results.

Conclusions: A single preoperative acupuncture treatment decreased incidence and severity of PON in patients undergoing coronary artery bypass graft or cardiac valve surgery, or both, and caused no adverse effects.

	Introduction

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Postoperative nausea (PON) is a frequent complication for patients undergoing coronary artery bypass graft (CABG) and cardiac valve procedures. The incidence of PON among cardiac surgical patients reportedly averages about 37% [1, 2]. Postoperative nausea is an important problem because it interferes with the patient's sleep and appetite and causes interruption of diet, nutrition, and oral drug therapy [3]. Furthermore, PON and vomiting may lead to such complications as dehydration, electrolyte disturbances, aspiration, increased tension on suture lines, and venous hypertension [4]. In a study by Macario and colleagues [5], patients reported that avoidance of PON and vomiting, along with avoidance of pain and gagging on the endotracheal tube, was of greatest concern to them after anesthesia. In a separate study, patients reported that they were willing to pay out of pocket for an effective antiemetic [6].

Several factors cause PON, including surgery type, surgery duration, anesthetic agent used, individual patient factors (eg, female sex), previous history of PON, and postoperative factors (eg, pain, dizziness, ambulation, timing of first oral intake, opioid administration) [4, 7]. Although various antiemetic medications are currently available, they are not always effective or tolerated by patients. Because different antiemetic medications act at different receptor sites, some evidence suggests that combination antiemetic therapy may be more effective than single-drug therapy in prophylaxis of PON [4, 8]; however, this approach may also increase the incidence of adverse effects [4]. Hence, there clearly exists a need for safe therapy with few adverse effects. Nonpharmacologic methods, such as acupuncture, transcutaneous electrical nerve stimulation, acupoint stimulation, and acupressure have shown promise in prevention of PON [9, 10].

Acupuncture, a component of traditional Chinese medicine, involves placement of needles at specific acupuncture points with subsequent manual or electrical stimulation. Studies suggest that acupuncture achieves therapeutic effects by evoking physiologic changes in the nervous system [7]. Several research trials have showed the positive effect of acupuncture and acupoint stimulation in prevention of PON after abdominal or gynecologic operations and various other types of surgical procedures [11, 12]. The National Institutes of Health Consensus Development Panel on Acupuncture in 1998 concluded that acupuncture was an effective treatment of PON, as well as postoperative vomiting, postoperative dental pain, and chemotherapy-induced nausea and vomiting [13].

To our knowledge, no clinical study to date has evaluated the efficacy of acupuncture for the treatment of PON in cardiac surgery patients. We evaluated the efficacy of a single preoperative acupuncture treatment in prevention of PON in patients who underwent CABG or cardiac valve surgery, or both.

	Material and Methods

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Preliminary Study
As part of a quality improvement initiative, we conducted a medical record review to estimate PON incidence in patients who had cardiac surgery at Saint Marys Hospital, Rochester, Minnesota, over a 30-day period. Our results showed that, despite antiemetic medication therapy, 40.7% of patients had documented PON. Other published studies reported rates of PON after cardiac surgery that ranged from 23% to 50% [1, 2].

Subsequently, a 2-day clinical pilot was performed with the participation of 5 patients as part of a continuous improvement project that uses a multidisciplinary approach to evaluate conventional and complementary therapies to enhance the care of cardiac surgery patients. The patients in the pilot received preoperative acupuncture, and none reported PON. However, we also learned that the time available in the preoperative area when the patient was being prepared for surgery was limited and did not allow sufficient time for a traditional Chinese medicine evaluation and individualized acupuncture. So, a standardized approach was chosen for this study.

Study Design
This study was a prospective, randomized controlled trial stratified by surgery type. The primary aim was to evaluate the efficacy of a single preoperative acupuncture treatment and standard postoperative care in decreasing the incidence of PON in cardiac surgery patients compared with standard postoperative care alone. The secondary objective was to evaluate the efficacy of preoperative acupuncture in decreasing the severity of PON. The study was conducted at Saint Marys Hospital. The Mayo Clinic Institutional Review Board approved the study on October 18, 2007, and all patients gave written informed consent. Recruitment began in October 2007 and was concluded in February 2008.

The cardiovascular surgical practice of Mayo Clinic consists of local, regional, and tertiary referred patients. Patients scheduled for surgery who met the inclusion criteria were approached by a research coordinator at least one day before their procedure and offered the option to participate in the study. Those patients who chose to participate and gave informed consent were randomly assigned to either the acupuncture group or the control group. This randomization was performed by means of three computer-generated random assignment sequences, each corresponding to the type of procedure the patient was to undergo; specifically, CABG or valve surgery, or both. This approach was taken to ensure a balanced distribution of patients with different types of surgeries.

All patients in the acupuncture group received one acupuncture treatment 0.5 to 3 hours before surgery. The treatment was administered by either of the two licensed acupuncture practitioners involved in the study; a physician trained in acupuncture with more than 300 hours of experience and a licensed acupuncturist with more than 5 years of clinical experience. Sterile, single-use stainless-steel needles (size, 0.20 x 40 mm) were inserted bilaterally at SP 4, SP 6, HT 7, PC 6, ST 44, shen men, autonomic point, ST 21, CV 12, ST 40, ST 38, ST 36, CV 6, and CV 10. When the needle was in the correct anatomic position, it was manually stimulated and de qi sensation was achieved. The needles were left in place for a maximum of 20 minutes. Patients in both groups (acupuncture and control) received standard postoperative care.

The randomization of the study was masked to anesthesia staff, surgical staff, and nursing staff. Anesthesiologists chose the intraoperative anesthesia for each patient individually. The patients in both groups received similar postoperative care, with antiemetic and pain medications administered according to the clinical decision of the surgical team, both administered on an as-needed, as well as prophylactic, basis. Dietary progression in both groups was in accordance with standard postoperative care. Because our objective was to evaluate efficacy of the addition of a single preoperative acupuncture to standard postoperative care in prevention of PON, we did not standardize anesthetics, antiemetics, or pain medications.

Patients
To be eligible for study participation, patients had to be scheduled for CABG or cardiac valve surgery, or both. Exclusion criteria were an age less than 18 years and infection, breakdown, or inflammation of the skin. Randomization was stratified by type of surgery to ensure a balanced assignment of treatment among patients undergoing each type of operation.

Sample Size
Sample size was based on data from previously published studies. It has been estimated that 42 patients are needed per group to detect a clinically significant difference in PON incidence with 90% power and a type I error of 0.05. To account for the possibility of dropouts, we enrolled 90 patients in the study (Fig 1).

View larger version (28K): [in this window] [in a new window]   Fig 1. Randomization scheme of patient participation.

Outcome Measures
The data collected included patient characteristics, date and type of surgical procedure, prior acupuncture experience, severity of preoperative and postoperative nausea, number of postoperative emesis episodes, names and amounts of antiemetic and pain medications given intraoperatively and postoperatively, and type and amount of intraoperative anesthesia. The primary outcome was the incidence of PON, defined as the presence of nausea, regardless of severity, on postoperative day (POD) 2 and POD 3. The secondary outcome was the severity of PON. The data of nausea severity and number of emesis episodes were collected by questioning the patient on POD 2 and POD 3 (where POD 1 is the day of surgery). Nausea severity was recorded on a 4-point scale in which 0 was no nausea; 1, mild nausea; 2, moderate nausea; and 3, severe nausea. Patients were instructed to rate the nausea severity according to the worst sensation of nausea they had experienced in the preceding time period. This tool has been used in other studies, including one on antiemetic prophylaxis in cardiac surgery by Woodward and colleagues [1]. Episodes of emesis were recorded as the number of occurrences per day. Information on patient characteristics, postoperative pain, antiemetic medications received, and the type of anesthesia used intraoperatively was collected from the electronic patient record.

Statistical Analysis
Descriptive statistics for categoric variables (eg, sex, surgical procedure, previous acupuncture experience) were reported as percentage of patients; continuous variables (eg, age) were reported as mean (SD). Categoric variables were compared between the acupuncture group and the control group by using the ² test or Fisher's exact test; continuous variables were compared by using the 2-sample t test or Wilcoxon rank sum test where appropriate. Logistic regression models were used to find the univariate and multivariate predictors of postoperative nausea. Because the mean age and previous acupuncture experience were significantly different between the two patient groups, they were forced in the multivariate model together with acupuncture to adjust for their potential effects on outcome. All statistical tests were 2-sided with the level set at 0.05 for statistical significance.

	Results

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Patients
A total of 90 patients consented to the study; 43 were randomly assigned to the acupuncture group and 47 to the control group (Fig 1). Two patients in the acupuncture group dropped out at the time of treatment because of anxiety about the needles.

Baseline Characteristics
Baseline characteristics were similar between the two groups except age and previous acupuncture experience (Table 1). The mean age of patients in the acupuncture group was 62 years compared with 65 years for patients in the control group. Of the patients overall, 70% were men, 14% were scheduled for both CABG and cardiac valve surgical procedures, 59% had valve surgery only, and 26% had CABG surgery only. In the control group about 18% of patients reported previous acupuncture experience, in contrast to none in the acupuncture group.

View larger version (11K): [in this window] [in a new window]   Fig 2. Nausea incidence on postoperative day (POD) 2 and 3. ( = control; = acupuncture.)

View larger version (10K): [in this window] [in a new window]   Fig 3. Nausea severity on postoperative day 2. Severity scale: 0, no nausea; 1, mild nausea; 2, moderate nausea; and 3, severe nausea. ( = control; = acupuncture.)

View larger version (10K): [in this window] [in a new window]   Fig 4. Nausea severity on postoperative day 3. Severity scale: 0, no nausea; 1, mild nausea; 2, moderate nausea; and 3, severe nausea. ( = control; = acupuncture.)

	Comment

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

The strengths of this study include the straightforward approach used for acupuncture, which made it feasible to administer acupuncture before surgery in a busy preoperative area, and the safety and generalizability of incorporating such a treatment into existing care methods. Because our objective was to evaluate the efficacy of a single preoperative acupuncture treatment added to standard hospital care for prevention of PON, we did not standardize anesthetics, antiemetics, or pain medications in either group. Analysis of the data regarding administered antiemetic medications, pain medications, and anesthetic agents was not significantly different between the acupuncture group and the control group and could not have influenced the results. Although the argument could be raised that antiemetic use was not less in the acupuncture group, the counter argument is that we did nothing to control the use of antiemetics because this study was a pragmatic trial. Nevertheless, medication use was similar in both groups; the only difference between them was that one group received acupuncture preoperatively. Our data are consistent with the data of previous studies showing that preoperative acupuncture can prevent PON [14].

One limitation of this study was that the treatment was blinded to neither the acupuncturist nor the patients. The reason we chose a comparison with standard care as the most logical control intervention for an acupuncture study is that sham or placebo-controlled designs are largely viewed as inadequate by the acupuncture community [15]. Another limitation was the lack of a predefined intervention in the control group, which will be addressed in the design of a future, larger randomized controlled study. A confounder in our study was that the 8 patients who reported to have previous acupuncture experience were all randomly assigned to the control group. This assignment occurred in a stratified randomization scheme used to ensure a balanced number of patients undergoing different types and combinations of surgeries in both acupuncture and control groups. We did not have or collect this acupuncture information at consent or randomization because it was not part of our criteria for the randomization of patients. It was collected as baseline data only after the patient enrolled in the study and was randomly assigned to either the acupuncture or the control group. This difference between the two groups was addressed in the data analysis by including this variable in the multivariate model, to adjust for its potential effect on outcomes, and it did not influence the outcome. Finally, there is a possibility that the patients were self-selected, to some extent, for participation in the study, because a number of patients who did not consent to participate had indicated that they had no interest in the subject because they had no history of PON.

Of note, we chose a standardized approach to acupuncture treatment instead of an individualized approach for several reasons that made the former more feasible for our patient subset. The acupuncturist met the patient for the first time in the preoperative area on the day of the surgery. Given that patients spend on average, approximately 60 to 90 minutes in the preoperative area, during which they also have to complete a full nursing admission and anesthesia evaluation, the acupuncturist did not have sufficient time to conduct the evaluation and the pattern diagnosis that are characteristic of individualized treatment. In most cases during this study, the acupuncturist had 30 minutes or less to spend with the patient. Moreover, we faced the challenge of incorporating a complementary care method into conventional care without causing delays in the patient's surgical time. This requirement was important in our setting because delays in operating-room time are expensive in a busy tertiary center with consecutively scheduled surgical procedures.

This study also provides important information about the personal experience of patients participating in acupuncture research, in the form of comments volunteered by patients during follow-up. Among patients in the acupuncture group, 3 patients with a self-reported history of PON for prior surgical procedures indicated, without being asked for this information, that they had either no PON or a significant decrease in PON symptoms during the current hospital stay. Similarly, another 2 patients in the acupuncture group noted that they felt calmer after the preoperative acupuncture treatment. Furthermore, a number of patients from both the acupuncture group and the control group reported an interest in acupuncture as a treatment method and a desire to explore acupuncture for treatment of other ailments; most commonly, back or joint pain. The overwhelmingly positive patient response to this trial indicates the interest of this patient subset in using complementary medical methods to augment the traditional treatment of various conditions and predicts potential interest in participation in similar studies in the future.

The importance of this study is its focus on evaluating the efficacy of acupuncture treatment in prevention of PON in cardiac surgery patients, who are known to have a relatively high rate of PON. This trial provides critical new information about the efficacy of one preoperative acupuncture session in decreasing the incidence and the severity of PON. Our results suggest that preoperative acupuncture should be available as an adjunct to standard pharmacologic therapy for the interested patients undergoing CABG or cardiac valve surgery, or both, to decrease PON incidence and severity.

	Acknowledgments

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
This study was funded by the Division of Cardiovascular Surgery, Mayo Clinic, Rochester, Minnesota. Moreover, the authors are grateful to the Healing Enhancement Program team members for supporting this research effort.

	References

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Thoralf M. Sundt, III Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Korinenko, Y. Articles by Sundt, T. M. Search for Related Content PubMed PubMed Citation Articles by Korinenko, Y. Articles by Sundt, T. M., III Related Collections Anesthesia