Postoperative nausea and vomiting (PONV) is a longstanding problem for anesthesia practitioners.1 Despite the introduction of many new antiemetics, routine use of prophylactic antiemetic drugs, and the availability of practice guidelines, the incidence of PONV remains high in “at-risk” patients undergoing ambulatory surgery.2 According to a recently published review article,3 PONV is the most common complaint after surgery, with an overall incidence of 30% after elective operations and up to 70% to 80% in high-risk populations in the absence of antiemetic prophylaxis. The issue of postdischarge nausea and vomiting (PDNV) has become particularly important for the growing outpatient population undergoing ambulatory and office-based surgical procedures because they may not have ready access to “rescue” antiemetic drug therapies after their discharge home.4,5
Previous clinical studies have demonstrated that the use of a combination of prophylactic antiemetic drugs,6,7 so-called multimodal antiemetic drug therapy, can reduce the incidence of PONV and PDNV while improving patient satisfaction with their quality of recovery and may facilitate a more rapid resumption of normal activities of daily living compared with the use of a single antiemetic drug modality alone. Droperidol, ondansetron, and dexamethasone possess similar antiemetic efficacies with limited side effect profiles. Thus, these drugs have become increasingly popular for antiemetic prophylaxis in the ambulatory and office-based surgical settings.3,8 – 12
Previous studies with various types of noninvasive acustimulation devices (e.g., simple acupressure and transcutaneous acupoint electrical stimulation [TAES]) are effective in reducing PONV when applied at the P6 acupoint without drug-related side effects.13 – 15 In an earlier study, we demonstrated that the combination of ondansetron and transcutaneous electroacustimulation was more effective than ondansetron alone in preventing PONV.16 Our preliminary findings were subsequently confirmed by Gan et al.17 who further suggested that acustimulation could produce analgesic effects.
Therefore, we designed a sham-controlled study to evaluate the antiemetic efficacy of a disposable acupressure device (Pressure Right® [Fig. 1]; Pressure Point Inc., Grand Rapids, MI) as part of a multimodal regimen for preventing PONV in patients undergoing laparoscopic surgery procedures. The primary objective of this preliminary study was to test the hypothesis that the use of the Pressure Right device in combination with the most frequently used multidrug prophylactic antiemetic regimen, namely, ondansetron and dexamethasone, would result in a lower incidence of nausea, vomiting, and/or retching at 24 hours compared with the drug combination alone. The secondary objectives of the study were to assess the effect of this multimodal combination therapy on the incidence of emetic symptoms from 24 to 72 hours, the need for rescue antiemetic drugs, patient satisfaction with PONV management, and quality of recovery, as well as times to resumption of their normal activities of daily living.
After obtaining IRB approval and written informed patient consent, 100 ASA physical status I and II outpatients scheduled to undergo major laparoscopic (e.g., cholecystectomy, bariatric gastric banding) surgery procedures participated in this prospective, randomized, double-blind study. The study patients received either a “sham” strip (control group) or Pressure Right strip (acupressure group) according to a computer-generated randomization scheme. The strips appeared to be identical after placement by a coinvestigator who was not involved in patient evaluation during the perioperative period. Patients who had received any antiemetic drugs within the preceding 24 hours, those who had previous experience using an acustimulation technique (i.e., acupuncture, acupressure, or TAES) for either management of pain or emetic symptoms, a history of alcohol or drug abuse within the last 3 months, or a skin lesion or irritation at the P6 acupoints were excluded from participating in this study.
In the preoperative holding area, 30 to 60 minutes before entering the operating room, a “sham” strip or a Pressure Right strip was placed bilaterally at the P6 point (located 3 of the patient's finger breaths proximal to the distal crease on the plantar surface of the wrist between the palmaris longus and flexor carpi radialis tendons). Patients were instructed to leave the strips in place for 72 hours after their operation. All patients were premedicated with midazolam, 20 μg/kg IV, approximately 5 minutes before entering the operating room. General anesthesia was induced with propofol, 2 to 2.5 mg/kg IV, and fentanyl, 0.75 to 1.5 μg/kg IV. Cisatracurium, 0.2 to 0.4 mg/kg IV, or rocuronium, 0.6 to 1.2 mg/kg IV, was used to facilitate tracheal intubation and insertion of the laparoscopic instruments. Immediately before the start of surgery, dexamethasone (4 mg IV) was administered to all patients. Maintenance of anesthesia consisted of desflurane 3% to 6% end-tidal concentration in an air/oxygen mixture. In addition, intermittent bolus doses of fentanyl, 50 μg IV, were administered as needed for intraoperative analgesia. Ketorolac, 30 mg IV, was administered 15 minutes before removal of the laparoscope. Ondansetron, 4 mg IV, was administered at the end of surgery upon withdrawal of the laparoscope and local anesthesia (2–3 mL of bupivacaine 0.25%) was administered at the fascial level of each portal site. Upon completion of the operation (i.e., skin closure), residual neuromuscular block was reversed with neostigmine, 2.5 to 5 mg, and glycopyrrolate, 0.3 to 0.6 mg IV, and the maintenance anesthetic (desflurane) was discontinued. All patients received 15 to 25 mL/kg of IV fluids during the perioperative period. Postoperative pain was treated with hydromorphone (Dilaudid) either IV (before discharge) or orally (after discharge).
Emergence times were determined at 1-minute intervals from discontinuation of the volatile anesthetic to awakening (i.e., opening eyes on verbal command) and orientation (i.e., correctly stating their name, date of birth, and name of the hospital). The times to postanesthesia care unit (PACU) discharge were assessed at 10-minute intervals according to the modified Aldrete criteria.18 The incidences of patient complaints of nausea, or vomiting (or retching), drowsiness, and restlessness were recorded before discharge from the PACU at the ambulatory center, and at 24-, 48-, and 72-hour intervals postoperatively by a blinded observer (JT) who directly questioned each patient before discharge and via telephone interviews about the occurrence of PONV symptoms and any other postoperative side effects. PONV symptoms (e.g., nausea, vomiting, or retching) and side effects were recorded as binary categorical responses (i.e., presence or absence). The need for any rescue antiemetic medication to treat recurrent episodes of nausea and/or emesis during the postoperative follow-up intervals was also noted. Rescue medication in the predischarge period consisted of metoclopramide, 10 mg IV, and prochlorperazine, 25 mg suppository, was prescribed to treat postdischarge emetic symptoms. A “complete response” to the prophylactic antiemetic treatment regimen was defined as the absence of any emesis (or retching) and no need for antiemetic rescue medication during the entire 72-hour study period. “Complete control” of emetic symptoms after surgery was defined as the absence of any nausea, no episodes of vomiting or retching, and no requirement for rescue antiemetic therapy during the 72-hour postoperative study period.2
Patient satisfaction with their PONV management was assessed at 72 hours using a 3-point verbal rating scale (1 = dissatisfied, 2 = satisfied, and 3 = highly satisfied). The patient's quality of recovery (QoR) score was assessed using a standardized 9-item questionnaire at 48 hours and 72 hours after surgery.19 The ability to tolerate normal dietary intake, return of normal bowel function, and ability to resume the normal activities of daily living (e.g., return to work) after surgery were queried at the 24-hour, 48-hour, 72-hour, and 30-day follow-up evaluations, and the recovery times (in days) were recorded by the blinded interviewer. The definition of “constipation” was as follows: 1 bowel movements occur less often than usual, 2 no bowel movement in the first 3 days after surgery, or 3 unusually hard stools that were painful or difficult to pass.
A power analysis (α = 0.05, β = 80%) was performed before the initiation of the study using the software nQuery Advisor™ (version 1.0, Janet D. Elashoff, 1995). This analysis suggested that group sizes of 50 each should be adequate to detect a 25% to 30% absolute decrease in the number of patients experiencing PONV symptoms in the acupressure + antiemetic drug treatment (acupressure) group compared with sham acupressure + antiemetic drugs (control) group assuming a 65% incidence in these at-risk surgical patients undergoing major laparoscopic procedures.20 The Student t test with unequal variances was used to analyze the parametric data (e.g., emergence and recovery times); χ2 test or Fisher exact test was used to analyze the nonparametric data (e.g., episodes of vomiting). Calculations of 95% confidence intervals (CIs) were used to determine significant differences. Continuous non-normally distributed data were analyzed using a Mann-Whitney U test (e.g., presence of nausea). Differences in QoR scores at 48 hours and 72 hours after surgery were analyzed using repeated measures of analysis of variance. P value <0.05 was considered statistically significant.
One hundred patients completed the study and all participants completed the follow-up evaluations. Demographic characteristics, including age, body weight, smoking status, and histories of PONV or motion sickness were not significantly different in the 2 antiemetic study groups (Table 1). The active acupressure and sham devices remained in place over the P6 acupoint for 24 hours in all cases. In addition, there were no significant differences in the type of laparoscopic surgery procedures, the duration of anesthesia and surgery, or in the dosages of preoperative medication, induction and maintenance anesthetics, neuromuscular blockers, and drugs used for reversal of residual neuromuscular blockade. Importantly, there were no differences in the use of intraoperative (Table 1) and postoperative (Table 2) opioid analgesic medications in the 2 study groups. The incidences of nausea and emetic symptoms and use of rescue antiemetic drugs in the PACU did not differ significantly between the 2 study groups (Table 2).
The incidence of postoperative vomiting (emesis) was significantly reduced in the acupressure group (versus sham control group) from 0 to 24 hours (10% vs 26%, P = 0.04, 95% CI 1%–31%) and from 0 to 72 hours (12% vs 30%, P = 0.03, 95% CI 2%–33%) (Table 3). However, the need for rescue antiemetic was not significantly reduced at 24 hours, 48 hours, or 72 hours after surgery. With respect to the recovery profiles (Table 2), including time to discharge, there were no significant differences between the 2 treatment groups. Later recovery times (e.g., time to resumption of physical activities and to return to work) also failed to achieve a statistically significant difference between the 2 treatment groups (Table 2). Compared with the control group receiving antiemetics alone, the complete response and complete control rates were nonsignificantly higher in the Pressure Right group (72% vs 54% [P = 0.06, 95% CI for absolute risk reduction: −1% to 35%], and 54% vs 42% [P = 0.23, 95% CI −7% to 30%], respectively) (Table 3).
Finally, use of the Pressure Right device as an adjunct to standard antiemetic therapy seemed to enhance patient satisfaction with their PONV management, and their QoR scores at 48 hours after surgery (Table 2). However, the incidences of postoperative side effects did not differ between the 2 study groups (Table 4). In the 10 patients in whom the active (n = 6) or sham (n = 4) device failed to remain in place for the entire 72-hour study period (Table 4), the incidence of vomiting at 24 to 72 hours did not differ between the 2 study groups.
Recent studies2 – 5 have demonstrated that despite the administration of multimodal antiemetic drug prophylaxis, patients at risk for developing PONV continue to experience an unacceptably high incidence of emetic symptoms that interfere with their recovery after ambulatory surgery. For example, in outpatients undergoing major laparoscopic and plastic surgery procedures, >40% of these patients reported that nausea and/or vomiting interfered with their postoperative functioning during the first 72 hours after surgery2 despite receiving prophylactic antiemetic therapy according to the PONV guidelines published by the Society for Ambulatory Anesthesia.9
Acustimulation has been reported to produce sedation, reduce preoperative anxiety levels, and decrease the severity of postoperative pain, nausea, and vomiting in the ambulatory setting.21 A variety of acustimulation techniques have been used to control emetic symptoms in the postoperative period, including acupressure,13,22 acupuncture,23,24 and transcutaneous electrical stimulation.14,16,17 A systematic review of P6 acupoint stimulation (versus sham or nonacupoint treatments) for PONV demonstrated that acustimulation reduced nausea, vomiting, and the need for rescue antiemetic therapy after surgery.25 Furthermore, these investigators and others26 have concluded that there was no difference in the efficacy of invasive (e.g., acupuncture) and noninvasive (e.g., acupressure, TAES) acustimulation techniques for preventing emetic symptoms after surgery. However, the timing (pre- versus postoperative) of the acupoint stimulation is important in achieving an optimal benefit. Acupressure is clearly more effective when administered in the postoperative period.27
Although some acustimulation studies14,17,28 have suggested that these techniques are more effective in reducing nausea than vomiting (or retching), the current study demonstrated greater efficacy in reducing emetic symptoms (namely, vomiting and retching). The failure to demonstrate a statistically significant effect on postoperative nausea (and the incidence of complete control) may have been related to the insensitive method used to assess postoperative nausea (i.e., a binary [Yes or No] response) rather than the more conventional 100-mm visual analog scale, the 11-point verbal rating scale (0 = none to 10 = intolerable), or a 4-point scale (e.g., 0 = none, 1 = mild, 2 = moderate, or 3 = severe).
Acustimulation seems to be comparable to the popular 5-HT3 antagonist, ondansetron, in the prevention of PONV.16,17 Given the importance of a multimodal approach to controlling the uncomfortable symptoms of PONV,29 we thought it was important to evaluate the use of this simple, noninvasive, disposable acupressure device as part of a standard multimodal antiemetic regimen to determine whether it would prove added value to the standard antiemetic drug regimen in everyday clinical practice. The Pressure Right pressure-sensitive adhesive wrist strip does not extend completely around the entire circumference of the wrist to avoid a “tourniquet effect” that might result in ischemia in the hand (Fig. 1). The adhesive material that holds the band in place is porous and breathable and the backing material is a hypoallergenic polyacrylate adhesive (Transpore® tape; 3M Corp., Minneapolis, MN), which has no dry rubber or natural rubber latex.
With the exception of the Sea Band® and Relief Band®, none of the other commercially available acustimulation devices have undergone clinical testing to establish their efficacy in preventing PONV and PDNV. The most extensively investigated acustimulation device is the Relief Band, a TAES device, which has the appearance of a plastic wristwatch with an elastic adjustable Velcro band,14,16,17,27 and is worn on the ventral (palmar) aspect of the wrist and stimulates the P6 acupoint using a low-level, variable-intensity electrical current. In addition to undergoing mechanical (bench) testing to demonstrate that the Pressure Right acupressure device can maintain a pressure of 5 to 7 psi at the P6 acupoint, the Food and Drug Administration required evidence that the device remains on a person's wrist for at least 24 hours without separation of the pressure bead on the adhesive wrist strip from the skin. This observation was important because of the need for more effective antiemetic therapies in the postdischarge period.5 There is a clear need for additional studies evaluating risk factors for PDNV and the impact of current pharmacologic and nonpharmacologic therapies.30
The issue of PDNV remains a concern for practitioners because of the continuing growth in the number of ambulatory, office-based, and short-stay surgical procedures. It has been reported that one-third of the patients undergoing ambulatory surgery continue to experience emetic symptoms after returning home, and that the prophylactic treatment of this complication would ideally extend well beyond the time of discharge from the hospital.2 – 5 The current options for achieving antiemetic efficacy in the postdischarge period include drugs that are either extremely expensive (e.g., aprepitant [Emend®], palonosetron [Aloxi®]) or have potential long-lasting side effects (e.g., transdermal scopolamine).20 Therefore, an inexpensive nonpharmacologic approach involving acustimulation could be a cost-effective adjuvant to ondansetron and dexamethasone.
In conclusion, this preliminary sham-controlled study demonstrated that the adjunctive use of the disposable, noninvasive Pressure Right acupressure device enhanced the emetic efficacy of the most frequently used prophylactic antiemetic drug combination for preventing emetic symptoms during the first 24 hours after major laparoscopic surgery. Further studies are needed to determine the cost benefit of using this disposable acupressure device for routine antiemetic prophylaxis in the ambulatory setting.
Name: Paul F. White, PhD, MD, FANZCA.
Contribution: This author helped with design, consultation, and preparation of the manuscript.
Name: Manxu Zhao, MD.
Contribution: This author helped with IRB communication, prepared the randomization list, consented the study patients, and helped with placement of the study device.
Name: Jun Tang, MD.
Contribution: This author helped prepare the study document, collected the data, performed statistical analysis, and prepared the manuscript.
Name: Ronald H. Wender, MD.
Contribution: This author helped with consultation, IRB communication, consented study patients, and performed the anesthesia.
Name: Roya Yumul, MD, PhD.
Contribution: This author helped with consultation, consented the study patients, and performed the anesthesia.
Name: Alejandro V. Sloninsky, MD.
Contribution: This author consented the study patients and performed the anesthesia.
Name: Robert Naruse, MD.
Contribution: This author consented the study patients and performed the anesthesia.
Name: Robert Kariger, MD.
Contribution: This author consented the study patients and performed the anesthesia.
Name: Scott Cunneen, MD.
Contribution: This author consented the study patients and performed the operations.
This manuscript was handled by: Peter S. A. Glass, MB, ChB.
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© 2012 International Anesthesia Research Society
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