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The Analgesic Effects of Capsicum Plaster at the Zusanli Point After Abdominal Hysterectomy

Kim, Kyo S., MD, PhD; Nam, Yu M., MD

doi: 10.1213/01.ane.0000228864.74691.9f
Analgesia: Research Report

BACKGROUND: Acupuncture has been used to supplement opioid analgesics for postoperative pain control. We designed this double-blind, sham-controlled study to assess the effectiveness of capsicum plaster (PAS) at Zusanli (ST-36) acupoints on postoperative opioid analgesic requirement, side effects, and recovery profile.

METHODS: Ninety women undergoing total abdominal hysterectomy were randomly assigned to 3 treatment regimens (n = 30 each): group Zusanli = PAS at Zusanli acupoints, group sham = PAS at the nonacupoints on the shoulders, and group control = placebo tape at Zusanli acupoints. The PAS was applied before induction of anesthesia and maintained for 8 h per day for 3 postoperative days.

RESULTS: The total amount of morphine administered in the first 24 h after the operation was significantly decreased in group Zusanli (31.5 ± 6.8 mL) compared with groups control (44.3 ± 10.1 mL) and sham (44.6 ± 10.4 mL) (P < 0.01). The incidence of postoperative side effects and the use of rescue antiemetics during the 72 h after surgery were significantly reduced in group Zusanli compared with other groups (P < 0.01).

CONCLUSION: PAS at Zusanli points decreased the postoperative opioid requirement and opioid-related side effects of patients undergoing abdominal hysterectomy.

IMPLICATIONS: Capsicum plaster at a classical Chinese acupoint may be a simple, inexpensive alternative to acupuncture for decreasing the need for opioid analgesics in the postoperative period. In this study, application of capsicum plaster at Zusanli (ST-36) acupoints reduced postoperative opioid analgesic requirements and opioid-related side effects in patients undergoing abdominal hysterectomy.

From the Department of Anesthesiology, Hanyang University Hospital, Seoul, Korea.

Supported, in part, by Research Fund HY 2005-1894 of the Hanyang University.

Accepted for publication May 11, 2006.

Address correspondence to Kyo Sang Kim, MD, PhD, Department of Anesthesiology, Hanyang University Hospital, #17 Haengdang dong, Sungdong gu, Seoul 133-792, Korea. Address e-mail to

Acupuncture and related techniques can potentially serve as important adjuvants for postoperative pain control, reducing opioid requirements and the adverse effects associated with opioids (1). Some investigators have reported that acupressure, acupuncture and a related electrical stimulation technique (transcutaneous electrical nerve stimulation) to a classical Chinese acupoint site on the leg (Zusanli, also known as ST-36) can improve pain relief, decrease narcotic requirements, shorten the recovery room stay, and reduce postoperative side effects after abdominal hysterectomy (2–4). Others have failed to identify any significant beneficial effects (5,6).

Capsaicin, the compound in chili peppers that makes them taste hot, binds to nociceptors in the skin, causing an initial excitation of the neurons and a period of enhanced sensitivity (7). Capsicum plaster (PAS) (Sinsin Pharm. Korea) is a low-capsaicin (0.046% w/w) mixture of powdered capsicum 345.80 mg and capsicum tincture 34.58 mg on a sheet (12.2 × 16.4 cm2). Its use as an alternative to acupuncture was first developed and described by the Korean Buddhist priest Namsan (8). Although this method is widely used in Korea, Western medicine has hardly noticed it, and little research is being performed in this field. PAS applied to the Korean hand acupuncture point (K-D2 or K-A20) has been reported to be effective in preventing postoperative nausea and vomiting (9) and postoperative sore throat (10) in patients undergoing gynecological procedures. Although acupuncture and related techniques may not provide sufficient pain relief as the sole modality for the treatment of postoperative pain, it could prove valuable as an adjuvant to patient-controlled analgesia (PCA) in the management of acute postoperative pain (2–4).

This randomized, double-blind, sham-controlled study was designed to test the hypothesis that application of PAS to Zusanli points reduces postoperative opioid analgesic requirements and side effects and improves recovery in the early postoperative period in patients undergoing abdominal hysterectomy.

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The protocol was approved by the hospital ethics committee. Informed consent was obtained from all patients. In this double-blind, placebo- and sham-controlled study based on a preliminary study, 90 female patients (ASA I-II) scheduled for elective abdominal hysterectomy were assigned randomly to the Zusanli group (n = 30), sham group (n = 30), or control group (n–= 30). Randomization was based on computer-generated codes that were prepared in sealed, opaque envelopes. The operational aspects of the PCA device (WalkMed PCA; McKinley Medical, Wheat Ridge, CO) were explained to each patient at the initial preoperative visit and were again reviewed with each patient before initiating PCA therapy in the recovery room. Patients with chronic opioid use for chronic pain, sensitivity to opioid-related side effects, or with clinically significant cardiovascular, pulmonary, renal, hepatic, or neurologic diseases were excluded.

In the Zusanli group, PAS (5 × 5 mm2) was applied to the Zusanli point, located four finger breadths below the lower margin of the patella and one finger breadth laterally from the anterior crest of the tibia on both legs. We chose the Zusanli acupoint because this point is traditionally considered to have the most therapeutic effect on lower abdomen pain (2–4). In the sham group, PAS (5 × 5 mm2) was applied bilaterally at the deltoid region of both shoulders as a sham acupoint (2). In the control group, inactive tape (5 × 5 mm2) without PAS was applied to the Zusanli point of both legs. Both PAS and placebo treatments were performed by an experienced acupuncture practitioner 30 min before induction of anesthesia and were maintained for 8 h per day for 3 postoperative days. After either PAS or inactive tape was applied to the above sites, the entire region was covered by a plastic adhesive. Patients and evaluators were blinded as to treatment. The acupuncturist was not blinded.

No premedication was given. Anesthesia was induced by IV administration of thiopental 5 mg/kg and rocuronium 0.6 mg/kg. After tracheal intubation, anesthesia was maintained with 2%–3% sevoflurane and nitrous oxide in 33% oxygen. Muscle relaxation was maintained with rocuronium, titrated to provide one or two twitches in response to supramaximal electrical stimulation of the ulnar nerve at the wrist. A nasogastric tube was inserted after anesthesia had been established. The usual monitors were used intraoperatively. No additional opioid analgesic medications were administered during the intraoperative period. At the end of anesthesia, residual neuromuscular blockade was reversed with a combination of neostigmine 0.05–0.075 mg/kg and glycopyrrolate 0.005–0.01 mg/kg IV. Active surface warming was used to keep the core temperature normothermic (>36°C).

Patients were sent to the recovery room postoperatively, where they immediately received a bolus of IV fentanyl 50 μg and ketorolac 30 mg for pain control. The PCA device continued a solution of fentanyl 6.5 μg/mL and ketorolac 1.2 mg/mL in normal saline. The PCA was programmed to provide a 1 mL/h basal infusion, with a minimal lockout interval of 15 min and a maximal hourly dose of 4 mL. Supplemental bolus doses of ketorolac 30 mg were administered IM if the patient was unable to achieve adequate pain relief from the PCA device. At 48 h, PCA therapy was discontinued and analgesia was comprised of supplemental doses of ketorolac if required. An anesthesiologist blinded as to group allocation evaluated the patients and recorded the data when the patients were sufficiently awake and alert postsurgery.

Pain scores at rest and during coughing were assessed with a standard 100-mm visual analog scale (0 = no pain to 100 = worst pain imaginable). The postoperative analgesic requirement, the number of PCA demands, doses of rescue analgesic, opioid-related side effects (yes or no), and the need for rescue antiemetic drugs were recorded at 1, 6, 24, 30, 48, 54, and 72 h during the postoperative period. At 72 h, patients evaluated the global quality of their postoperative analgesia in the overall recovery process using a 4-point rating scale (1 = very satisfied, 2 = satisfied, 3 = unsatisfied, 4 = very unsatisfied).

Statistical analyses were performed using SPSS 11.0 for Windows (SPSS, Chicago, IL). Initial sample size estimation showed that 27 subjects should be included in each group to ensure a power of 0.80 for sufficiently detecting a decrease of 20% in the PCA opioid analgesic requirement during the first 24 h after surgery. Alpha error was assumed to be 0.05, and sd of 5.7 was estimated from initial pilot observations. Parametric data were analyzed using one-way analysis of variance in combination with the Tukey test. Nonparametric data were evaluated using the Kruskal-Wallis test in combination with Dunn's test. Classification of the side effects, the number of patients who vomited or were nauseous, the number of patients asking for a rescue antiemetic, and patient satisfaction were analyzed using the χ2 or Fisher's exact tests, as deemed appropriate. A value of P < 0.05 was considered statistically significant for all results.

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There were no significant intergroup differences in the patients' ages, weights, heights, or durations of anesthesia (Table 1). The total PCA volume, the number of PCA demands, and doses of rescue analgesic during the 48 h postoperatively were significantly decreased in the Zusanli group compared with groups control and sham (P < 0.01) (Table 2). The total amount of PCA administered in the first 24 h after the operation was significantly decreased in group Zusanli (31.5 ± 6.8 mL) compared with groups control (44.3 ± 10.1 mL) and sham (44.6 ± 10.4 mL) (P < 0.01) (Table 2).

Table 1

Table 1

Table 2

Table 2

Pain scores revealed similar trends between measurements taken at rest and during coughing. Coughing pain intensity and rest pain intensity were significantly greater in patients in the control and sham groups compared with the group Zusanli (P < 0.01) (Fig. 1). The incidences of nausea, vomiting, urinary retention, and pruritus during the 72 h after surgery were significantly reduced in Zusanli group compared with the other groups (P < 0.01) (Table 3). The need for rescue antiemetics was significantly less in group Zusanli (n = 3) compared with groups control (n = 8) and sham (n = 7) (P < 0.001). On the postoperative interview at 72 h, 83%–93% of the patients reported that their postoperative pain was adequately treated, and the overall satisfaction score was significantly greater in group Zusanli compared with the other groups (P = 0.019) (Table 4). The only side effect noted in this study was a mild burning sensation with erythema in one patient in group Zusanli and two patients in the sham group, which resolved spontaneously within 24 h after removing capsicum adhesive tape.

Figure 1.

Figure 1.

Table 3

Table 3

Table 4

Table 4

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The major findings of our study are that preoperative application of PAS at the Zusanli acupoints reduced postoperative analgesic consumption by approximately 30% during the immediate 24 hours postoperatively and significantly reduced the incidence of postoperative side effects (nausea, vomiting, urinary retention, and pruritus) and the number of patients asking for rescue antiemetics compared with patients in control and sham groups after abdominal hysterectomy.

PAS is noninvasive, simple, painless, and easy to apply. The plaster firmly adhered to the application site. Unlike acupuncture, it is neither invasive nor unpleasant and is not time limited. Noninvasive acupressure could be applied for longer durations than invasive acupuncture techniques. The initial cost of either acupressure ($8) (11) or a transcutaneous acupoint electrical device (ReliefBand®) ($30) (12) is greater than that of PAS ($1 per 5 sheets). There is no cost associated with maintaining the applied plaster. PAS is easy to use, requires no special training, and is a good alternative to the routinely prescribed nonpharmacologic techniques. Moreover, the size (5 × 5 mm2) of PAS is convenient, and capsicum is being delivered from the PAS to the skin surface within 8–12 hours (8).

Preoperative acupuncture stimulation at Zusanli points has been reported to have opioid-sparing effects of 38% (2), 61% (3) and 31% (4) during the early postoperative period, and reduces the incidence of opioid-related side effects. In contrast, opioid-induced analgesia may have masked the putative benefit of electroacupuncture (5) or minute sphere acupressure (6) as a result of high doses of meperidine or low doses of morphine, respectively. Because many factors can influence the effect of this nonpharmacologic therapy on postoperative pain, we designed this study to examine the effect of the specific site of stimulation (i.e., acupoint versus nonacupoint) (2) on the opioid analgesic requirement and the incidence of opioid-related side effects. The current study demonstrated that PAS at the Zusanli acupoints significantly decreased the requirement (30%) of opioid analgesics and the incidence of postoperative nausea and vomiting (30%) in the postoperative period, compared with the nonacupoint (shoulder) and control groups. The reduction in these common postoperative side effects may have been both the result of the decreased opioid requirement and an effect of improved pain relief postoperatively, which may have increased the satisfaction score in the Zusanli group.

De-Qi is a sensation typically associated with proper acupuncture needle positioning. Many practitioners consider this sensation to be crucial in achieving the effect of acupuncture (13). However, when PAS is applied on an acupoint, De-Qi is unlikely to be elicited. In the present study, the Zusanli acupoint was first confirmed by the acupuncturist using an acupuncture needle prior to application of the PAS or inactive tape. However, this study may be criticized because a point locator was not used.

After a preliminary study for the appropriate analgesic doses of PCA, we controlled pain intensity with the PCA to be the mild to moderate level. The better analgesia in the Zusanli group can be clearly proven by the reduction in analgesic requirement and analgesic-related side effects.

In conclusion, application of PAS to the Zusanli acupoints decreased postoperative opioid requirements and reduced opioid-related side effects in patients after abdominal hysterectomy.

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