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OBSTETRIC ANESTHESIOLOGY

A Randomized Controlled Trial of Pudendal Nerve Block for Pain Relief After Episiotomy

Younès Aissaoui, MD^*, Rémi Bruyère, MD^*, Hassan Mustapha, MD, Dominique Bry, MD^*, Noureddine Drissi Kamili, MD, PhD, and Chantal Miller, MD^*

From the *Département d’Anesthésiologie, Centre Hospitalier d’Auxerre, France; Département d’Anesthésie Réanimation et Urgences, Hôpital Militaire d’Instruction des Armées Mohammed V, Faculté de Médecine et de Pharmacie, Université Mohamed V Souissi, Rabat, Morocco; and Département de Gynécologie Obstétrique. Centre Hospitalier d’Auxerre. France.

Address all correspondence and reprint requests to Younès Aissaoui, Département d’Anesthésie Réanimation et Urgences, Hôpital Militaire d’Instruction des Armées Mohammed V. Rabat. Address e-mail to younes.aissaoui{at}hotmail.com.

Abstract

BACKGROUND: Pain from episiotomy or perineal tears during childbirth is associated with significant pain in the postpartum period. We performed this randomized, double-blind, controlled trial to investigate the efficacy of nerve stimulator-guided unilateral pudendal nerve block for pain relief after episiotomy.

METHODS: Forty women who gave birth vaginally with mediolateral episiotomy were randomized to receive pudendal nerve block with 15 mL of either ropivacaine 7.5 mg/mL (pudendal group) or normal saline (control group) after repair of the episiotomy. Episiotomy pain was assessed with a visual analog scale at rest at 3, 6, 12, 24, and 48 h postepisiotomy and during activities (walking and sitting). Breakthrough pain (visual analog scale >30 mm) was treated with niflumic acid suppositories 700 mg every 12 h. The primary outcome variables were pain scores at rest and during activities over 48 h postpartum.

RESULTS: Demographic and obstetric characteristics were not different between groups. Successful pudendal nerve stimulation was achieved in all patients. Patients in the pudendal group reported significantly lower pain scores at rest than those in the control group at 3, 6, 12, 24, and 48 h after delivery (P < 0.05). They also reported better analgesia while sitting and walking (P < 0.05). Additional analgesia was required by three patients (15%) in the pudendal group versus 17 patients (85%) in the placebo group (P < 0.001).

CONCLUSION: This study demonstrates that nerve stimulator-guided unilateral pudendal nerve block with ropivacaine 7.5 mg/mL is associated with decreased pain and need for additional analgesics during the first 48 h postepisiotomy.

Episiotomy or tearing of perineal tissues during childbirth is associated with significant pain in the postpartum period.1–5 Although the use of episiotomy is often debated, it remains the most common surgical procedure experienced by women.6 Pain from episiotomy is poorly treated, though it may be severe and can result in significant discomfort and interference with basic daily activities and adversely impact motherhood experiences.2,3,6 Furthermore, episiotomy may increase the risk of chronic perineal pain which is estimated to occur in 13% to 23% of women after episiotomy.2,7 Postepisiotomy pain has been treated with systemic analgesia, including nonsteroidal antiinflammatory drugs (NSAID) and oral or IV opioids as well as epidural opioids and local anesthetics.2–5,8–14

There are limited data in the literature regarding the use of regional analgesia for the relief of postepisiotomy pain. Pudendal nerve block (PNB) provides analgesia of the perineum.15 It has been used by obstetricians as an alternative to epidural analgesia during the second stage of labor. Anesthesiologists have improved the efficacy of PNB by using nerve stimulation for specific nerve identification. We hypothesized that nerve stimulator-guided PNB would decrease postepisiotomy pain and designed and executed a randomized, double-blind, placebo-controlled study to test the hypothesis.

METHODS

This study was conducted from March to June 2007 at the maternity unit of a regional teaching hospital in France. After approval of the local and hospital ethics committee, we included pregnant women with a term singleton fetus (37–40 wks) in a vertex position, who were at least 18-yrs-old, had delivered vaginally under epidural analgesia (ropivacaine-sufentanil), and who had required a mediolateral episiotomy. The episiotomy was performed with scissors by an obstetrician or a midwife. It was defined as a 6-cm incision at 45 degrees angle from the inferior portion of the hymeneal ring. Exclusion criteria were presence of an associated perineal tear, local anesthetic allergy, coagulation disorder, and local infection. Patients with diabetes mellitus, history of illicit drug use, chronic pain syndromes, or chronic pain medication use, and women with postpartum bleeding or any other major postpartum complication, were also excluded.

Episiotomy repair was performed after verification of epidural analgesia extending to the perineum. If analgesia was not complete, 5 to 10 mL of lidocaine 20 mg/mL was injected into the epidural catheter.

After the episiotomy was repaired and after obtaining written informed consent, 40 patients were randomly assigned to one of two groups using a computer-generated list. Women in the pudendal group received unilateral PNB with ropivacaine 7.5 mg/mL (Naropin® AstraZenaca) on the same side as the episiotomy, and those in the control group received PNB with normal saline.

To maintain blinding, randomization cards were maintained in opaque envelopes, and opened by an independent nurse, who prepared the study solution (15 mL of saline or ropivacaine 7.5 mg/mL) in an unlabeled syringe outside the delivery room. The randomization code was not broken before the end of the study. Patients, midwives, obstetricians, and anesthesiologists were all blinded to group assignment.

All women had peripheral venous access and standard monitoring, including electrocardiography, pulse oximetry, and noninvasive arterial blood pressure. PNBs were performed immediately after episiotomy repair. The blocks were performed by the same anesthesiologist, with women in the lithotomy position, according to the transperineal approach described by Bolandard.15 The puncture site was located at the intersection of a line running from the superior aspect of the anus with the medial edge of the ischial tuberosity. After skin disinfection, a 100-mm short bevel insulated needle (Stimuplex A, B Braun, Melsungen, Germany) connected to a nerve stimulator (Stimuplex HNS 11, B Braun, Melsungen, Germany) was introduced. The needle direction was perpendicular to the skin in all planes. Stimulation was begun using 2 mA current for 0.1 ms at 1 Hz. Motor responses indicating successful stimulation of the pudendal nerve included anal sphincter contraction, vulva constrictor muscle contraction, or movement of the clitoris.15 When the best motor response at the lowest intensity (0.5–0.6 mA) was obtained, the study solution was injected in 5 mL increments with negative aspiration before each increment. Women were monitored in the delivery room for a minimum of 2 h after the block.

All women received oral acetaminophen, 1 g every 6 h, starting in the delivery room and for 48 h postpartum. If analgesia was not satisfactory (visual analog scale [VAS] >30 mm), women were given niflumic acid suppositories 700 mg every 12 h for 48 h (niflumic acid is a NSAID). The protocol described above is the usual practice for postpartum analgesia in our institution.

Patients were asked to assess their episiotomy pain using a VAS from 0 (no pain) to 100 mm (worst pain possible) during the first 2 days postpartum. Midwives not involved in the study obtained the pain scores. They specified to women that pain in their abdomen (e.g., uterine cramps) or rectum and anus (hemorrhoidal pain) were not to be included.

Pain was assessed at rest (bed rest) and during activities (walking and sitting):

• At rest, women were asked to mark their pain scores at 3, 6, 12, 24, and 48 h after delivery.
  
• Twenty-four hours postpartum, women were asked to mark their maximum VAS scores while walking and while sitting during the first day after delivery.
  

The need for additional analgesia was also noted. Data collection included demographic data (age, weight, height, ASA physical status), obstetric data (gestational age, parity, duration of labor, spontaneous or instrumental vaginal delivery and birth weight), and data related to the PNB (depth of needle penetration to achieve motor response, minimal intensity of stimulation). Complications and side effects related to PNB were not specifically addressed, but were noted if they occurred.

The primary outcome variables were pain scores at rest and during activities over 48 h postpartum.

Sample size calculation was based on previous research performed by Dannecker et al.1 They found a mean (±sd) pain score at rest after mediolateral episiotomy (first day postepisiotomy) of 39 ± 28 mm using a VAS from 0 to 100 mm. To detect a clinically significant reduction in pain scores from 39 to 20 mm (with a similar sd), it was necessary to recruit 17 women per group (5% level of significance with 80% power). Therefore, we decided to include 20 women per group. The sample size calculation was made using Primer of Biostatistics Statistical Software, version 4.02 (McGraw-Hill, San Francisco).

Normal distribution of the collected data was verified using the Kolmogorov-Smirnov test. Demographic data, obstetric data, and data related to PNB were compared between groups using the Student’s t-test for continuous variables and the Fisher’s exact test for categorical variables. The VAS scores were compared using analysis of variance for repeated measures followed by Bonferroni’s post hoc test. P < 0.05 was considered significant. Analysis of data was performed using SPSS for Windows (Version 10; SPSS Inc., Chicago, IL).

RESULTS

During the period of the study (March to June 2007), 70 women were eligible but, for convenience reasons, only 42 women were invited to enter the study. Two patients refused to be included in the study and there were no drops-out.

The two groups were comparable in demographic, as well as in obstetric characteristics (Table 1). All instrumental vaginal deliveries were done using vacuum extraction, and there were no forceps-assisted deliveries. Three patients received 5 mL epidural lidocaine 20 mg/mL for episiotomy repair: one patient in the pudendal group and two patients in the control group. Successful pudendal nerve stimulation was achieved in all patients. The mean depth of the pudendal nerve was 52 ± 14 mm in the pudendal group and 47 ± 17 mm in the control group (P = 0.33). The mean minimal intensity of stimulation was 0.6 mA for both groups.

The VAS scores of the two groups were not normally distributed. At rest, patients in the pudendal group reported significantly lower pain scores than those in the control group at 3, 6, 12, 24, and 48 h after delivery (Fig. 1). Maximal pain scores while walking and sitting in the first 24 h were also significantly lower in the pudendal group (Fig. 2). Additional analgesia was required by three patients (15%) in the pudendal group versus 17 patients (85%) in the control group (P < 0.001). Additional analgesia was administered at an average of 6 ± 3 h after delivery. No maternal complications related to PNB in the 48 h after delivery (e.g., infection, hematoma) were noted in either group.

View larger version (16K): [in this window] [in a new window]   Figure 1. Episiotomy site visual analog scale (VAS) pain scores at rest in women randomized to pudendal nerve block with ropivacaine 7.5 mg/mL (pudendal group: white box plot) or saline (control group: gray box plot). The box-plot shows the median (the solid line), 25th and 75th percentiles (lower and upper limits of the box), and the minimum and maximum observations (whiskers).

View larger version (13K): [in this window] [in a new window]   Figure 2. Maximum episiotomy site visual analog scale (VAS) pain scores while sitting and walking during the first 24 h post delivery in women randomized to pudendal nerve block with ropivacaine 7.5 mg/mL (pudendal group: white box plot) or saline (control group: gray box plot). The box-plot shows the median (the solid line), 25th and 75th percentiles (lower and upper limits of the box), and the minimum and maximum observations (whiskers).

DISCUSSION

This randomized, double-blind study demonstrated that nerve stimulator-guided PNB with ropivacaine was associated with decreased pain at rest and during activity, and reduced need for analgesics during the first 48 h postepisiotomy without obvious side effects. Surprisingly, we noted that the duration of pain relief in the pudendal group exceeded the expected duration of ropivacaine (16–18 h).16,17 In fact, there was still a difference in the duration of analgesia at 48 h after delivery. The observed duration of postoperative analgesia may have resulted from prevention of peripheral and central hyperalgesia by adequate treatment of pain.18,19 Another benefit of PNB is the reduction in the need for supplemental analgesia. This may be particularly helpful for women who are breastfeeding and who are sometimes reluctant to take oral medication because of the fear of excretion of these drugs in breast milk.

The treatment of postpartum perineal pain has not been well studied. Numerous treatments are used in clinical practice, including topical lidocaine ointment, oral and rectal analgesics, epidural opioids, therapeutic ultrasound, different methods of suturing and nonpharmacologic techniques, such as bath and ice packs.2–5,8–14 Topical anesthetics were not found to be effective in relieving episiotomy or perineal laceration pain.13,14 Codeine alone or in combination with acetaminophen is frequently used, but side effects (constipation, nausea, vomiting, and dizziness) limit its appeal.4 Both oral and rectal NSAIDs have been assessed and have not been shown to be particularly effective.2–5,9 Studies which investigated the efficacy of epidural morphine 1 to 2 mg found that the need for oral pain medication is reduced in the first 24 h by a small amount without reducing pain scores.10–12 However, epidural morphine caused important significant side effects (nausea, pruritus, and urinary retention).10–12

There are limited data in the literature regarding the use of PNB for postoperative analgesia. Arslan et al.20 compared the efficacy of PNB and local infiltration with prilocaine 20 mg/mL during episiotomy repair in 90 patients. Although PNB was performed without nerve stimulation, it provided superior analgesia compared with infiltration. A study by Naja et al.21,22 showed that nerve stimulator-guided PNB combined with general anesthesia resulted in less posthemorrhoidectomy pain, reduced need for analgesics, shorter hospital stays, and earlier return to normal activity compared with general anesthesia without PNB. Similar to our study, the authors demonstrated that the duration of pain relief associated with PNB considerably exceeded the expected duration of the local anesthetic mixture they used for PNB (up to 6 days postoperatively).

Abramov et al. tested the effect of PNB with bupivacaine 2.5 mg/mL on pain relief after transvaginal pelvic reconstructive surgery. In contrast to the previously discussed studies, PNB did not affect postoperative pain intensity or opioid consumption in this setting.23 However, PNB was performed without nerve stimulation and the patient sample was not homogenous (surgical procedures included transvaginal hysterectomy, colporrhaphy, enterocele repair among others). The negative result of this study is probably explained by the fact that PNB without nerve stimulation frequently fails.

We elected to perform PNB after the episiotomy repair. Although performance of PNB before episiotomy repair would have provided perineal anesthesia without the need for supplemental injection of lidocaine in the epidural catheter, we chose to perform PNB after repair of episiotomy for two reasons. First, the control group receiving PNB with saline would have inadequate anesthesia for the episiotomy repair. Second, the time to achieve adequate PNB anesthesia may be prohibitively long, particularly for patients who are bleeding from an episiotomy site.

The decision to use any regional anesthesia technique requires assessment of the risks and benefits of the procedure. The PNB is a simple and useful technique that can improve postoperative multimodal analgesia and early rehabilitation. The required equipment and supplies include a short bevel insulated 100 mm needle, a nerve stimulator, and a local anesthetic. Although the required learning curve has not been rigorously studied, we have observed that 10 procedures are sufficient to become adept at this technique. The average duration of the procedure is about 3 to 5 min. Complications of PNB are unusual. Potential complications include local anesthetic toxicity, extension of the nerve block to the sciatic nerve, ischio-rectal hematoma, infection or deep abscess and pudendal nerve damage.

In our institution, only mediolateral episiotomies are performed and, therefore, unilateral PNB is appropriate. Midline episiotomy, however, is still used in other areas of the world and this would require bilateral PNB to achieve adequate analgesia. Midline episiotomy is widely condemned in the literature because of the risk of anal sphincter rupture.24

This study has some limitations. First, in order to have a homogenous sample of patients, we included only women with episiotomy. However, pain after vaginal delivery can also be caused by perineal tears. Second, there is a possibility that patients were not completely blinded. The study participants could have known which group they had been allocated to because of numbness. Finally, side effects and complications of PNB were not systematically and accurately researched and there was no long-term follow-up.

In conclusion, this randomized, double-blind study demonstrated that PNB provided superior analgesia with less need for supplemental analgesia after mediolateral episiotomy compared with conventional oral analgesics. We are currently incorporating this block into our usual practice of postvaginal delivery analgesia. Further studies with larger samples are needed to confirm the analgesic efficacy of PNB in perineal trauma after vaginal delivery, including high degree tears. The possibility that PNB could prevent chronic postpartum perineal pain is possible direction for future research.

ACKNOWLEDGMENTS

The authors gratefully acknowledge all the midwives who participated in this study. The authors also acknowledge Pr Redouane Abouqal from the Laboratoire de Biostatistiques – Faculté de Médecine de Rabat and Dr Maryam Fourtassi for their valuable help.

Footnotes

Accepted for publication April 23, 2008.

Financial support: Intramural departmental sources.

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Aissaoui, Y. Articles by Miller, C. Search for Related Content PubMed PubMed Citation Articles by Aissaoui, Y. Articles by Miller, C. Related Collections Obstetrics Regional Anesthesia