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Pediatric Anesthesiology: Research Report

The Effectiveness of Pudendal Nerve Block Versus Caudal Block Anesthesia for Hypospadias in Children

Naja, Zoher M., MD*; Ziade, Fouad M., PhD; Kamel, Raymond, MD; El-Kayali, Sabah, MD§; Daoud, Nabil, MD; El-Rajab, Mariam A., MD

Author Information
doi: 10.1213/ANE.0b013e3182a8ee52
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Abstract

Hypospadias is one of the most common congenital malformations of the penis with an incidence of 1 of 300 live births.1During the last decades, caudal block (CB) has become a commonly used regional anesthetic technique due to its favorable analgesia in hypospadia repair in children.2,3 However, a single injection of CB has a relatively short duration of action even when adjuvants are coadministered with long-acting local anesthetics to improve the quality and duration of analgesia.4–10

However, a recent study assessing the effect of pudendal nerve block (PNB) as an alternative anesthetic technique for circumcision demonstrated its effectiveness about reduced analgesic consumption and a prolonged pain-free postoperative period for pediatric patients, although in this study PNB was compared with dorsal penile nerve block, not to CB.11 Since the incision area in both settings (circumcision and hypospadias repair) is innervated by the same pudendal nerves, we hypothesized that PNB can produce favorable results for hypospadias repair.

Hence, the aim of this prospective randomized double-blinded study was to assess the analgesic efficacy and duration of PNB compared with CB for a pediatric population undergoing hypospadias repair regarding total analgesic consumption within 24 hours postoperatively.

METHODS

After obtaining approval from the IRB, informed written consent was obtained from the parents of 80 boys (ASA physical status I), aged 2 to 5 years scheduled to undergo hypospadias repair. Exclusion criteria were history of allergic reactions to local anesthetics, bleeding diatheses, coagulopathy, infection at the injection site, and spinal abnormality. This prospective, double-blinded study was conducted from July 2008 to October 2011. Patients were randomized into 2 groups (40 children each) either receiving PNB or CB, using the sealed envelope technique based on computer-generated randomized numbers.

PNB and CB were performed by an anesthesiologist who was not involved in the perioperative and postoperative management of patients. To maintain study blinding, a second anesthesiologist who was blinded to patient group assignment was responsible for all patients follow-up and data recording. In addition, parents, surgeons, and other personnel responsible for data collection were also unaware of the group to that the child had been assigned. Surgeons were not present when the anesthesiologist performed the block (CB or PNB). Aseptic preparation of the skin was done to all patients using Betadine. All patients had bandages placed at the 2 sites (CB and PNB). These measures ensured that the actual site of injection remained unknown.

Patient characteristics such as age, height, and weight were recorded. In addition, time of completing the administration of the local anesthetic solution and time needed to perform the block and surgery duration were also recorded. Any increase in the concentration of sevoflurane and its duration were noted during surgery. Mean arterial blood pressure, heart rate, respiratory rate, and oxygen saturation were observed systematically (using electrocardiogram and pulse oximeter) and recorded at a single point of time preoperatively (baseline), after incision and postoperatively in the recovery room.

All patients had inhaled induction of anesthesia by facemask using oxygen and 8% sevoflurane for 2 to 4 minutes followed by placement of an IV cannula. After the injections of local anesthetic were performed, the sevoflurane concentration was decreased to 0.4% to 0.8% that was maintained until completion of surgery. A T-piece was used for airway management. The concentration of sevoflurane used was low (0.4%–0.8%) since it was intended to provide sedation, not general anesthesia (GA).

During surgery, an increase in heart rate of >20% from baseline was regarded as inadequate analgesia in accordance with a previous publication.11The sevoflurane level was increased accordingly to a maximum concentration of 4%. A Guedel airway was placed to maintain regular respiration. If the sevoflurane increment was not sufficient, a bolus dose of 1 μg/kg fentanyl was administered.

Pudendal Nerve Block Technique

Patients were put in lithotomy position. An assistant supported the patients knees to maintain the position to facilitate performing the block (Figs 1 and 2). Two separate injection points were marked at 3 and 9 o’clock, about 2 to 2.5 cm from the center of the anus. After aseptic preparation of the skin, a nerve stimulator needle (Stimuplex, A Braun AG, Melsungen, Germany) was used. For patients whose weight was <15 kg, a 2.5 cm 25-gauge needle was used, and for those >15 kg, a 5 cm 21-gauge needle was used. The needle was subsequently advanced 1.5 to 3.5 cm perpendicular to the skin using a stimulation current of 2.5 to 5 mA and 2 Hz. The unilateral contraction of the anal sphincter indicated that the inferior anal nerve had been stimulated. The nerve stimulator needle was then progressively moved deeper until an up-and-down penile movement was observed. This movement is caused by the contraction of the perineal muscles through stimulation of the perineal branch of the pudendal nerve. After that, needletip placement was optimized to preserve muscle contractions while reducing the stimulation current to 0.5 to 0.6 mA. A previously published study on circumcision using PNB had applied 0.5 mA to the perineal nerve branch that was found to be the minimum necessary to achieve motor response. This same study and other adult studies also had no incidence of puncturing the accompanying pudendal vessels in the canal.11–15 After adjustment of the stimulation current, 0.3 mL/kg 0.25% bupivacaine and 1 µg/kg clonidine were injected (half of the quantity at 3 and the other half at 9 o’ clock). The maximum volume of bupivacaine used was 10 mL.

Figure 1
Figure 1:
Illustration showing the landmark and patient’s positioning during pudendal nerve block.
Figure 2
Figure 2:
Illustration showing pudendal nerve, vessels, and boney landmarks. (1) Pudendal nerve (2) Perineal nerve (3) Posterior scrotal nerve (4) Dorsal nerve of penis (5) Injection area (local anesthesia) (6) Ischial spine.

Caudal Block Technique

Patients were put in the lateral decubitus position. After aseptic preparation of the skin, a 2.5 cm 22-gauge needle was inserted at a right angle position to the skin until it pierced the sacrococcygeal ligament; the needle was then redirected at about 25° before being advanced to a depth of about 2 to 3 mm into the sacral canal.16 One milliliter per kilogram 0.25% bupivacaine and 1 µg/kg clonidine were then injected in 30 to 60 seconds while monitoring respiratory and hemodynamic variables. The maximum volume was 20 mL.

Surgical Technique

All procedures were performed using the Snodgrass technique. Most patients (80%) had subcoronal and distal hypospadia repair. The remaining had mid-shaft and proximal hypospadia repair. All patients had a urinary catheter placed at the end of the surgery that was kept up to 4 to 5 days. Accordingly, urinary retention was not assessed since all patients were catheterized.

Postoperative Pain Assessment

All patients were hospitalized for 24 hours postoperatively. During the study period, pain and motor block were recorded by experienced pediatric nurses blinded to patient groups. The analgesic effect was evaluated using the objective pain/discomfort scale (OPS) developed by Hannallah and Broadman17 This scale is based on 5 variables: mean arterial blood pressure, movement, agitation, crying, and position of the child.17,18 These variables were assessed with 3 grades (0 = none; 1 = moderate; 2 = severe) to give a cumulative score ranging from 0 to 10 points. The OPS score was observed during the first 24 hours postoperatively and was recorded at 24 hours. Every 6 hours if the OPS pain score was noted at anytime to be 2 to 3, paracetamol syrup (15 mg/kg) or 100 mg suppositories (Tylenol CILAG SA, Schaffhouse, Switzerland) were prescribed depending on the childs weight.11 Patients whose weights were ≤7 kg were given suppositories, and the remaining received 15 mg/kg syrup. Tramadol (Tramal drops) 1 mg/kg was given orally every 12 hours and not before if the pain score was ≥4 since the effect of anesthesia lasted for >6 hours in almost all patients. Motor blockade scoring was performed (hourly) by trained nurses unaware of the patients group using the Bromage scale (based on 4-point scale), where 0 = full motor that is flexion of knees and feet, 1 = partial flexion of knees, 2 = little movement of feet only, 3 = no movement of knees or feet.19

Surgeon and Parents Satisfaction

Both parents and surgeons satisfaction were assessed using a scale rating from 1 to 3 (1 unsatisfied, 2 partially satisfied, 3 satisfied). The 3-point scale was similar to the scale used in a previously published study on circumcision.11 Surgeons satisfaction was based on the overall intra- and postoperative status of the patient. The intraoperative criteria included movement of the patient and conversion to GA. The postoperative criteria included parental reassurance, patient agitation, and number of requests by parents during hospitalization and phone calls after discharge. The number of calls was based on surgeons impressions. Hence, surgeons were not asked to keep track of the number of phone calls made by parents; rather, they were asked to generally remember the number of calls. Parents satisfaction was assessed postoperatively depending on their childs comfort and activity. The childs comfort was assessed based on the following criteria: feeling of pain, postoperative nausea and vomiting (PONV), and negative or bad memory of the procedural experience. The childs activity was assessed by ability to walk and play, in addition to motor dysfunction within 24 hours. Satisfaction was assessed in person during the patients hospital stay and through phone calls after discharge.

Statistical Analysis

The data are reported as mean, standard deviation (SD), or number of patients (percentage) as appropriate. Lilliefors test for normality and Levene test for equality of variances were used for scale variables, Mann-Whitney test (2-tailed), and χ2 test were used to assess any significant difference between the 2 groups. The effect of multiple comparisons on P-values was corrected using Bonferroni correction and were reported (corrected) in the results. P < 0.05 was considered significant.

To detect a 50% reduction in the percentage of patients consuming analgesics in the CB group 24 hours postoperatively with 5% significance level and 80% power, a sample size of 36 patients in each study group was adequate.

RESULTS

Eighty patients were enrolled in the study, 40 in each group, and all were analyzed based on the intention to treat (Fig. 3). There were no significant differences between the 2 groups in the following aspects: age, weight, height, time to perform the block (ranged between 3–5 minutes), hemodynamic stability during surgery and in the recovery room, surgery duration, and recovery room stay (Table 1).

Figure 3
Figure 3:
Flowchart illustrating the selection of patients. CB = caudal block; PNB = pudendal nerve block.
Table 1
Table 1:
Patients’ Characteristics and Intraoperative Monitoring Data

In terms of analgesic consumption within 24 hours postoperatively, the number of patients who did not need analgesics was significantly higher in the PNB group compared with the CB group (P < 0.0001) (Table 2, Fig 4). The average amount of analgesics consumed per patient within 24 hours postoperatively was higher in the CB group (paracetamol P < 0.0001, Tramal P = 0.003) (Table 2). Initially, Lilliefors test for normality and Levene test for equality of variances were performed for the total quantity of paracetamol and Tramal in addition to the pain scores. The tests revealed that the variables were not normally distributed, and the variances between the groups were not equal. Since there was a major deviation from the normal distribution, we performed the Mann-Whitney test to obtain the P-values (P < 0.0001).

Table 2
Table 2:
Postoperative Monitoring Data
Figure 4
Figure 4:
Postoperative analgesic consumption in the 2 groups. *significantly different. GA = general anesthesia; PNB = pudendal nerve block.

To further demonstrate that our results are clinically important, the Mann-Whitney test was performed to compare parents’ satisfaction, surgeons’ satisfaction, and pain scores (Fig. 5) in patients who needed analgesics compared with those who did not require analgesics. Patients who consumed fewer analgesics had higher parents’ and surgeons’ satisfaction with lower pain scores (Table 3).

Table 3
Table 3:
Satisfaction with Pain Scores and Analgesic Consumption
Figure 5
Figure 5:
Objective pain scale pain scores at different time intervals. *significantly different. CB = caudal block; PNB = pudendal nerve block; OPS = objective pain/discomfort scale.

There were 4 patients (10%) in the CB group who experienced incomplete block and were given a bolus dose of fentanyl. This addition was adequate for 3 patients (3.5, 4, and 5 years old) because they tolerated the operation. Thus, they were not converted to GA. However, the fourth patient started to move and had to be converted to GA (4.5 years old) (Table 1).

One child experienced PONV (2.5%) in the CB group compared with none in the PNB group (P > 0.999). One patient was (2.5%, P > 0.999) reported to have early transient motor weakness compared with none in the PNB group (Table 2). The Bromage score for this patient was equal to 1 (partial flexion to knees). He had a relatively short operation duration (45 minutes). He spent 1.5 hours in the recovery room, then was moved to the ward. Motor weakness was detected 2 hours postoperatively and continued until 4 hours postoperatively. The patient (3 years old) was able to stand but could not walk. Later, the child progressively started to walk. All patients had the urinary catheter when they were discharged 24 hours after surgery. Patients returned after 5 days for catheter removal. However, 4 patients (2 patients from PNB group and 2 from CB group) had irritation from the catheter. One patient had irritation from a catheter that was displaced in the bladder. The other 3 patients had penis irritation. Therefore, the catheter was removed for 3 of the 4 patients on the third day, and the fourth patient had his catheter removed on the fourth day.

Surgeon satisfaction was significantly higher in the PNB group, where 90.0% reported “satisfaction” and 10.0% reported “partial satisfaction” compared with 55.0% and 35.0% in the CB group (P = 0.010).

Regarding parents’ satisfaction, 82.5% reported “satisfaction” and 15.0% reported “partial satisfaction” compared with 25.0% and 52.5% in the CB group (P < 0.0001) (Table 2).

DISCUSSION

The key finding of the present study is that PNB demonstrated prolonged postoperative analgesia and less analgesic consumption compared with CB for pediatric hypospadias repair.

Baseline demographic data did not reveal any significant difference between patients in the 2 groups, thus proving the effectiveness of the randomization process. Other measures including hemodynamic stability (during surgery, in recovery room), surgery duration, and recovery room stay were comparable between the 2 groups (P > 0.05).

Caudal anesthesia is considered a safe and reliable technique that is widely recommended for various procedures in children; however, it is associated with shorter duration of action than PNB.5 However, it is associated with a shorter duration of action than PNB, even when various adjuvants are used to prolong the duration of CB, including clonidine, which is the most common.5,10,20

Several studies reported that the use of clonidine centrally and peripherally leads to an increase in the duration of the postoperative analgesia.20–27In our experience, the addition of 1 µg/kg clonidine to local anesthesia prolonged postoperative analgesia. However, the addition of >2 μg/kg of clonidine with CB has been associated with sedation and could potentially cause other side effects such as hypotension and bradycardia.20None of these complications was observed in our patients. Motor weakness experienced by 1 patient in the CB group was early, transient, and did not affect recovery. It might have resulted from the effect of 0.25% bupivacaine since the surgery duration was short.28However, prolonged motor weakness has been reported with caudal administration of larger local anesthetic concentrations. The addition of less than a 2 μg/kg dose clonidine does not increase the risk of prolonged motor weakness.7

In our study, the single incidence of PONV was reported in the CB group compared with none in the PNB group. This occurred in the patient who was converted to GA.

In our study, 4 patients in the CB group required additional analgesia (fentanyl) due to an incomplete CB block, unlike the PNB group that required none. However, 1 μg/kg fentanyl was not sufficient for 1 (2.5%) of the 4 patients; thus, the patient was converted to GA.

Regarding surgeons’ satisfaction, they were unsatisfied with the case that required conversion to GA and with the 3 cases of patients who had inadequate CB block. Surgeons who were partially satisfied were those who received complaints from the parents postoperatively.

The possible reasons for parents’ dissatisfaction and partial satisfaction may have been due to motor weakness and pain in addition to urinary catheter irritation felt by their children. Although CB has been associated with good outcomes in pediatric surgery, PNB has been as effective as CB but also has additional favorable outcomes. PNB was more effective regarding denser intraoperative analgesia, reduced analgesic consumption, and a prolonged pain-free postoperative period for pediatric patients.

The effectiveness and success rate of PNB may be explained by several factors. Previous studies demonstrated that peripheral blocks promote better and extended postoperative analgesia compared with central blocks.28Another advantage of a peripheral block is that it is safer than central blocks since complications are rare and minor.29,30

Furthermore, PNB could be preferable over other peripheral techniques since the use of nerve stimulator guidance for PNB provides accuracy locating the area to be anesthetized, thus injecting the solution in the target location adjacent to the nerve.12,13,31,32

Moreover, PNB is considered a safe technique and easy to learn since it has fewer complications.12,13,31This might be related to the longer distance of the pudendal nerve from the site of injection that might be more preferable to the surgeon to reduce the possibility of contamination and infection. This may in turn provide a more comfortable setting when anesthetizing the surgical region since PNB is done in an area that is relatively far from the pubic and penis region.11In addition, neither clinical effects nor erection were observed during surgery in this study.

In conclusion, the present prospective, double-blinded, randomized controlled clinical trial showed that PNB was associated with reduced postoperative analgesic consumption and pain as well as prolonged analgesia compared with CB. PNB is an effective and novel approach that results in a better success rate.

DISCLOSURES

Name: Zoher M. Naja, MD.

Contribution: This author helped design the study.

Attestation: This author approved the final manuscript.

Name: Fouad M. Ziade, PhD.

Contribution: This author helped analyze the data.

Attestation: This author approved the final manuscript.

Name: Raymond Kamel, MD.

Contribution: This author helped in writing the manuscript.

Attestation: This author approved the final manuscript.

Name: Sabah El-Kayali, MD.

Contribution: This author helped conduct the study.

Attestation: This author approved the final manuscript.

Name: Nabil Daoud, MD.

Contribution: This author helped conduct the study.

Attestation: This author approved the final manuscript.

Name: Mariam A. El-Rajab, MD.

Contribution: This author helped conduct the study.

Attestation: This author approved the final manuscript.

This manuscript was handled by: Peter J. Davis, MD.

ACKNOWLEDGMENTS

The authors would like to acknowledge the help of Sirar Jaroudy, Hiba Abou Swaid, and Nadine Lawand for their collaboration in commenting and editing the article.

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