Anesth Analg 2003;96:396-399
© 2003 International Anesthesia Research Society
PEDIATRIC ANESTHESIA
EMLA® Cream Versus Dorsal Penile Nerve Block for Postcircumcision Analgesia in Children
W.Y. Choi, MB, BS*,
M.G. Irwin, MB, ChB, FRCA, FHKAM
,
T.W.C. Hui, MB, BS, FANZCA, FHKAM,
H.H. Lim, MB, BS, FHKAM, and
K.L. Chan, MB, BS, FRCS, FHKAM
*Department of Anaesthesia and Intensive Care, Pamela Youde Nethersole Eastern Hospital, Chai Wan; and
Department of Anaesthesiology and
Surgery, Queen Mary Hospital, Hong Kong
Address correspondence and reprint requests to W.Y. Choi, MB, BS, Department of Anaesthesia and Intensive Care, Pamela Youde Nethersole Eastern Hospital, Chai Wan, Hong Kong. Address e-mail to reginachoi{at}hotmail.com
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Abstract
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We conducted a prospective, randomized, double-blinded trial comparing preoperative application of EMLA® cream and sodium chloride solution dorsal penile block (n = 31) with placebo cream and bupivacaine dorsal penile nerve block (n = 32) for postcircumcision analgesia. Pain was assessed using modified Children’s Hospital of Eastern Ontario Pain Scale and the duration of block by the time to requirement of first dose of postoperative analgesic. There was no difference in Children’s Hospital of Eastern Ontario Pain Scale between the two groups, but bupivacaine dorsal penile nerve block resulted in longer analgesia (P = 0.003). There were no local or systemic complications related to either technique, and there was a very small incidence of vomiting. We conclude that preoperative application of EMLA® cream is an effective and simple method to produce postcircumcision analgesia with a very small incidence of adverse effects.
IMPLICATIONS: This study shows that topical application of EMLA® cream before circumcision is simple and effective with few side effects.
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Introduction
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Circumcision is a common pediatric surgical procedure and can be painful (1). Many techniques have been described for alleviating the pain, with local anesthetics being more effective than systemic opioids, nonsteroidal antiinflammatory drugs, or acetaminophen (2,3). The two most widely studied and acceptable methods for pain relief are caudal epidural block and dorsal penile nerve block (DPB) (4). However, these have disadvantages. The failure rate for DPB is 4%–8% (5,6) and may also cause bleeding or hematoma at the injection site (7). There is a less frequent failure rate with caudal blocks, but problems include prolonged time to micturition (6), lower limb motor block, and an increased potential for local anesthetic toxicity. Both techniques require some technical skill for performance.
A topical eutectic mixture of local anesthetic (EMLA®) cream is better than placebo but less effective than DPB in alleviating pain during circumcision (8–10). However, preoperative application of EMLA® cream has not been investigated in children older than 2 yr of age. The aim of this study was to compare the efficacy and complication rate of this technique with DPB in older children. The hypothesis to be tested was that there was no difference in analgesic efficacy and complication rate using DPB and EMLA® cream.
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Methods
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After local institutional ethics committee approval, 63 boys of ASA physical status I or II, aged between 2 and 12 yr old, and scheduled for elective inpatient circumcision were studied with written informed parental consent. Assuming a 30% reduction in Children’s Hospital of Eastern Ontario Pain Scale (CHEOPS) to be clinically useful, we calculated that 32 patients would be required in each group to achieve a power of 80% at the 0.05 level of significance. The study was randomized, double-blinded, and conducted over 6 mo. Exclusion criteria included allergy to amide type local anesthetics or EMLA® cream, recent ingestion of sulfonamides or nitrites, congenital or idiopathic methemoglobinemia, and atopic dermatitis.
By drawing a sealed envelope, patients were randomized to receive either EMLA® (Group E) or dorsal penile nerve block (Group D). Sedative premedication was not administered. All patients had 1 g of EMLA® cream applied to the dorsum of both hands under an occlusive dressing 1 h before the induction for venepuncture. In Group E, 2–4 g of EMLA® cream was administered with a syringe to the distal half of the penile skin (not on the mucosal surface) and covered with a clear plastic occlusive dressing at least 60 min before surgery. The amount of EMLA® cream applied was appropriate to cover the distal half of the penis where surgery would take place. This volume varied slightly from patient to patient, but there was the same degree of coverage in each individual. Group D patients received aqueous placebo cream in the same manner. This had a similar texture and appearance to EMLA® cream and was supplied by the hospital pharmacy. Anesthesia was induced by IV injection of propofol 3–4 mg/kg and maintained with spontaneous breathing of 66% nitrous oxide in oxygen and isoflurane (end-tidal isoflurane concentration, 0.6%–0.9%) via a face mask. The occlusive dressing on the penis was checked before the induction, and the patient was excluded if the dressing was dislodged. Group D patients received DPB using 0.2 mL/kg of 0.5% plain bupivacaine, whereas an equivalent volume of saline was injected with the same technique in Group E. The same surgeon performed circumcision 10 min after penile block using the same technique in all patients. The foreskin was excised with a scalpel after applying a straight clamp, and the mucosa was trimmed with scissors. Hemostasis was achieved with 4/0 catgut ligatures. The mucosa was approximated to the skin with interrupted 4/0 catgut. Baseline heart rate, respiratory rate, and blood pressure were recorded just before skin incision. During surgery, an increase in respiratory rate or heart rate of more than 25% from baseline was regarded as inadequate analgesia, and an IV bolus dose of fentanyl 0.5 µg/kg was administered every 5 min up to a maximum dose of 2 µg/kg. If this was unsuccessful in reducing sympathetic activity, it was considered as failed analgesia, and such patients were to be excluded from the rest of the study. After completion of surgery, the patients were observed in the recovery room by a nurse (blinded to the type of analgesia) who noted the time taken for patients to give their name coherently on questioning (time to self-recognition). A modified CHEOPS was recorded from time to self-recognition and at 0, 30, 60, 120, 240, and 360 min by a nurse blinded to the type of analgesia. The protocol allowed patients to be given IV boluses of fentanyl 0.5 µg/kg every 5 min if the CHEOPS was more than 5 in the recovery room. The criteria for postoperative paracetamol (15 mg/kg orally for 6 h) administration in the ward were either at the patient’s request or whenever the CHEOPS was more than 5. These supplemental analgesia criteria have been previously published (6). The incidence of vomiting was noted. Patients were allowed to eat and drink as soon as they wished. The next day, the surgeon examined the penis for signs of hematoma or infection.
Demographic data were compared using Student’s t-test. Time to self-recognition, dose of fentanyl used, and time to first dose of paracetamol were compared using Mann-Whitney U-test. 
2 analysis was used to compare ASA class, number of patients requiring fentanyl during surgery, and the number of paracetamol doses administered. Repeated-measures analysis of variance was used to compare serial CHEOPS between the two groups. Friedman test was used to compare the change in CHEOPS over time. A P value <0.05 was taken as significant.
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Results
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Three patients were excluded from the study. One patient from Group D was not cooperative during IV cannulation, and the gas induction was performed, whereas another was found to have hypospadias, and the operation was cancelled. A patient from Group E was excluded because of dislodgement of the occlusive dressing cover. These patients were not replaced to avoid unblinded data collection. As a result, there were 30 children in each group. Demographic data were similar (Table 1), and there was no difference in operation duration, time taken to postoperative self-recognition, number of patients requiring fentanyl during surgery, and total fentanyl dose requirement (Table 2). In Group E, 16 patients required an intraoperative fentanyl bolus alone, and 3 patients required a postoperative fentanyl bolus alone. The corresponding numbers in Group D were 11 intraoperative and 2 postoperative. No child was administered fentanyl both during and after surgery. The median duration of analgesia with DPB, judged from the first dose of paracetamol, was twice as long as with EMLA®. However, only 33.3% of patients in the EMLA® group actually required paracetamol compared with 50% of those who had DPB, although this was not a significant difference (P = 0.15). Of the 10 patients requiring postoperative acetaminophen in Group E, six had been given fentanyl. In Group D, 5 of 15 patients requiring postoperative acetaminophen had been given fentanyl, and there was no statistical difference between the two groups in this regard (P = 0.7). The total dose of fentanyl given in Group E was 12.5 µg/kg, whereas the dose given in Group D was 7 µg/kg. There was no vomiting in the recovery room or ward in Group D, whereas one patient in Group E vomited once in the recovery room. There were no injection site hematomata in either group. Four patients in Group D and six patients in Group E had mild oozing from the wound or wound edema, but there was no statistical difference (P = 0.49). Using repeated-measures analysis of variance, there was no difference in CHEOPS between the two groups (P = 0.45), although there was a significant decrease in CHEOPS over time in both groups (P < 0.0001).
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Discussion
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Circumcision is usually performed as a day-case surgical procedure. The ideal method for postcircumcision analgesia should have a frequent success rate with a small risk for complications. There has only been one study (11) on EMLA® versus DPB for circumcision analgesia in children (age 2–10 years). It showed that EMLA® was not as effective as DPB in terms of duration of pain-free period and level of pain score. However, the cream was applied immediately after surgery, just before recovery from general anesthesia. Although the authors postulated that EMLA® cream should start to work after several minutes when applied to mucosa, we believe that it is likely to be more effective and, possibly, provide preemptive analgesia when applied at least one hour before surgery.
In our study, the longer period of analgesia in the DPB was not unexpected because bupivacaine is likely to have a longer duration of action than EMLA® cream (once the cream has been removed during surgery). Thus, bupivacaine is a good choice of drug for this purpose, as corroborated by other investigators (2,5,12–14). Although EMLA® cream was an effective analgesic, the duration of pain relief may be a limitation.
Both EMLA® cream and DPB were effective in providing pain relief, with minimum supplemental analgesia required. The median dose of fentanyl administered was zero with DPB and only 0.5 µg/kg with EMLA®.
Most of the patients in the EMLA® group required either zero or one dose of paracetamol after surgery. Fewer patients required paracetamol in the EMLA® group than after DPB, and there was no difference between groups with regard to the total dose. Therefore, EMLA® cream seems to be an effective analgesic technique for circumcision.
In summary, we have demonstrated that preoperative application of topical EMLA® cream is a safe and effective method for providing postcircumcision analgesia. The use of EMLA® avoids the rare but serious complications of DPB and is technically simpler to perform.
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Acknowledgments
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We thank Ms S.F. Man for her technical assistance.
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References
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Accepted for publication October 29, 2002.
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Abstract
Introduction
