Elsevier

The Lancet

Volume 349, Issue 9052, 1 March 1997, Pages 599-603
The Lancet

Articles
Effect of neonatal circumcision on pain response during subsequent routine vaccination

https://doi.org/10.1016/S0140-6736(96)10316-0Get rights and content

Summary

Background

Preliminary studies suggested that pain experienced by infants in the neonatal period may have long-lasting effects on future infant behaviour. The objectives of this study were to find out whether neonatal circumcision altered pain response at 4-month or 6-month vaccination compared with the response in uncircumcised infants, and whether pretreatment of circumcision pain with lidocaine-prilocaine cream (Emla) affects the subsequent vaccination response.

Methods

We used a prospective cohort design to study 87 infants. The infants formed three groups—uncircumcised infants, and infants who had been randomly assigned Emla or placebo in a previous clinical trial to assess the efficacy of Emla cream as pretreatment for pain in neonatal circumcision. Infants were videotaped during vaccination done at the primary care physician's clinic. Videotapes were scored without knowledge of circumcision or treatment status by a research assistant who had been trained to measure infant facial action, cry duration, and visual analogue scale pain scores.

Findings

Birth characteristics and infant characteristics at the time of vaccination, including age and temperament scores, did not differ significantly among groups. Multivariate ANOVA revealed a significant group effect (p<0·001) in difference (vaccination minus baseline) values for percentage facial action, percentage cry time, and visual analogue scale pain scores. Univariate ANOVAs were significant for all outcome measures (p<0·05): infants circumcised with placebo had higher difference scores than uncircumcised infants for percentage facial action (136·9 vs 77·5%), percentage cry duration (53·8 vs 24·7%), and visual analogue scale pain scores (5·1 vs 3·1 cm). There was a significant linear trend on all outcome measures, showing increasing pain scores from uncircumcised infants, to those circumcised with Emla, to those circumcised with placebo.

Interpretation

Circumcised infants showed a stronger pain response to subsequent routine vaccination than uncircumcised infants. Among the circumcised group, preoperative treatment with Emla attenuated the pain response to vaccination. We recommend treatment to prevent neonatal circumcision pain.

Introduction

Neonatal circumcision is a common surgical procedure in male infants. Despite evidence that circumcision causes intense pain and short-term alterations in infant feeding, sleeping, and crying behaviours,1, 2, 3 analgesia is rarely given.4, 5, 6 There is a common belief that the effects of circumcision pain are short-lived and clinically insignificant, and, therefore, that the benefits of analgesic treatment do not outweigh the risks of adverse effects from currently available therapies.7, 8

We looked at the foundations for the belief that the effects of circumcision pain are short-lived by examining infant behaviour several months after surgery. We analysed data from a clinical trial that studied the use of topical lidocaine-prilocaine 5% cream (Emla, Astra Pharma, Canada) during routine vaccination at 4 or 6 months.9 Male infants showed a greater pain response than female infants. This difference may be linked with neonatal circumcision in male infants. Male infants who had been circumcised also exhibited a greater pain response than those who had not been circumcised.10 This initial analysis raised concerns about the possible longterm effects of untreated pain in infants, especially those who have repeated experience of pain. However, we could not draw definite conclusions because of the post-hoc nature of the analysis and the small sample size. The objectives of our study were, therefore, to investigate prospectively whether neonatal circumcision affects infant pain response to routine vaccination 4–6 months after surgery and whether vaccination response is affected by pretreatment of neonatal circumcision pain with Emla.

Section snippets

Methods

We carried out a prospective cohort study of 87 healthy, fullterm, male, newborn infants who had, when aged 5 days or less, participated in a clinical trial that investigated the safety and efficacy of Emla cream for neonatal circumcision.11 The participants in this study included uncircumcised boys, who served as controls (n=32), and circumcised boys who had been randomly assigned treatment with Emla (n=29) or placebo (n=26) during circumcision. All parents who had allowed their infants to

Results

87 (77%) of the 113 eligible infants participated in the study (table 1). Three infants in the uncircumcised group were circumcised after initial contact with the investigator. Two of the three infants were circumcised within 5 days of birth and the other at age 20 days. None of these infants received analgesia for circumcision pain and, therefore, their results were added to the group circumcised with placebo for data analysis.

There were no significant differences among the three groups in any

Discussion

This study showed that neonatal circumcision in male infants is associated with increased pain response in vaccination 4–6 months after surgery. The results support our previous finding of a higher pain response in circumcised than uncircumcised male infants during routine vaccination.10

We postulate that circumcision may induce long-lasting changes in infant pain behaviour because of alterations in the infant's central neural processing of painful stimuli. Transmission of noxious afferent input

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