ArticlesEffect of neonatal circumcision on pain response during subsequent routine vaccination
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.
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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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