Determining the technical and clinical factors associated with pain for children undergoing botulinum toxin injections under nitrous oxide and anesthetic cream

AimsTo determine technical and clinical factors associated with pain when using an analgesic protocol with 50% nitrous oxide/oxygen and anesthetic cream (lidocaine and prilocaine, Emla®) for children with cerebral palsy undergoing botulinum toxin injections.MethodsMonocentric prospective study including 50 children newly injected with a mean age of 6.6 years (±4.32, range 1–18) and 199 injected muscles. Pain was evaluated using the Children’s Hospital of Eastern Ontario Pain Scale (CHEOPS). The following variables were noted: gender, age, weight, Gross Motor Function Classification System, type of cerebral palsy (hemiplegic, diplegic, tetraplegic), muscles injected and severe cognitive impairment. The procedure was broken down into three phases for the purpose of pain evaluation: puncture, muscle localization using electrostimulation and injection of botulinum toxin.ResultsThe mean CHEOPS score was 8.16 (±3.5) and 38% of scores were above the therapeutic threshold of 9. The injection phase was significantly more painful (6.77 ± 3.30) than the puncture (4.88 ± 2.03) and localization (5.46 ± 2.68) phases. The adductor muscles were less painful than other muscles. Children with more severe cognitive impairment seemed to perceive higher levels of pain than the others. Other clinical factors were not associated with pain score.ConclusionClinical characteristics seem not strongly correlated to the success or failure of the 50% nitrous oxide/oxygen-Emla® protocol and this pain treatment protocol does not prevent equally all phases of botulinum toxin injections. Future research on the products and its dilution might help to reduce pain level.