A ketamine–propofol admixture does not reduce the pain on injection compared with a lidocaine–propofol admixture

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Abstract
Propofol injection pain is a well-known problem in pediatric anesthesia. Premixture of lidocaine with propofol although effective does not abolish injection pain in all children. Promising results have been reported with pretreatment of the vein with ketamine. The purpose of this prospective, double-blind randomized, clinical trial with active control was to evaluate the efficacy of premixing propofol with ketamine in the prevention of injection pain in children. After ethics committee and parental approval and children's assent, 116 children, aged 1-12 years, were randomly allocated to receive an IV induction dose of admixture of racemic ketamine 0.5 mg x ml(-1) (ketamine group) or lidocaine 1 mg x ml(-1) in propofol 10 mg x ml(-1) (lidocaine group). The outcome measures were signs and symptoms of injection pain (primary outcome: the incidence of injection pain), hemodynamic and respiratory parameters, and adverse effects during anesthesia induction (secondary outcomes). Patients' characteristics were similar in the two groups. Fewer children (13/58) in the lidocaine group than in the ketamine group (26/58) (mean difference 23%, 95% CI for difference 6-40%, P = 0.018) developed pain on injection of propofol. There were no differences in hemodynamic parameters between the two groups. One child in the lidocaine group developed laryngospasm, but no other adverse events were recorded. Injection pain was twice as common with ketamine-propofol admixture than with lidocaine-propofol admixture.