Randomization and blinding
pain
Simple random sampling was applied in this study. Eligible participants were randomly assigned to three groups via a computer-generated sequence. Opaque and sealed envelopes were sequentially numbered. The ward nurse, who was blinded to this study, assigned the intervention using the next randomization envelope. Children and their parents were informed to which group they had been assigned.The observer rated the children’s pain by watching the real-time surveillance video when the nurse performed cannulation. Only a child’s face and body, including the puncture site shown in the camera’s viewfinder to ensure the observer was blinded. The observer in this study is a senior pediatric nurse of the surgical department, who has received training in pain assessment and didn’t participate in research design and statistics and was ignorant of all the study interventions. The statisticians remained blinded until the final analysis. The child and parents couldn’t be blinded in this study.