Study population

This single-centre study was performed at the Seoul National University Children’s Hospital, a tertiary children’s hospital in South Korea. Sixty-six children aged 2–5 years (American Society of Anesthesiologists physical status I or II) who were scheduled for elective strabismus surgery under general anaesthesia were included. The exclusion criteria were as follows: history of hypersensitivity and malignant hyperthermia, currently taking an anti-epileptic drug, known myasthenia gravis, myasthenic syndrome, neuromuscular disease, arrhythmia, moderate cardiovascular, pulmonary, hepatobiliary, or renal disease, or overweight (body mass index > 85 percentile). The study protocol was approved by the Institutional Review Board of the Seoul National University Hospital (approval number: H1703–110-840; date of approval: May 8, 2017) and was registered at https://clinicaltrials.gov (number: {"type":"clinical-trial","attrs":{"text":"NCT03132701","term_id":"NCT03132701"}}NCT03132701; principal investigator: Hee-Soo Kim; date of registration: April 9, 2017). The anaesthesiologists involved in the study obtained written informed consent from the parents or their guardians after explaining the study protocol to them.