Anesthesia maintenance
The same surgical approach was used for all children. During the procedure, sevoflurane 1.5% by inhalation, propofol (6–10 mg/kg/h) and remifentanil (0.05–0.1ug/kg/min) were pumped to all children to maintain an electroencephalographic bispectral index (BIS) of 40–60, while the pumping rate of intravenous anesthetic drugs was adjusted according to the BIS values, heart rate and blood pressure of the children.