90 pediatric patients(age 2-10years) in the BeiJing Ji Shui Tan Hospital and The Second Affiliated Hospital of Wen Zhou Medical University with American Society of Anesthesiologists (ASA) physical status I or II, who are scheduled to undergo open reduction surgeries （Salter acetabular osteotomy，combined with proximal femoral rotation osteotomy）are selected and divided into 3 equal groups with 30 subjects.The consent forms are approved by the institutional Ethics Committee.