Safety of Etomidate-propofol Mixture vs. Propofol for Total Intravenous Anesthesia in Elderly Patients Undergoing Abdominal Surgery

Patients will receive etomidate - propofol mixture during induction and maintenance. Sufentanil 0.2-0.7 μg/kg，Cisatracurium 0.15 mg/kg，EP mixture（E：P=1:2） 0.1-0.25 ml/kg for induction, EP mixture 0.4\~ 1.2 ml/kg/h and remifentanil 0.05μg/kg/min \~0.3 μg/kg/min for maintenance.

Patients will receive propofol during induction and maintenance.Sufentanil 0.2-0.7 μg/kg，Cisatracurium 0.15 mg/kg，propofol 0.1-0.25 ml/kg for induction, propofol 0.4\~ 1.2 ml/kg/h and remifentanil 0.05μg/kg/min \~0.3 μg/kg/min for maintenance.