Comparison of Postoperative Pain Application of Alfentanil or Remifentanil in TIVA

Anesthesia induction: midazolam 0.02 mg/kg, propofol（TCI） 3 μ g/mL, alfentanil 20 μ g/kg and rocuronium 0.6 mg/kg . Anesthesia maintenance: target-controlled infusion of propofol combined with alfentanil(0.5-2ug/kg/min)

Anesthesia induction: midazolam 0.02 mg/kg, propofol（TCI） 3 μ g/mL, remifentanil 1μ g/kg and rocuronium 0.6 mg/kg . Anesthesia maintenance: target-controlled infusion of propofol combined with remifentanil(0.1-0.3ug/kg/min)