After adequate oxygenation anesthesia will be induced with fentanyl (3 mcg/kg), propofol (2-2.5 mg/kg) and Rocuronium (0.6 mg/kg) or Succinylcholine (1 mg/Kg). The maintenance of anesthetic level will be obtained by the use of Sevoflurane 0.7 - 1.3 MAC (minimum alveolar concentration), and bolus doses of Fentanyl (1mcg /kg) and possibly of Rocuronium (0.15mg/kg) every 45 minutes until the end of surgery.