Anesthesia is maintained at a manner of inhalation anesthesia with 0.8-1.5% sevoflurane and continuous intravenous infusion of propofol and remifentanil respectively at a speed of 3-5 mg/kg/h and 0.01-0.02 mg /kg/h. The drug dose is adjusted hemodynamically to maintain MAP values at a range of 60-90 mmHg.