The effectiveness and safety of Ropivacaine combined with Dexmedetomidine for TAP blockage in postoperative analgesia of kidne transplatation: a prospective, randomized clinical trial

INTERVENTION: Group C:TAP block performed with 25 ml of 0.9% saline;Group R:TAP block performed with 25 ml of 0.4% ropivacaine;Group RD:TAP block performed with 25 ml mixture solution of 0.4% ropivacaine with 1ug/kg Dexmedetomidine; CONDITION: acute postoperative pain PRIMARY OUTCOME: morphine consumption; SECONDARY OUTCOME: visualized analgesic score;the degree of sedation;the incidence of complication;fentanyl consumption; INCLUSION CRITERIA: Patients scheduled for RT under general anesthesia,within American Society of Anesthesiologists (ASA) class II and III