METHODS	After induction of anaesthesia and placement of a laryngeal mask airway ( LMATM ) , the patients were randomly divided into three groups to receive either caudal ropivacaine alone ( 0.4 % , 2 mg x kg ( -1 ) ) in group R ( n = 32 ) or ropivacaine ( 0.2 % , 1 mg x kg ( -1 ) ) plus ketamine ( 0.25 mg x kg ( -1 ) ) in group RK ( n = 33 ) or ropivacaine ( 0.2 % , 1 mg x kg ( -1 ) ) plus tramadol ( 1 mg x kg ( -1 ) ) in group RT ( n = 34 ) with a total volume of 0.5 ml x kg ( -1 ) .\