After surgery patients were randomly allocated in a double-blind fashion to receive PCEA with either 0.2 % ropivacaine ( n = 16 ) or 0.2 % ropivacaine/2 microg/mL fentanyl ( n = 16 ) [ background infusion ranging between 4 and 6 mL/hr , with 1.5-mL incremental doses and a 20-min lock-out time ] .
