Continuous epidural infusion of ropivacaine for the prevention of postoperative pain after major orthopaedic surgery: A dose-finding study

The present study investigated the dose relationship of ropivacaine with regard to analgesia and motor block when administered as a continuous 21 hour epidural infusion following major orthopaedic surgery.Forty six patients scheduled for elective total knee or hip arthroplasty were compared in this double-blind study. Patients were randomly assigned to one of four treatment groups: saline (n=12); ropivacaine 0.1% (n=11); ropivacaine 0.2% (n=12); ropivacaine 0.3% (n=11). Initial epidural analgesia was established with 0.5% ropivacaine and general anaesthesia was then induced for surgery. Within 30 minutes of the end of surgery, epidural infusions were commenced at a rate of 10 ml/hour for 21 hours. All patients had access to PCA morphine. Morphine consumption, VAS pain scores at rest, sensory and motor block and overall quality of treatment were assessed at regular intervals.The morphine consumption and VAS scores were lower overall in the ropivacaine groups than in the group receiving only PCA morphine. The difference was more evident during the first 8 hours of postoperative infusion, when significant differences between the ropivacaine 0.2% and 0.3% groups and the saline group were found. The incidence and degree of motor block were dose dependent. There was significantly higher patient satisfaction in all ropivacaine groups compared to the saline control group.In conclusion, 21 hour epidural infusion of ropivacaine, combined with PCA morphine, provides effective pain relief following major joint surgery and without significant adverse events. Morphine consumption and pain scores were lowest in the 0.3% ropivacaine group but this group had a higher degree of motor block. Pain relief with the combination of ropivacaine and PCA morphine is superior to that of PCA morphine alone.