The advantage of ropivacaine for postoperative epidural analgesia following leg orthopedic surgery

Background: Epidural administration of local anesthetics may lead to effective pain relief. However, tachyphylaxis or other problems following prolonged epidural anesthesia may develop and in many cases difficulties exist in the maintenance of the similar degree of sensory blockade. The present study was therefore performed to investigate the analgesic effect of continuous postoperative epidural infusion of ropivacaine with fentanyl in comparison with that of bupivacaine or ropivacaine alone. Methods: After leg orthopedic surgery with lumbar combined spinal-epidural anesthesia, thirty-six patients were randomized to one of the three postoperative epidural infusion groups: bupivacaine 0.125%, ropivacaine 0.2%, or ropivacaine 0.2% with 2.2 μg · ml^-1 (400 μg · 180 ml^-1) of fentanyl. Continuous epidural infusion was started at a rate of 6 ml · h ^-1 with possibility of an additional bolus injection of 3 ml at least every 60 min. Pain was assessed using a 10-cm visual analog scale (VAS) just before and 15 min after epidural bolus injections, and 15-20 h after the start of continuous epidural infusion as the severe at pain through the observation. The spread of analgesia (loss of sharpness in pinprick perception) and motor block (Bromage scale) were evaluated bilaterally. Systolic and diastolic blood pressure and heart rate were also measured. Results: The epidural bolus infusion was associated with a significant decrease of VAS (P< 0.001) and stable blood pressure and heart rate in all groups. The maximal VAS in patients receiving 0.2% ropivacaine+fentanyl was significantly less compared to that in the other two groups. The regression of sensory blockade was significantly prolonged in patients treated with ropivacaine+ fentanyl. There was no significant difference in the spread of sensory analgesia between 20 min and 15 -20 h after the continuous epidural anesthesia in this group. None of the patients developed adverse effects such as respiratory depression, nausea, and pruritis. Conclusions: Epidural injection of ropivacaine with fentanyl decreased postoperative pain with stable vital signs in patients undergoing leg orthopedic surgery, as compared to bupivacaine or ropivacaine alone, possibly because of the maintenance of sensory blockade by ropivacaine and enhancement of this sensory blockade by fentanyl.