RESUMEN
Levobupivacaine 0.125% provides satisfactory analgesia with lumbar and thoracic epidural catheter placement. Two studies performed in 1999 suggest that ropivacaine may be 40% less potent than bupivacaine whereas this difference is only 2% for levobupivacaine. Ninety-two patients undergoing total hip or knee replacement were selected to participate in double-blind randomized, study comparing ropivacaine 0.165% with levobupivacaine 0.125% to which was added sufentanil 1ug/ml for postoperative analgesia by the epidural route. The total dose of ropivacaine was 60% greater than that of levobupivacaine. The larger consumption of ropivacaine does not necessarily suggest that the potency difference between both newer local anesthestics is even more than the 25% assumed in the present study design. A shorter duration of action of ropivacaine may have caused a requirement for additional demand, although it would be unwise to believe that a 50% larger dose can be entirely explained by a difference in duration of action. Both local anaesthestics levobupivacaine and ropivacaine provided effective postoperative analgesia but, even in a 25% weaker concentration a small volume of levobupivacaine and opiate substance was consumed. These differences may be explained by a potency difference or by the duration of action of levobupivacaine