What concentration of sufentanil should be combined with ropivacaine 0.2% wt/vol for postoperative patient-controlled epidural analgesia?

In this randomized double-blinded study, we sought to determine an optimal dose-combination of sufentanil with ropivacaine 0.2% wt/vol as postoperativ e epidural analgesics. One hundred twenty patients undergoing major abdomin al surgery under general and thoracic epidural anesthesia (T9-11) were assi gned to groups receiving patient-controlled epidural analgesia with ropivac aine 0.2% wt/vol (R), ropivacaine 0.2% wt/vol + sufentanil 0.5 mu g/mL (R+S 0.5), 0.75 mu g/mL (R+S0.75), 1.0 mu g/mL (R+S1). A visual analog score of less than 40 was considered effective, and all side effects were recorded. In randomized subgroups (10 patients per group), plasma pharmacokinetic dat a were obtained for both epidural drugs. Four patients in Group R and two i n Group R+S0.5 were excluded because of inadequate analgesia. The drug infu sion rates (range of means: 5.4-5.9 mL/h) were similar in all patients. Ana lgesia was superior for sufentanil 0.75 mu g/mL with no further enhancement by the larger sufentanil concentration of 1 mu g/mL. Sufentanil plasma lev els were within the range of the minimal effective concentrations (highest in R+S1), and there was no covariation between plasma levels and pain relie f. Free ropivacaine plasma concentrations remained stable for 96 h. No seve re side effects were detected, although pruritus correlated with an increas ing dose of sufentanil. We conclude that the combination of ropivacaine 0.2 % wt/vol and 0.75 mu g/mL sufentanil provided the best analgesia with the f ewest side effects of the three combinations tested. Implications: Sufentan il is added to epidural infusions of ropivacaine 0.2% wt/vol to improve the effectiveness of postoperative pain management. Regarding the risk of side effects, however, it is still unclear what concentration of sufentanil sho uld be added to the local anesthetic. For postoperative thoracic epidural a nalgesia after major abdominal surgery, the combination of ropivacaine 0.2% wt/vol and 0.75 mu g/mL sufentanil resulted in an appropriate cost: benefi t ratio between good analgesia and side effects.