Ropivacaine 0.25% and 0.5%, but not 0.125%, provide effective wound infiltration analgesia after outpatient hernia repair, but with sustained plasma drug levels

Background and Objectives. Ropivacaine is a long-acting local anesthetic similar to bupivacaine, but with lower cardiac toxicity and intrinsic vasoconstrictive properties that may reduce the risk and extent of systemic plasma absorption, Plasma levers and risks are associated with the total dose used and the extent of absorption, with lower doses potentially representing less risk. Although both 0.5% and 0.75% ropivacaine provide adequate analgesia for wound infiltration after hernia repair, the efficacy of lower doses and the early systemic absorption have not been reported. Methods. We studied postoperative pain and systemic plasma levels following either the injection of 30 mt of saline or 0.125%, 0.25%, or 0,5% ropivacaine into the wounds in 110 healthy patients following hernia repair under spinal anesthesia. Pain was assessed using visual analog scale (VAS) scores and algometer readings at rest and after coughing, and oral analgesic requirements were assessed in the first 5 hours after surgery and for the week after discharge. Results. Both 0.25% and 0.5%, ropivacaine provided pain relief following surgery when compared with saline or 0.125%. No adverse reactions to the drug were reported in any group. Plasma levels of ropivacaine peaked between 30 and 60 minutes, at 0.109, 0.249, and 0.399 mg/L for 0.125%, 0.25%, and 0.5% concentrations, respectively. Although the levels were below those producing clinical symptoms, they remained elevated for the entire 2-hour sampling period. This implies an absorption-dependent elimination which is substantially longer than reported with other routes of injection. Conclusions, Ropivacaine 0.25% and 0.5% is adequate for pain relief after outpatient hernia repair, whereas the 0.125% solution is no more effective than saline. Prolonged systemic absorption from peripheral injection may be associated with prolonged elevations of plasma concentrations, which potentially could be associated with unexpectedly high plasma levels if repeated injections are performed in the perioperative period with higher concentrations or doses.