Epinephrine does not prolong the analgesia of 20 mL ropivacaine 0.5% or 0.2% in a femoral three-in-one block

We tested the effect of epinephrine added to 20 mL ropivacaine 0.5% and 0.2 % on postoperative analgesia via a femoral catheter after total knee replac ement. Forty-one patients undergoing total knee replacement under combined peripheral block/general anesthesia were randomly allocated to two groups. After insertion of a femoral catheter, 21 patients in the Ropivacaine-Epine phrine (ROPI-EPI) group received 20 mL ropivacaine 0.5% plus epinephrine 1: 200,000, whereas 20 patients in the Ropivacaine group (ROPI) received 20 mL plain ropivacaine 0.5%. Thereafter, a sciatic block with 30 mL bupivacaine 0.5% plus epinephrine 1:200,000 was performed in all patients, followed by general anesthesia. After surgery, patient-controlled analgesia (PCA) with ropivacaine 0.2% plus epinephrine 1:200,000 for Group ROPI-EPI and plain r opivacaine 0.2% for Group ROPI was available via the femoral catheter (200 mL ropivacaine 0.2% - epinephrine, bolus 20 mL, lockout 120 min). The patie nts were instructed to use PCA when the knee pain score was >3 cm. The inte rval between the initial ropivacaine injection and the first PCA injection determined the duration of 20 mL ropivacaine 0.5% +/- epinephrine, whereas the interval between the first and second PCA injection determined the dura tion of 20 mL ropivacaine 0.2% epinephrine. The average duration of ropivac aine 0.5% was 657 +/- 345 min for the ROPI-EPI group and 718 +/- 423 min fo r the ROPI group (NS), whereas for ropivacaine 0.2%, the average duration w as 409 +/- 245 min for the ROPI-EPI group and 419 +/- 339 min for the ROPI group (not significant). We conclude that epinephrine does not influence th e duration of analgesia of the ropivacaine concentrations investigated.