A DOUBLE-BLIND COMPARISON OF THE ABDOMINAL-WALL RELAXATION PRODUCED BY EPIDURAL 0.75-PERCENT ROPIVACAINE AND 0.75-PERCENT BUPIVACAINE IN GYNECOLOGIC SURGERY

Background and Objectives. Ropivacaine is a long-acting local anesthet ic agent with similar potency to that of bupivacaine when administered for epidural anesthesia. Ropivacaine, however, may be less cardiotoxi c than bupivacaine. Epidural bupivacaine and ropivacaine have been sho wn to be equally effective in providing sensory block for lower extrem ity surgery, but they have not been compared for their ability to prod uce abdominal wall relaxation. Methods. Sixty-six American Society of Anesthesiologists I-III women, 18-70 years old undergoing elective gyn ecologic surgery were studied in a randomized, double-blind manner aft er giving informed consent in an institutionally approved protocol. Th irty-four patients received a single epidural injection of 20 mL 0.75% bupivacaine at the L2-L3 or L3-L4 interspace and 32 patients received 20 mL. 0.75% ropivacaine in a similar manner. Sensory block was teste d with pinprick; motor block with a modified Bromage scale, rectus abd ominis muscle (RAM) test and surgeon satisfaction. Statistical analysi s was performed using the SigmaStat for Windows computer software. Par ametric data were analyzed with Student's t-lest, while nonparametric data was analyzed using the Mann-Whitney rank sum lest. Results. Resul ts are expressed as mean +/- SD. Times to maximal sensory block and pe ak sensory level achieved were similar in both groups. However, time t o complete sensory regression was significantly longer with bupivacain e than ropivacaine (457 +/- 77 vs. 404 +/- 62 minutes, P <.03). Bupiva caine lower extremity motor block onset was significantly faster than ropivacaine (9 +/- 3 vs. 12 +/- 3 minutes, P < .0013). Time to maximum lower extremity motor block was significantly shorter with bupivacain e than ropivacaine (28 +/- 12 vs. 40 +/- 15 minutes, P <.0234). Durati on of lower extremity motor block was significantly longer with bupiva caine than ropivacaine (371 +/- 97 vs. 310 +/- 65 minutes P <.069). Th ere was no significant difference between the two groups for changes i n RAM scores or the time to achieve those changes. Maximum motor block scores using the modified Bromage score and surgeon satisfaction with operating conditions also did not demonstrate a significant differenc e between the two groups. In one instance (with ropivacaine), anesthes ia was judged clinically inadequate despite evidence of bilateral epid ural anesthesia. Conclusions. Both 0.75% ropivacaine and 0.75% bupivac aine provide adequate surgical anesthesia for lower abdominal surgery when administered epidurally. However, lower extremity motor block wit h ropivacaine is significantly shorter and of slower onset and sensory block shorter at these concentrations.