[Ropivacaine 1% versus bupivacaine 0.75% without a vasoconstrictor. A comparative study of epidural anesthesia in orthopedic surgery].

The long-acting local anaesthetic agent ropivacaine, S(-)-1-propyl-2',6'-pipecoloxylidid, is characterised by lower lipid solubility and lower cardiotoxicity compared with bupivacaine. This study was designed to evaluate its clinical efficacy and motor blocking properties when using lower volumes and higher concentrations of both plain substances. METHODS. In a randomised, double-blind study plain ropivacaine (ro) 1% (150 mg) and bupivacaine (bu) 0.75% (112.5 mg) were compared in 44 patients. In the lateral position, epidural anaesthesia was performed at L2/3 or L3/4 using the loss-of-resistance technique. A test dose of 3 ml was given followed by 12 ml (total volume 15 ml). Sensory blockade was registered by the pin-prick method after 2 min at 5-min intervals up to maximal levels and after the operation at 30-min intervals. Simultaneously, the motor block was determined by means of the Bromage scale. Results are given as median values. RESULTS. The onset of analgesia was 6.0 min for both substances (L2), the time to level L5 16.0 and 17.0 min, respectively. The median maximum upper level of sensory analgesia was achieved after 24.5 min with ro (Th 5) and after 21.0 min (Th 7) with bu. The maximum durations (regression to L2) were 321.5 (ro) and 266.0 min (bu) (P < 0.05). Times for 2-segment regression were comparable at 177.5 and 176.0 min, respectively, and for 4-segment regression at 201.3 and 222.0 min. Twenty-one of the 22 patients developed a first-degree motor block (latency 15 and 12 min); 16 patients in the ro group developed a second-degree block, as did 14 in the bu group (latency 24 and 22 min). Third-degree motor block was recorded in 3 patients (latency 45 and 38 min). The duration of first-degree motor block was 233 min and 207 min, of second-degree block 150 and 155 min, and third-degree block 135 min in both groups. The mean arterial pressures and heart rates did not differ. The diastolic pressures were lower after bu (-8.3%) than after ro (-0.4%) at 30 min. No major side effects were observed. Theodrenaline and/or dihydroergotamine (1:10 diluted) was administered to 38.6% of the patients; 34.1% received atropine for the treatment of bradycardias (decrease > or = 12%) and hypotension of more than 20%. No significant differences were found in frequency of analgesia (pin-prick) between both groups. One of 22 patients in the ro group and 6 of 22 in the bu group required additional analgesics or general anaesthesia. The difference is not statistically significant, but is of clinical relevance. With 2 patients after ro and 4 patients after bu the relaxation was insufficient for good operating conditions. CONCLUSION. Ropivacaine 1% produced a longer duration of analgesia and better clinical efficacy than bupivacaine 0.75%. The clinical difference in motor blockade was not statistically significant. The Bromage scale is not representative for a substance with good analgesic effects and moderate motor blocking properties, as has been shown in sophisticated studies on ropivacaine motor blockade.