PLAIN ROPIVACAINE 1-PERCENT VERSUS BUPIVA CAINE 0.75-PERCENT IN EPIDURAL-ANESTHESIA - A COMPARATIVE-STUDY IN ORTHOPEDIC-SURGERY

The long-acting local anaesthetic agent ropivacaine, S(-)-1-propyl-2', 6'-pipecoloyxlidid, is characterised by lower lipid solubility and low er cardiotoxicity compared with bupivacaine. This study was designed t o evaluate its clinical efficacy and motor blocking properties when us ing lower volumes and higher concentrations of both plain substances. Methods. In a randomised, double-blind study plain ropivacaine (ro) 1% (1 50 mg) and bupivacaine (bu) 0.75% (112.5 mg) were compared in 44 p atients. In the lateral position, epidural anaesthesia was performed a t 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 blockad e was registered by the pin-prick method after 2 min at 5-min interval s up to maximal levels and after the operation at 30-min intervals. Si multaneously, the motor block was determined by means of the Bromage s cale. Results are given as median values. Results. The onset of analge sia was 6.0 min for both substances (L2), the time to level L5 16.0 an d 17.0 min, respectively. The median maximum upper level of sensory an algesia 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 (r o) and 266.0 min (bu) (P<0.05). Times for 2-segment regression were co mparable at 177.5 and 176.0 min, respectively, and for 4-segment regre ssion 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 pat ients (latency 45 and 38 min). The duration of first-degree motor bloc k 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 pressure s and heart rates did not differ. The diastolic pressures were lower a fter 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 greater-than-or-equal-to 12%) and hypotension of more than 20%. No significant differences were fou nd in frequency of analgesia (pin-prick) between both groups. One of 2 2 patients in the ro group and 6 of 22 in the bu group required additi onal analgesics or general anaesthesia. The difference is not statisti cally significant, but is of clinical relevance. With 2 patients after ro and 4 patients after bu the relaxation was insufficient for good o perating conditions. Conclusion. Ropivacaine 1% produced a longer dura tion of analgesia and better clinical efficacy than bupivacaine 0.75%. The clinical difference in motor blockade was not statistically signi ficant. The Bromage scale is not representative for a substance with g ood analgesic effects and moderate motor blocking properties, as has b een shown in sophisticated studies on ropivacaine motor blockade.