[Ropivacaine for peridural anesthesia. Studies on the dose-response relationship in orthopedic surgery]

In an open, nonrandomized dose response study, the efficacy of 0.75% ropivacaine (plain) for epidural analgesia was evaluated during 46 orthopedic surgical procedures (18 total hip replacements, 10 knee prostheses, 3 forefoot operations, 14 arthrotomies or osteotomies). Group 1 received 15 ml (112.5 mg); group 2 20 ml (150 mg); and group 3 25 ml (187.5 mg). The times to initial onset (6.7-7.9 min) and to the maximum level of sensory analgesia (25.7, 27.1, and 30.7 min) hardly differed. The mean maximum level of sensory analgesia increased from T6 (group 1), to T5 (group 2) and T3 (group 3), with an absolute maximum level of C3 (statistically not significant). Times for two-segment regression increased from 146 min and 169 to 192 min, for regression of analgesia to T10 from 193 and 189 to 246 min and to T12 from 220 min and 244 to 296 min (significant). The mean maximum durations were 239(+/- 54), 267(+/- 49.8) and 355(+/- 59.2) min. The degree of motor blockade varied with the volume. Motor block grade I was recorded in 100% of cases, and motor block grade II in 64% of patients in group 1, in 73% in group 2, and in 100% in group 3. Motor block grade III was only seen in 7.1% in group 1, 20% in group 2, and 47% in group 3. The duration was 102 min, 133 min and 188 min for grade I, 158 min, 199 min and 263 min for grade III when this occurred. MAP, HF and RPP varied by a maximum of -8.3%, -11.5% and -17.6% from the initial value.(ABSTRACT TRUNCATED AT 250 WORDS)