Femoral nerve block with ropivacaine or bupivacaine in day case anterior crucial ligament reconstruction

BACKGROUND/OBJECTIVE: Our aim was to evaluate analgesia, motor block and pharmacokinetics of ropivacaine 0.2% and 0.75% in a femoral nerve block (FNB) in day case patients for anterior crucial ligament (ACL)-reconstruction compared with bupivacaine 0.25% and placebo. METHODS: Following ethics committee approval and informed consent, 280 patients were randomly allocated to four groups for single-shot FNB [30 ml ropivacaine 0.2% (group RO2.0), 0.75% (RO7.5), bupivacaine 0.25% (BU2.5) and NaCl 0.9% (NaCl)]. Analgesia (pain scores, primary outcome) and motor block were assessed at 4 h (dismissal) and up to 24 h. Plasma concentration was determined up to 240 min thereafter. RESULTS: Pain scores at 4 h were significantly higher for NaCl 4 (0-8) (median, range) (vs.) BU2.5 2 (0-8), RO2.0 3 (0-9) and RO7.5 2 (0-8) (NS within the LA groups). Patients of the NaCl group needed analgesics significantly more often (93%) within 4 h after surgery vs. 16% of group RO2.0, 19% of group RO7.5 and 19% of group BU2.5. Motor block was significantly increased with all local anesthetics without a significant difference within the LA groups 3 (0-5) in RO2.0, 3 (0-5) in RO7.5 and 3 (0-4) in BU2.5 vs. 0 (0-3) in group NaCl (median (range); scale from 0=full strength to 5=complete paralysis). Peak plasma concentrations differed significantly: RO7.5: 1.4 +/- 0.4 (0.73-2.6) [microg/ml, mean +/- SD (range)] after 33 +/- 14 (10-40) min, RO2.0: 0.6 +/- 0.3 (0.13-1.0) after 22+17 (10-60) and BU2.5: 0.3 +/- 0.16 (0.05-0.62) at 31 +/- 17 (10-60), respectively. CONCLUSION: FNB for ACL reconstruction with ropivacaine or bupivacaine provided better post-operative analgesia than placebo without reaching toxic plasma concentrations. Significant motor block was observed after 4 h in all groups including the lowest concentration of ropivacaine but occurred even with placebo.