Combined sciatic-femoral nerve block with 0.75% ropivacaine: effects of adding a systemically inactive dose of fentanyl

To evaluate the effects of adding low-dose fentanyl to 0.75% ropivacaine du ring peripheral nerve blocks, 30 ASA physical status I-II patients undergoi ng hallux valgus repair under combined sciatic-femoral nerve block were ran domly allocated in a double-blind fashion to receive nerve block placement with 30 mL of either 0.75% ropivacaine alone (group: ropivacaine, n = 15) o r 0.75% ropivacaine plus fentanyl 1 mu g kg(-1) (group: ropivacaine-fentany l, n = 15). A blinded observer recorded haemodynamic variables and sedation , as well as the time required to achieve surgical block and the first requ est for analgesia. Readiness to surgery required 10 min (5-20 min) with 0.7 5% ropivacaine and 10 min (3-20 min) with the ropivacaine-fentanyl mixture. No differences in the degree of sedation, peripheral oxygen saturation, an d haemodynamic variables were observed between the two groups. The degree o f pain measured at first analgesic request, and the consumption of postoper ative analgesics, was similar in the two groups, while the mean time from b lock placement to the first request for pain medication was 13.7 h (25-75th percentiles: 11.8-14.5 h) in the ropivacaine group and 13.9 h (25-75th per centiles: 10.5-14.5 h) in the ropivacaine-fentanyl group (P = not significa nt). We conclude that adding fentanyl 1 mu g kg(-1) to 0.75% ropivacaine di d not provide clinically relevant advantages in terms of onset time, qualit y and duration of combined sciatic-femoral nerve block in patients undergoi ng elective hallux valgus repair.