Intermittent versus continuous sciatic block combined with femoral block for patients undergoing knee arthroplasty. A randomized controlled trial.

purposeMany institutions perform peripheral femoral and/or sciatic nerve blocks for analgesia after total knee arthroplasty. The aim of the present investigation was to compare the analgesic effect of an intermittent sciatic block (boluses on demand only) with a continuous infusion.

methodsOne hundred and forty patients receiving a femoral and a sciatic nerve block (SNB) by catheter were assessed. The femoral catheter was infused continuously in both groups. In the continuous group (n = 70), the sciatic catheter was used continuously as well. In the intermittent group (n = 70), after a single injection of 20 ml ropivacaine 0.75 %, injections into the sciatic catheter were performed on demand only. Frequency of injections, ventral and dorsal numerical pain scores (NRSs) of the knee, functional outcome (degree of flexion/extension) and additional opioid requirements were assessed during the post-operative period.

resultsIn both groups, dorsal and ventral NRSs were below 3 at rest and below 5 during mobilisation over the complete period of assessment. Differences between the groups could not be observed. The cumulative number of supplemental injections into the sciatic catheter was higher in the intermittent group (52) compared with the continuous group (24; p < 0.05). Groups did not differ from each other with regard to functional outcome and opioid consumption.

conclusionsThe use of a sciatic block performed as intermittent bolus injection on demand only did not affect post-operative outcome parameters with regard to pain scores, functional outcome or opioid requirements. This approach might therefore be considered as an alternative to a continuous infusion concept. ClinicalTrials.gov Identifier: NCT01843153.