Background and objectives Foot and ankle surgery is associated with severe pain that can be reduced with continuous popliteal sciatic nerve block. We tested the hypothesis that programmed intermittent bolus (PIB) delivery of local anesthetic provides superior analgesia to a continuous infusion (CI) regimen.

Methods 60 patients undergoing major foot and ankle surgery were randomized to receive PIB (10 mL of ropivacaine 0.2% every 2 hours) or CI (5 mL/hour) continuous popliteal sciatic nerve block with patient-controlled regional analgesia (5 mL every 30 min as needed) provided for all. Primary outcome was the average of static and dynamic numerical rating scale (NRS) pain scores through 48 hours. Secondary outcomes included rest and movement NRS pain scores at different timepoints, opioid consumption, local anesthetic consumption, intensity of sensory and motor block, patient satisfaction and the incidence of opioid-related side effects.

Results There was no significant difference in the primary outcome of average NRS pain score through 48 hours, opioid consumption or the volume of local anesthetic administered. Patients in group PIB had significantly decreased strength of toe dorsiflexion at 6 hours (p=0.007) and 12 hours (p=0.001) and toe plantarflexion at 12 hours (p=0.004). Patient satisfaction and the incidence of side effects was similar between groups.

Conclusions Both CI and PIB regimens provided excellent analgesia, low opioid consumption and high patient satisfaction. While there was no difference in analgesic outcomes, PIB dosing resulted in a more profound motor block.

Trial registration number NCT02707874.