Programmed, intermittent boluses versus continuous infusion to the sciatic nerve - a non-inferiority randomized, controlled trial.

Abstract

Trials comparing programmed, intermittent boluses (PIB) and continuous infusion in catheter-based nerve blocks found no analgesic differences. However, as these trials used equal doses of local anesthetic (LA), the time of action of each bolus was not accounted for. Therefore, the dose-sparing benefits of PIB may have been overlooked. We compared the analgesic effect of boluses administered in intervals resembling the time of action of each bolus with continuous infusion. We hypothesized that PIB provided non-inferior analgesia despite consuming less LA. Eighty-one patients undergoing fore- and midfoot surgery receiving a catheter-based sciatic nerve block were randomized to ropivacaine 0.2% as PIB of 10ml every 8th hour or as continuous infusion, 6ml h-1 . All participants could also receive boluses of 10ml every 4th hour as needed. A non-inferiority randomized controlled design was used. Primary outcome was pain (VAS, 0-100mm) for 72h using area under curve (AUC) calculation. We assumed a linear relationship between mean VAS and AUC-VAS and used a non-inferiority margin of VAS=20mm, corresponding to AUC-VAS=1440mm h. Mean difference in AUC-VAS was -416mm h (95% CI -1076 to 244; p=.217) between continuous infusion (mean AUC-VAS 1206mm h) and PIB (mean AUC-VAS 1621mm h), establishing non-inferiority. Mean total LA consumption was significantly larger for continuous infusion compared to PIB ((468ml (95% CI 458 to 478) vs. 136ml (95% CI 123 to 148); p < 0.0001)). PIB provided non-inferior analgesia compared to continuous infusion for 72 postoperative hours despite using significantly less LA.