What is the ED95 of prilocaine for femoral nerve block using ultrasound?

Abstract

Background: Our aim was to estimate the ED95 of prilocaine 1% w/v for femoral nerve block.

Methods: This two-stage dose-finding sequential clinical trial followed an adaptive design based on the continual reassessment method (CRM). Adult patients undergoing Vastus medialis muscle biopsy under ultrasound-guided femoral nerve block were recruited. Data from previously published studies and our own previous experience were used to set the dose levels and their guesstimate probabilities of response.

Results: Forty patients were recruited in the trial (n=26 in the first stage and n=14 in the second stage). Using the CRM, the estimated response probabilities with 13 and 17 ml prilocaine 1% w/v were 90.4% (95% credibility interval: 68-98%) and 99.1% (95% credibility interval: 89-100%), respectively.

Conclusion: Our study demonstrates that the dose closest to the ED(95) of prilocaine 1% w/v for ultrasound-guided femoral nerve block is 17 ml. The study also illustrates the value of CRM in dose-finding experiments.