The ED95 of lidocaine and prilocaine for ultrasound-guided brachial plexus blocks for surgical anaesthesia: a randomised controlled clinical trial.

Abstract

Background: Our trial addresses the gaps in the current literature by directly estimating the ED95 of short-acting local anaesthetics for ultrasound-guided axillary and supraclavicular brachial plexus blocks for surgical anaesthesia. Methods: Four double-blind prospective studies were organized in two separate arms. Patients were randomised between studies A (lidocaine 1% with adrenaline) and B (lidocaine 2% with adrenaline) for axillary blocks and between studies C (prilocaine 1%) and D (lidocaine 1% with adrenaline) for supraclavicular blocks. All statistical modelling and analysis were performed using the modified continual reassessment method. The primary endpoint of the studies was the loss of cold and pin-prick sensations in the sensory distributions of the median, musculocutaneous, radial, and ulnar nerves. Results: For axillary blocks, the estimated ED95 of lidocaine 1% with adrenaline was 40 ml (95% credibility interval: 89.5-99.2%), and lidocaine 2% with adrenaline was 15 ml (95% credibility interval: 87.4-97.5%) (studies A and B: 41 and 40 patients, respectively). The ED95 could not be determined for supraclavicular blocks as it fell outside the dose range considered in the studies (studies C and D: 31 and 42 patients, respectively). Conclusions: We achieved a 95% success rate for axillary blocks using lidocaine (1% and 2%) with adrenaline within our dosing limits. For supraclavicular blocks, >40 ml of prilocaine 1% or lidocaine 1% with adrenaline may be required to consistently achieve a 95% success rate. Our studies highlight the continual reassessment method as a credible methodology for dose-finding studies in regional anaesthesia. Clinical trial registration: EudraCT ref: 2010-018466-22.