The ED

Background: Our trial addresses the gaps in the current literature by directly estimating the ED 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 ED 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.