Ultrasound-guided nerve blocks are quickly becoming integrated into emergency medicine practice for pain control and as an alternative to procedural sedation. Common, but potentially catastophic errors have not been reported outside of the anesthesiology literature. Evaluation of the brachial plexus with color Doppler should be standard for clinicians performing a supraclavicular brachial plexus block to determine ideal block location and prevention of inadvertant intravascular injection.