Failure of supraclavicular block under ultrasound guidance: clinical relevance of anatomical variation of cervical vessels.

We describe a case with partial analgesia after ultrasound-guided supraclavicular block for elbow surgery. The failure of the block was caused by the limited spread of local anesthetic because of blockage by a vessel (either transverse cervical artery or dorsal scapular artery) running through the brachial plexus. Anesthesiologists should be aware that cervical anatomy is complex and has anatomical variations. Thus, careful ultrasound screening of anatomical structure, especially using color Doppler, is important in performing brachial plexus block.