[Ultrasound-guided supraclavicular brachial plexus block with small volumes of local anesthetic: technical description and analysis of results].

OBJECTIVE: To assess the use of ultrasound guidance to enable injection of 10 mL of 2% mepivacaine into the brachial plexus to maintain an effective block and surgical conditions comparable to those that can be provided with larger volumes and higher doses. MATERIAL AND METHODS: This was a prospective study of 200 consecutive adults in whom a 7.5 Mhz linear array was used for ultrasound guidance of a 40-mm 21-gauge needle with a 15 degrees bevel tip. The probe was placed in the coronal oblique plane and the needle was inserted along its axis to the outer edge. The anesthetic was injected at 3 locations. The quality of sensory block was assessed at 30 minutes and effectiveness at the end of surgery. RESULTS: The patient sample consisted of 87 women and 113 men with a mean (SD) age of 40 (13) years and body mass index of 26 (4) kg x m(-2). Most procedures were on the hand and elbow (82%). All blocks were performed by the same anesthesiologist. Sensory block of pain was achieved in 97% of the patients and analgesia was effective for 95%. Paresthesias were noted by 28% when the needle was moved and by 71.5% during injection. The only complications observed were 2 arterial punctures (1%). CONCLUSIONS: Ultrasound guidance enables use of less local anesthetic for supraclavicular brachial plexus blocks. The surgical conditions possible are comparable in quality to those achieved at higher volumes and doses. The incidence of complications is minimal.