Compared with dual nerve stimulation, ultrasound guidance shortens the time for infraclavicular block performance.

PURPOSE: The success rate for infraclavicular brachial plexus block using nerve stimulation reportedly ranges from 60 to 80%. Ultrasound guidance may be associated with greater success. This study compared ultrasound guided infraclavicular block with a dual motor endpoint nerve stimulation technique. METHODS: One hundred three hand surgery patients were randomized to receive either ultrasound-guided (ultrasound group) or dual motor endpoint nerve stimulation (stimulation group) infraclavicular block using 2% lidocaine 15 mL and 0.5% bupivacaine 15 mL with epinephrine. Block success was defined as loss of sensation to pinprick in each of the radial, ulnar, median, and musculocutaneous nerve distributions when measured 20 min after block performance. Block performance time, readiness for surgery (no supplemental block, skin infiltration, or general anesthesia), and complications were also assessed. RESULTS: Patient characteristics were similar between groups. Success rate was 92% in the ultrasound group and 80% in the stimulation group (P = 0.18). Block performance time was shorter in the ultrasound group (median 5 min) compared with the stimulation group (median 10.5 min) (P < 0.001). Paresthesiae were more frequent in the stimulation group (45%) than in the ultrasound group (6%) (P < 0.001). After final injection, more patients were ready for surgery in the ultrasound group (85%) than in the stimulation group (65%) (P = 0.04). At 1 week postoperatively, complications were minor and transient and did not differ between groups. CONCLUSION: There was no statistically significant difference in the success rate between ultrasound guidance and dual motor endpoint stimulation for infraclavicular block. However, ultrasound guidance shortens performance time and improves readiness for surgery compared with dual motor endpoint stimulation.

Minimum effective volume of local anesthetic for ultrasound-guided supraclavicular brachial plexus block.

BACKGROUND AND OBJECTIVES: The aim of this study was to determine the minimum effective anesthetic volume required to produce an effective supraclavicular block for surgical anesthesia using an ultrasound (US)-guided technique. METHODS: Twenty-one adults undergoing elective upper limb surgery received a US-guided supraclavicular block. The initial volume of local anesthetic (LA; 50:50 mixture of lidocaine 2% and bupivacaine 0.5% with epinephrine) injected was 30 mL, which was subsequently varied by 5 mL for each consecutive patient according to the response of the previous patient. The minimum effective anesthetic volume in 50% of patients was determined using the Dixon and Massey up-and-down method. The effective volume in 95% of patients (ED95) was calculated using probit transformation and logistic regression. RESULTS: The minimum effective anesthetic volume in 50% and calculated effective volume in 95% of patients were 23 mL (95% confidence interval, 13-39 mL) and 42 mL (95% confidence interval, 19-65 mL), respectively. Seven patients received supplemental LA, with no patient requiring a general anesthetic. CONCLUSION: In this study, the minimum volume required for US-guided supraclavicular block in 50% of patients was 23 mL, and in 95% of patients was 42 mL. Under the present study conditions, the calculated volume of LA required for US-guided supraclavicular block does not seem to differ from the conventionally recommended volume required for supraclavicular blocks using non-US-based nerve localization techniques.