Abstract
Background:
We aimed to determine the minimum effective volume (MEV) of 0.5% bupivacaine for infraclavicular brachial plexus block.
Methods:
We assigned patients to volume groups consisting of five consecutive patients. Local anesthetic was sequentially reduced from a starting dose of 30 mL by 2 mL to form the volume groups. Five patients were included in each volume group, and at least 3 of 5 injections had to be successful to consider the volume of the anesthetic as sufficient. The study ended when the anesthetic volume of a group was determined to be unsuccessful (two or fewer successful blocks). Block was successful if the patient reported a sensorial block score of 7 or more on an 8- point scale and sensorial and motor block’s total score of 14 on a 16-point scale.
Results:
The MEV of 0.5% bupivacaine for infraclavicular brachial plexus block was 14 mL. A successful block was achieved in all patients (n = 45) in 9 volume groups, which received 30 mL down to 14 mL. Three blocks were unsuccessful in the 12-mL group. Time to onset of block and time to first postoperative anesthetic administration was 15 (10-15) min and more than 24 h in the 30-mL bupivacaine group, but 40 (30-45) min and 14 (10-24) h were determined for the 14- mL group, respectively.
Conclusions:
The MEV of 0.5% bupivacaine for ultrasound-guided infraclavicular brachial plexus block was 14 mL. However, this low-dose block hasa long onset time of 40 (30-45) min on average.
KEYWORDS
Brachial plexus block; Bupivacaine; Drug dose-response relationship; Regional anesthesia