Low-Concentration Brachial Plexus Block.

Purpose: We devised a low-concentration brachial plexus block (LCBB) that allows for intraoperative, active motion by blocking only sensory nerves. This study evaluated the efficacy of the LCBB.

Methods: Thirty-eight patients (14 men and 24 women; mean age, 60.0 years) underwent surgery with the LCBB. An ultrasound-guided supraclavicular brachial plexus block with 30-40 mL of 0.6 mg/ml ropivacaine hydrochloride hydrate was performed approximately 2 hours before starting the surgery. A local anesthetic (LA) was administered as a local infiltration if the intraoperative pain relief was locally insufficient. The surgery was performed using a tourniquet as usual, which was released for approximately 1 minute when there was a requirement to check for intraoperative, active motion. We recorded the waiting time required between LCBB administration and surgery, the total surgery time, the total tourniquet time, the number of patients administered an LA, the total LA volume (1% lidocaine equivalent), and the muscle strength at intraoperative, active motion (evaluated by manual muscle testing and categorized as ≥grade 4 or ≤grade 3).

Results: The mean waiting time was 137.0 minutes, the mean surgery time was 124.6 minutes, and the mean tourniquet time was 70.6 minutes. In 2 patients, the anesthetic effect was not achieved, and we switched to other methods of anesthesia (1 patient was switched to an intravenous, regional anesthesia; 1 patient was switched to a standard brachial plexus block). Excluding those 2 cases, the mean LA volume was 8.7 mL among 22 cases (61.1%), and 33 cases (91%) had manual muscle testing of ≥grade 4. In 36 of 38 cases (94.7%), surgery could be performed by LCBB.

Conclusions: Although an LCBB may require additional LA, it is a useful anesthesia method that allows intraoperative active motion and tourniquet use.

Type Of Study/level Of Evidence: Therapeutic IV.