Ultrasound-Guided Selective Versus Conventional Block of the Medial Brachial Cutaneous and the Intercostobrachial Nerves: A Randomized Clinical Trial

BACKGROUND AND OBJECTIVESFor superficial surgery of anteromedial and posteromedial surfaces of the upper arm, the medial brachial cutaneous nerve (MBCN) and the intercostobrachial nerve (ICBN) must be selectively blocked, in addition to an axillary brachial plexus block. We compared efficacy of ultrasound-guided (USG) versus conventional block of the MBCN and the ICBN. METHODSEighty-four patients, undergoing upper limb surgery, were randomized to receive either USG (n = 42) or conventional (n = 42) block of the MBCN and the ICBN with 1% mepivacaine. Sensory block was evaluated using light-touch on the upper and lower half of the anteromedial and posteromedial surfaces of the upper arm at 5, 10, 15, 20 minutes after nerve blocks. The primary outcome was the proportion of patients who had no sensation in all 4 regions innervated by the MBCN and the ICBN at 20 minutes. Secondary outcomes were onset time of complete anesthesia, volume of local anesthetic, tourniquet tolerance, and quality of ultrasound images. RESULTSIn the USG group, 37 patients (88%) had no sensation at 20 minutes in any of the 4 areas tested versus 8 patients (19%) in the conventional group (P < 0.001). When complete anesthesia was obtained, it occurred within 10 minutes in more than 90% of patients, in both groups. Mean total volumes of local anesthetic used for blocking the MBCN and the ICBN were similar in the 2 groups. Ultrasound images were of good quality in only 20 (47.6%) of 42 patients. Forty-one patients (97.6%) who received USG block were comfortable with the tourniquet versus 16 patients (38.1%) in the conventional group (P < 0.001). CONCLUSIONSUltrasound guidance improved the efficacy of the MBCN and ICBN blocks. CLINICAL TRIAL REGISTRATIONThis study was registered at ClinicalTrials.gov, identifier NCT02940847.