A randomized controlled trial to verify the efficacy of alkalinized local anesthetics in ultrasound-guided supraclavicular brachial plexus block

Abstract

Purpose: Alkalinization of local anesthetics to enhance their efficacy is controversial in peripheral nerve block. To define the efficacy of alkalinized mepivacaine 1% for supraclavicular brachial plexus block, we verified the onset and duration of sensory block using an ultrasound-guided technique.

Methodology: A randomized, double-blinded, controlled, prospective trial was conducted at our hospital after ethical committee approval and informed consents. Twenty patients, 47 – 82 years old and ASA physical status 3, scheduled for vascular access surgery, were randomly divided into Group M (n = 10), receiving 20 ml of mepivacaine 1% alone for nerve block, and Group MSB (n = 10), receiving mepivacaine 1% with sodium bicarbonate for nerve block. Supraclavicular brachial plexus block was performed with a 22-gauge, 50 mm insulated peripheral block needle, peripheral nerve stimulator and ultrasound imaging. Needle placement was confirmed at 0.5 mA, and the drugs were injected. Time to onset of sensory block and duration of sensory block were recorded. Data were statistically analyzed with the t test and Fisher’s exact test, as appropriate, using SPSS Statistics version 22.0 software (SPSS, Chicago, IL). Values of p < 0.05 were considered significant.

Results: Time to onset of sensory block was 9.5 ± 5.5 min in Group M and 7.8 ± 3.4 min in Group MSB, showing no significant difference. Likewise, no difference in duration of sensory block was observed between groups; 257.3 ± 198.0 min vs. 197.3 ± 90.6 min in Group M and Group MSB respectively.

Conclusions: Alkalinization of mepivacaine does not provide faster onset or longer duration of ultrasound-guided supraclavicular brachial plexus block