Influence of the local anesthetics solutions’ temperature on muscular action potential amplitude decrease at brachial plexus block

Aim. To study influence of temperature of local anesthetics solutions on effectiveness of brachial plexus block using axillary access. Methods. Patients who underwent arm and hand surgeries were randomized either to the main group (n=25) or to the control group (n=25). In the main group, 1% lidocaine (20 ml) and 0.25% ropivacaine (40 ml - males, 30 ml - females) at 38 °C were used for brachial plexus block using axillary access. In the control group, anesthetics at room temperature were used. Brachial plexus block was performed using the axillary access at m. pectoralis major margin above the a. axillaris pulsation point. To register provoked muscular action potentials, a portative neurodiagnostic system «Nicolet One» was used. The percentage of provoked muscular action potential amplitude decrease was counted with results of a measurement before the block as a baseline. For additional analgesia and sedation phentanylum 0.005% was used until Ramsay sedation score II was achieved. «EZSAT-E» software package was used for data analysis. Results. In the main group brachial plexus block was achieved 14.2±3.4 minutes earlier than in the control group. Phentanylum dose required to provide psychic and emotional comfort was 45.4% lower in the main group (3.0±0.9 μg/kg per hour) compared to the control group (5.5±1.7 μg/kg per hour). Conclusion. The use of local anesthetics solutions at body temperature increases the efficiency of brachial plexus block and reduces the time of it’s achievement, increases it’s analgesic potential and decreases the need for narcotic analgesics to provide psychic and emotional comfort for the patient.

brachial plexus block, local anesthetics, drug temperature, electromyography