Evaluation of alkalinized lidocaine solution in brachial plexus blockade

The effect of alkalinization of lidocaine solution in brachial plexus blockade was evaluated in a double blind study. Commercial 1.5% lidocaine with epinephrine 1 : 200,000 (pH 5.72) was compared with an alkalinized solution of lidocaine (pH 7.12). 10 mg.kg(-1) of each solution was administrated by the axillary perivascular technique in 34 adult patients scheduled for elective surgery. The onset and spread of sensory blockade and the intensity of motor blockade were determined. An alkalinized lidocaine solution produced more complete sensory blockade in all of four main nerves of the upper extremity as compared with the control lidocaine solution. The onset of sensory blockade in the musculocutaneous, radial, ulnar and median nerves was shortened 58%, 40%, 30% and 28%, respectively, by employing the alkalinized lidocaine solution. Also the analgesic onset in the radial and musculocutaneous nerves was significantly faster than the other two nerves ( P < 0.05 and P < 0.01). Furthermore, the intensity of motor blockade was greatly potentiated when alkalinized lidocaine solution was employed. There was no significant increase in plasma concentration of lidocaine in patients who were given alkalinized solution.