Alkalinization of 0.5% lidocaine for intravenous regional anesthesia

Although remaining a controversial issue, alkalinization of lidocaine or bupivacaine may shorten the time to onset and increase the duration of the sensory block. The aim of this study was to evaluate the effect of pH adjustment on the sensory and motor blocks during intravenous regional anesthesia (IVRA) with lidocaine. Thirty-one patients scheduled for minor hand surgery performed under IVRA were randomized into two groups: Group 1 (n = 14): 1% lidocaine, 3 mg/kg, diluted with the same volume of physiological saline solution (pH = 6.63 +/- 0.05), and Group 2 (n = 17): 1% lidocaine, 3 mg/kg, diluted with the same volume of 1.4% sodium bicarbonate (pH = 7.34 +/- 0.05). final concentration of lidocaine was thus 0.5% in both groups. Sensory block was assessed by pinprick every 2 minutes in areas corresponding to six terminal nerves: ulnar, median, radial, musculocutaneous, medial cutaneous nerve of arm and intercostobrachial, and medial cutaneous nerve of forearm. The time between release of tourniquet (at the end of surgery) and appearance of pain was recorded. Motor blockade was evaluated by asking the patient to squeeze strongly a blood pressure cuff previously inflated to 40 mmHg. This maneuver was performed before and every 2 minutes after injection. No statistical differences were found between the two groups whatever the parameter studied. In conclusion, there is no advantage (over plain solutions) to using pH-adjusted lidocaine during IVRA for hand surgery.