Alkalinization of Lidocaine Does not Hasten the Onset of Axillary Brachial Plexus Block

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Abstract
We assessed the onset of sensory and motor blockade as well as the distribution of sensory blockade after axillary brachial plexus block with 1.5% lidocaine hydrochloride 1:200,000 epinephrine with and without sodium bicarbonate in 38 patients. The onset of analgesia and anesthesia was recorded over the distributions of the median, ulnar, radial, and medial cutaneous nerves of the forearm, medial cutaneous and lateral cutaneous nerves of the arm, and musculocutaneous nerve. The onset of motor blockade of elbow and wrist movements was also recorded. Data were analyzed by using survival techniques and compared by using log rank tests. Only the onset of analgesia in the medial cutaneous nerves of the arm and forearm, and the onset of anesthesia in the medial cutaneous nerve of the arm were significantly faster (P < 0.05) with alkalinization of lidocaine. Our study showed that alkalinization of lidocaine does not significantly hasten block onset in most terminal nerve distributions. Implications: We examined whether alkalinizing a local anesthetic would quicken the onset of a regional upper limb nerve blockade. We found that alkalinization of lidocaine did not offer a significant clinical advantage in axillary brachial plexus blockade. (Anesth Analg 1998;86:566-8)