Do the Concentration and Volume of Local Anesthetics Affect the Onset and Success of Infraclavicular Anesthesia?

BACKGROUND: Although local anesthesia is a suitable method for upper limb surgeries, there is debate regarding the effects of appropriate dosing. OBJECTIVES: In the current study, we investigated the effects of the concentration and volume of a local anesthetic on the beginning and quality of anesthesia during upper limb orthopedic surgeries. PATIENTS AND METHODS: This double-blinded, randomized, clinical trial was conducted on 60 patients aged between 18 and 85 years candidated for upper limb orthopedic operations. The patients were equally and randomly distributed into two groups (n = 30). Under ultrasound imaging guidance, the first group received 7 mL of 2% lidocaine and the second group 10 mL of 1.3% lidocaine into the brachial plexus cords. The onset of block and the level of sensory and motor block were documented for each nerve territory. RESULTS: The onset of sensory and motor block was significantly shorter in the 1.3% lidocaine group than in the 2% lidocaine group (P ≤ 0.05). The success rate of sensory and motor block was not different. The quality (completeness) of sensory block for the musculocutaneous nerve and that of motor block for the radial nerve were significantly better in the 1.3% lidocaine group than in the 2% lidocaine group. CONCLUSIONS: The volume of the injected anesthetic accelerated the onset of sensory and motor block without affecting the rate of success in our patients.