The effect of local anesthetic concentration and volume on the block onset time and success rate in infraclavicular approach

Local anesthesia techniques are suitable for upper limb surgery but the effects of anesthetic agent’s concentration، volume and total dose on motor and sensory block success rate is controversial. The aim of the present study was to investigate the effect of anesthetic agent’s concentration and volume on the sensory and motor nerve block onset time and its quality in upper limb orthopedic surgeries. In this double blind clinical trial 60 patients ASA class I، II who were candidate for upper limb surgeries were enrolled to the study and were randomly divided into two groups; lidocaine 2% (7ml) and lidocaine 1. 3% (10ml). Vertical infra-clavicular technique using ultrasound guide was applied. Onset time and quality of sensory and motor block of Radial، Median، Ulnar and MSN nerves were recorded and compared every 5 minutes for 20 minutes. Onset time of sensory and motor block in the lidocaine 1. 3% was significantly shorter than lidocaine 2% (p>0. 05). The success rate of sensory and motor block in group of lidocaine 1. 3% was higher than lidocaine 2% but there was no significant difference between the two groups (82. 8% and 78. 6% respectively، p>0. 05). The quality of motor block of Radial nerve and sensory block of MSN were significantly better in the group of lidocaine 1. 3%. The volume of anesthetic agents can affect the onset time of sensory and motor block of brachial plexus but there was no statistically significant effect on success rate of blockade.