The Influence Of The Nerve-needle Distance And The Orientation Of Needle Bevel Surface On The Magnitude Of Electrical Stimulation In Nerve Block Procedure

Objective: To explore the relationship of electrical stimulation and the nerve-needle distance in nerve block procedure and provide the basis for the clinical application of nerve block.Method: Seven New Zealand white rabbits were selected for experiment. Pentobarbital (30mg/kg) was employed for general anesthesia. A longitudinal incision was performed in the posterior thigh to expose the tibial nerve. Totally 14 nerves were studied. The nerve-needle distance was located by using a 3-dimensional manipulator. The nerve-needle distances of 0mm, 1mm, 2mm, 3mm, 4mm and 5mm were chosen for testing motor response to the electrical stimulation (pulse width: 2ms; pulse frequency: 2Hz) from the needle. The lowest intensity of electrical current to induce muscle contraction was recorded for all distances.Results: The lowest intensity of electrical current was 0.28±0.07mA(0mm), 0.34±0.08mA(1mm), 0.44±0.10mA(2mm), 0.58±0.15mA(3mm), 0.74±0.17mA(4mm) and 0.91±0.21mA(5mm) respectively. Taking nerve-needle distances as independent variables X, lowest intensity of electrical current as Y, linear regression analysis showed linear relationship between X and Y (Y=0.13X+0.22, r~2=0.974). Conclusion: A positive-linear relationship of the nerve-needle distance and electrical stimulation exists in nerve block procedure, which could be used as important reference for localization of injection needle in the clinical practice.