In Vivo Microultrasound Visualisation of Nerve Trauma Due to Regional Anaesthesia Needle Insertion and Injection

Regional anesthesia is indicated and commonly used for many surgical procedures. However, intraneural needle insertion and injection is frequent, though unintended, resulting in 10% of patients having post-operative peripheral nerve pain, affecting recovery. The incidence of neuropathy has not decreased over the last decade despite the adoption of ultrasound guided regional anesthesia because of the difficulty interpreting the needle tip position relative to nerves with standard clinical ultrasound imaging systems. This study uses microultrasound for visualising the anatomy of the nerve in the pig model and for confirming the placement of the anesthetic needle while delivering injectate near or in a nerve. The in-line fluid pressure is measured during the injection for different clinical flow rates used during the regional anesthesia procedure. The change in shape and the displacement of the nerve due to the injection is evaluated, and fluid pressure associated with intraneural and extraneural injection. The analysis of the different factors contributing to the nerve trauma showed that there was significant change in pressure measurement with different pigs, flow rate and tissue layers where the needle tip was placed.