Ultrasound-guided administration of lidocaine into the sciatic nerve in a porcine model: correlation between the ultrasonographic evolution of the lesions, locomotor function and histological findings.

Intraneural puncture of local anaesthetics has been associated with permanent or transitory nerve injury. The use of ultrasound (US)-guided techniques for the blockade of peripheral nerves has revealed that intraneural puncture is a relatively common complication, which is not frequently associated with neurological deficits. In this study, 2.5 mL of lidocaine were administered using US-guidance into the sciatic nerve (ScN) of 12 piglets. The punctured nerves were sequentially evaluated by US (cross sectional area and relative echogenicity) before and immediately after the injections, and then at 1, 2, 4, 7 and 14 days. At these times, animals were euthanased two by two at each time point, and ScN samples were removed for histological examination. Cross sectional area and relative echogenicity values were statistically different immediately after the injections, returning to pre-puncture values within 4 days. The inflammatory process observed by histopathology showed a similar trend indicating that the integrity of the perineurium was maintained. Locomotor deficits were not observed. The increase in size of the ScN produced by the injection of lidocaine intraneurally did not induce motor deficits in piglets in the current study.