Nerventrauma in der peripheren Regionalanästhesie: Histopathologische Untersuchung peripherer Nerven nach Applikation von Stimulationsstrom am Tiermodell

Introduction: For the performance of peripheral regional anaesthesia electrical nerve stimulation is used for nerve localization in clinical routine. The present experimental study challenged the hypothesis whether currents -as applied for electrical nerve stimulation– should be considered a trigger for the occurrence of nerve injury. Hence, for the detection of myelin damage, intraneural bleeding or trauma-related aseptic inflammation histological analysis was applied following electrical nerve stimulation in pigs. Methods: The axillary brachial plexus of five anaesthetised pigs was bilaterally exposed. Isolated stimulation needles were placed 5mm apart from 20 peripheral nerves stimulating about 40 seconds with an electrical current intensity of 1.5mA (frequency 2Hz; pulse duration 0.1ms). After 48 hours of maintaining general anaesthesia 45 nerves including negative and positive controls were resected. The specimens were processed for visual examination and the detection of inflammatory cells (haematoxylin eosin, i.e. immunohistochemistry for visualisation of macrophages), myelin damage (Kluver-Barrera staining), and intraneural haematoma. Considering myelin, haematoma and inflammatory cells, the grade of nerve injury was scored ranging from 0 (no injury) to 4 (severe injury). Results: Statistical analysis showed no significant nerve lesions following nerve stimulation procedure (1[0/1]) (Median [interquartile range]) compared to the negative control (0[0/1]);p=0.257. Conclusion: According to the experimental data, electrical nerve stimulation with a current intensity of 1.5mA –without needle-nerve contact- does not trigger histological changes with respect to aseptic inflammation or myelin impairment. Hence, electrical nerve stimulation in clinical practise should not be suggested a relevant trigger for neurological complications (i. e. nerve injury).