Evaluation of Lumbar Plexus Block Success With Near Infrared Spectroscopy (NIRS)

Tests such as the pin-prick test, cold application or the Bromage scale are currently used to measure the success of nerve blocks and are considered subjective assessments as they require verbal consent from the patient. Near Infrared Spectroscopy (NIRS) measures the differential absorption and reflection of near infrared light transmitted by human tissues, providing a tissue-oxygen saturation index. Modern NIRS-based instruments use multiple detectors to filter spectroscopy data from skin structures to detect subcutaneous tissue oxygenation. Successful regional anesthesia results in decreased sympathetic activity within the distribution of blocked nerves. Regional oxygen saturation (rSO2) has been shown to increase in innervated areas after sympathetic block.