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.

The aim of this study was to show whether the success of lumbar plexus block applied in lower extremity orthopedic surgeries can be evaluated by Near Infrared Spectroscopy (NIRS), which is used to measure tissue oxygenation.

Inclusion Criteria:

• 18-90 years old
• femoral neck fracture,
• femoral shaft fracture,
• hip replacement surgery
• who will undergo velumbar plexus block will be included in the study.

Exclusion Criteria:

• BMI>40 kg/m2
• infection in the block area
• peripheral neuropathy,
• hemoglobinopathy
• peripheral vascular disease
• allergy to local anesthetics
• patients with contraindications for lumbar plexus block