Comparative Impacts of Two Anesthesia Methods on Peripheral Tissue Oxygenation in the Upper Limb

This study will aim to compare the effects of two different anesthesia techniques-general anesthesia (GA) and interscalene brachial plexus block (ISB)-on forearm tissue oxygenation in patients undergoing shoulder surgery. A total of 49 patients aged 18 to 65 will be enrolled. After standard monitoring, a pulse oximeter will be placed on the second finger of the operative limb, and a regional oxygen saturation (rSO₂) sensor will be applied to the forearm to measure the perfusion index (PI) and rSO₂. Brachial artery parameters will be evaluated using ultrasound imaging approximately 2-3 cm proximal to the antecubital fossa. Patients will be assigned to either the GA group (Group 1) or the ISB group (Group 2). Mean arterial pressure (MAP), heart rate (HR), peripheral oxygen saturation (SpO₂), flow volume (FV), brachial artery diameter (BAD), and near-infrared spectroscopy (NIRS) variables (rSO₂, ΔcHbi, ΔO₂Hbi, ΔHHbi), along with PI values, will be recorded at baseline (before the procedure) and at 10, 20, 30, and 60 minutes following the completion of the block procedure.