Perfusion Index for Assessing Femoral and Sciatic Nerve Block Success in Lower Extremity Surgery

Overview

Peripheral nerve blocks are increasingly used in lower extremity surgery as an alternative to general anesthesia. However, traditional methods used to assess block success, such as sensory and motor testing, are subjective, time-consuming, and dependent on patient cooperation. The perfusion index (PI), measured non-invasively using pulse oximetry, reflects peripheral perfusion changes associated with sympathetic blockade and may serve as an early indicator of block effectiveness. This study aims to evaluate whether PI can be used as an early and reliable marker for assessing the success of combined femoral and sciatic nerve block in patients undergoing elective lower extremity surgery. A total of 80 patients aged 18-65 years with ASA physical status I-III will receive ultrasound- and nerve stimulator-guided combined femoral and sciatic nerve block. Hemodynamic parameters and perfusion-related variables, including PI, capillary refill time, and skin temperature, will be recorded at baseline and at 5, 10, 20, and 30 minutes after block administration. The results will be compared with traditional sensory and motor block assessments to determine whether PI provides an earlier and objective assessment of block success.

Peripheral nerve blocks are widely used in lower extremity surgery due to their advantages over general anesthesia, including reduced systemic complications and improved postoperative analgesia. The success of a nerve block is traditionally evaluated using sensory and motor block assessments; however, these methods are subjective and require patient cooperation. Perfusion index (PI), measured non-invasively using pulse oximetry, reflects peripheral perfusion and is influenced by sympathetic blockade. Following a successful nerve block, sympathetic nerve inhibition leads to vasodilation and increased peripheral blood flow, which may result in an increase in PI. This prospective clinical study includes 80 patients aged 18-65 years with ASA physical status I-III scheduled for elective lower extremity surgery. All patients receive combined femoral and sciatic nerve block using ultrasound guidance and nerve stimulation techniques. For the sciatic block, 30 mL of a mixture of 0.25% bupivacaine and 1% lidocaine is administered, and for the femoral block, 20 mL of the same solution is used. Hemodynamic parameters, including heart rate, mean arterial pressure, and oxygen saturation, as well as perfusion-related parameters such as perfusion index, capillary refill time, and distal skin temperature, are recorded at baseline and at 5, 10, 20, and 30 minutes after block administration. Sensory and motor block assessments are performed using cold sensation, pin-prick test, and motor block scales. The primary objective is to evaluate whether PI can serve as an early, objective, and non-invasive indicator of block success compared to traditional assessment methods.