BACKGROUND: It has been reported that noninvasive, objective tests arc needed for determining the success of peripheral nerve blocks because conventional methods necessitate the cooperation of the patient. It is also known that the brachial plexus block causes vasodilatation and an increase in blood flow due to its sympathectomy effect. Our study aimed to determine whether Perfusion Index (P1) and measured regional hemodynamic changes using ultrasound were reliable parameters in evaluating the early success of an infraclavicular block.,METHODS: Forty ASA I-III patients who were administered a successful infraclavicular block were included in this study. In addition to the baseline hemodynamic measurements. PI and regional hemodynamic parameters, such as brachial artery diameter (BAD), brachial arterial area (BAA), blood flow (BF), end-diastolic velocity (EDV), Resistance Index (RI), peak systolic velocity (PSV), and time average velocity (TAV) were measured. After completing the block procedure, all values were rerecorded at the 10th, 20th, and 30th minute. Patients with a successful block during the first 10th minutes were assigned to Group A. while patients with a successful block after the 10th minute were assigned to Group B.,RESULTS: Statistically significant differences were observed for all regional hemodynamic variables and PI after 10 minutes. When the regional hemodynamic data and PI were compared between the groups, differences were identified for PI, BF, PSV, EDV, and TAV. Within the measured parameters, EDV was the parameter showing the greatest proportional change.,CONCLUSIONS: Changes in EDV, especially RI and PI, provide more effective and objective results for the assessment of early regional block success.