Perfusion Index as an Indicator of Successful Ultrasound-Guided Supraclavicular Brachial Plexus Block: A Prospective Observational Study

Background and Aims: Ultrasound-guided supraclavicular brachial plexus block (SCB) is a preferred regional anaesthesia technique for upper limb surgeries because of its rapid onset, dense sensory and motor blockade. Conventional methods used to assess block success are subjective, time-consuming, and unsuitable in sedated or anaesthetised patients. Perfusion index (PI), derived from pulse oximetry, reflects changes in peripheral perfusion secondary to sympathetic blockade and may serve as an objective indicator of block success. The present study evaluates the effectiveness, accuracy, and reliability of perfusion index as an objective indicator of successful ultrasound-guided SCB. Methods: This prospective observational study included 66 adult patients (ASA physical status I–II) undergoing elective upper limb orthopaedic surgeries. Ultrasound-guided SCBs were performed using 0.5% Bupivacaine with Fentanyl. Perfusion index was recorded at baseline and at regular intervals up to 20 minutes following block administration. Sensory and motor block characteristics were assessed concurrently using standard clinical methods. Statistical analysis included descriptive statistics and receiver operating characteristic (ROC) curve analysis. Results: A statistically significant increase in perfusion index was observed following block administration. Mean PI increased from 1.67 ± 0.60 at baseline to a peak of 12.17 ± 0.60 at 12 minutes. The rise in PI preceded the onset of sensory and motor blockade. Sensory block onset occurred at a mean of 8 minutes, while motor block onset occurred at 9 minutes. Haemodynamic parameters remained stable throughout the study period. Conclusion: Perfusion index is a simple, non-invasive, and reliable real-time indicator of successful ultrasound-guided SCB. Its early rise correlates well with clinical block onset and may be effectively utilised for objective assessment of block success in routine anaesthesia practice.