Evaluation of Perfusion Index in Predicting Successful Supraclavicular Brachial Plexus Block for Upper Limb Surgeries: An Observational Study

Introduction: Sensory and motor function assessments to evaluate success of peripheral nerve block are time consuming subjective means. Present study aimed to evaluate perfusion index (PI), as an objective indicator of success of supraclavicular blockade. Material and Methods: This Observational study included 90 patients aged 18 to 60 years, ASA grade I &II, undergoing elective unilateral upper limb surgery under brachial plexus block, performed using ultrasonography. All patients were continuously monitored for PI using pulse oximeter. Simultaneously, block was also assessed for sensory and motor blockade at every 5 minutes interval. Block was declared as failed, if there was no sensory or motor blockade after 30 minutes of injecting LA mixture. The PI ratio was calculated as the ratio between the PI at 10 min post injection and the PI at baseline. Results: Block was successful in 90% cases. In blocked arm an increase in PI was observed compared to unblocked arm from 5 to 20 min post anesthesia (p<0.01). A successful block was paralleled by an increase in PI compared to unsuccessful block (p<0.001). The PI ratio was also higher in successful block as compared to unsuccessful block (p<0.001). For identifying successful block, Area under ROC curve for both PI and PI ratio at 10 minutes after the anaesthetic injection was 1.000. At the optimal cutoff point of PI>3.48, and PI ratio of >1.77, a Sensitivity and Specicity of 100% was achieved. Conclusion: Perfusion Index and Perfusion Index ratio is a useful, simple, early and objective assessment tool for evaluation of success and failure of supraclavicular nerve block.