To Predict the Success of Supraclavicular Brachial Plexus Block by Using Perfusion Index as an Indicator: A Randomised Prospective Study

Background: Peripheral nerve blocks provide longer and localised pain relief. Classical methods to confirm motor and sensory block success are subjective, tedious, and require patient compliance. The perfusion index is a simple and objective method used with the help of a pulse oximeter. Aims: We aimed to compare the perfusion index in blocked and unblocked limbs and assess the adequacy of the perfusion index in successful and failed supraclavicular blocks. Methods: The study included seventy patients posted for upper limb surgery under an ultrasound-guided (USG) supraclavicular block using 30 ml of local anaesthetic (injection of 15 ml of 0.5% bupivacaine and injection of 15 ml of 2% lignocaine). The perfusion index (PI) in the index finger of both the blocked and unblocked limbs was measured using a pulse oximeter at baseline, 5, 10, 20, and 30 minutes after local injection. The PI Ratio was assessed at 5 and 10 minutes. Results: Both PI and PI Ratios in the blocked limb were higher than the baseline compared to the unblocked limb. A PI value >3.5 is an optimal cut-off for predicting the successful USG-guided supraclavicular block. Conclusion: Perfusion Index derived from pulse oximetry used as an early predictor for the supraclavicular nerve block success.