Relationship Between Pulse Oximetry Perfusion Index and Anesthetic Brachial Plexus Block for Upper Limb Surgery in Adults.

Introduction Brachial plexus block is widely used as a regional anesthetic technique in upper extremity surgery. However, its routine assessment using clinical criteria, such as sensation and motor function, is limited by the subjective nature of the assessment and the dependence on the patient. The perfusion index, obtained by pulse oximetry, could be an objective, early method of predicting block success. Objective To establish the relationship between the increase in perfusion index and the success of anesthetic brachial plexus block in adult patients undergoing upper extremity surgery. Methods An observational, descriptive, cross-sectional study was conducted with 82 adult patients undergoing upper extremity surgery with anesthetic brachial plexus block using four different approaches. Block success was assessed using the Modified Bromage Scale at five, 10, and 15 minutes. The perfusion index was measured with pulse oximetry before the block and at the same intervals afterward. Odds ratios with Haldane-Anscombe correction and the Mantel-Haenszel test were used to adjust for confounders. Results A progressive increase in the perfusion index was observed at five, 10, and 15 minutes after the block. A value less than 3 had a negative predictive value of 100% for predicting anesthetic failure. At 10 minutes, a mean perfusion index of 4.96, a 6.2-fold increase over baseline, was associated with successful blockade, reaching a success rate of 73.2% at 15 minutes. Conclusions The perfusion index proved to be an objective and sensitive tool for predicting the success of brachial plexus blockade, allowing for earlier and more accurate assessment than traditional clinical signs. Its implementation could optimize anesthetic decision-making and reduce response times to ineffective blocks.