Predictive Value of Perfusion Index for Assessing Success of Supraclavicular Brachial Plexus Block: A Prospective Observational Study

Abstract

Background: Perfusion index (PI) is a simple, objective, and noninvasive method for evaluating the success of brachial plexus blocks. There is only one study which assessed the time point at which the PI had the best predictive value. Aims: Of the 5 measured outcome variables (i.e.; PI at baseline, at 5 min, at 10 min, and at 15 min and PI ratio), we wanted to determine the one which had the best predictive value for block success. Materials and Methods: It is a prospective observational study done in a tertiary care teaching hospital. Sixty-nine patients of either sex, American Society of Anesthesiologists Physical Status I and II, between the ages of 18 and 65 years posted for elective upper limb surgery were included. Patients were given supraclavicular blocks with a peripheral nerve stimulator. PI recorded at baseline, 5 min, 10 min, and 15 min. A PI ratio was calculated. Sensory and motor blocks were assessed at 5-min intervals. Statistical Analysis: Descriptive analysis was applied by mean and standard deviation for quantitative variables and frequency and proportion for categorical variables. Receiver operating characteristic (ROC) curves were constructed. SPSS version 22 was used to detect an area under the ROCs (AUROC) curve and calculated to assess how good a test PI at 10 and 15 min and PI ratio are in predicting the outcome of a block. Results: The mean PI increased continuously from the baseline till 15 min in successful blocks, but in unsuccessful blocks, the rise was not seen. ROC curves showed an AUROC curve of 0.93 in case of PI at 15 min and 0.84 for PI ratio. Conclusion: We conclude that PI at 15 min is the best in our study and PI ratio is the next best as a predictor for evaluating success of supraclavicular blocks.

Keywords

• brachial block
• perfusion index
• predictive value