Introduction: Nerve block success is commonly assessed through a variety of techniques, including testing sensations for temperature over the relevant dermatomes and evaluating pain response (e.g., pin-prick). This meta-analysis aimed to investigate the diagnostic efficacy of Perfusion Index (PI) in identifying failed nerve blocks in patients undergoing upper extremity surgery.
Evidence acquisition: A literature search was conducted using four databases, including Medline (OVID), Google Scholar, EMBASE (OVID), and the Cochrane Database of Systematic Reviews, to identify relevant studies from the inception of the databases until June 2023. The main purpose of this study was to evaluate the diagnostic accuracy of PI values and PI ratios in identifying failed nerve blocks.
Evidence synthesis: Nine studies (published from 2006 to 2022) involving 533 participants (age ranged from 31 to 52 years) were included. The failure rate of nerve blocks ranged from 0% to 18.9%. Pooled results demonstrated promising diagnostic accuracy when using PI values as a predictor of failed nerve block (sensitivity, 77%; specificity, 88.1%; diagnostic odds ratio [DOR], 30.585). Additionally, the analysis of PI ratios as a diagnostic measure showed even higher diagnostic efficacy than using PI values alone, with a sensitivity of 82.9%, specificity of 93.1%, and DOR of 74.543.
Conclusions: Our meta-analysis confirmed that the PI values and ratios are promising objective predictors of nerve block failure. The simplicity of these techniques supports their feasibility for routine clinical practice. Further studies focusing on different patient populations, such as pregnant women or the elderly, are needed to validate and expand upon our findings.