Assessment of the oxygen perfusion index as a predictor of the degree of axillary anesthetic block of the brachial plexus

Abstract

Introduction: Oxygen perfusion index is measured with a special pulse oximeter that provides objective data resulting from changes in limb perfusion. This technique can be very practical for evaluating the effectiveness of peripheral nerve blocks, considering the vasodilation they produce. Objective: Determine the association between the oxygen perfusion index values and the degree of sensory-motor block achieved after an axillary block. Methodology: Observational, descriptive and longitudinal study in 32 patients in whom axillary brachial plexus blocks were performed. The Oxygen Perfusion Index was measured at 5, 10 and 15 minutes after the axillary block and the IP ratio was calculated. The degrees of sensory and motor blockade were recorded. Results: 93.8% of patients reached an adequate level of sensory and motor block. The perfusion index values measured on the blocked side were: at baseline =3.44, at 5 minutes = 7.9, at 10 minutes = 10.03 and at 15 minutes = 11.18. The calculated IP ratio relationships were: at the beginning = 1, at 5 minutes = 2.3, at 10 minutes = 2.9 and at 15 minutes = 3.25 Conclusion: The perfusion index and the IP ratio provide important data to evaluate early the success of the axillary brachial plexus block. A progressive increase in IP and an increase in the IP ratio could be considered good predictors of success of the axillary brachial plexus block.