Clinical Validation of Near Infrared Spectroscopy for Free Flap Monitoring and Establishing Intervention Thresholds Using the Masimo O3 Device

Free flap failure secondary to microvascular thrombosis remains a significant complication in reconstructive surgery, and timely detection of vascular compromise is critical to maximize salvage. This retrospective cohort study evaluated 932 free flaps performed over a four-year period at a tertiary center, of which 302 were monitored postoperatively using Masimo's O3® Regional Oximetry system's near-infrared spectroscopy (NIRS) device in addition to standard clinical assessment. Primary outcomes included re-exploration, complete flap failure, and salvage following take-back. The overall re-exploration rate was 7.9%. Flaps monitored with NIRS demonstrated higher salvage rates following re-exploration and lower complete flap failure rates compared with clinical monitoring alone. Use of NIRS during the index reconstruction was independently associated with improved flap survival. Receiver operating characteristic analysis demonstrated good discriminative performance of NIRS trend changes for predicting flap compromise, and a 22.5% reduction in regional oxygen saturation was identified as the optimal threshold for detecting early vascular compromise. These findings support the use of adjunctive NIRS surveillance as a reliable modality for postoperative free flap monitoring and provide an objective threshold to assist clinical decision-making.