Intraoperative Near-infrared Spectroscopy Correlates with Skin Flap Necrosis: A Prospective Cohort Study

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Abstract
Background: Skin flap necrosis (SFN) is a morbid complication that is disfiguring, leads to acute and chronic wound issues, often requires further surgery, and can delay adjuvant chemotherapy. Although most surgeons rely on the clinical examination, near-infrared (NIR) spectroscopy can extrapolate tissue oxygenation and may serve as an important tool to assess flap perfusion intraoperatively. This cohort study was undertaken to evaluate the capacity of NIR spectroscopy to detect clinically relevant differences in tissue perfusion intraoperatively. Methods: Patients undergoing oncologic resection of breast cancer, sarcomas, and cutaneous tumors requiring flap reconstruction (local, regional, or free) between January 2018 and January 2019 were analyzed in this study. Clinicians were blinded to device tissue oxygen saturation (StO2) measurements taken intraoperatively after closure and at follow-up appointments in the first 30 days. Measurements were categorized as (1) control areas not affected by the procedure, (2) areas at risk, and (3) areas of necrosis. These areas were retrospectively demarcated by 2 blinded assessors on follow-up images and transposed onto anatomically correlated intraoperative StO2 measurements. Mean StO2 values were compared using a single-sample t test and analysis of variance (ANOVA) to determine differences in oxygenation. Results: Forty-two patients were enrolled, and 51 images were included in the analysis. Oncologic procedures were predominantly breast (22), postextirpative melanoma (13), and sarcoma (3) reconstructions. Flap reconstruction involved 30 regional skin flaps, 3 pedicled flaps, and 3 free flaps. Nine patients (20.9%) and 11 surgical sites developed SFN. Mean intraoperative StO2 measurements for control areas, areas at risk, and areas of SFN were 74.9%, 71.1%, and 58.3%, respectively. Relative to control areas, mean intraoperative StO2 measurements were lower by 17.5% (P = 0.01) in ultimate areas of SFN and in areas at risk by 5.8% (P = 0.003). Relative to areas at risk, mean StO2 measurements from areas of ultimate SFN were lower by 8.3% (P = 0.04). Conclusion: These preliminary data suggest that measuring skin flap tissue oxygenation intraoperatively, with NIR spectroscopy, can differentiate objective variations in perfusion that are associated with clinical outcomes.

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