The Intra.Ox Near-Infrared Spectrometer Measures Variations in Flap Oxygenation That Correlate to Flap Necrosis in a Preclinical Rodent Model

Background: Mastectomy flap necrosis affects 7 to 40 percent of patients undergoing immediate breast reconstruction, with many cases resulting in infection and/or explantation. The Intra.Ox near-infrared spectrometer is a novel device that assesses tissue perfusion by measuring the interactions of light with oxygenated and deoxygenated hemoglobin. This handheld device facilitates serial flap perfusion assessment and may objectively identify at-risk tissues and guide evidence-based treatment algorithms. In this preliminary study, we hypothesized that the Intra.Ox spectrometer detects differences in tissue oxygenation that correlate to tissue necrosis. Methods: Dorsal, random-pattern flaps measuring 10 x 3 cm were raised in eight male Sprague-Dawley rats. Intraoperative tissue oxygen saturation was measured using Intra.Ox in 10 standardized locations. On postoperative day 7, the skin flaps were evaluated for full-thickness necrosis. Data were analyzed using the chi-square test and one-way analysis of variance. A receiver operating characteristic curve assessed the accuracy of intraoperative tissue oxygenation in predicting the risk of flap necrosis. Results: Tissue oxygen saturation exhibited a strong negative correlation to distance from the flap pedicle (r = -0.798). Oxygen saturation in tissue that developed necrosis averaged 32 percent, compared to 59 percent in tissues that did not (p < 0.001). The area under the receiver operating characteristic curve was 0.969. Post hoc oxygen saturation cutoffs with 100 percent specificity and sensitivity in predicting necrosis were identified at 46 percent and 54 percent, respectively. Conclusions: Intra.Ox detects significant differences in tissue oxygenation saturation that are associated with the risk for flap necrosis. This technology can be used to identify at-risk tissues and represents an avenue for research aimed at preventing flap necrosis.