Comparison of flap and contralateral donor site tissue perfusion for flap monitoring in microvascular head and neck reconstruction - a retrospective study.

Introduction: Postoperative flap monitoring in microvascular head and neck reconstruction based solely on flap tissue perfusion measurements relative to predefined thresholds may be influenced by systemic tissue perfusion alterations. This study compared flap and contralateral donor site tissue perfusion and evaluated the utility of the flap-to-donor site ratio in detecting vascular flap compromise. Materials & methods: Tissue perfusion measured with the O2C analysis system at a tissue depth of 3 mm at 0, 12, 24, 36, and 48 h postoperatively was retrospectively analyzed in 62 patients who underwent head and neck reconstruction with a fasciocutaneous free flap (FFF) (radial free forearm flap) or a perforator free flap (PFF) (anterolateral thigh flap or fibula free flap) between 2020 and 2022. Flap and contralateral donor site tissue perfusion parameters (blood flow, hemoglobin concentration, and hemoglobin oxygen saturation) were compared, and flap-to-donor site ratio cut-off values indicating vascular flap compromise, based on the minimum (blood flow and hemoglobin oxygen saturation) or maximum (hemoglobin concentration) value of all 5 measurement timepoints, were determined. Results: Blood flow, hemoglobin concentration, and hemoglobin oxygen saturation were in general higher at the flap than the donor site (p < 0.05). Cut-off values for the flap-to-donor site ratio indicating vascular flap compromise were as follows for FFFs and PFFs, respectively: <1.063 and <0.224 for blood flow, >1.792 and >1.597 for hemoglobin concentration, and <0.673 and <0.199 for hemoglobin oxygen saturation (sensitivity all 100 % [confidence interval (CI) range 2.5-100.0 %]; specificity all >65 % [CI range 49.0-100.0 %]). Conclusion: The postoperative course of tissue perfusion differs between flap and contralateral donor sites in FFFs and PFFs. The flap-to-donor site ratio could be used to detect vascular flap compromise in microvascular head and neck reconstruction, with further studies needed to confirm the determined cut-off values for the flap-to-donor site ratio indicating vascular flap compromise.