Mean Arterial Pressure (MAP) influence on free flap oxygen saturation (StO2) measured by Near-Infrared Spectroscopy

Background Free flap monitoring techniques still rely on gold standard methods such as skin color evaluation, temperature, and puncture tests that are time-consuming, discontinuous, and prone to human error. Near-Infrared Spectroscopy represents a continuous, non-invasive technique that aims to avoid subjective errors by detecting early stages of vascular compromise, providing enough time for successful salvage surgery. Methods This retrospective study includes 56 patients undergoing microvascular reconstruction and 24-hour NIRS monitoring. All other patients without detailed MAP charts were excluded. The NIRS system used was the HemoSphere-ForeSight by Edwards Lifesciences; this platform enabled the detection of StO2 values and their integration with real-time intra-arterial catheter-detected MAP values. Data were recorded by an adhesive sensor, chosen according to the height and width of the flap. Results Forty-seven (83%) patients showed a positive correlation between MAP and StO2 data (ρs > 0.450, p < 0.0001), validating the theory that MAP values positively correlate with flap perfusion, tissue oxygenation, and survival rate. Nine patients did not show a direct correlation between MAP and StO2 data; their values were influenced by vasopressors or psychophysical conditions during their admission to the Intensive Care Unit (ICU) after surgery. Conclusion Comparing MAP and StO2 values, their trend charts play a crucial role in flap monitoring, contributing to the best possible survival rate outcome and, if necessary, leading to micro-anastomosis checks and eventual flap salvage surgery. MAP data analysis should, indeed, be considered in future guidelines for free flap monitoring techniques.