Correlation between systemic blood pressure and free flap perfusion: A photoplethysmography study

Background: Microvascular tissue transfer is the method of choice for oncological and trauma reconstruction. Successful free tissue transfer requires technical expertise and management of patients and surgery related factors. However, whether systemic blood pressure (SBP) affects perfusion of free flaps remains unclear. Methods: Photoplethysmography (PPG) is a relatively new technology used in many wearable medical devices to measure blood pressure and heart rate. It is a simple optical technique that detects changes in blood volume within the underlying microvascular bed of tissue. This study aimed to evaluate the relationship between systemic blood pressure (SBP) and free flap perfusion using PPG. Results: Twenty-five patients who underwent free flap reconstruction for head-neck cancers or traumatic soft tissue defects were enrolled in this study. All patients were clinically normotensive without needing postoperative vasopressors. The study did not find a statistically significant correlation between systolic or mean blood pressure and free flap perfusion. Conclusion: Beyond a critical threshold of mean arterial pressure (MAP), free flap perfusion is not directly correlated with blood pressure. In clinically normovolemic patients, elevations of BP above MAP ~65 mm Hg did not enhance flap perfusion.