Blood Gaseous Changes in Patients Undergoing a Dangling Protocol after Lower Leg Free Flap Reconstruction

Abstract Patients undergoing free flap reconstruction of the lower extremity are typically started on a postoperative dangling protocol. This protocol gradually exposes the free flap to increasing gravitational forces. This study aimed to quantify the internal blood gaseous changes within the free flap over the course of a dangling protocol. Three patients who underwent lower leg free flap reconstruction were included. Capillary blood gas samples were taken daily for six consecutive days (postoperative days 7–12) from the free flap before and after dangling, as well as from the contralateral, “healthy” leg. Mean blood gas curves were created for partial pressure of oxygen (pO2), partial pressure of carbon dioxide (pCO2), and potential hydrogen (pH) levels. A paired t-test was used to compare mean blood gas values. Baseline mean pO2 was decreased (p = 0.002), pCO2 was increased (p < 0.001), and pH levels were lowered (p = 0.021) at the site of the free flap, compared with the contralateral, “healthy” leg. Mean pre- and post-dangling pO2 levels were not significantly different (p = 0.380). Mean pCO2 levels significantly increased after dangling (p = 0.028). Over the course of the dangling protocol, mean pO2, pCO2, and pH curves remained considerably stable. Blood samples taken from the free flap show that the mean pO2 and pH levels are lower, and pCO2 levels are higher compared with the contralateral, “healthy” leg. Furthermore, an increase in dangling duration does not cause significant changes in blood gas values. This raises the question of whether the current form of the dangling protocol accomplishes its intended goal of gradually challenging the flap.