Using blood glucose and lactate levels for early detection of venous congestion following a free flap procedure for lower extremity open fractures

Purpose Gustilo–Anderson type IIIB and IIIC open fractures of the lower extremities require reconstruction of extensively injured soft tissues using a free flap; however, impaired blood flow through the flap is an early postoperative complication. To detect flap congestion due to venous thrombosis, blood glucose and lactate level measurements within the flap are taken to determine variations in these levels. We aimed to detect early-stage venous congestion and to perform salvage operations. Methods We included 22 limbs with lower leg and foot open fractures, with fracture sites covered using a free flap. A pinprick test was used to measure blood glucose and lactate levels. Results Of 7 and 15 congested and non-congested limbs, respectively, the 7 congested limbs had a mean flap blood glucose level immediately before salvage surgery of 3.8 ± 2.0 (7.4–1.8) mmol/L. The ratio to blood glucose levels in healthy fingertips was 0.6 ± 0.2 (0.8–0.3). Lactate levels increased to 13.3 ± 5.1 (9.4–22.8) mmol/L. The ratio of blood glucose levels in congested flaps and in healthy fingertips was significantly lower than that in non-congested flaps and in healthy fingertips ( p = 0.0016). Lactate levels were significantly higher in patients with congestion ( p = 0.0013). Salvage surgery was performed, thrombi were removed, and six limb flaps were viable. Conclusion Flap blood glucose and lactate levels provide a quantitative method of evaluating blood flow and detecting flow abnormalities postoperatively, and are useful in detecting early congestion due to venous thrombosis.