Application of a Flash Glucose Monitoring System for the Evaluation of Blood Flow in Free Flaps

The key to salvaging free flaps following postoperative hemodynamic compromise is early detection and prompt intervention. Although clinical examinations, such as observing flap color, are often used for monitoring, they are subjective and have limited accuracy. This underscores the need for a low-cost, simple, and objective alternative. A potential solution is the use of a flash glucose monitoring (FGM) system for flap monitoring. In this study, we retrospectively investigated whether FGM is beneficial for monitoring flap blood flow.

We retrospectively evaluated the medical records of patients who underwent breast reconstruction using a deep inferior epigastric perforator flap transfer. An FGM sensor was applied to each monitoring flap, and interstitial fluid glucose (IFG) levels were measured regularly during a 7-day postoperative period.

A total of 37 flaps were evaluated. Five flaps required surgical revision due to hemodynamic compromise; 1, in a patient with diabetes, completely failed, whereas 3 were successfully salvaged. The remaining flap developed arterial occlusion on the sixth day and was partially necrotic. In all cases requiring revision, except for the patient with diabetes, IFG levels dropped to less than 40 mg/dL before any clinical examination changes were observed. The IFG cutoff value, defined as less than 40 mg/dL, was calculated to have 100% sensitivity and 91% specificity within 48 hours postoperatively, with a negative predictive value of 100%.

Measuring IFG using FGM is a noncontact, simple, and low-cost method. This method can provide a highly effective screening method for human and economic resource use.