The accuracy of an automatic free flap temperature monitor: a proof-of-concept study

Free flap monitoring is a topic of interest in microsurgery around the globe. Anastomosis thrombosis continues to be associated with a flap loss rate of 5–10%. Jones described several criteria for an ideal monitor in free flap surgery. Many monitoring methods are available; however, to our knowledge, none meet all of the criteria. We developed a device that registers comparative temperatures from the flap and other adjacent skin surfaces. When the temperature changes ± > 2 °C, it automatically sends a text message to the surgeon. The aim of this study is to determine the accuracy of the device in measuring changes in temperature. We simulated a flap and adjacent tissue by heating two different plastic containers of water. To simulate the event of thrombosis, we shut down the power to one heater. In time, the water lost heat dropping the temperature. The data were registered automatically, for later analysis with Excel and R-Studio. We calculated sensitivity and specificity for detecting drops in temperature. The prevalence of events was 18.75%, with a sensitivity of 7.99%. The specificity was 100%, with a positive predictive value of 100% and a negative predictive value of 82% for detecting simulated thrombosis events. The device accurately measured the temperature changes. The high specificity and positive predictive value validated the concept. This device is easy to assemble and easy to use. It meets 6 out of 7 of the Jones criteria, making it an attractive option for microsurgeons. The main advantage is that temperature can be monitored remotely and autonomously.