Buried free flaps which are not accessible for standard monitoring techniques such as clinical or hand-held Doppler examination are often monitored using an implantable Doppler device. This has the advantages of simple application and a continuous monitoring signal, but suffers from a relatively high rate of false positive signal loss. We have found that color duplex ultrasonography is a rapid and non-invasive technique that can be used on an emergent basis to evaluate perfusion of a buried free flap. This is most useful when the implantable Doppler signal of a buried free flap is lost, and there is a low suspicion for microvascular anastomotic thrombosis.

We reviewed our institution’s experience with buried free flaps that were monitored using an implantable Doppler device. During the past three-year period, 20 such cases were performed. In eight of these cases (40%), the implantable Doppler signal was lost or substantially changed post-operatively. Due to a low index of suspicion for microvascular flap failure, only three of these eight cases were returned to the operating room for exploration, and only one had a true flap problem. All 20 flaps survived. Overall, seven of the eight implantable Doppler signal changes (88%) were false positive results. This high false positive rate, and thus low specificity, has lead to our reluctance to return to the operating room based solely on the loss of an implantable Doppler signal.

Recently, we have employed emergent color duplex ultrasound to conclusively demonstrate viability of a buried free flap which had lost its implantable Doppler signal. This additional test averted a negative surgical exploration. Duplex ultrasound examination of the buried flap revealed arterial and venous flow both within the flap and recipient vessels, confirming flap viability. Based on this experience, we suggest some guidelines for the use of the implantable Doppler and the possible uses of color duplex ultrasound, instead of surgical exploration, for evaluation of loss or change of implantable Doppler signals in buried free flaps.