Monitoring buried free flaps: limitations of the implantable Doppler and use of color duplex sonography as a confirmatory test.

Background: Postoperative monitoring of free flaps is important to minimize the risk of flap failure, but monitoring buried free flaps is difficult because the standard methods of clinical examination and surface Doppler monitoring are not possible. Buried free flaps are often monitored using an implantable 20-MHz ultrasonic Doppler probe.

Methods: The authors conducted a retrospective clinical study of buried free flaps to assess the reliability of the implantable Doppler probe in postoperative monitoring of free flaps.

Results: During the 38-month study period, 956 free flap operations were performed at the authors' institution. Twenty (2.1 percent) of these cases involved completely buried free flaps in which an implantable Doppler probe was used for flap monitoring. Implantable Doppler probe monitoring had a 100 percent sensitivity rate in detecting loss of flap perfusion, making it a good screening test for free flap viability. However, it suffered from a high false-positive rate of 88 percent, which resulted in a high proportion of subsequent negative surgical explorations. In one case, color duplex sonography, a rapid and noninvasive test, revealed that the loss of signal from the implantable Doppler probe was a false-positive result.

Conclusions: The implantable Doppler probe is a sensitive method for postoperative monitoring of free flaps but is prone to false-positive signals. The use of color duplex sonography to confirm implantable Doppler probe findings may avert unnecessary surgical exploration, thereby improving postoperative monitoring of free flaps.