Deciphering the True Utility of the Implantable Doppler in Free Flap Monitoring
Edward I. Chang, MD, Amir Ibrahim, MD, Hong Zhang, PhD, Gregory P. Reece, MD, Peirong Yu, MD.
MD Anderson Cancer Center, Houston, TX, USA.
Purpose: The efficacy of implantable Dopplers (iD) remains an area of considerable debate. We aim to provide a comprehensive analysis of the utility of iD in free flap monitoring.
Methods: A retrospective review of all free flaps with an iD was performed between 2000-2012.
Results: Overall 446 flaps had an iD placed for monitoring, predominantly for head and neck reconstruction (n=370) with some for breast (n=54) and extremity (n=22) free flaps. The overwhelming majority were Cook-Swartz Dopplers (n=438) with 8 Flow couplers (Synovis). The Doppler was placed on the artery in 266 patients, the vein in 108 patients, and 72 monitored both the artery and vein. The overall sensitivity and specificity was 100% and 91.1% respectively. Subgroup analysis demonstrated significantly greater specificity for monitoring the artery than the vein (94.2% vs. 83.0%, p=0.004), but no benefit to monitoring both the artery and vein (p=0.26). Venous monitoring was significantly associated with a takeback (OR: 3.17, CI: 1.70-5.91; p=0.0003). There was a trend towards higher specificity with the Cook-Swarz Doppler (p=0.09). 284 flaps had a monitoring segment along with iD which significantly increased specificity (OR: 17.71, CI: 3.39-92.23; p=0.0006). Overall, 58 flaps (13%) required a return to the operating room, with 24 total flap losses (5.4%) which translated into a 58.6% salvage rate.
Conclusions: The use of iD has high sensitivity and specificity for free flaps in all regions, but is associated with higher specificity when monitoring the artery than the vein. Clinical exam is still the gold standard for flap monitoring.
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