Abstract
Background Despite attempts to solve the problem of flap monitoring, assessing the patency of
vascular anastomoses postoperatively remains challenging. In addition, experimental
data suggest that near-total vessel occlusion is necessary to produce significant
changes in clinical appearance or monitoring devices. We sought to develop an ultrasound-based
system that would provide definitive data on anastomotic function.
Methods A system was developed consisting of a resorbable marker made from poly-lactic-co-glycolic
acid (PLGA) implanted during the time of surgery coupled with ultrasound software
to detect the anastomotic site and perform Doppler flow analysis. Surgical procedures
consisting of microvascular free tissue transfer or femoral vessel cutdown were performed
followed by marker placement, closure, and ultrasound monitoring. Transient vascular
occlusion was produced via vessel-loop constriction. Permanent thrombosis was induced
via an Arduino-controlled system applying current to the vessel intima.
Results Four surgeries (one femoral vessel cutdown and three microvascular tissue transfer)
were successfully performed in Yorkshire swine. The markers were readily visualized
under ultrasound and provided a bounding area for Doppler analysis as well as orientation
guidance. Transient spasm and partial occlusion were detected based on changes in
Doppler data, while complete occlusion was evident as the total loss of color Doppler.
Conclusion In this preliminary report, we have conceptualized and developed a novel system that
enables the real-time visualization of vascular pedicle flow at the bedside using
Doppler ultrasound and a surgically implanted marker. In a large animal model, use
of the system allowed identification of the anastomosis, flow analysis, and real-time
detection of flow loss.
Keywords
free flap - microvascular reconstruction - flap monitoring - ultrasound - Doppler
