DIRECT VISUALIZATION AND MEASUREMENT OF MICROSURGICALLY INDUCED THROMBOEMBOLISM

A common cause of free flap and replant failure is thrombotic occlusio n of the anastomosed pedicle vessel(s). Clinical observations and subs equent experimental studies showed that platelet emboli generated at t he arterial anastomosis caused significant alterations in the downstre am microcirculation. To study both the thrombogenic arterial (anastomo sis) site and the downstream microcirculation, we developed an animal model (the isolated rat cremaster) in which we could directly view and quantitatively analyze thrombus formation and the appearance of embol i in the downstream microcirculation. Using this model we studied the effect that reducing blood flow across the arterial anastomotic site h ad on thrombus formation at the anastomotic site and the appearance of emboli in the downstream microcirculation. In 40 male Sprague-Dawley rats we found that reducing blood flow velocity to approximately half of normal during reperfusion nearly eliminated emboli appearing in the downstream microcirculation compared with controls, 43.9 +/- 31.5 vs. 259.5 +/- 117.8 emboli, respectively. We also found that the same low flow had no effect on thrombus size at the pedicle artery injury site yet significantly decreased the rate at which thrombus formation occu rred (time to maximum thrombus size; low flow = 25.3 +/- 8 minutes, no rmal flow = 6.6 +/- 3 minutes). From these studies we conclude that re ducing pedicle artery blood flow in our rat model during reperfusion c an protect the downstream microcirculation from platelet emboli-induce d injury; however, the same reduction in flow does not affect thrombus formation in the pedicle artery. Further studies using direct observa tion/measurement techniques are needed for a better understanding of t he mechanisms regulating free flap and replant failure.