BACKGROUND: Free tissue transfer is used widely for reconstruction of complex defects throughout the body. The most common cause for free flap failure remains vascular thrombosis. Currently, there exists no animal model for anastomotic vasospasm. Botulinum toxin type A has been successfully used to treat vasospasm in Raynaud's phenomenon. A blinded, vasospasm animal model was designed to determine its ability to prevent anastomotic thrombosis. METHODS: Ten Sprague-Dawley-derived rats were pretreated with botulinum toxin type A subcutaneously to a randomly determined femoral vessel. Animals acted as their own controls, receiving saline to the contralateral limb. Five days postoperatively, femoral vessels were measured to determine the effect of neuromuscular blockade on diameter. Vessels were then divided and reanastomosed. Animals were subjected to a systemic treatment with a peripheral vasoconstrictor, phenylephrine, and a lower extremity thermic challenge in an ice bath. Vessel patency was recorded before cold challenge and 1 hour after. RESULTS: Vessel diameter was consistently larger in all neuromuscularly blocked vessels. The botulinum toxin type A-treated arterial average was significantly larger than the matched control average, and the venous average was significantly larger than the matched control average. Difficulty of anastomosis and time of suturing were significantly less in the pretreated botulinum toxin type A group. Patency was maintained in 100 percent of vessels treated with botulinum toxin type A and in 44 percent of saline-treated vessels at 1 hour after vasospastic challenge. CONCLUSIONS: Botulinum toxin type A was successful in preventing thrombosis within this model. Its ability to decrease vasospasm and thrombosis may have applications for improving free flap survival in select patients.
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