Effects of perivascular botulinum toxin-A application on vascular smooth muscle and flap viability in the rat

Botulinum toxin-A (BTX) has become a widely used pharmacologic agent for esthetic surgeons and those who treat neuromuscular and gastrointestinal conditions. Until recently, there has been very little basic science research related to how this powerful agent may be useful when applied to vessels. The mechanism of action of this agent suggests that it may be useful in treating vasospastic conditions and ischemic tissues. We present data from experiments conducted to establish whether perivascular application of BTX decreases skin flap necrosis in an island pedicle skin flap in the rat.Using an ischemic ventral pedicled island cutaneous flap model, 30 adult Sprague-Dawley rats were divided into groups and treated with BTX, papaverine, or saline to the intact vascular pedicle to determine the percentage of tissue necrosis and ischemia. Flaps were elevated, and the pedicle treated with 1 of the 3 agents, and the flaps reinset. Analysis of the percentage of flap necrosis and areas of flap ischemia were evaluated on postoperative day 4.There were no differences in area of flap necrosis between BTX-, papaverine-, and saline-treated animal groups. There was a significant decrease in flap ischemia in the papaverine-treated group compared with both BTX and saline (P < 0.01). When necrotic and ischemic areas were combined, papaverine again showed a protective effect when compared with the BTX- and saline-treated groups (P < 0.04).In our ischemic pedicled island cutaneous flap model, papaverine showed the greatest protective effect against skin flap ischemia compared with BTX and saline. However, our data suggest that BTX may provide a protective effect after the first several days following flap elevation.