The authors developed an animal model to study anastomotic vasospasm. The goal of the study was to determine if the pretreatment of blood vessels at the site of the planned microvascular anastomosis could increase vessel size, improve anastomosis ease, and decrease the incidence of thrombosis.
Sprague-Dawley rats were pretreated with a femoral vessel perivascular injection of Botulinum Toxin A and saline control in the contralateral limb. Five days postoperatively, the vessels were measured, divided, and reanastomosed. The animals were then subjected to peripheral vasoconstriction by exposure to hypothermia and systemic phenylephrine. The results revealed that the botulinum toxin type A treated arteries and veins were consistently larger than their matched controls and their anastomosis easier. Furthermore, anastomotic patency was 100% in the botulinum group versus only 44% in the control.
In skilled hands, microvascular transfer carries very high success rates. However, the most common cause for failure is anastomotic thrombosis with precipitous drop in salvage rates. This study proposes a novel intervention to increase vessel diameter in an effort to improve anastomosis ease and combat postoperative vasospasm in a rat model. There are some obvious limitations to this study that should be accounted for prior to application to the clinical setting. These include 1) is the same effect observed in humans, 2) what is the best method for reliable drug delivery that avoids vessel injury, and 3) is this intervention even warranted with such high microvascular success rates? Another consideration is that neuromuscular blockade may not be useful for urgent procedures such as replantation/revascularization given Botulinum Toxin A’s several day delayed onset of action. However, select procedures that are particularly prone to vasospasm (toe transfer in children) or patients with risk factors for thrombosis (smoking, diabetes, renal failure) may be good candidates for neuromuscular blockade prior to microvascular tissue transfer.