The effects of botulinum toxin A on the survival of a random cutaneous flap

Background: Although interest in flap surgery has increased, a satisfactory research study on supportive drugs or methods for flap surgery has not been seen in the literature thus far. Despite several studies using botulinum toxin A for flap surgery being reported, their efforts to clarify the mechanisms are not sufficient. Therefore, the authors have studied the effect of botulinum toxin A on random cutaneous flap survival in a rat model under the hypothesis that it affects the microvascular system. Method: Thirty 10-week-old Sprague-Dawley rats were divided into experimental (n = 15) and control groups (n = 15). The experimental group used 1.5 IU (International Units) of botulinum toxin A, and the control group used normal saline. A 2 x 8 cm random cutaneous flap was designed on the rats and then elevated. Normal saline (0.05 cc) and 1.5 IU of botulinum toxin A (0.05 cc) (Botox, Allergan, USA) were injected into the dermis layer of the central portion in the proximal one-third of the flap. Gross photographs were taken at days 1, 3, 5 and 7 after the operation. Laser-induced fluorescein fluoroscopy was performed on postoperative day 7 and tissues were retrieved for histological analysis. In addition, reverse transcriptase polymerase chain reaction (RT-PCR) was carried out for quantitative analysis. Results: Gross photos and laser-induced fluorescein fluoroscopy reveal the survival rate of the Botox group was 8.3% higher than the control. In the histologic study, the diameter of vessels is larger and the number of immature vessels is more in the Botox group. The result of RT-PCR shows increased expression of VEGF (vascular endothelial growth factor), CD 31 (PECAM1, platelet/endothelial cell adhesion molecule) and iNOS (inducible nitric oxide synthase), which are considered to be related to vasodilation and endothelial proliferation. Conclusion: Our results suggest that botulinum toxin A increases the survival rate of random cutaneous flaps by means of selective suppression of sympathetic neurons of the cutaneous microcirculation system. (C) 2009 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.