Answer:
Nicotine acts as a vasoconstrictor and studies in dogs and rabbits by Rao et al. have shown decreased blood flow in microvascular anastomoses but still with high patency rates. This may be due to nicotine's ability to inhibit platelet aggregation. Reus et al studied human smokers and non-smokers and found that while there did not appear to be a higher incidence of anastomotic complications between smokers and non-smokers, there was almost one-third greater wound healing complications, and smokers were twice as likely to require secondary procedures to acheive wound closure. Therefore, smoking appears to affect free flaps not at the anastomosis but rather at the interface of the flap to its bed which reflects the effects that smoking has on microcirculation and wound healing in general.