There may occasionally be venous congestion in a free flap lacking venous anastomosis blockage or other biological causes of decreased venous drainage (hematoma, seroma compressing the pedicle). The researchers advise applying a nitroglycerine patch in this situation very few hours before to the surgical investigation of the anastomosis in the crowded area of the flap. The surgical exploration could be avoided if the clinical characteristic of the flap improves quickly. The researchers emphasize that using a nitroglycerin patch should not be viewed as a treatment for free flap venous thrombosis but rather as a helpful tool that should only be employed when a surgeon is unsure of whether or not to review the anastomosis.