Tranexamic Acid Concentration and Flap Survival in Rats.

BACKGROUND: Random-pattern skin flaps are prone to distal necrosis, a major challenge in reconstructive surgery. Tranexamic acid (TXA) reduces perioperative bleeding, but its impact on flap viability remains controversial. OBJECTIVES: To investigate the concentration-dependent effects of local TXA application on random-pattern flap survival, with and without surgical delay, in the McFarlane dorsal rat flap model. METHODS: Sixty-four female Wistar albino rats were randomized into eight groups (n=8): control, TXA 10, 30, and 100 mg/mL, delayed control, and delayed TXA at the same concentrations. A 3×9 cm caudal-based dorsal flap was elevated and 1 mL of saline or TXA was administered locally before closure. Flap necrosis was quantified using ImageJ software. Two-way ANOVA assessed the independent effects of delay and TXA concentration; subgroup analyses used one-way ANOVA with Tukey HSD (non-delayed) and Kruskal-Wallis with Dunn's test (delayed). RESULTS: High-concentration TXA (100 mg/mL) significantly increased necrosis in non-delayed flaps (40.39% ± 7.41%, p = 0.016 vs. control). Delayed flaps showed markedly reduced necrosis across all groups (delayed control: 1.00% ± 1.45%, p < 0.001). No significant differences were observed among delayed subgroups regardless of TXA concentration. Two-way ANOVA identified the delay procedure as the dominant main effect (F(1,56) = 665.97, p < 0.001, partial η2 = 0.922). CONCLUSIONS: High-concentration local TXA impairs random-pattern flap survival, while low-concentration TXA (10 mg/mL) appears well tolerated. The surgical delay procedure markedly reduces TXA-associated necrosis risk across all concentrations. Careful concentration selection is recommended when TXA is used in cutaneous flap surgery.