Inhibitory effects of low-level laser therapy on skin-flap survival in a rat model

BACKGROUND: Although several studies have demonstrated the effects of low-level laser therapy (LLLT) on skin flap viability, the role of higher doses has been poorly investigated. OBJECTIVE: To investigate the inhibitory effect of the LLLT (lambda = 670 nm) on the viability of random skin flaps in a rat model using an irradiation energy of 2.79 J at each point. METHODS: Sixteen Wistar rats were randomly assigned into two groups: sham laser irradiation (n = 8); and active laser irradiation (n = 8). Animals in the active laser irradiation group were irradiated with a 670 nm diode laser with an energy of 2.79 J/point, a power output 30 mW, a beam area of 0.028 cm(2), an energy density of 100 J/cm(2), an irradiance of 1.07 W/cm(2) for 93 s/point. Irradiation was performed in 12 points in the cranial skin flap portion. The total energy irradiated on the tissue was 33.48 J. The necrotic area was evaluated on postoperative day 7. RESULTS : The sham laser irradiation group presented a mean (+/- SD) necrotic area of 47.96 +/- 3.81%, whereas the active laser irradiation group presented 62.24 +/- 7.28%. There was a significant difference in skin-flap necrosis areas between groups (P = 0.0002). CONCLUSION: LLLT ( lambda = 670 nm) increased the necrotic area of random skin flaps in rats when irradiated with an energy of 2.79 J (100 J/cm(2)).