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

Abstract

L ow-level laser therapy (LLLT) has been investigated as a noninvasive and sterile alternative for improvement of microcirculation and, consequently, increasing the viability of ischemic skin flaps (1-13). It is known as an athermal treatment modality due to the relatively low doses and low powers that are unable to promote any change in tissue temperature.Several studies have demonstrated the efficacy of LLLT in accelerating the healing process, the promotion of analgesia, and an increase in microcirculation and capillarity (5,6,11). Skin flaps may progress to necrosis due to intrinsic and extrinsic factors that compromise local microcirculation (14); LLLT has been used to increase skin flap viability.Several parameters must be considered when applying LLLT. These include wavelength, output power, emission mode, spot size and shape of the beam, irradiance, energy density, irradiation time, application technique, energy per point and total energy delivered to the tissue (9). Although all of these parameters appear to be important in modulating physiological and therapeutic responses, wavelength, energy and application time have been suggested by the World Association for Laser Therapy (WALT) as key factors (15). Both infrared (1,2,4,6,11) and red (5,8-10) lasers have been used to increase skin flap viability. Despite the positive results demonstrated with both types of lasers, some studies suggest that lasers with wavelengths in the red spectrum are more effective at increasing skin flap viability (16). The energy used in previous studies assessing the effects of red lasers in dorsal random skin flaps ranged from 0.06 J to 1.44 J per point (3,9,5,10,12). Energies <0.3 J were ineffective (3,9), whereas energies from 0.3 J to 1.44 J (5,10,12) increased skin flap survival. According to Arndt-Schulz' law, very low doses are ineffective, and intense stimuli may result in negative responses in tissue physiology. It appears that energies from 0.3 J to 1.44 J are in the therapeutic window for improving skin flap survival. Nevertheless, to the best of our knowledge, no studies have demonstrated an inhibitory effect on skin flap survival using higher energies of LLLT. Thus, the present study aimed to test an energy greater than those proven to be effective. Accordingly, the objective of the present study was to investigate the inhibitory effect of LLLT (λ=670 nm) on the viability of random skin flaps in rats when irradiated with 2.79 J of energy at each point. METHODS Study designThe present study was approved by the Ethics and Research Committee of Paulista University (São Paulo, Brazil) under protocol number CEP 008/11.The present analysis was an experimental, interventional, randomized study with a blinded assessor. All animals received humane care in strict compliance with the Ethical Guidelines for Animal Experiments, Council for International Organizations of Medical Sciences, Standards of Brazilian Science Society for Laboratory Animals, and current national legislation on Procedures for the Scientific Use of Anima...

A Comparison of Three Methods for the Analysis of Skin Flap Viability: Reliability and Validity

“…[6][7][8][9][10][11][12] The evaluation of the results of interventions performed in experimental models of skin grafts and flaps include some methods, such as gene expression analysis, 10,13 protein expression analysis, 11,12,[14][15][16] assessment of histological changes, 11,12,15 and the percentage of viable tissue. 6,7,17,18 The latter is widely used for being fast, inexpensive, and efficient. Three methods can be used to evaluate the percentage of viable tissue: weight of paper template (WPT), 17,18 paper template area (PTA), 19 and photographic area (PA).…”

“…6,7,17,18 The latter is widely used for being fast, inexpensive, and efficient. Three methods can be used to evaluate the percentage of viable tissue: weight of paper template (WPT), 17,18 paper template area (PTA), 19 and photographic area (PA). 11,14,16 The paper template method was first described by Sasaki and Pang in 1980 20 and since then it has been used to evaluate the percentage of flap necrosis on the seventh postoperative day.…”