Multiple laser pulses in conjunction with an optical clearing agent to improve the curative effect of cutaneous vascular lesions

Jun Ma, Bin Chen, Dong Li, Yue Zhang, Zhaoxia Ying

Port-wine stain (PWS) birthmark is a congenital microvascular malformation of the skin. A 1064-nm Nd:YAG laser can achieve a deeper treatment, but the weak absorption by blood limits its clinical application. Multiple laser pulses (MLPs) are a potential solution to enhance the curative effect of a Nd:YAG laser. To reduce the pulse number (pn) required for the thermal destruction of the blood vessel, the effect of glucose in conjunction with MLP was investigated. In vivo experiments were performed on a dorsal skin chamber model. Different concentrations (20, 25, 30, and 40%) of glucose were applied to the sub-dermal side of the hamster skin before laser irradiation. Identical vessels with diameters of 200 ± 30 and 110 ± 20 μm were chosen as representatives of typical PWS vessels. Instant thermal responses of the blood vessel were recorded by a high-speed camera. The required pn for blood vessel damage was compared with that without glucose pretreatment. Results showed that the use of glucose with a concentration of 20% combined with MLP Nd:YAG laser to damage blood vessels is more appropriate because severe hemorrhage or carbonization easily appeared in blood vessels at higher glucose concentration of 25, 30, and 40%. When 20% glycerol is pretreated on the sub-dermal hamster skin, the required pn for blood vessel damage can be significantly decreased for different power densities. For example, pn can be reduced by 40% when the power density is 57 J/cm2. In addition, generation of cavitation and bubbles in blood vessels is difficult upon pretreatment with glucose. The combination of glucose with MLP Nd:YAG laser could be an effective protocol for reducing the pn required for blood vessel damage. Randomized controlled trial (RCT) and human trials will be conducted in the future.