Glucose in Conjunction with Multiple Laser Pulses on Laser Treatment of Port-wine Stain: An in vivo Study.

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.

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

Port-wine stains (PWSs) usually respond poorly to pulsed dye laser treatment because of the shallow penetration and light absorption of melanin in the epidermis. Multiple laser pulses (MLPs) Nd:YAG laser in conjunction with an optical clearing agent can help to reduce the total laser energy required for blood coagulation. The quantitative optical clearing effect (OCE) of glycerol was investigated by using a tissue-like phantom. Thereafter, an in vitro capillary tube experimental system and an in vivo hamster dorsal skin chamber experiment for the laser treatment of PWSs were established to visually obtain the quantitative relationship between the OCE and the blood coagulation properties under the irradiation of 1064 nm MLPs. Diffuse reflection coefficient decreases by 36.69% and transmission coefficient increases by 38.73% at 1064 nm, after applying 0.5 mL anhydrous glycerol for 10 min on the surface of the tissue-like phantom. The number of laser pulses required for blood coagulation decreases by 25% after the application of 0.5 mL anhydrous glycerol for 4 min, thrombosis appears after 10 min, and the 0.0854 clotting area completely blocks the capillary tubes in 6 pulses. For 10 min, the incident energy can be reduced by 35.09 and 29.82%. When the 0.3-mm vessel's buried depths are 1 and 0.5 mm, the pulse number can be reduced from 11 to 8 and from 6 to 4, respectively. Adding anhydrous glycerol directly on the hamster dorsal skin is an effective way to reduce the number of laser pulses from 4∼5 to 2∼3 for similar capillary tube diameter. Therefore, the MLPs of 1064 nm Nd:YAG demonstrates a substantial curative effect for large capillary tubes. In conjunction with glycerol, this approach may treat deeply buried cutaneous capillary tubes and prevent the unwanted thermal damage of normal dermal tissue.