Background: In 25 % to 50 % of patients with port wine stains treated with pulsed dye laser (even in multiple sessions), only a partial improvement is obtained that is often unsatisfactory for the patient. Various factors have been proposed to explain the resistance to treatment, such as the presence of deep, small-caliber, or very thick vessels that cannot be coagulated with a single laser pulse. Certain mathematical models suggest that multiple pulses would be effective in coagulating those vessels without losing the selectivity of photothermolysis, since more energy could be delivered to the target structures without damaging the surrounding tissue. The aim of this study was to assess the efficacy and selectivity of photothermolysis with multiple laser pulses.
Methods: Twelve patients with port wine stains were included in the study. Various areas of each lesion were treated with pulsed dye laser (Candela V-beam, 595 nm) using different parameters. Immediately afterwards, the treated areas were biopsied.
Results: The risk of exceeding an appropriate dose was greater with small spot size, long pulse duration, short intervals between pulses, and high fluences. Heat damage was less with spots of 10 mm, short pulses, intervals of 1 minute between pulses, and low fluences. In selected cases, multiple pulses were effective and selective where single pulses did not successfully coagulate the vessels.
Conclusions: Our results indicate the enormous possibilities of multiple laser pulses for the treatment of refractory vascular lesions. In addition, we have addressed the variables defining the complex thermodynamic interaction between the laser and the cutaneous tissue and indicated the safest parameters. We discuss the possible usefulness of this approach with other lasers and skin diseases.