SINGLE OR MULTIPLE PULSES IN THE USE OF THE PULSED DYE-LASER FOR THE TREATMENT OF PORT-WINE STAINS

The pulsed dye laser was developed for the treatment of vascular cutan eous lesions using single non-overlapping pulses. However, in practice , overlap and multiple pulses to the same site are commonly used. This study was undertaken to examine the effects of single vs two, three a nd five pulses to the same site on penetration depth of the laser beam and vascular selectivity. Two albino pigs were treated with a 577 nm, 450 mu s, 3 mm-diameter pulsed dye laser. The effect of multiple puls es to the same site over a range of fluences was analysed histological ly from biopsies acquired immediately and at 1 and 4 days after laser irradiation. The results show that multiple pulses to the same site do not increase the penetration depth (maximum depth from the dermo-epid ermal unction where damaged blood vessels are observed) of irreversibl e vascular injury. Cumulative pulses do increase the extent of tissue injury, including both desired vascular changes and unwanted effects s uch as extravasation. No clinical changes were observed following mult iple pulses below 2J cm(-2). It was concluded that 577 nm, 450 mu s mu ltiple pulses to the same site do not increase penetration depth of va scular injury of the laser beam.