Evaluation of pulse-duration on purpuric threshold using extended pulse pulsed dye laser (Cynosure V-Star)

Background and Objectives: Pulsed dye lasers (PDL) with extended pulse-durations create new opportunities in the treatment of vascular lesions. Development of extended pulse methods requires understanding of tissue effects of extended pulse-durations. We evaluated tissue effects of extended pulse-duration PDL (EPDL) with cooling. Effects of increasing pulse-duration, fluence, and multiple passes were evaluated to determine purpuric threshold and delayed purpuric response. Study Design/Patients and Methods: Ten patients were treated with EPDL and air-cooling on normal buttocks skin. Exposure pulse-durations of 0.5, 2, 20, and 40 milliseconds and increasing fluences 3-20 J/cm(2), pulse-duration dependent. Exposures were evaluated 0.5, 1, and 24 or 48 hours determining purpuric threshold and side effects. Results: Immediate purpuric threshold increased from 6.2 to 8, 10.4, and 13.8 J/cm(2) at pulse-durations of 0.5, 2, 20, and 40 milliseconds, respectively. Purpuric threshold dropped after 24 hours to 5.2, 7.1, 9.3, and 11.9 J/cm(2), respectively. Multi-pass treatment lowered purpuric threshold by 1 J/cm(2). EPDL purpura resolved in less time than traditional PDL. No side effects were noted. Conclusions: EPDL exhibits increasing purpuric threshold with increasing pulse-durations, and risk of delayed onset of purpura. (C) 2002 Wiley-Liss, Inc.