Laser technologies seem to have a knack for recapitulating. Just as the ruby laser reappeared in the late 1980s after a 20-year hiatus, so renewed interest in green lasers for vascular lesions and a renewed understanding of the importance of chilling reappeared in the mid- to late 1990s, particularly by Wellman Lab (199,200) and Beckman Lab. Part of the interest in chilling was fostered by the large amounts of energy required to destroy or alter hair follicles and the need to protect the epidermis even better than theoretical thermokinetics alone. In 1994 Nelson's group (193) at the Beckman Institute began a series of theoretical (194) and clinical (193,195-198,409) studies and first described the use of a spray cooling device using 20-80 ms bursts of a cryogen to cool and protect the epidermis during port-wine stain therapy. They saw no blistering appear after even 20-36 J/cm2 with cooling spray but both blistering and necrosis without it. With this apparatus they could not only diminish intraoperative pain (197) and diminish epidermal injury with the 585 nm pulsed dye laser and with the 532 nm solid state laser (202) but, with the continuous Nd:YAG laser applied for thick vascular lesions in a cockscomb model (410), they could produce deep thermal effects to 6 mm without epidermal injury. Such dynamic cooling was adapted also for long-pulsed alexandrite hair removal systems.
In the late 1990s, doubled-frequency 532 nm Nd:YAG laser with intermediate pulse widths of 2-10 ms and coupled with a sapphire water-cooled chill tip was introduced for treatment of vascular lesions without purpura. The chill tip was able to protect the epidermal integrity by keeping epidermal temperature at 5-5.5°C and fluences of 9.5-15 J were employed (190). Chill tips were consolidated with various long-pulsed ruby and diode lasers for hair removal also. Chilling by spray can be used just prior to, during, or even after the laser burst as a type of "thermal quenching."
Despite the dramatic and novel benefit of laser resurfacing, public demand has been driven by market forces as fast as development of the Web. Yesterday's technology even for laser surgery rapidly and unjustifiably really becomes considered yesterday's practice. Marketing forces the public to search for newer and quicker medical "fixes," hence the appearance of the "lunchtime peel," the "lunchtime microdermabrasion" and ultimately the lunchtime (i.e., no "downtime") laser resurfacing by nonablative lasers (411,412).
The public is confused into believing that these techniques all produce the same results as a true wounding resurfacing and without any hazard.
Kelly et al. (294) in 1999 and Nelson et al. (409) showed that a small but statistically evident improvement in rhytids could be safely achieved with a 1320 nm Nd:YAG and dynamic cooling; there was rare blistering and hyperpigmentation and rarer pitted scarring. However, Ross et al. (413) thought that this process is too variable and prone to deep dermal collagen injury with resultant granulomatous inflammation, fibrosis, and pitted scarring. Muccini et al. (414) reported 18% shrinkage of collagen and new collagen synthesis without epidermal destruction in treating rhytids with a 980 nm diode laser with a spherical optical handpiece that focused the energy into the dermis. Goldberg and Whitworth (415) discovered subtle yet visible improvement of rhytids after slight epidermal ablation with uncooled Q-switched Nd:YAG laser, and Goldberg and Cutler (416) found that intense pulsed light sources with a precooled light guide did the same without epidermal ablation. Patients treated with pulsed dye laser for vascular lesions also report improved skin textures as have those treated for atrophic and hypertrophic scars. Nonablative skin remodeling has ballyhooed the promise of reduction of wrinkles, pore size, and oiliness, improvement of skin texture, and removal of pigmentary dyschromias, both brown and red, with no epidermal damage, no downtime from work, and no morbidity (417). Amazingly, the lasers and light sources touted to produce these changes have included the entire spectrum from 532 to 1540 nm—clinical improvement or histologic evidence of procollagen, new collagen synthesis or deposition was noted for 532 nm, 2 ms laser (418), 585 nm, 450 ms pulsed dye laser (419), low-fluence 595 nm long-pulse chilled pulsed dye laser (420), 585 nm, 360 ms pulsed dye laser (421), chilled 1320 nm Nd:YAG laser (422, 423), and chilled 1540 nm Er:glass laser (424). Similar claims were made for intense pulsed light (389,392). More realistic assessments of improvement indicated that though most subjects showed some improvement, it was at most minimal—only 18% by grading in Rostan's study (420)—and could lead to patient dissatisfaction as for 80% of Trelles patients (423) even though they had histologic evidence of new collagen.
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