Suggested Readings

Singer—CHAPTER 28

Adrian RM. Pulsed carbon dioxide and erbium-YAG laser resurfacing: a comparative clinical and histologic study. J Cutan Laser Ther 1999;1:29-35

Anderson RR, Parish JA. Selected photothermolysis: precise microsurgery by selective absorption of pulsed irradiation. Science 1983;220:524-527

Baker TJ, Stuzin JM, Baker TM. Facial skin resurfacing. St. Louis: Quality Medical Publishing; 1998

Green HA, Burd E, Nishioka NS, Bruggemann U, Compton CC. Middermal wound healing: a comparison between dermatomal excision and pulsed carbon dioxide laser ablation. Arch Dermatol 1992;128:639-645

Fitzpatrick RE, Tope WD, Goldman MP, Satur NM. Pulsed carbon dioxide laser, trichloroacetic acid, Baker-Gordon phenol, and dermabrasion: a comparative clinical and histologic study of cutaneous resurfacing in a porcine model. Arch Dermatol 1996;132: 469-471

Skin Resurfacing—Laser or Peel

CHAPTER 29

Milton Waner

Since the mid-1990s, laser-assisted skin resurfacing has rapidly replaced chemical peels and physical dermabrasion as the most common means of skin exfoliation. Remarkably, this has taken place with alarming rapidity and despite the lack of comparative trials. Evidence-based medicine has taught us the value of comparative trials. Without these we must ask ourselves the fundamental questions, how and why has this happened and is it justified?

The first of these questions must be answered against the backdrop of the state of the art at that time (i.e., when laserassisted skin resurfacing first emerged). Chemical skin exfoliation (chemical peels) developed almost in parallel with mechanical skin exfoliation and both became established modalities during the mid- to late 1960s.1-5 Chemical peeling is a process whereby a chemical cauterant is applied to the skin to induce exfoliation. A variety of agents can be used that produce a variety of effects, ranging from a light peel, in which the stratum corneum is affected, to a deep peel, in which necrosis can extend all the way to the reticular dermis. These include salicylic acid, trichloroacetic acid (TCA), the a-hydroxy group of acids, Jessner's solution (i.e., salicylic acid, resorcinol, lactic acid, and ethanol), and phenol.6-10 By contrast mechanical skin exfoliation refers to dermabrasion usually accomplished with a power-driven rotary dermabrader. A direct comparison of these two modalities revealed consistent changes.11 In general, the papillary dermis enlarged and the depth of the injury correlated well with the benefit derived from treatment to a point. Hayes et al.12 showed that the upper reticular dermis heals by regeneration from residual adnexial structures, whereas the deeper reticular dermis heals with scar tissue formation. An injury extending down to the reticular dermis is therefore likely to leave irreversible scarring. A more superficial injury is likely to heal by regeneration. This is the fundamental basis of aesthetic and therapeutic skin exfoliation. Kligman et al.10 studied the long-term histologic changes associated with chemical peels and noted a newly formed wide band of thin compact collagen bundles, parallel to the overlying skin. They also noted elastin fibers within the neocollagen and, once again, parallel to the surface of the overlying skin. The clinical correlation was apparent as a smoothing of the skin. Obliteration and subsequent regeneration of the epidermis from residual adnexiae resulted in elimination of dyschromias, keratoses, and the reestablishment of the normal vertical polarity of skin. The benefits of limited skin exfoliation were thus obvious.

Despite some excellent results, several limitations and some devastating complications became evident.13 The major limitations related to a lack of precision. With regard to chemical peeling, it became evident that there was variability in the suc cess rate among patients and that this was probably due to an inherent lack in the control of the depth of exfoliation. So many variables determined the depth of exfoliation that any classification of peeling agents was virtually meaningless.14 For example, the application of 25% TCA with a cotton-tipped swab to the face of a patient with thick oily skin that has not been primed before treatment will result in superficial intradermal sloughing of the skin. If a piece of gauze, saturated with the same concentration of TCA (25%), is rubbed repeatedly on the face of a thin-skinned woman whose skin was primed before treatment with 0.1% retinoic acid, the extent of injury will be much deeper and will probably extend to the midpapillary dermis. The variables that determine the depth of the peel appear to be related to the type of agent used and to the technique with which it is applied:

Peeling agent and its concentration

Number of coats applied

Technique used to apply the agent

Method of skin cleansing prior to the application

Whether the skin was pretreated in the weeks just before the peel Skin type

Anatomic location of the peel Duration of contact with skin

Not only were there complications relating to the actual peel, such as scarring, hypopigmentation, and hyperpigmentation, but complications resulting from an adverse effect of the specific agent used became evident. Resorcinol and salicylic acid can cause systemic toxicity, and even death in rare instances, several of the other agents can provoke an allergic reaction.13'15'16 As with chemical peeling, during dermabrasion, an appreciation of the depth of the treatment at any point in time is difficult and only comes with experience. Once again, this lack of precision led to variability in results.4,17 Profuse bleeding not only obscures the endpoint, but aerosolization of blood and tissue by the high-speed burrs, with the attendant risks of airborne infection, should discourage against using this technique.

This lack of precision, variability in results, and the relatively high risk of side effects kept these techniques from widespread popularity. One needed considerable experience to master these techniques and approach the safety standards demanded of cosmetic surgeons. An additional factor to consider was the changing climate of medical practice. The diminishing reimbursement rates paid out by third-party carriers and the rapid rise of managed care left many physicians disenchanted with traditional medical practice. By contrast, cosmetic procedures were strictly fee for service and were also very lucrative. Patients usually paid in advance of the service, obviating the need to generate the seemingly endless reams of paperwork demanded by the third-party carriers. Laser-assisted skin resurfacing could hardly have come at a more opportune time. The vacuum created by the problems of dermabrasion and chemical peels, together with the disaffection many physicians felt with the general trends in medicine, led to the enormous popularity of laserassisted skin resurfacing. The next and most fundamental question is: is this justified?

The fundamental principle of laser-assisted skin resurfacing (skin resurfacing) is the limitation of thermal damage. The following sequence of events takes place during tissue vaporization:

1. Optical penetration: The light emitted by the laser will penetrate to a given depth. This is a wavelength-dependent phenomenon. Infrared light is strongly absorbed by water and will thus only penetrate to a limited depth. In skin, this is generally around 60 to 80 ^m.

2. Vaporization: The light absorbed by water will raise the temperature of the intra- and extracellular water to the point of vaporization (100°C), at which point a layer of desiccated dead tissue will be left behind. If this dead tissue is again vaporized, it will heat to about 300°C and carbonize. It should therefore always be wiped away before any further vaporization takes place.

3. Thermal transmission. Once the tissue has vaporized, the thermal energy is transmitted to surrounding tissue. In the case of skin resurfacing, this is not desirable and should be prevented.

Thermal transmission can be limited by turning off the laser just after the tissue has vaporized and before the start of thermal transmission. This span of time (i.e., the time the laser is left on to allow only optical penetration and thermal transmission) is roughly equivalent to what is known as the thermal relaxation time. The thermal relaxation time of epidermis is about 1000 ^s. Therefore, if the patient's skin is exposed to < 1000 ^s one is able to vaporize to a specific depth with very little thermal damage beyond that.18 With CO2 lasers, the depth of vaporization will vary from 50 to 1000 ^m depending on the power setting selected.19'20 The depth of thermal damage approximates an additional 30 to 50 ^m. With the Er:YAG laser, the depth of vaporization is 4 ^m/joule (J) of energy used.20,21 Therefore, at 5 J/cm2, the depth of vaporization is 20 ^m. The depth of thermal damage with this laser is only 5 Therefore regardless of who is operating the laser, at a particular fluence, one pass with a CO2 laser will reliably vaporize to a depth of 50 ^m with 30 ^m of thermal damage. An Er:YAG laser operated at 5 J/cm2 will reliably vaporize to a depth of 20 ^m and effectively heat a further 5 ^m of tissue. This meant that one could vaporize skin with a degree of precision not seen with chemical peeling and dermabrasion. Furthermore, the same degree of precision was attainable regardless of the experience of the operator. The learning curve was much shorter, and the results were readily reproducible. Needless to say, there was still a learning curve, requiring a fundamental understanding of wound healing and light-tissue interaction. Provided one remained within the well-defined parameters, complications were few. Although no prospective comparison with chemical peeling or dermabrasion has been done, the precision, reliability, and reproducibility of laser-assisted skin resurfacing should yield a lower complication rate.22,23

With the passage of just a few years, advances in technology have not only given us greater precision in laser-assisted skin resurfacing, we have more versatility in what we are able to do. We now have three generations of skin-resurfacing lasers and, with each successive generation, our versatility has increased.

The first-generation lasers were the CO2 skin-resurfacing lasers. With these we are able to vaporize skin to the desired depth both accurately and precisely. The limited thermal transmission beyond the zone of vaporization was found to be advantageous in that a degree of thermally induced collagen denaturation took place within this zone and resulted in immediate shrinkage. This appeared to persist, and its effect was advantageous. This laser was found to be most useful for patients with class 2 and class 3 rhytids.19'20'23

The second-generation lasers were the Er:YAG lasers. With these lasers, we are able to vaporize skin with even more precision but with significantly less thermal damage.20,21 The resultant collagen shrinkage is present, but to a much lesser degree. It is generally accepted that this device is preferred for patients with class 1 and for some with class 2 rhytides. The main advantage is a quicker healing time and less postoperative erythema.20 The third-generation devices combine the above two effects and with an alteration of parameters one can obtain anywhere from a "light" predominantly Er:YAG effect, to a "deeper" peel with more thermal damage, as with a CO2 laser. With these devices, one is more versatile and can thus tailor the treatment to suit the patient. For example, in a patient with more pronounced rhytides on her upper lip and much less obvious changes over the rest of her face, one is able to "lightly" peel the entire face with a more pronounced effect, using more thermal damage over the patient's upper lip. This added versatility meant that these devices could replace the first- and second-generation devices and that any physician purchasing a laser for the first time need only buy a third-generation device.

One of the major criticisms leveled against lasers concerns their cost. This is especially true when one compares it with the cost of a small volume of lactic acid or any other of the exfoliants. Although it is true that some skilled individuals can obtain excellent results with chemical peels, as stated previously, the learning curve is long and the risk of complications appears to be much greater. Furthermore, their lack of precision and the variability of results clearly justify the added cost of lasers. Because the standards for cosmetic surgery have become so high, the added safety afforded with a laser, as well as their greater versatility, further justifies their continued use. Lastly, given the long learning curve for the use of chemical peels, any recently trained physician is much more likely to be comfortable using a laser than with the techniques of chemical peeling. It is therefore likely that with the passage of time, fewer and fewer physicians will use chemical peeling techniques.

REFERENCES

Waner—CHAPTER 29

1. Baker TJ. Chemical face peeling. Plast Reconstr Surg 1962;29:199

2. Baker TJ, Gordon HL. Chemical face peeling and dermabrasion. Surg Clin North Am 1971;51:387-401

3. Kurtin A. Corrective surgical planing of the skin. Arch Dermatol 1953;68(suppl):389

4. Yarborough J. Dermabrasive surgery. ClinDermatol 1987;5:75

5. Spira M, Freeman R, Arfai P, Gero FJ, Hardy SB. Clinical comparison of chemical peeling, dermabrasion, and 5-FU for senile keratosis. Plast Reconstr Surg 1970;46:61-66

6. Rubin M. Trichloroacetic acid and other non-phenol peels. Clin Plast Surg 1992;19:525-536

7. Stegman S, Tromovitch TA. Cosmetic Dermatologie Surgery. Chicago: Year Book; 1984:27-46

8. Kligman A. Results of a pilot study evaluation the compata-bility of topical tertinoin in combination with glycolic acid. Cosmet Dermatol 1993;6:10:28-32

9. Resknik SS, Lewis LA, Cohen BH. Trichloroacetic acid peeling. Cutis 1976;17:127-129

10. Kligman AM, Baker TJ, Gordon HC. Long-term histologic follow-up ofphenol face peels. Plast Reeonstr Surg 1985;75:652-659

11. Stegman SJ. A comparative histologic study of the effects of three peeling agents and dermabrasion on normal and sun damaged skin. Aesth Plast Surg 1982;6:123

12. Hayes DK, Berkland ME, Stambaugh KI. Dermal healing after local skin flaps and chemical peel. Arch Otolaryngol Head Neck Surg 1990;116:794

13. Spira M, Gerow FJ, Hardy SB. Complications of chemical face peeling. Plast Reconstr Surg 1974;54:397-403

14. Brodland DG, Cullimore KC, Roenighk RK, et al. Depths of chemexfoliation induced by various concentrations and application techniques of trichloroacetic acid in a porcine model. J Dermatol Surg Oncol 1989;15:967-971

15. Pascher F. Systemic reactions to topically applied drugs. Bull NY Acad Med 1973:49:613-617

16. Stagnone G, Orgel M, Stagnone J. Cardiovascular effects of topical 50% trichloroacetic acid and Baker's phenol solution. J Dermatol Surg Oncol 1987;13:999-1002

17. Rubin M. Manual of Chemical Peels: Superficial and Medium Depth. Philadelphia: Lippincott-Raven; 1995

18. Fitzpatrick E, Goldman MP. CO2 laser surgery. In: Goldman MP, Fitzpatrick RE, eds. Cutaneous Laser Surgery. St Louis: CV Mosby; 1994;198-258

19. Hohenleutner U, Hohenleutner S, Baumler W, Landthaler M. Fast and effective tissue ablation rates and thermal damage zones. Laser Surg Med 1997;20:242-247

20. Adrian RM. Pulsed carbon dioxide and erbium YAG laser resurfacing: a comparative clinical and histological study. J Cutan Laser Ther 1999;1:29-35

21. Kaufman R, Hibst R. Pulsed erbium YAG laser ablation in cutaneous surgery. Lasers Surg Med 1996;19:324-330

22. Weinstine C, Ramirez OM, Pozner JN. Postoperative care following carbon dioxide laser resurfacing: avoiding pitfalls. Plast Reconstr Surg 1997:100:1855-1866

23. Fitzpatrick RE, Goldman MP, Satur NM, et al. Pulsed carbon dioxide laser resurfacing for photoaged facial skin. Arch Dermatol 1996:132:395-402

The demand for facial skin rejuvenation has seen unprecedented growth in recent times. The explosion of interest in facial skin resurfacing by the public has paralleled that on the part of the cosmetic surgeon. As newer technologies have become available, the cosmetic surgeon's armamentarium for treating aged and actinically damaged facial skin has blossomed. While the media continue to bombard the public with the latest therapies, and as we address better informed, Internet-saavy patients, facial plastic surgeons have a responsibility to be knowledgeable and to understand the advantages and disadvantages of the various types of facial skin resurfacing techniques.

Many options are available to physicians who treat patients interested in facial skin rejuvenation. The latest advances in technology have allowed physicians to treat many facial skin conditions with laser therapy. As laser technology continues to develop, many different types of lasers are becoming available. The recent debate, however, is whether the laser will supplant more traditional chemical peeling procedures. Chemical peeling agents have been used for many centuries. The contemporary use of these agents began during the 1960s, and their use has flourished. Well-documented research has shown the beneficial clinical and histologic changes present after the application of various chemical peeling agents. Similar findings have recently been shown after laser facial skin resurfacing.

Regardless of the modality used, success with these agents is based on many variables. Along with a thorough understanding of the chemical agent or laser, and its proper use by the operator, patient selection remains a crucial factor in determining a successful outcome. No single therapy can be used successfully for all patients or all skin conditions. Currently, we use both modalities in our practice and continue to do so for a variety of different problems to help our patients achieve optimal rejuvenation of their skin.

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