Trichloroacetic acid (TCA)

See Fig. 79.1.

Fig. 79.1 TCA peel. A, Pre-procedural. B, Two days post-procedural. C, Four days post-procedural. D, Six days post-procedural.

Trichloroacetic acid (TCA) is a derivative of acetic acid that has been used in the treatment of aging skin since the early 1960s. Trichloroacetic acid is mostly commonly used in 35% concentration for medium depth peeling, penetrating the papillary and into the upper reticular dermis. In concentrations above 40%, TCA can penetrate the reticular dermis, providing deeper and increased morbidity and risk of scarring. TCA is not absorbed systemically. TCA is versatile and can be used in a wide range of skin types. TCA is useful for treatment of pigmentation disorders, dysplasias, photoaged skin and wrinkles. TCA produces limited neocollagen formation and some improvement in facial wrinkling but it is limited in treating deep facial wrinkles, especially in the perioral area.

Pretreatment for TCA peels improves the penetration of the acid and provides more consistent results. Prior to TCA peeling, the skin is degreased with acetone and/or alcohol to remove surface oils from the skin, which can decrease absorption and result in an uneven peel. Sedation is usually not necessary with 35% TCA. The solution is applied regionally to each facial unit with brush-like strokes. Adequate penetration of the solution usually occurs between one to two minutes. Trichloroacetic acid is a keratocoagulant and frosting is the key to judging the depth of the peel. Initial frosting is pink or white in color and progresses to more uniform white as penetration proceeds to the papillary dermis. A gray appearance can signal penetration to the reticular dermis and may cause abnormal healing. Once the desired degree of frosting occurs, the acid is washed with water. The water serves to dissipate some of the generated heat, but since trichloroacetic acid is an aqueous solution, it cannot be neutralized but only diluted. If after inspection the frost is not as deep as anticipated, it is appropriate to retouch those areas. During the entire peeling process, a fan can be used to aid in patient comfort.

Chemical peeling is a technique-dependent procedure. Depth of treatment correlates with the concentration of TCA, but variables such as skin type and thickness, concentration of sebaceous glands, pretreatment, skin degreasing, amount of acid applied and the rigor of application must be taken into account. Patients with thicker skin will tolerate higher concentrations of TCA or multiple reapplications of acid, but care must be taken in patients with dry and atrophic skin as penetration is increased. TCA has broad applications but the learning curve can be prolonged.

Phenol

See Fig. 79.2.

Fig. 79.2 Phenol peel. A, Pre-procedural; B, post-procedural.

Phenol, also known as carbolic acid, is protein precipitant, causing extremely rapid denaturation and coagulation of surface keratin. It provides a relatively deep and predictable injury to the dermis, penetrating to the level of the upper reticular dermis. It has become a standard to which other resurfacing methods are compared. It treats both coarse and fine wrinkles and irregular pigmentation.

Phenol is detoxified in the liver and excreted by the kidney. Toxic doses of phenol can injure both the liver and the kidney and may depress respiration and the myocardium. Atrial and other arrhythmias can be seen after rapid phenol absorption.

Chemical peeling with phenol–croton oil is used to improve significant actinic damage and moderate wrinkling of the skin.

The Baker–Gordon formula is the standard phenol formula. It consists of 3 mL USP liquid phenol, 2 mL tap water, eight drops of liquid soap and three drops of croton oil (Table 79.2). Soap lowers the surface tension of the mixture and croton oil has been thought to act as a vesicant, increasing local inflammation and penetration of phenol. Water prepares a solution of 50% phenol concentration. It has been shown through histologic studies that the Baker–Gordon formula penetrates deeper than pure phenol (Stegman, 1980).

Table 79.2 Baker–Gordon formula

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

Cardiac monitoring, pulse oximetry and accessible resuscitation equipment is recommended if the entire face is peeled. The skin is cleansed in a fashion similar to that discussed for TCA peels. The phenol solution is applied with a contact tip applicator with care being taken to avoid dripping. Missed spots must be avoided. After phenol application, the skin frosts a grayish white color and a burning sensation is experienced. Small subunits are peeled at 15- to 20-minute intervals with a full-face peel being completed in about 1 to 2 hours. An occlusive dressing applied to the treated area prevents evaporation and increases phenol penetration and depth of the peel. Either tape or a petroleum-based ointment dressing can provide occlusion, although the former may be more painful and morbid for the patient.

The depth of treatment with phenol does not correlate with its concentration. A lower concentration does not necessarily produce a lighter peel and higher concentrations may produce less of a peel because of keratin coagulation in the epidermis.

Hetter (2000) varied the concentration of croton oil and demonstrated that it was the concentration of croton oil and not the concentration of phenol that was the factor that controlled depth of penetration. He asserted that phenol is simply the carrier. Minute variations in the concentration of croton oil are critical to the outcome of the peel. The different proportions according to depth of peel desired and anatomic site are summarized in what Hetter calls “the heresy phenol formulas”. As a result of this work, phenol peels are probably more properly referred to as “phenol–croton oil” peels.

Dermabrasion

See Fig. 79.3.

Fig. 79.3 Dermabrasion. A, Pre-procedural; B, post-procedural.

Dermabrasion, which was developed in the 1950s, mechanically abrades the epidermis and upper portion of the dermis. It is technique dependent and the depth can be precisely controlled. The epidermis is entirely obliterated and there is partial removal of the dermis, which undergoes incomplete regeneration. Both coarse and fine wrinkling can be treated with dermabrasion. Wrinkles can be lowered and smoothed mechanically. For resurfacing, dermabrasion is most useful for perioral lines and particularly those of the upper lip. Baker (1998) describes the current technique of dermabrasion and reviews the various adjuncts, instruments, indications, contraindications, and complications of the procedure.

Dermabrasion patients may receive premedication and/or regional nerve blocks may be used. The hand-held dermabrader is motor-driven and operates at 12,000–15,000 rpm. There is a wide variety of diamond-tipped burrs, differing in shape, size and coarseness. Protection against aerosolized particular matter must be taken. Wrinkles are marked before infiltration of anesthesia and regions are treated according to anatomic subunits. The handpiece should be kept moving, with light pressure applied. The edges of treated areas are feathered to blend with those not treated. Providing treatment to the proper depth is important. After the epidermis is removed, the pink epidermal–dermal junction is encountered. As treatment continues, fine punctate bleeding indicates the level of the papillary dermis. At the papillary–reticular junction, bleeding is increased and the surface becomes rougher, indicating the endpoint of treatment for most patients. Following treatment, the entire face is covered with gauze soaked in lidocaine with epinephrine to provide both anesthesia and hemostasis. Once bleeding has stopped, ointment is applied and the treated area either covered with petroleum or xeroform gauze, or is left uncovered. There appears to be neocollagen formation following dermabrasion.