As with any other chemical peeling procedure, the art and science of TCA chemical peels is dependent on the proper peeling technique. TCA is a versatile peeling agent and depending on its concentration, can be used for superficial, medium, or deep chemical peels. However, the cleaning and peeling technique is essentially the same for each depth. In general for the superficial peels patients do not require any sedation; however, for medium-depth peels, a mild sedative such as diazepam 5-10 mg p.o. or ativan 0.25-0.5 mg p.o. may be used. The patient should be comfortably positioned with the head at a 30- to 45-deg angle. A topical anesthetic such as 4% lidocaine may be used prior to application of the TCA to reduce patient discomfort with burning and stinging.
Prior to the application of TCA, a thorough cleaning is of vital importance for defatting the skin to allow for even penetration of the peeling solution. The skin is first cleaned with either Hibiclens or Septisol. Subsequently either acetone or alcohol is used to remove the residual oils and scale until the skin feels dry.
After thorough cleaning, TCA is applied, using either 2-4 cotton-tipped applicators or folded 2 x 2 gauze in a pre-determined sequential manner, starting from the forehead, to temples, cheeks, lips and finally to the eyelids. It is imperative that following application to each area,the physician observes not only the degree of frosting, but also the duration to this reaction before proceeding to the next area. If the desired level of frosting is not reached within 2 to 3 min, an additional application of the agent should be performed. Care must be taken not to overcoat TCA as each application will result in greater depth of penetration. Patients experience a burning sensation, particularly with the higher concentrations of TCA.
If a Jessner's-35% TCA peel (Monheit) is performed, Jessner's solution is applied first prior to the TCA in an even sequential fashion from the forehead to the rest of the face, waiting 2 to 3 min to allow for penetration and assessment of frost. Typically this will produce a level 1 frost, erythema with faint reticulate whitening
(see below). An additional one or two coats of Jessner's may be applied if a level 1 frost is not obtained. Patience must be practiced before proceeding to the application of TCA, as the physician might perform a more aggressive peel than intended if they had waited the proper time to evaluate the degree of frosting produced by the application of the chemical. Always be mindful of this lag effect.
As noted previously, TCA results in kerato-coagulation or protein denaturation which is manifested by frosting of the skin. As the extent of frosting appears to correlate with the depth of penetration of TCA, the following classification can be used as a general guideline for TCA peels. It is imperative to keep in mind, however, that the results are dependent on multiple factors including type/thickness of skin, priming of skin, and technique of application of the TCA:
■ Level 1: Erythema with blotchy or wispy areas of white frosting.This indicates a superficial epidermal peel as can be achieved with TCA concentrations <30%. This peel will result in light flaking lasting 2-4 days.
■ Level 2:White frosting with areas of erythema showing through.This level of peel is indicative of a full-thickness epidermal peel to the papillary dermis and can be achieved with TCA concentration of >30%.This peel will result in full exfoliation of the epidermis (Fig. 4).
■ Level 3: Solid white frosting with no erythema.This is indicative of penetration of TCA through the papillary dermis and can also be achieved with TCA concentrations >30%, depending on the number of applications (Fig. 5).
TCA in concentration of 10-25% can be used safely for superficial depth peels and in concentrations >30% can be used for medium-depth peels. However, multiple coats of even the lower concentrations of TCA can result in a deeper penetration of this agent, thus essentially re-suiting in a medium-depth peel. In general, use of TCA in concentrations >40% is not recom-
mended as it results in uneven depth of penetration and a greater risk of scarring and pigmentary dyschromias.
Several areas of the face require particular consideration. Care must be taken in the periorbital area to prevent any excess TCA solution from rolling into the eye, and as such TCA
should not be applied to the upper eyelid. If tearing occurs, this can be gently wicked using a cotton-tipped applicator. With areas of deeper rhytides such as in the perioral area, the wrinkled skin should be stretched and the TCA applied over the folds. In addition, TCA should be applied evenly over the lip skin to the vermillion.
Once the desired frost is achieved, the skin can be rinsed off with water, or cooled down with cool wet compresses which are applied to the skin. The wet compresses can provide a welcome relief to the burning induced by the peel. Unlike glycolic peels the water does not neutralize the peel, as the frosting indicates the end-point of the reaction; rather, it dilutes any excess TCA. The compresses can be repeated several times until the burning sensation has subsided. Subsequently, a layer of ointment such as plain petrolatum or Aquaphor is applied and post-peel instructions and what to expect are reviewed with the patient prior to discharge to home.
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