TINTAS HIPSOMÉTRICAS

CO

LASER

Preoperative Considerations

Ideal Patient: The ideal patient for treatment, regardless of disease, is either very dark or very light skinned, as patients tend to return to their constitutive color after CO₂ laser surgery.

Bronzed patients with Type II and III skin are at high risk for permanent hypopigmentation with increasing depth of injury.

Any patient with decreased adnexal structures from previous radiation therapy or even laser hair removal or electrolysis should probably receive at least a test site. This advice is controversial for laser hair reduction, as there are no reports of compromised healing in CO₂ laser induced areas previously treated with hair reduction lasers.

The recommended minimum time interval between isotretinoin treatment and resurfacing (and vice versa) ranges from 6 months to 2 years. Preoperative Regimen

For adnexal tumors, test sites, and small-scar abrasions, no systemic or topical medications are prescribed. We have found that topical retinoids and bleaching preparations do not appear to alter the postoperative course.

Intraoperative Technique

Defocussed mode is ideal for vaporization while focused mode is used for cutting. For most dermatological indications a pulsed laser is ideal. For patients where a deeper ablation is required a superpulsed mode or a Cw (interrupted pulse) can be used. Prolonging the pulse duration in a super pulsed mode is another method of increasing the energy.

1. Modes (shuttered continuous wave, pulsed or scanned beam at 0.1–0.2 s): Most CO₂ lasers have Cw (continuous wave), repeat, single, Sp (super Pulse) and Up (ultraPulse) modes. The repeat and single are basically CW modes.

As a thumb rule for small, appendageal tumours (e.g. milia) the single pulse mode is ideal. For a larger lesion (xanthelasma), the repeat mode in appropriate settings (see below) should be used.

2. Spot size (defocused beam) with spot size of 2–3 mm at skin surface. 3. The power density may be varied by changing the power output, beam

configuration, spot size, movement speed of hand piece, or shuttering the laser beam. These changes may be done either by hand or with the

use of a mechanical scanning device (details are given in the preceding chapters).

Steps

1. After setting the power (at least 5 J/cm2_{) one pass is given.}

Method: Air brush-like movements with the defocused laser beam of the

continuous wave carbon dioxide laser or discrete pulses of the pulsed or rapidly scanned carbon dioxide laser create visible vaporization and/or coagulation.

2. The surgeon should rely on visual inspection of the treatment site after each pass of the laser and wiping the site with wet and dry sponges in order to determine the extent of the lesion and surrounding tissue damage.

First Pass: Vaporization of skin results in a white and slightly scaly surface. Once the treated area is gently wiped with a wet sponge, the epidermis may still be visible if the treated lesion is particularly thick or the power density was very low and the speed of movement was very fast. If the epidermis is thin and a greater power density is delivered, the superficial dermis is seen with normal dermatoglyphic markings. Dermis: When the dermis is heated or vaporized, visible collagen

contraction is noted. If coarse and woven collagen bundles are seen, the

tissue has been ablated into the deep dermis.

Subcutaneous: If ablation is continued further, subcutaneous fat will be obvious.

If charring is seen, there has been slow tissue burning at very high temperatures resulting in heat diffusion to surrounding tissues rather than tissue ablation. Charring is therefore not desired.

Postoperative Care

1. With the exception of excised wounds, in which sutures should be left in 3–5 days longer than in scalpel wounds, wounds are left to heal by secondary intention and will heal optimally when kept moist and clean. Dressings will speed healing if they are changed (at least every 2 days). 2. We have used a combination of fucidin cream (less sensitizing than

neomycin) with application of aloe vera gel (Jula or Aloekem 75) till the crusting falls off. We routinely recommend an antibiotic, starting one day prior to 4 days after the surgery (Levofloxacin 750 mg HS) with an antinflammatory drug for two days (Zymoflam-D).

3. To avoid PIH a combination of sunscreen and non HQ/steroid based creams is given. A physical block sunscreens is advisable.

4. More disturbing than the almost always temporary, especially on the face, postinflammatory hyperpigmentation, is the delayed onset of hypopigmentation after the CO₂ laser in some cases. Thus as far as possible Cw CO₂ should be restricted to small areas of the face.

Pitfalls/Pearls

1. Optimal use of the carbon dioxide as an ablative instrument includes many steps.

2. The most important is to determine the desired clinical end point which varies depending on the lesion treated.

¾ Actinic cheilitis: End point is coagulation or white discoloration of the entire external lower mucosal lip is seen.

¾ Epidermal Nevus: Evidence of some coagulation in the dermis under the ablated area.

¾ Plantar Wart: The presence of normal dermis under the visible wart as well as 5–10 mm surrounding it.

¾ Appendageal Tumors: The clinical end point for the treatment of small appendageal tumors of the face includes vaporization of epidermis and dermis to a depth just beneath the surrounding uninvolved skin.