Biomedical Engineering Reference
In-Depth Information
regimens. The regimens outlined previously appear to enhance
wound healing and decrease erythema. In addition, the infl am-
matory reaction related to slough of thermal necrotic tissue
may be a factor in prolonging erythema. Removal of this layer
with the Er:YAG laser has been shown to be effective both in
reducing erythema and infection and in enhancing the healing
process and speeding its conclusion.
despite antiherpetic prophylaxis, it is best to switch from valacy-
clovir to famciclovir, or vice versa, and to increase the dosage.
When candidal infections are encountered, a 400-mg dose
of fl uconazole should be given and occlusive topical regimens
discontinued.
Bacterial infections should be treated according to culture
and sensitivity results. Serious consideration should be given
to prophylactic use of ciprofl oxacin (500 mg twice daily) start-
ing the evening before surgery and continuing for 10-14 days
postoperatively.
Itching
Itching is a common postoperative complaint, particularly dur-
ing the second postoperative week. It can indicate infection,
particularly candidiasis, but is then often accompanied by other
signs, such as poor wound healing, beefy erythema in patches,
and exudate. Contact dermatitis must be considered as well
when pruritus occurs, particularly if any topical medications
are being used. If these conditions are excluded, generally the
itching will respond well to an antihistamine such as diphen-
hydramine (Benadryl, 10 or 25 mg) or loratadine (Claritin®,
10 mg) or a topical steroid such as Synalar, as described earlier.
Acne and Milia
Many physicians report an unusually high incidence of milia
formation after laser resurfacing as well as increased or exacer-
bation of acne. Although the use of petrolatum-based oint-
ments may be an exacerbating factor in many patients,
particularly those with a prior history of acne, the incidence of
this complication appears to parallel the degree of thermal
injury to the tissue. Thermal injury may lead to a shock effect
on sebaceous glands, causing their disruption and dedifferen-
tiation of adnexal structures and producing an aberrant
re-formation of the canal (230). Dermabrasion, by contrast,
generally results in improvement in acne; some physicians
believe this is an invariable consequence of dermabrasion,
although degree of improvement may vary.
Treatment of acne and milia is that traditionally used for
acne: minimize occlusive ointments, reinstitute tretinoin and
AHAs, and administer systemic tetracycline or minocycline.
Gentle acne surgery performed at 2- to 4-week intervals may
be benefi cial as well. Isotretinoin (Accutane®) may be started
if the acne fails to respond to more conservative measures.
Infection
The combined incidence of bacterial, viral, and candidal infec-
tion has been found to be 4.7% in a multicenter study (226)
and 4.3% in a retrospective study (43), 12% in Burns' study
(personal communication), 7.6% in Goldman and Fitzpat-
rick's study, and 8.4% in the study of Waldorf et al. (97). Mul-
tiple organisms are typically found, and the microorganisms
identifi ed (
Staphylococcus
and
Pseudomonas
species) are simi-
lar to those found in burn injuries (227-229).
The moist wound care and the layer of thermal necrosis pro-
vide an environment conducive to bacterial and candidal
growth. The absence of the protective epidermal barrier fur-
ther invites infection and allows dissemination of the infection
across the surface of the treatment area. Bio-occlusive dress-
ings further complicate the situation by trapping bacteria and
increasing the incidence of infection (43).
Infection should be suspected in the following situations:
Hyperpigmentation
Hyperpigmentation is generally related to the degree of natu-
ral pigmentation and occurs in 20-30% of those with Fitzpat-
rick type III skin and nearly 100% of patients with type IV skin
if treatment is performed without preoperative preparation
(104). Almost all episodes will resolve within 2-4 months if
aggressively treated. Strict sun avoidance is a fundamental
aspect of treatment and is enhanced by daily use of full-spec-
trum sunscreens containing titanium dioxide or Parsol 1789.
Hydroquinone is cytotoxic to melanocytes and is the mainstay
of treatment. Tretinoin promotes melanosome transfer and
keratinocyte turnover and is almost always benefi cial as well.
Azelaic acid, kojic acid, and glucosamine inhibit tyrosinase
and pigment synthesis and may be added to the regimen when
patients are responding slowly. Topical vitamins C and E func-
tion as free-radical scavengers and help prevent further stimu-
lation of melanocytes by UV radiation. Pretreatment with
these agents will minimize the occurrence of hyperpigmenta-
tion, as well as its degree of severity and its favorable response
to therapy.
1. Patient complains of persistent or new onset of pain.
2. Burning or intense itching is reported after day 2 or 3.
3. Patient has patchy, intense erythema, yellow exudate
or crust, papules, pustules, or erosions.
4. “Reversal of healing” is seen; that is, previously
reepithelialized areas become eroded.
Eighty percent of infections become symptomatic within
7 days and pain is the most common complaint, reported by
50% of patients. However, as previously mentioned, the use of
antibiotics may alter this pattern, and antibiotics used for
10-14 days may eliminate postoperative bacterial infections.
A sensation of burning and itching is the second most com-
mon symptom, reported by a third of patients.
When an infection is suspected, direct smears and cultures
for bacteria, yeast, and herpes virus should be taken, because
the physical fi ndings of infection may be atypical, with the
absence of the epithelium and presence of a necrotic layer and
edema. Correct diagnosis requires proper identifi cation of the
infectious agent.
All patients should be given appropriate antiviral medication
at surgery, because the laser resurfacing procedure may be a
potent factor in herpetic reactivation (44). Should this occur
Hypopigmentation
Hypopigmentation is a delayed phenomenon, generally not
apparent for 6-12 months. True hypopigmentation must be dif-
ferentiated from pseudohypopigmentation, a situation in which
the resurfaced area has normal pigmentation refl ective of non-
sun-exposed skin, but contrasts distinctively with the more
darkly pigmented sun-damaged skin. True hypopigmentation
