Biomedical Engineering Reference
In-Depth Information
This mixture of fatty acids also signifi cantly enhances the
ability of pyruvate and vitamin E to inhibit reactive oxygen
production and improve membrane function and cellular
viability. These three components, vitamin E, pyruvate, and
essential fatty acids, have been shown to be synergistic in
reducing oxidative stress to keratinocytes and enhancing
wound healing (194).
Patients treated with an open wound care regimen are seen
on the fi rst and third day postoperatively, and any excess crust
is gently removed with saline. The frequency of soaks and oint-
ment application is tapered off as reepithelialization progresses.
Once reepithelialization is complete, a mild facial cleanser
(i.e., Neutrogena fresh foaming cleanser or Cetaphil facial
cleanser) and a daily moisturizer-sunscreen are introduced.
The benefi t of occlusive dressings in accelerating wound
healing was fi rst demonstrated in 1962 (197) and confi rmed
in numerous studies (190,198-208). Reepithelialization was
shown to occur 30-45% more quickly, with decreased pain
and infl ammation and more cosmetically acceptable scar for-
mation. In addition, new collagen formation has been shown
to begin 3 days earlier than in open wounds (209), with an
increased rate of collagen synthesis (210). The increased rate
of reepithelialization produced by occlusive dressings is gener-
ally attributed to the moist wound environment and the
absence of a crust that may impede cellular movement. In
addition, occlusive dressings provide an environment that
maximizes exposure to various endogenous growth factors.
Continued exposure to epidermal growth factor has been
shown to quicken epidermal resurfacing (211).
Studies of varying the time of application or removal of an
occlusive dressing have shown that for optimal healing, dress-
ings need to be applied within 2 hours after wounding and
should be left in place for at least 24 hours (212). Waiting
24 hours before application almost precludes the occlusive
dressing's effect on wound healing, but it still may have ben-
efi t in pain reduction. Early removal of the dressing greatly
reduces the occlusive effects, but not if 24 or 48 hours has
passed.
Moreover, several studies have demonstrated that closed
wound care techniques utilizing occlusive dressings for the fi rst
48-72 hours after laser skin resurfacing reduce crusting, ery-
thema, and edema (Fig. 6.33). Moreover, occlusive dressings
have been reported to signifi cantly decrease postoperative pain
and patient discomfort and simplify wound care for patients
compared with open wound care techniques (42,48-52).
The most popular commercially available closed-occlusive
dressings for laser skin resurfacing wounds belong to one of the
following categories: composite foams, polymer fi lms, polymer
meshes, hydrogels, hydrocolloids, and alginates. These closed-
occlusive dressing categories are summarized in Table 6.7.
Some studies have shown that bacterial colonization under
occlusion does not impair wound healing (213-216), and
that wound fl uid and exudate collecting under an occlusive
dressing have bactericidal activity (217,218). Oliveria-Gandia
et al. demonstrated that occlusive dressings can act as barriers
to invading wound organisms and that dressing composition
can infl uence the growth of various pathogens (219). More-
over, several studies found that wounds covered with occlu-
sive dressings had reduced infection rates when compared
with nonocclusive dressings (193,206,208,218,220-224).
Figure 6.33
Silon II, a polyurethane fi lm with multiple small slits, allows
soaking directly through fi lm and enhances wound healing during fi rst
72 hours.
Christian et al. reported four cases of culture-positive infec-
tions among 354 patients who underwent full-face CO
2
laser
resurfacing (1.13% rate of infection) and were treated with
occlusive dressings and empiric oral cephalexin. Three of the
four infections developed 3-5 weeks after the laser resurfac-
ing (225). Newman et al. evaluated the effi cacy and safety of
four different types of closed dressings following full-face
laser resurfacing in 40 patients and observed no cases of
infection (50).
However, a study comparing semiocclusive dressings exposed
to open air showed not only an increased number of micro-
organisms, but also a shift toward gram-negative organisms
(213). Other investigators have shown a similar pattern on nor-
mal skin occluded with a plastic fi lm (216,223). Moreover, an
increased incidence of infection after laser skin resurfacing has
been reported in some studies when antibiotics have not been
used (43,100).
An increased susceptibility to gram-negative infections in
resurfacing patients would refl ect our clinical experience as
well. If semiocclusive dressings are to be used postoperatively,
most physicians now would advise that (
i
) antibiotic coverage
should include gram-negative organisms; (
ii
) dressings should
be changed frequently, if not daily; and (
iii
) occlusive dressings
should be used for no more than 72 hours.
After reepithelialization, the next phase of wound healing
lasts another 7-10 days. During this phase, no further weeping
occurs and swelling has usually resolved. Maturation of the
epithelium still requires a moist environment. Of note, contin-
ued use of occlusive ointments such as petrolatum beyond
complete re-epithelialization has been associated with the
occurrence of folliculitis in some patients (121). Lighter
