Overview of lasers in burns and burn reconstruction

INTRODUCTION — An understanding of the applications and practical use of skin lasers is within the grasp of all clinicians managing burn injuries. A multitude of laser and light-based technologies are available. Rather than trying to provide a comprehensive review of all the possibilities, we will focus on what lasers are, applications within the context of burn care, which lasers to use, and how to use them in practical terms based upon the general groupings of these lasers.

We aim to discuss laser therapy in plain language to encourage interested clinicians to delve further into this subject. Increasing the participation of burn professionals in delivering laser treatments benefits the patient and improves access to this exciting technology.

Lasers used in burns and burn reconstruction, which include a variety of vascular lasers and ablative lasers, are reviewed. The use of vascular lasers to treat non-burn-related cutaneous vascular lesions is reviewed separately. (See "Laser and light therapy for cutaneous vascular lesions".)

Nonablative lasers are also designed to deliver thermal energy to the skin while leaving the epidermis intact. These are used mainly in aesthetic practice for skin rejuvenation and the treatment of conditions such as acne and are reviewed separately; however, some burn practitioners include their use to improve some of the superficial irregularities of burn scars, but they are not the mainstay of treatment of hypertrophic scarring. (See "Ablative laser resurfacing for skin rejuvenation" and "Laser and light therapy for cutaneous hyperpigmentation" and "Light-based, adjunctive, and other therapies for acne vulgaris".)

LASER THERAPY — The use of laser therapy in burns and postburn scarring followed decades of scientific innovations. These advances were built upon discoveries by science pioneers who were awarded the Nobel prize for their work. The strong evidence-based experimental research that has continued since 1965, when the first laser was built, has provided clinicians with a wide range of equipment that covers a variety of medical disciplines.

Over the past two decades, there has been a flurry of clinical laser use in burns and postburn scarring. Laser has generated great enthusiasm among clinicians and their patients that has unfortunately blurred the need for mechanistic and clinical efficacy research, which is necessary to demonstrate improved outcomes. (See 'Efficacy of laser treatment in burns' below.)

General principles and definitions — The word laser is an acronym for light amplification by stimulated emission of radiation. Lasers are comprised of an energy source, a resonant chamber, and an active medium; the active medium determines the wavelength produced and usually gives the laser its name. For medical applications, the active medium can be a gas (eg, CO₂, argon); solid crystalline materials (eg, sapphire, ruby), which are doped with ions (eg, neodymium, chromium, erbium); semiconductor materials (eg, diode laser); and liquid dye solutions (eg, pulsed dye laser [PDL]). (See "Basic principles of medical lasers".)

The main types of lasers used in burns and burn reconstruction can be broadly grouped as "vascular" lasers and "ablative" lasers. Other laser applications used in the treatment of burns and burn reconstruction include hair removal and lasers to assist delivery of medications. (See 'Lasers for hair removal' below and 'Laser-assisted drug delivery for scars' below.)

●Vascular lasers – "Vascular laser" is a term that can be used to encompass a group of lasers that targets the oxyhemoglobin chromophore, with wavelengths in the region of 500 to 600 nm (figure 1). These include the argon laser, PDL, and potassium titanyl phosphate (KTP) laser. The term is also sometimes used to refer to intense pulsed light (IPL) devices when filters are used to select the appropriate wavelengths of light (although these are not actually lasers). Each of these lasers has a role in treating a variety of vascular lesions (eg, congenital vascular lesions). PDL (585 to 595 nm) is considered the gold standard for the laser treatment of vascular lesions. While laser systems with longer wavelengths (such as neodymium, yttrium aluminum garnet [Nd:YAG; 1064 nm], alexandrite [755 nm], or diode lasers [800 to 900 nm]) can be used to achieve greater depths of penetration in the treatment of resistant vascular lesions, these also target the melanin chromophore. (See 'Vascular lasers' below.)

●Ablative lasers – Ablative lasers are a group of lasers that target water in tissues as their primary chromophore. The term "ablative" refers to the effect of the laser beam, which in essence vaporizes tissue. It may also add a thermal component to the adjacent nonablated tissue. Ablative lasers most commonly used in burns and burn reconstruction are the CO₂ laser with a wavelength of 10,600 nm and the erbium-doped yttrium aluminium garnet (Er:YAG) laser with a wavelength of 2940 nm (figure 1). The 2940 nm light emitted by the Er:YAG laser (in the mid-infrared zone of the electromagnetic spectrum) is close to the peak absorption range of water. Thus, the Er:YAG laser has a much greater absorption coefficient than the CO₂ laser and hence does not penetrate as deeply into the skin. Laser delivery systems are also available that offer a combined dual wavelength platform of CO₂ /Er:YAG. Ablative laser therapy can be delivered in a fractionated or nonfractionated mode [1]. This refers to whether the whole of the skin surface in the treated area is acted on by the laser (nonfractionated) or a certain equally distributed proportion is targeted with intervening tissue spared (fractionated). (See 'Ablative lasers' below.)

Treatment of burns and burn reconstruction — The development of the argon laser made a great impact on treating vascular anomalies. The early work by Apfelburg was followed by many other centers during the 1980s as laser therapy became a standard of care for treating port-wine stains, ending the era of disfigurement by surgical management of these anomalies [2,3]. Extrapolating from the impressive outcome, clinicians began to use vascular lasers for postburn hypertrophic scarring to improve erythema in the mid-1980s; itching was also improved. In the meantime, ablative CO₂ laser began to be widely used for facial rejuvenation but with mixed results.

When physicists collaborated more closely with clinicians and cell biologists, significant progress occurred using laser therapy for treating skin conditions and scarring. In a landmark 1983 publication, the principle of selective absorption of pulsed radiation, "selective photothermolysis," was demonstrated [4]. Introducing the concepts of ablative and nonablative laser therapy, a Candela vascular laser was used to target blood vessels, and a xenon fluoride (XeF) excimer laser targeted cutaneous melanosomes in healthy volunteers. This early work proved the feasibility of vascular, cellular, and ultrastructural-specific targeting without affecting the integrity of overlying epidermis [4].

The concept of "selective photothermolysis" was taken a step further in 2004, when the same group introduced the novel concept of fractional laser treatment. They used two laser prototypes to produce microscopic channels of controlled thermal injury 50 micrometers in diameter and 300 micrometers in depth, which spared the intervening skin, which allowed rapid healing of these microscopic channels (figure 2). The channels' density within the treated area could be varied according to the laser's desired effects; however, the distance between the channels was determined to be at least 250 micrometers for best results [1]. This work was later confirmed by a histologic study using ablative fractional CO₂ laser [5].

Efficacy of laser treatment in burns — Laser therapy for hypertrophic scarring specifically after burn injury has revolutionized the care of these patients. There is now a widely accepted consensus on the clinical protocols of laser management of hypertrophic scarring [6].

While there is quality literature published with strong evidence-based data for the use of laser in vascular anomalies, the situation is different for hypertrophic scarring, which is difficult to assess subjectively and objectively, and reliable validated methodology of scar assessment is still lacking [7,8]. In addition, hypertrophic scarring is known to improve over time, casting shadows over the long-term assessments and the efficacy of treatment modalities. These factors contribute to the challenge when designing controlled trials for laser therapy, especially for post-burn scarring. Nevertheless, during the last decade, well-structured unbiased randomized trials have been conducted proving the efficacy of laser therapy in scar management [9,10].

Although there are descriptive histologic data on the effect of laser on the treated tissues, these do not go further to investigate the mechanism by which laser works. As our knowledge has increased on the fibroblasts subclasses, including profibrotic deep dermal fibroblasts, it may be possible in the future to examine the laser effect at the cellular level [11]. This may allow a better understanding about the biology of hypertrophic scarring and how best to modulate it.

VASCULAR LASERS — Vascular lasers useful for treating patients after burn injury are typically pulsed dye laser (PDL) and intense pulsed light (IPL) systems, as specified below.

Indications for vascular lasers — Vascular lasers are used following burn injury primarily with the aim of improving or influencing the following aspects of wound healing and scarring:

●Delayed wound healing

●Postburn pruritus

●Hypervascularity and erythema

●Hypertrophic scarring

Delayed wound healing — Vascular lasers can be used for burn wounds and donor sites with either delayed healing or secondary breakdown, particularly if associated with hypergranulation, when more traditional dressing approaches have failed.

The promotion of wound healing by laser has mainly involved the use of low-level laser therapy delivered via a diode laser system [12], which has been reported to be effective for wounds in experimental [13-16] and clinical studies [17,18], including for skin graft donor sites in burn patients [19]. There have also been reports of successful PDL treatment in chronic nonhealing surgical wounds [20-22].

Postburn pruritus — Itching is a very troublesome symptom after burn injury and is known to be related to depth and extent of burns and presence of raised or thickened scars [23,24]. In a multicenter study, most of the children studied continued to experience symptoms two years after injury [25]. Although not currently regarded as first-line therapy [26], both PDL and IPL have been shown to be effective for reducing itching during the period of scar maturation and in hypertrophic scarring [27-29].

Persistent hypervascularity/erythema — Following healing, most burn scars will gradually become less red as the scar matures. However, in some cases, redness can persist for a prolonged period or fail to resolve. Even when not associated with hypertrophic scarring or troublesome itching, treating hypervascularity can be worthwhile to improve scar cosmesis.

Hypertrophic scarring — The management of hypertrophic scarring after burns routinely includes the use of moisturizers, massage, topical silicone, and pressure garments, as appropriate [30]. Other treatments such as intralesional steroid injections and microneedling are also used [31,32]. (See "Hypertrophic scarring and keloids following burn injuries".)

Vascular lasers have been used to modulate postburn hypertrophic scarring [33]. PDL has been used with variable success in the treatment of postburn hypertrophic scarring, with some studies reporting a good degree of improvement [34], while others have reported PDL to be less effective [27]. PDL therapy may be more effective at preventing hypertrophic scars, rather than for treating established scars [35,36]. There is also interest in the use of PDL to prevent the development of hypertrophic scarring in burn wounds that have been slow to heal. However, evidence suggests that early improvements in scar appearance do not persist with longer-term follow-up [37]. It is known that many hypertrophic scars will mature and improve over time, with a decrease in both modified Vancouver Scar Scale (mVSS) and the Patient and Observer Scar Assessment Scale (POSAS) scores. This fact, along with the lack of control groups in many studies, may confound outcomes.

Symptomatic improvement can be achieved with the best effects on scar erythema/vascularity and pruritus and less effect on scar height/thickness and elasticity [28]. Since vascular lasers target primarily the redness in the scar tissue, treatment is likely to be more effective in early hypertrophic scarring compared with mature burn scars. In longstanding burn scars where redness has persisted, an effect may still be obtained, which will reduce the visual impact of the scar, even though it is unlikely to flatten or soften the scar tissue at that stage.

Use and timing of vascular lasers — The subject of much debate is how early after burn wound healing a vascular laser can be used to good effect, without an increased risk of complications [36].

For treatment of postburn pruritus or hypertrophic scarring, most clinicians recommend that the burn wound is well healed prior to undertaking laser treatment. Thus, many would suggest commencing laser treatment at three to six months following wound healing [38], although it can still be effective on older scars. Other studies propose that treatment could be started earlier, during the inflammatory phase of wound healing, without problems and potentially with better effect [39,40]. Earlier treatment may give the opportunity to reduce scar proliferation as has been reported for laser treatment of surgical scars [41].

Thus, although six months is a good starting point for those new to laser practice, two to three months is likely to be quite safe, and when there are still small recalcitrant unhealed areas, earlier treatment may induce the wound to progress to complete healing.

The optimal interval between treatments has not been defined, with different protocols in use ranging from 4 to 12 weeks [28,37,38,41]. A standard interval of four to six weeks may be appropriate, particularly if laser therapy is being combined with other therapies such as intralesional steroid injections. It is important to ensure that any bruising or crusting from the previous treatment has fully resolved before a further treatment session is undertaken.

Parameters for vascular lasers — Treatment parameters (laser settings) will depend on the type of laser used, as manufacturers produce specific guidance for each device. Other factors to consider are the stage of wound healing, any fragility of the skin, and maturity of the scar. A series of two to six treatment sessions is recommended to allow for adjustment of laser settings depending on the patient's response. If the treatment has been well tolerated and without complications, then the energy can be sequentially increased in subsequent sessions to achieve the best response. However, it should be noted that the main benefit is usually seen within the first three treatment sessions, so if at that stage there is no discernible improvement, it may not be worthwhile to continue treatment.

Suggested laser settings for the first PDL treatment would be to select a spot size of 7 to 10 mm, a fluence of 5 to 8 J/cm², and a pulse duration of 0.45 to 3 milliseconds. Shorter pulse durations will produce more bruising (purpuric response), and while this is a good end point to aim for in mature hypertrophic scars, it is prudent to start with a longer pulse duration in fragile scars to avoid causing wound breakdown.

Advantages and disadvantages — One of the main advantages of vascular lasers is that the treatment in most cases can be tolerated well with the addition of cooling or in some cases topical anesthesia. Therefore, this is a comfortable outpatient intervention for most adults. In small children, particularly if a larger surface area is to be treated, sedation or general anesthesia is usually required. General anesthesia may well be justified for an intervention to relieve intense pruritus in a child. However, when considering attempts to decrease firmness or improve scar elasticity, the risk/benefit ratio needs to be considered, given the limited impact of PDL on established hypertrophic scarring.

Extra care should be taken when treating patients with Fitzpatrick skin phototypes IV to VI (table 1), as there is a risk of producing pigmentary change, which may be permanent. Treatment is more likely to produce hyperpigmentation rather than hypopigmentation, but both are a possibility. In many patients recovering from burns, there is already alteration of pigmentation, and the patient may feel that the potential benefit of the laser treatment outweighs this risk. Selecting laser settings with a longer pulse width (for example 2 ms or longer) will reduce the purpuric response and should reduce the risk of pigmentary alterations in those with higher skin phototypes.

Using a vascular laser in patients with burns is a quick, comfortable, and simple intervention that can usually be easily incorporated into the patient's care pathway. For burn clinicians interested in starting a laser service for their patients, the technology and facilities will often already exist in their institution and provide a gateway into gaining experience and setting up a more comprehensive laser service. Many health care facilities already have vascular lasers for use in other patient groups, and extending their use to burn patients requires minimal further investment. Treatment is performed under clean conditions but does not require a sterile environment, and running costs are low.

Complications of vascular lasers — The main complications that can arise from vascular laser treatment to burn scars are bruising, blistering, scabbing, and wound breakdown. It is essential that the patient is informed of these risks in the consent process, even if the procedure is undertaken in an outpatient setting. Purpuric response/bruising may be anticipated; however, the skin should not break or scab, so the risk of superimposed infection is generally low. If wound breakdown does occur, there is an additional risk of wound infection and in fact worsening of any hypertrophic scarring. When this occurs, further wound dressings and on some occasions antibiotics will be required.

There is the additional risk of changes in skin pigmentation, which can occur after any laser treatment, and thus, a requirement for sun protection post-treatment.

ABLATIVE LASERS

Indications for ablative lasers

●Burn wound debridement

●Treatment of unstable burn scars/slow-to-heal wounds

●Modulation of existing scars and contractures, including hypertrophic scars

Burn wound debridement — Ablative lasers can be used on the acute burn wound, either to excise nonviable tissue or to perform a superficial debridement prior to applying, for example, a biological dressing. In the latter scenario, the laser is essentially being used as a dermabrasion tool. Neither of these indications are in widespread routine therapeutic use. (See "Treatment of superficial burns requiring hospital admission", section on 'Cleansing and debridement' and "Treatment of deep burns", section on 'Early burn excision'.)

Treatment of unstable burn scars/slow-to-heal wounds — Particularly in patients who have suffered major burns, there may be residual areas of unstable scarring and recurrent wound breakdown. These can arise because of burn wound infection, graft loss, fragile skin cover (due to paucity of donor sites) and excess skin tension, among other reasons. The affected areas are a source of discomfort for patients, leaving them vulnerable to recurrent infections, and can delay progress with rehabilitation including the wearing of pressure garments. Fractionated laser treatment of these unstable scars, including both the area of the wound and the surrounding healed skin, improves wound healing [42].

Modulation of existing burn scars, hypertrophic scars, and contractures — By far the most prevalent use of ablative lasers in the field of burns is the treatment of scars and contractures. Historically, fractionated CO₂ laser has been used with good effect on mature burn scars [9,43-46]. Later work has suggested that laser treatment can be safely introduced earlier in the wound-/scar-healing process alongside its application in chronic unhealed areas [47,48]. (See 'Treatment of unstable burn scars/slow-to-heal wounds' above.)

Fractional ablative lasers are useful for confluent areas of hypertrophic scarring to relieve tightness, reduce thickness, and improve elasticity [6,49-52]. In a large prospective study, fractional CO₂ laser therapy improved the signs and symptoms of hypertrophic burn scars, as measured by objective and subjective instruments [9]. They can also be targeted to specific contracture bands to "release" scar tissue and improve range of movement, potentially reducing the requirement for surgical contracture releases [53]. Although the primary aim is to achieve collagen remodeling, symptomatic improvement is also seen with respect to discomfort, reduction of pruritus [9,54,55], and resolution of erythema.

In terms of surface irregularities, laser treatment can be useful to improve surface dyschromia and texture, minimize residual mesh patterns from skin grafting, and reduce small ridges.

Use and timing of ablative lasers — Some clinicians recommend starting scar treatments with pulsed dye laser (PDL) in the early phase to improve erythema and itch and then moving to CO₂ as the scar matures to address firmness, tightness, and inelasticity. However, there is a growing body of evidence that early intervention with CO₂ laser may address the same symptoms for which PDL is beneficial, along with having a more profound impact on the characteristics of burn scarring that can be measured objectively.

Treatment of burn scarring with fractional ablative laser commencing at three to six months post-wound healing has been suggested, with more evidence likely to emerge that earlier treatment of the immature scar is both safe and effective. (See 'Modulation of existing burn scars, hypertrophic scars, and contractures' above.).

A 6- to 12-week interval between treatment sessions (to the same scarred area) allows for healing and collagen remodeling to occur. Treatment interval protocols vary between different centers. If any residual pigment change or other complications are present from the previous treatment, the subsequent treatment should be delayed until that has fully resolved.

For reasonably localized scarring, most improvement will generally be achieved by the second or third sessions. However, burn patients with extensive scarring can go on to have more treatment sessions, addressing different regions and aspects of their scars.

Pretreatment and care after laser therapy — It is important to have protocols for pretreatment and aftercare. Each institution has its own local protocols based upon expert opinion and consensus, rather than any sound scientific basis.

Wound infection is most likely if the skin is already heavily colonized or there are areas of unstable scars/minor breakdown pretreatment. Local protocols vary, but a short course of antibiotics may prevent secondary infection of the treated area.

A proportion of the population will have dormant herpes simplex or herpes zoster infection. Especially for laser treatments on the face, there is a risk of reactivation of the virus [56]. Thus, some clinicians recommend antivirals for patients undergoing facial scar treatment.

Aftercare is directed at preventing infection, crusting, or scabbing of the treated area and focuses on cleansing, emollients, and moisturizing, alongside, in some practices, dressings. Sun protection is advised in all cases both before and after treatment.

Parameters for ablative lasers — Numerous fractional ablative devices are available from different manufacturers, and treatment parameters vary based upon which is used. Parameters should also be adjusted based upon characteristics of the scar tissue (eg, atrophic versus hypertrophic scar, thick bands of scar contracture). Thus, scar assessment is essential prior to embarking on a series of laser interventions, as this will help direct the therapy and allow a more objective evaluation of outcomes.

Whichever brand of ablative laser is used, a test patch in a less visible area is advisable, particularly for those of Fitzpatrick skin types III to VI. To reduce the complications of burns or wound breakdown, it is best to avoid or have minimal overlap and to apply topical skin cooling. Depending on results achieved and patient response, fluences and/or density can then be increased incrementally or, if necessary, decreased. Experienced operators will quickly learn to observe the laser. The UltraPulse CO₂ laser and the CO₂RE device are two of the more popular lasers for this application; however, other fractionated CO₂ lasers are also available.

●The UltraPulse has several treatment modes; the DeepFX and SCAAR FX modes are used for hypertrophic burn scars.

•Relatively conservative initial parameters for clinicians offering this therapy for thick hypertrophic scarring would be DeepFX at a fluence of 17.5 to 20 mJ, density 5 percent, shape 2 at size 10 (which produces a square), and a rate of 300 Hz. A single pass is used over the area to be treated. The beam will penetrate up to 1.5 mm into the skin. This is suitable for large confluent areas of hypertrophic scarring.

•For distinct bands of scar tissue 3 mm or more thick, SCAAR FX is the more effective mode. Here, the laser beam penetrates up to 3.5 to 4 mm below the skin surface and can be very beneficial for scar band contractures. Again, starting parameters of 110 to 130 mJ, density 3 percent, shape 2 (size selected depending on the breadth of the scar band), and a frequency of 250 to 300 Hz should be within a good safety margin and can be adjusted once the effect is observed. For thicker scar bands, it can be useful to increase the pulse energy up to 150 mJ, along with decreasing the density to 1 percent to reduce the risk of wound healing problems.

•A third fractional mode, ActiveFX, is available on the UltraPulse laser. Delivered via a different handpiece, this has a larger spot size of 1.3 mm and less depth of penetration than the other two modes, therefore producing a more superficial effect to target surface irregularities and dyschromia. Clinicians can use these three modes in different combinations for patients according to the thickness of their scarring and desired effect on the skin surface [42].

●The CO₂RE laser system has four fractional modes available (Lite, Mid, Deep, and Fusion). The Deep mode is the one regularly used to achieve dermal remodeling in hypertrophic burn scarring. Typical treatment parameters are a fluence of 50 to 70 mJ, density/coverage of 4 to 5 percent, and a 7.5 x 7.5 mm square shape. The Fusion mode allows simultaneous treatment of both superficial and deeper layers, akin to using the Active FX mode of the UltraPulse laser in conjunction with DeepFX.

For specific ridges, edges, and margins of skin grafts, ablative lasers can be used in a nonfractionated mode. This allows for precise ablation of the targeted area (using a small spot size such as 2 mm) to remove small amounts of tissue to improve aesthetic appearance. In this mode, there is confluent ablation of tissue, so there is a higher risk of wound healing problems leading to new scarring if an extensive area is treated.

Dual-platform devices (comprising two ablative lasers of different wavelengths) or combinations of lasers can be used during the same treatment session [47,57,58]. This can be particularly useful in children, addressing different aspects of scarring with the different technologies, all while under sedation or general anesthesia [59-61]. Authors reporting a combined PDL/fractionated CO₂ approach have not always reported their treatment parameters; however, these would need to be reduced from the settings when only a single laser is used.

Advantages and disadvantages — Ablative lasers produce the most noticeable outcomes and impact on burn scarring. The intervention can be more or less guaranteed to produce an effect, unlike PDL, in which the response to treatment from hypertrophic scars is variable. Thus, as a more high-powered technology, there is the potential to produce quite a dramatic improvement in scarring, alongside a greater potential for complications. Particular care must be taken if working near the orbital region.

Ablative lasers can certainly be effective in very mature burn scars, which is a great advantage for patients who may not have had access to this type of service in the early years after their burn injury. Treatment with ablative lasers may help to avoid repeated surgical interventions and yet can be used incrementally to achieve the desired result.

The procedure of ablative laser is painful, and consideration needs to be given to pain management both during and after treatment [62]. There is a wide variation in patient tolerance. Some patients cope well with topical anesthetic, particularly if they underwent a deep excision of their original burns and the area is relatively insensate. For others, topical anesthesia will need to be augmented with injections of local anesthetic, particularly where a greater depth of penetration of the laser beam will be used. In more extensive treatments and the majority of pediatric cases, general anesthesia will be required.

Overall, a higher level of resources and facilities are required to run an ablative laser service for burn patients. Fractionated CO₂ laser is a high-powered device, and although it can be operated by advanced laser clinicians, it is most usually administered by trained staff, which makes this a more costly procedure. However, analysis suggests that this can still be cost effective [63,64].

A greater degree of sterility is required due to the fact that the laser penetrates the intact skin surface, and there is consequently a higher risk of infection than for vascular lasers. This requires an operating room or clean treatment room environment, further adding to running costs.

Complications of ablative lasers — The main complications arising after ablative laser therapy are scabbing, wound breakdown, infection, and subsequent delayed healing, resulting in further or worsened scarring [65]. (See 'Pretreatment and care after laser therapy' above.)

Cooling is advised either during or immediately after treatment. Bleeding can occur, especially if large areas are treated with the SCAAR FX mode. Although bleeding is usually reported as mild, in such cases it may be best to apply a dressing post-treatment.

Changes in skin pigmentation, including hypopigmentation and postinflammatory hyperpigmentation, may be transient, but in some cases are permanent.

LASERS FOR HAIR REMOVAL — A wide variety of lasers are used for hair removal, which is mostly undertaken in the beauty and cosmetic sector, rather than for medical indications. There are a few specific clinical scenarios for burn patients in which hair removal may be warranted. The laser classes used for this purpose include diode lasers; alexandrite; long-pulsed neodymium, yttrium aluminum garnet (Nd:YAG); and intense pulsed light (IPL). (See "Removal of unwanted hair" and "Principles of laser and intense pulsed light for cutaneous lesions".).

Indications for laser hair removal — Hair removal may be sought after burns in the following circumstances:

●A full-thickness graft has transferred hair to an undesirable location (eg, the hand).

●A thick split-thickness graft (particularly scalp) has transferred hair to an undesirable location, such as the face.

●A transferred flap has unacceptable hair growth in the recipient area.

●Pre-existing normal hair growth in an area of burn scarring is causing recurrent infection, irritation, or folliculitis, which is difficult to manage.

Use and timing of laser hair removal — In most circumstances of undesirable hair growth, other options are available for hair removal, including trimming, shaving, and depilatory creams (see "Removal of unwanted hair"). It would usually be advised to use these until later in the recovery period and to only attempt laser hair removal when wounds are healed and stable.

The laser treatment should be regarded as aiming to achieve permanent hair reduction (in terms of number of hair shafts and their thickness) rather than total hair removal. However, when successful, it is very effective and makes the situation of the unwanted hair much more manageable for patients.

Any of the laser categories listed above can be used as long as the operator is familiar with the equipment and trained in its use.

Prior to laser hair removal, the area to be treated should be photographed and marked. The hair is then shaved, and local anesthetic cream is applied topically. Cooling is used during treatment. Most patients find the treatment tolerable, although for sensitive areas such as the face, some oral analgesia may also be provided.

Laser devices have recommended treatment parameters (laser settings) for hair removal based upon Fitzpatrick skin phototype (table 1), site of the body where the hair is located, and whether the hair is coarse or fine. Attention should thus be paid to where hair was transferred from, rather than its current location, as this will help to guide in selecting the correct parameters for treatment.

A program of up to six treatment sessions at eight-week intervals will be required to achieve optimum hair reduction.

Complications of laser hair removal — The complications of any laser hair removal include erythema and blistering of the skin, potential skin breakdown and wound infection, scarring, lack of effectiveness, and temporary or permanent alteration in skin pigmentation. There is also a risk of paradoxical hypertrichosis (PH) following laser hair removal. The incidence is reported to vary from 0.6 to 10 percent of patients treated, with predisposing factors including underlying hormonal conditions and concurrent medications including systemic steroid therapy. The incidence of PH in patients who have previously suffered from burns is not currently known; however, this highlights the importance of obtaining a full medical history, including prescribed medications, prior to proceeding.

Laser hair removal is the laser procedure associated most frequently with litigation, possibly related to the fact that a high proportion of procedures are undertaken by clinicians who are not adequately trained.

LASER-ASSISTED DRUG DELIVERY FOR SCARS — Intact stratum corneum is an important protective skin barrier that poses challenges to skin drug delivery. Nutrients and drugs passing through the barrier must have a low molecular weight and be water- and fat-soluble. Otherwise, the delivery needs to be assisted by technologies such as ionophoresis or by removal/breaching the stratum corneum [66].

Development of laser assisted drug delivery — Percutaneous drug delivery was first investigated by Wurster in 1960 when the absorption rate of methyl salicylate was tested on healthy volunteers [67]. Scopolamine, on other hand, was the first drug to be delivered topically as antiperspirant in 1964 [68]. Later in 1976, scopolamine was introduced via a postauricular patch where the stratum corneum is thinnest to provide programmed and sustained delivery [69]. Patch refinement was fast-tracked to be used by astronauts working on space lab missions and for sailors [70]; other drugs such as insulin, fentanyl, clonidine, nitroglycerine, and nicotine followed [71].

At about the same time, examination of the ultrastructure of the stratum corneum showed that transient "permeabilization" allowed drug delivery in the skin of healthy volunteers when stimulated by laser photomechanical waves by forming transient lacunar channels within the stratum corneum [72,73]. A nude mouse model examined the permeation/flux of 5-fluorouracil (5-FU) through the stratum corneum following pretreatment of skin with laser; erbium:YAG, ruby, and CO₂ lasers were used as ablative tools of the stratum corneum [74]. Skin permeation of 5-FU was highest with pretreatment with erbium:YAG, followed by high fluence of the CO₂ laser and moderate effect with the high fluence of the ruby laser. Histologic analysis showed, as expected, that the higher the stratum corneum ablation, the higher the 5-FU flux into the epidermis and dermis. In addition, there was dermal destruction with the high-fluence CO₂ that was not demonstrated with erbium:YAG laser. This work showed that stratum corneum ablation could effectively facilitate drug delivery. The work confirmed that photomechanical waves of laser, by creating confined ablations, form a transient lacunar system within the stratum corneum that acts as channels for drug delivery [75].

The introduction of ablative fractional laser in 2004 by Anderson made the use of laser safer and more widely used for different disciplines. Gradually, ablative fractional laser became the forefront of drug delivery as more experimental work was conducted, improving the understanding of how it works and how to refine the delivery for better outcomes. In a comparison study, drug permeation was almost doubled, with fractional erbium:YAG laser compared with conventional erbium:YAG laser treatment using the same energy fluence and number of passes [76]. This is not surprising, since conventional nonfractionated laser almost denuded the stratum corneum. This was explained further by Anderson's group in their work on the impact of the ablative fractional laser treatment density, the fraction of the skin occupied by laser microthermal channels. They reported that laser treatment density could be varied to optimize delivery of molecules of different molecular weight into the dermis and the subcutaneous fat [77]. Further experimental work demonstrated the efficacy of ablative fractional laser for drug delivery [78-83].

Clinical applications in burn care — Clinical applications of conventional ablative and fractional ablative laser started to emerge during the last 10 years, mostly for nonmelanotic skin cancer [84-86], followed by use for hypertrophic scar drug delivery [87]. A wide range of drugs that may modulate hypertrophic scarring were used, including triamcinolone, botulinum toxin, verapamil, 5-FU, and betamethasone [29,88-96]. However, as shown in a systematic review with qualitative synthesis of randomized controlled trials, all studies have either some concern or high risk of bias with heterogenicity of the participants, methodology, and outcome assessment. The authors recommended larger samples of participants and longer follow-up to adequately assess the benefits and the potential harm of laser-assisted drug delivery [87].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Care of the patient with burn injury".)

SUMMARY AND RECOMMENDATIONS

●Laser therapy – Lasers used in burns and burn reconstruction can broadly be grouped as vascular lasers and ablative lasers. Other applications used in the treatment of burns and burn reconstruction include laser hair removal and lasers to assist delivery of medications. (See 'General principles and definitions' above.)

•Vascular lasers are a group of lasers that target oxyhemoglobin (figure 1). The term is also sometimes used to refer to intense pulsed light (IPL) devices, although these are not lasers. Vascular lasers for the treatment of burns and burn reconstruction are typically the pulsed dye laser (PDL) and IPL systems.

•Ablative lasers are a group of lasers that target water (figure 1). The effect of the laser is to vaporize tissue. Ablative lasers may also have a thermal effect on adjacent nonablated tissue. Ablative laser therapy can be delivered in a mode in which the whole of the treated skin surface is targeted (nonfractionated) or just a portion is targeted (fractionated).

-Ablative lasers commonly used in burns and burn reconstruction are the carbon dioxide (CO₂) laser (wavelength 10,600 nm) and the erbium: yttrium aluminium garnet (Er:YAG) laser (wavelength 2940 nm).

-Combined dual wavelength CO₂/Er:YAG laser platforms are also available.

•Lasers and light-based technologies used for hair removal include diode lasers; alexandrite; long-pulsed neodymium, yttrium aluminum garnet (Nd:YAG; wavelength 1064 nm); and IPL.

●Vascular lasers – Vascular lasers treat lesions with vascularity and aim to improve or influence wound healing and scarring. They can be used to manage delayed burn wound or donor site healing, wound breakdown, postburn pruritus, and hypertrophic scarring. (See 'Vascular lasers' above.)

•For modulating postburn hypertrophic scarring, treatment is more effective with early hypertrophic scarring compared with mature burn scars. The best effects are seen with respect to scar erythema/vascularity and pruritus and less so for scar height/thickness and elasticity. (See 'Indications for vascular lasers' above.)

•Many suggest starting laser treatment at three to six months following wound healing; however, others propose that treatment can be started during the inflammatory phase of wound healing (two to three months), potentially with better effect. (See 'Use and timing of vascular lasers' above.)

•An interval of four to six weeks between treatments is appropriate, particularly if laser therapy is combined with other therapies (eg, intralesional steroid injections). Any wound breakdown or infection should be fully resolved before commencing the next treatment session. (See 'Use and timing of vascular lasers' above.)

•Complications associated with vascular lasers include bruising, blistering, wound breakdown, infection, and pigmentation change (which can be permanent). (See 'Complications of vascular lasers' above.)

●Ablative lasers – Ablative lasers are used for burn wound debridement, treatment of unstable burn scars and slow-to-heal wounds, and modulation of existing scars, including hypertrophic scarring and contractures. Fractional ablative lasers relieve tightness, reduce thickness, and improve elasticity and are particularly useful in areas of confluent hypertrophic scarring. They can also target specific contracture bands to "release" scar tissue and improve range of movement. Ablative laser treatment can also improve surface dyschromia and texture. (See 'Ablative lasers' above.)

•Early intervention with CO₂ laser may address the same symptoms for which PDL is beneficial. Ablative lasers can also be effective in very mature burn scars, which is useful for those who did not have access early after their burn injury. (See 'Indications for ablative lasers' above.)

•Treatment of burn scarring with fractional ablative laser commencing at three to six months post-wound healing has been suggested, with a 6- to 12-week interval between treatment sessions to allow healing and collagen remodeling and after any complications from the previous treatment have resolved. Multiple treatment sessions are usually required. (See 'Use and timing of ablative lasers' above.)

•Complications include skin breakdown, infection, the potential for worsened scars, and pigment change (which can be permanent). To prevent infection, maintaining sterility, and for some applications, prophylactic antimicrobials are important. (See 'Complications of ablative lasers' above.)

●Hair removal – Hair removal may be needed to manage unwanted hair on full-thickness or split-thickness grafts or flaps, or removal of preexisting normal hair growth that is contributing to complications in an area of burn scarring. Laser treatment aims to permanently reduce hair in terms of number of hair shafts and their thickness, rather than total hair removal. Laser hair removal is used later in the recovery period after wounds are healed and stable. Up to six treatment sessions at eight-week intervals are needed to achieve optimal hair reduction. Complications included skin breakdown, infection, and paradoxical hypertrichosis. (See 'Lasers for hair removal' above.)