Lasers Flashcards

Question

A 45-year-old woman comes to the office because of a rash and a burning sensation on her face 1 week after undergoing carbon dioxide cutaneous laser resurfacing. Physical examination shows erythematous pustules on the right side of the face in the V3 distribution. Which of the following agents is the most appropriate treatment? A ) Oral acyclovir B ) Oral cephalexin C ) Oral prednisone D ) Topical bacitracin E ) Topical petrolatum

Answer 1

The correct response is Option A. The patient €™s symptoms are consistent with a viral infection. Viral, bacterial, and fungal infections can develop after cutaneous laser resurfacing, usually at the time of the first postoperative week during the reepithelialization process. The most frequent infectious complication associated with resurfacing is a reactivation of the herpes simplex virus (HSV). It is suspected that direct laser trauma to the skin leads to latent viral activation and shedding. Herpetic outbreaks are experienced by roughly 2 to 7% of all laser-treated patients despite antiviral prophylaxis. In addition, due to the high incidence of latent HSV infection, any patient (regardless of prior HSV history) planning to undergo full-face or perioral resurfacing should be given oral antiviral prophylaxis in an effort to reduce viral reactivation, which could subsequently lead to scarring. Early postlaser detection of HSV is often difficult because there is no intact epithelium, and, rather than the characteristic grouped vesicles or pustules, infection is manifested by small, superficial erosions. Symptoms of HSV reactivation include tingling, burning, or discharge from isolated foci within the treated areas. Extensive eruptions can result in disseminated infection and atrophic scarring, and therefore, must be recognized early and treated aggressively. Oral antiviral agents, such as acyclovir, famciclovir, or valacyclovir, are routinely administered 1 to 2 days before the laser resurfacing procedure and are continued for another 7 to 10 days until reepithelialization is complete. If a herpetic outbreak occurs despite prophylaxis, patients should either be switched to a different antiviral agent or have their dosage increased to maximal herpes zoster doses (acyclovir 800 mg 5 times daily or famciclovir or valacyclovir 500 mg 3 times daily). Cephalexin would be more appropriate for bacterial skin infections. Bacitracin does not have antiviral coverage. Topical petrolatum is a bland emollient and would not treat the HSV outbreak. Oral corticosteroids do not have any role in the treatment of viral infections.

Answer 2

Correct answer is option B. Higher Fitz level patients are more prone for post inflammatory hyperpigmentation (PIH). Preventative measures such as hydroquinone can decrease the risk of PIH.

Answer 3

The correct response is Option B. Laser resurfacing of the skin (as well as other resurfacing modalities such as dermabrasion and chemical peels) is contraindicated in patients who have used isotretinoin (Accutane, an oral retinoid) within 18 months. Isotretinoin suppresses skin appendageal activity and, therefore, prevents normal reepithelialization after resurfacing. If the wounded skin is not reepithelialized within 10 days, scarring may result. Many clinicians wait 24 months after the last oral retinoid dose was administered before performing skin resurfacing. Note that topical retinoids such as isotretinoin (Retin-A) do not have this effect on skin appendages and their use is not a contraindication to skin resurfacing. Hydroquinone is a tyrosinase inhibitor and results in lightening (bleaching) of the skin. It is frequently used before and after skin resurfacing to prevent hyperpigmentation. Valacyclovir, an oral antiviral, is indicated in patients with a history of oral herpes simplex outbreaks. It should be started before the procedure and continued until reepithelialization occurs. Oral contraceptives and nicotine patches have not been shown to cause complications after skin resurfacing.

Answer 4

The correct response is Option B. In patients who have certain types of foreign material embedded in the skin, especially road asphalt, carbonaceous material, or ink from amateur tattoos, the most appropriate method of removal is multiple treatments with the Nd:YAG laser. In the past, traumatic tattoos were removed with mechanical abrasive techniques, including dermabrasion, salabrasion, and the rubbing of table salt into the skin, each of which produced satisfactory results in superficial tattoos. However, better results have recently been demonstrated with laser therapy, which involves the removal of successive layers of skin to expose the intradermal pigment, which is subsequently vaporized. The surgeon should take great care while administering Nd:YAG laser treatments in any patient who has sustained injuries resulting from a gunpowder or fireworks accident, as the unburned, embedded gunpowder can actually combust during treatment, leading to unacceptable scarring. Although laser therapy is the treatment of choice for traumatic tattoos, the carbon dioxide laser is not recommended because it does not effectively remove embedded carbonaceous material. In addition, this laser has no selective absorption; as a result, epidermal structures are injured more easily and scarring is increased. Deep dermabrasion and wide local excision combined with thin split-thickness skin grafting are excessively invasive procedures that will yield poor cometic results.

Answer 5

The correct response is Option B. Laser hair removal targets the melanin in the hair follicle. It is not useful in fair-haired patients who have low levels of melanin in their hair follicles. Although all the devices listed here have been employed for hair reduction, only electrolysis would be likely to work in this patient.

Answer 6

The correct response is Option A. Patients classified as higher Fitzpatrick types have a higher risk for hypopigmentation after carbon dioxide laser therapy. For example, punctate hypopigmentation has been found in up to 35% of facial burn patients presenting 2 months after being treated with fractionated carbon dioxide laser therapy. To decrease the risk for further hypopigmentation, the dwell time needs to be decreased. Increasing the dwell time prolongs the time of exposure, increasing the risk for hypopigmentation. Increasing or decreasing the spot size only increases or decreases the surface area treated. Increasing the energy would also increase the risk for hypopigmentation.

Answer 7

The correct response is Option A. Choice of lasers for the treatment of tattoos is guided by the absorption spectrum of the ink colors present within the tattoo. Orange and yellow tattoo inks are targeted specifically by lasers in the low (500-nm) range, making the 532-nm Q-switched Nd:YAG laser or the 510-nm pulsed-dye laser optimal for treatment. The Q-switched alexandrite (755-nm) and Q-switched ruby (694-nm) lasers can be used for black, blue, and green pigments. The Q-switched Nd:YAG (1064-nm) laser is optimal for black pigment. Nd:YAG, long-pulsed 1320-nm laser treatment was the first system developed solely for nonablative skin remodeling.

Answer 8

The correct response is Option E. Lasers generate heat in the target tissue that dissipates by conduction. The amount of heat generated is a function of the wavelength of the laser and the duration of exposure. Selective tissue injury is caused by the choice of a wavelength of energy that is specific for a particular target chromophore within the skin. The Er:YAG laser is an ablative laser with a wavelength of 2940 nm and a target chromophore of water. There is less thermal diffusion to the surrounding tissues with an Er:YAG laser than with a CO2 laser, although both have the same target chromophore. Fractional photothermolysis uses a blue dye template, which also serves as the target chromophore, and divides the skin into microscopic thermal zones. The Nd:YAG laser affects blood vessels, red blood cells, collagen, and melanin. Intense pulsed light targets water, hemoglobin, and superficial or deeper pigment, depending on the wavelength.

Answer 9

The correct response is Option B. Erythema following laser resurfacing is an anticipated consequence of therapy. Posttreatment erythema is more severe and of longer duration with carbon dioxide laser resurfacing when compared to the fractionated carbon dioxide or Er:YAG laser. Postoperative topical application of ascorbic acid has been shown to decrease the duration as well as the severity of erythema. Topical therapy with ascorbic acid should be applied following reepithelialization. Antibiotics or antivirals have not been shown to decrease erythema. Hydroquinone is a skin bleaching agent that does not treat erythema. Topical corticosteroids postoperatively may delay reepithelialization and have not been associated with a decrease in erythema.

Answer 10

The correct response is Option B. Along with ocular hazards and fire hazards, laser smoke plume is a significant occupational hazard, which is often ignored when lasers are used. There are numerous substances, some carcinogenic and mutagenic, released during laser pyrolysis of tissue. Viable skin bacteria, including coagulase-negative Staphylococcus, Corynebacterium, and Neisseria, have been recovered from the laser plume following laser skin resurfacing. In addition, intact viral DNA, particularly of human papillomavirus, has been isolated from carbon dioxide laser plume. Most surgical masks only filter particles that are 5 microns in diameter or larger; however, 77% of particles in the laser plume are 1 micron or smaller. Therefore, well-fitted high-filtration or laser masks should be used instead of standard surgical masks. A high-efficiency smoke evacuator should also be used, but it needs to be within 1 to 2 cm of the laser smoke plume source. The effectiveness of the smoke evacuator is decreased from 99 to 50% as the distance from the laser-treated site is increased from 1 to 2 cm, so 20 to 25 cm away is ineffective.

Answer 11

Correct answer is option B. The three main chromophores that lasers target are hemoglobin, melanin, and water.

Answer 12

The correct response is Option A. The patient described has a presumptive diagnosis of cutaneous herpes simplex. Herpes simplex commonly is activated by laser resurfacing, spreads readily, and may scar. To avoid this complication, antiviral prophylaxis with one of the established drugs (acyclovir [Zovirax], famciclovir [Famvir], or valacyclovir [Valtrex]) should be started 24 to 48 hours before a laser resurfacing procedure and continued for 10 days until re €‘epithelialization is complete. Herpes simplex is difficult to recognize on resurfaced skin. Moreover, primary or secondary bacterial infection cannot be overlooked. Therefore, antibiotic coverage is prudent, particularly until culture results are available. When a patient experiences an outbreak of herpes simplex despite the use of antiviral prophylaxis, the physician should perform a Tzanck smear and send viral, fungal, and bacterial cultures. The anti €‘herpetic dosage should be increased to zoster levels as well (acyclovir 800 mg five times a day, valacyclovir 500 mg three times a day). This patient presented with signs and symptoms of systemic herpetic infection, which may include disseminated cutaneous lesions, shortness of breath, high fever and chills, malaise, headache, and neurologic changes. When these are present, hospital-based treatment with intravenous antiviral and antibiotic therapy is warranted.

Answer 13

The correct response is Option D. Unlike the other pretreatments, isotretinoin (Accutane) is contraindicated in any skin resurfacing procedures. Although its use for the treatment of acne is regulated, because of its significant risk for causing birth defects, it may also interfere with healing after resurfacing procedures. This complication may occur even if the medication has not been used for one year. For this reason, all patients should be asked about isotretinoin use before any resurfacing procedure is performed. The remaining treatments are not a contraindication to facial skin resurfacing. Acyclovir is frequently administered before and after resurfacing procedures, particularly in patients with a history of herpes virus outbreaks. A glycolic acid peel may also be administered before resurfacing; however, little data show that it will prevent pigment changes or decrease inflammation after resurfacing. Hydroquinone may also be administered, but again, there is lack of good data that it provides significant improvement of pigment changes. Although similar to isotretinoin, tretinoin (Renova, Retin A) does not cause an increased risk of healing complications after laser resurfacing. It is frequently used as a pretreatment in such cases.

Answer 14

The correct response is Option D. The Nd:YAG laser is most appropriate for removal of this patient's tattoo. This laser emits light at a wavelength of 1064 nm and is preferentially absorbed by dark pigments, such as blue and black. It penetrates the skin to a depth of 2 to 6 mm, which will result in disruption of the tattoo pigment. Multiple treatments are typically required. Both carbon dioxide and erbium lasers are inappropriate for tattoo removal because they are chromophores of water. These lasers are typically used to resurface scarred or wrinkled areas of skin. The carbon dioxide laser emits light at a wavelength of 10,600 nm and can be used in a continuous mode to cut skin. The erbium laser emits light at a wavelength of 2940 nm. The copper vapor and pulsed dye lasers produce light at wavelengths from 500 to 600 nm. Although their beams penetrate skin, their shortened wavelengths preclude deep penetration. These laser wavelengths are absorbed by red and brown chromophores.

Answer 15

The correct response is Option D. The Q-switched Nd:YAG and alexandrite lasers are best used for removal of blue-green tattoo pigments. In contrast, the Nd:YAG laser works best for red, brown, and orange pigments, while the Q-switched ruby laser is used to remove tattoos with violet and purple pigments. Because professional tattoos often extend deep within the dermis, multiple treatments are required. Because it causes minimal damage to adjacent tissues, the carbon dioxide laser is effective for ablation (skin resurfacing), cutting, and coagulation. Although serial excision can be used in the treatment of traumatic tattoos, scarring is a common sequela. Dermabrasion is recommended for small traumatic tattoos.

Answer 16

The correct response is Option B. Nonablative fractional lasers are commonly used for acne scar resurfacing in darker skin types. Nonablative lasers work by denaturation of dermal collagen with subsequent remodeling, without any vaporization or damage to the epidermis. Erbium-doped fiber laser (1550 nm) is a nonablative laser while Erbium:YAG (2940 nm), carbon dioxide (10,600 nm), and Erbium:YSGG (2790 nm) are ablative lasers.

Answer 17

The correct response is Option C. ``` Intense pulsed (broadband) light is a high-intensity light source that emits polychromatic energy. It supplies noncoherent light over a broad spectrum of wavelengths from 510 to 1200 nm. This broad spectrum allows variability regarding target selection and skin types. Intense pulsed-light systems are commonly used to treat hyperpigmentation, telangiectasis, rosacea, excessive or unwanted hair, rhytids, and vascular malformations. When used for photoaging, they have been shown to produce long-term positive results on the face, neck, and chest. They have also demonstrated improvement in telangiectasis and pigmentation. Adverse effects of intense pulsed light include crusting, erythema, and purpura. Alexandrite, diode, pulsed-dye, and YAG laser systems emit monochromatic coherent light. Each device has a specific wavelength and chromophore. ```

Answer 18

The correct response is Option E. Use of nonsurgical skin rejuvenation has increased exponentially over the past 20 years, with over 4.6 million cases performed annually. This increase has led to expansion of different types of devices for resurfacing. The use of lasers for facial resurfacing has been discussed since the 1980s, initially with carbon dioxide lasers and then with erbium-doped yttrium aluminium garnet (Er:YAG) lasers in the late 1990s. Ablative laser treatments have been used to target actinic skin damage and moderate to heavy rhytides. Lasers work by means of a wavelength of light being absorbed by specific targets (chromophores) in the tissue, causing thermal damage. The targeted chromophore absorbs energy, which is converted to heat. The Er:YAG laser has a wavelength of 2940 nm. The peak absorption of water is nearly 2900 nm, which means that an Er:YAG laser has an absorption 12- to 16-fold greater than carbon dioxide laser. Targeting hemoglobin would not be appropriate since this will not lead to rejuvenation of perioral rhytides. The treatment of melanin is not the correct target since this would only lead to hypopigmentation or absorb the laser wavelength and lead to a possible burn. Collagen and elastin are essential elements of maintaining a youthful dermis; these dermal proteins are not the target of lasers, but rather induced by the trauma occurring from the laser itself.

Answer 19

' correct answer is option E. Use of retin-a as a pretreatment prior to laser treatment, allows for a more uniform skin layer for the laser to target. This can allow a more even distribution of the laser treatment throughout the treatment area.

Answer 20

The correct response is Option E. The principle of selective photothermolysis as applied to skin resurfacing (ablation) is based upon water content. The epidermis is composed of 90% water and is vaporized at temperatures in excess of 212°F (100°C). The carbon dioxide laser has water as its chromophore. The carbon dioxide laser has a wavelength of 10,600 nm and has a water absorption coefficient of 800/cm. The collagen, elastin, hyaluronic acid, and melanin content of skin may be affected by the temperature change from the laser energy, but water is the chromophore that is targeted by an ablative, fractionated carbon dioxide laser.

Answer 21

The correct response is Option C. 5-Aminolevulinic acid (ALA) is a topical medication that, when placed on the skin, penetrates the altered epithelial epidermis and is absorbed into the keratinocytes, whereby it is converted enzymatically into protoporphyrin IX. The application of light results in the release of cytotoxic radicals, which render this drug useful for the treatment of cutaneous lesions. Protoporphyrin IX has a maximum absorption at 410, 630, and 690 nm. Because of this, blue light systems (400B450 nm), pulsed-dye systems (585B595 nm), and photo rejuvenation systems (560B1200 nm) all may activate the drug. Recently, it has been used for the treatment of acne vulgaris as well as aging. It requires up to one hour of application time before initiation of therapy and may result in several days of swelling, erythema, and exfoliation. Patients also tend to be photosensitive for up to 48 hours after treatment. Radiofrequency and erbium (2940-nm) laser systems are not within the visible spectrum and will not activate protoporphyrin IX. Topical agents such as phenol and tretinoin will not activate this drug.

Answer 22

The correct response is Option D. The chromophore for the pulsed-dye laser at a wavelength of 585 nm is oxyhemoglobin. Thus, this laser is best suited to treat vascular lesions. Rhytides, acne scars, and dyschromias can also be managed by ablative resurfacing techniques, such as a carbon dioxide laser, which is absorbed by water. Er:YAG has a wavelength of 2940 nm and is absorbed by water. This laser causes less collateral thermal necrosis than a carbon dioxide laser. Acne scarring is best managed with infrared lasers at wavelengths of 1064 to 1540 nm. These include the Nd:YAG, diode, and erbium lasers. Tattoos are best managed with a Q-switched ruby laser at a wavelength of 694 nm, which is absorbed by melanin and carbon pigments.

Answer 23

The correct response is Option C. Use of nonsurgical skin rejuvenation has increased exponentially over the past 20 years, with over 4.6 million cases performed annually. This increase has led to expansion of different types of devices for resurfacing. The use of lasers for facial resurfacing has been discussed since the 1980s, initially with carbon dioxide lasers and then with erbium-doped yttrium aluminium garnet (Er:YAG) lasers in the late 1990s. Ablative laser treatments have been used to target actinic skin damage and moderate to heavy rhytides. Post-inflammatory hyperpigmentation (PIH) is a common sequela of laser resurfacing procedures. Pretreatment with various topical agents can optimize the skin, decreasing the risk for this well-known adverse event. Hydroquinone decreases melanin production by enzymatically inhibiting the conversion of tyrosine to dihydroxyphenylalanine. Tretinoin promotes cornified cell detachment and enhances shedding. It also increases mitotic activity, thereby increasing loosely adherent corneocytes turnover. Tranexamic acid is a synthetic derivative of the amino acid lysine and binds the five lysine binding sites on plasminogen. This inhibits plasmin formation and displaces plasminogen from the fibrin surface. In melasma, the hypothesized mechanism of action of tranexamic acid includes the shrinkage of dermal vasculature and decreased melanin synthesis by altering the interaction of keratinocytes and melanocytes and decreasing tyrosinase activity. Fluocinolone acetonide is a potent corticosteroid that is often used in conjunction with tretinoin and hydroquinone to treat pre-existing PIH and/or for pretreatment of the skin prior to laser resurfacing. By itself, fluocinolone does not have the aforementioned mechanism of action. Brimonidine gel, originally approved for the treatment of facial rosacea, causes direct vasoconstriction. This alpha-adrenergic receptor agonist is often used in conjunction with topical steroids to help decrease the risk for PIH. Zinc oxide is a physical barrier sunscreen. REFERENCES: 1. Wong ITY, Richer V. Prophylaxis of post-inflammatory hyperpigmentation from energy- based device treatments: a review. J Cutan Med Surg. 2021;25(1):77-86. doi: 10.1177/1203475420957633 2. Farshidi D, Hovenic W, Zachary C. Erbium:yttrium aluminum garnet ablative laser resurfacing for skin tightening. Dermatol Surg. 2014;40 Suppl 12:S152-6.

Answer 24

The correct response is Option D. The erbium:YAG (Er:YAG) laser emits light at a wavelength of 2940 nanometers (nm) and is absorbed by water within the epidermis a minimum of 10 times more efficiently than the carbon dioxide laser. Its mechanism of action involves photomechanical injury to the targeted tissue. The 585-nm pulsed-dye laser is used in the treatment of cutaneous vascular lesions. The lesser-energy, variable pulsed-width frequency, double Q-switched Nd:YAG laser and the higher-energy, millisecond pulsed Nd:YAG laser both have a wavelength of 1064 nm. The double Q-switched Nd:YAG laser is appropriate for the removal of hair or tattoos, and the millisecond pulsed Nd:YAG laser is indicated for treatment of vascular lesions. The 1320-nm wavelength is incorporated by many nonablative lasers that stimulate collagen production within the dermis. Although the target of these 1320-nm lasers is water, they have 50% less affinity for water than the Er:YAG laser. The carbon dioxide laser emits light at a wavelength of 10,600 nm. In contrast to the photomechanical action of the Er:YAG laser, the carbon dioxide laser produces photothermal injury. In addition, it has less specificity for its target, resulting in greater collateral injury, including greater contraction of the skin and dermis and increased collagen remodeling. As a result, recovery time is prolonged, and the risk for hyperpigmentation and other associated complications is greater.

Answer 25

The correct response is Option A. The 532-595 nm wavelength is the most appropriate choice, as it has the highest affinity for the vessels and can be more effective with the appropriate settings. Carbon dioxide and erbium lasers are both ablative lasers with a higher affinity for water. The 1064-nm laser can be used for hair reduction or collagen stimulation but works on the deeper layers and is more specific for darker pigmentation of vessels, such as blue. It can be used for vessel reduction in the leg; however, facial vessels are more superficial and often more red than blue in coloration. The 694nm laser would not be the first-line laser for this treatment. Lasers in Surgery and MedicineVolume 55, Issue 8 pp. 734-740 CLINICAL REPORT Open Access A new 532 nm, variable-pulse-structure, dual-wavelength, KTP laser incorporating cryogen spray cooling, effectively treats rosacea Eric F. Bernstein MD, MSE First published: 07 July 2023 https://doi.org/10.1002/lsm.23700

Lasers Flashcards

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