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Fall 2014 - CM Dermatology > Photodermatoses, Mucocutaneous Reactions, Cold Injuries > Flashcards

Photodermatoses, Mucocutaneous Reactions, Cold Injuries Flashcards

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1
Q

Photosensitivity

A
  • abnormal response to UV radiation or visible light
  • diagnosis made primarily from history and physical exam
  • skin biopsy may be useful in some cases
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2
Q

Sunburn Characteristics

A
  • exposure to excessive UVA and UVB causes inflammatory response in the skin
  • clinical manifestations include painful erythema and blistering
  • erythema noted 3-5 hours post-exposure, peaks at 12-24 hours, subsides at 72 hours
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3
Q

Sunburn Prevention

A
  • limit sun exposure in summer between 10 and 4 pm
  • protective clothing like long sleeves and hats
  • broad spectrum sunscreen with SPF 30+, reapply every 2 hours
  • infants younger than 6 months avoid sun exposure
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4
Q

Sunburn Treatment

A
  • self limiting condition
  • may require hospitalization if pain and blistering severe
  • topical agents like aloe vera and cool compresses may help discomfort
  • oral OTC analgesics (tylenol/ibup)
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5
Q

Polymorphous Light Eruption (PMLE)

A
  • sun poisoning or sun allergy
  • papulonodular lesions symmetrically distributed on sun-exposed skin
  • pruritic
  • angular chelitis is a distinguishing characteristic
  • there is a genetic component
  • treat: sun avoidance, topical/oral corticosteroids, phototherapy
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6
Q

Phototoxicity

A
  • results from cellular damage following sun exposure when taking a precipitating compound (including sulfonamides, NSAIDS, tar compounds)
  • endogenous causes: lupus, porphyria (rare blood disorder), dermatomyositis
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7
Q

Stevens Johnson Syndrome

A
  • dermatologic emergency
  • skin detachment is < 10% of BSA
  • mucous membranes affected in > 90% of patients
  • usually 2 different mucous membranes at one time (ocular, oral, genital)
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8
Q

Toxic Epidermal Necrolysis

A
  • dermatologic emergency
  • same as Stevens Johnson, but more severe
  • detachment of >30% of BSA
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9
Q

Stevens Johnson/Toxic Epidermal Necrolysis Clinical Appearance

A
  • prodrome of fever and flu like symptoms 1-3 days
  • coalescing erythematous macules
  • vesicles and bullae on skin and mucous membranes then skin sloughing
  • lesions begin on face and trunk then spread rapidly
  • palms and soles become erythematous, painful and swollen
  • positive Nikolsky sign: gentle pressure on skin results in blister formation
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10
Q

Stevens Johnson/Toxic Epidermal Necrolysis Triggers

A
  • medications: allopurinol (gout), anticonvulsants, sulfonamides, NSAIDS
  • infections: mycoplasma, CMV (cytomegalovirus)
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11
Q

Stevens Johnson/Toxic Epidermal Necrolysis Complications

A
  • shock
  • hypotension
  • renal and respiratory failure
  • corneal ulcerations, ocular scarring, blindness
  • vulvovaginitis or balanitis
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12
Q

Stevens Johnson/Toxic Epidermal Necrolysis Treatment

A
  • discontinue the causative agent (if a medicine)
  • referral to burn center is necessary
  • treatment similar to major burn: fluid resuscitation, wound care, prevention/treatment of infection
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13
Q

Populations Most At Risk of Cold Injuries

A
  • winter athletes
  • mountaineers
  • military personnel
  • elderly
  • homeless
  • employed in the cold
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14
Q

What can cause frostbite?

A
  • environmental exposure to cold
  • direct exposure to freezing materials, eg ice packs applied to musculoskeletal injuries
  • inhalation of hydrocarbons (frostbite of upper airway)
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15
Q

What areas of the body are most sensitive to cold injuries?

A

-hands, feet, face (nose and cheeks), ears

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16
Q
  1. Frostnip

2. Immersion Foot/Trench Foot

A
  1. pre-frostbite; cold-induced, local paresthesias that resolve with rewarming; no ice crystals formed in the cells
  2. injury to sympathetic nerves and vasculature of the feet; feet are red, edematous, numb or painful and covered with hemorrhagic bullae
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17
Q

Pernio (Chilblain)

A
  • results from acute or repetitive exposure to damp cold above the freezing point
  • lesions are edematous, red/purple, and may be painful or pruritic
  • exposure to cold causes vasoconstriction of small blood vessels
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18
Q

Frostbite

A
  • tissue cooling with vasoconstriction and ischemia; cooling of nerves causes paresthesia or hyperesthesia
  • ice crystals form in ICF and ECF; causes abnormal electrolyte balance, cell dehydration, lysis and death
  • thawing process initiates an inflammatory response which causes progressive tissue ischemia, emboli within microvessels and thrombi in larger vessels
19
Q

Clinical Appearance of Frostbite

A
  • patients complain of cold, numbness, and clumsiness of the area
  • skin is insensate, white or gray in color and hard or waxy to the touch
  • bullae may develop upon rewarming
20
Q

Frostbite Diagnosis

A
  • largely clinical
  • look for other co-morbidities
  • diagnostic studies not needed, but do help later when considering surgical options
21
Q

1st Degree Frostbite

A
  • superficial
  • central area of pallor and anesthesia of the skin surrounded by erythema
  • no tissue infarction
22
Q

2nd Degree Frostbite

A
  • large blisters containing clear fluid surrounded by edema and erythema
  • develops w/in 24 hours of rewarming
  • extends to the tips of digits
  • no tissue loss
23
Q

3rd Degree Frostbite

A
  • injury deeper than 2nd degree
  • blister are hemorrhagic and more proximal
  • skin forms a black eschar in one week+
24
Q

4th Degree Frostbite

A
  • extends to muscle and bone

- complete tissue necrosis

25
Q

Pre-Hospital Frostbite Treatment

A
  • do not walk on frostbitten feet if possible; walk on frozen feet
  • splint or pad frozen extremities
  • do not rewarm frostbitten tissue if there is a chance of freezing again (increases tissue damage)
  • do not rub areas to rewarm (increases tissue damage)
26
Q

Hospital Frostbite Treatment

A
  • rewarming by placing affected area in water 37-39C; it is painful; higher temps will not warm it faster
  • rewarming by ambient heat (fire, oven) less consistent and may cause a burn
  • air dry the tissues or gently blot dry to prevent further damage
  • thawing is usually complete when tissue is red or purple and soft to the touch
27
Q

Frostbite Wound Care

A
  • apply nonstick gauze to area covered with sterile fluff dressing
  • elevation of extremity to reduce edema
  • blisters: management is controversial; debride nonhemorrhagic; drain hemorrhagic but do not debride
  • tetanus prophylaxis
  • topical antibiotics increase maceration and should be avoided
28
Q

Frostbite: Thrombolytic Therapy

A
  • goal is to save tissue from microvascular thrombus
  • tissue plasminogen activator use w/in 24 hours of thaw may benefit
  • for use in deep injuries with potential for serious morbidity
29
Q

Complications of Frostbite

A
  • infection, gangrene, autoamputation
  • ischemic neuritis - very painful
  • long term hypersensitivity to cold: cold exposure contraindicated for 6 months after minor, 12 months after major injury
30
Q

Amputation with Frostbite

A
  • complete demarcation of tissue injury may take 1-3 months
  • angiography, MRI, technetium-99 bone scan may be used to determine surgical margins
  • amputation may take place after definitive demarcation if no signs of sepsis
31
Q

List the 5 mechanisms by which body heat is lost to the environment.

A
  • radiation
  • conduction
  • convection
  • evaporation
  • respiration
32
Q

Hypothermia - General Info

A
  • normal set point for human core temp is 37C
  • body, in response to cold stress, stimulates heat production through shivering and increased catecholamines
  • body also vasoconstricts vessels in the peripheral tissues to prevent conductive heat loss
33
Q

Hypothermia Causes

A
  • dermal diseases: burns, exfoliative dermatitis
  • drug induced: ethanol, sedatives
  • environmental
  • iatrogenic: aggressive fluid resus, heat stroke Tx
  • metabolic: hypothyroid, hypoadrenal
  • neurologic: acute spinal cord transection, head trauma
  • neuromuscular inefficiency: extreme age, impaired shivering, lack of acclimatization
  • sepsis
34
Q

Mild Hypothermia

A
  • initial excitation phase to combat cold: HTN, shivering, tachycardia and tachypnea, vasoconstriction
  • with time and onset of fatigue: apathy, ataxia, cold diuresis, impaired judgment
35
Q

Moderate Hypothermia

A
  • atrial dysrhythmias
  • decreased HR, RR, BP
  • decreased LOC
  • dilated pupils
  • no shivering
  • hyporeflexia, decreased gag reflex
  • J wave on EKG
  • paradoxical undressing
36
Q

EKG Changes with Hypothermia

A
  • baseline artifact from shivering
  • J waves (Osborne waves): a positive deflection at the J point; height of J point is roughly proportional to degree of hypothermia
  • bradycardia
37
Q

Severe Hypothermia

A
  • apnea
  • coma
  • nonreactive pupils
  • oliguria
  • pulmonary edema
  • minimal to no activity on EEG
  • ventricular dysrhythmias/asystole
38
Q

Temperature Monitoring for Frostbite Patients

A
  • accurate temp monitoring essential
  • rectal probe thermometer
  • temporal therms are not accurate for hypothermia
  • esophageal is most accurate
  • bladder and rectal not accurate b/c they lag behind core temp
39
Q

Passive External Rewarming

A
  • used for mild hypothermia
  • patient’s cold/wet clothing is removed and pt is covered with blankets or other types of insulation
  • reduction in heat loss combined with pt’s intrinsic heat production produces rewarming
  • pt must have intact thermoregulatory mechanisms, normal endocrine function, and adequate energy store to create endogenous heat
  • warm the trunk before extremities
40
Q

Active External Rewarming

A
  • used for moderate to severe or those who fail passive external rewarming
  • application of heat directly to the skin
  • effective only if there is intact circulation that can return peripherally rewarmed blood to the core
41
Q

Risks of Active External Rewarming

A
  • afterdrop: cold peripheral blood rapidly returns to the heart; minimize the risk by also using minimally invasive core rewarming
  • rewarming acidosis: cold, acidemic blood in extremities moves into the trunk, dropping core temp and pH
42
Q

Active Internal/Core Rewarming

A
  • most aggressive strategy
  • for patients with severe hypothermia
  • warm IV fluids: saline with dextrose heated to 40-45C
  • warmed humidified oxygen: warmed to 40C
  • extracorporeal blood warming: accomplished by cardiopulmonary bypass; most effective method; increase core temp 1-2C every 3-5 minutes
43
Q

Hypothermia-Associated Abnormalities

effects on other conditions, normal physiology

A
  • cardiac arrhythmias (v fib)
  • insulin ineffective below 30C
  • hematocrit increases 2% for each 1C drop
  • rewarming associated w/ unpredictable changes in electrolytes
  • inhibition of clotting factors

Fall 2014 - CM Dermatology (11 decks)

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