Thermal and Radiation Injury Flashcards
What are the three types of thermal burns?
- Superficial burns - limited to epidermis (i.e. sunburn)
- Partial thickness burns - extend into the dermis
- Full thickness burns - destruction through dermis, can involve subcutaneous tissue, tends, skeletal muscle, and bone
How does the skin regenerate in a partial thickness burn? What structure will exist on an acute lesion?
Via the remaining stem cells in the adnexal structures (i.e. matrix cells of the epidermis)
Lesion typically features a prominent blister
How does pathology of superficial / partial thickness burns differ from full thickness burns with respect to inflammaton / appearance?
Superficial / partial thickness -> acute inflammation with coagulative necrosis. Pain will be present.
Fullthickness -> extensive damage to blood vessels, nerve endings, and adnexal structures (i.e. sweat glands)
-> no pain at site of lesion, which will be black and leathery. Periphery may have pain due to partial thickness components.
What type of shock do burns cause initially and why?
Hypovolemic
- > increased vascular permeability due to inflammation and vessel damage (subsequent hypercoagulability)
- > evaporation of interstitial fluid due to loss of skin
What electrolyte imbalance happens in burns and why?
Hyperkalemia, due to cellular lysis from heat (high K+ in cells is released into interstitium)
Also hyponatremia due to loss of plasma into the interstitium and evaporation
What other type of shock can burns cause and how? What will this result in?
Septic shock, due to bacteremia which results from loss of skin barrier.
Septic shock can lead to multisystem organ failure and diffuse alveolar damage -> adult respiratory distress syndrome (ARDS) = respiratory failure
What GI side effect is a result of the acute, extreme physiological distress of burns?
Curling ulcers (think “Curling irons can burn”) -> gastric ulcers in the setting of a burn
What are the chronic results of burns in some people, and especially in children?
Children - contractures
Adults - Hypertrophic scars and keloids (extensive form of scar overgrowth)
What are the three responses to hyperthermia, from mildest to most severe?
- Heat cramps
- Heat exhaustion
- Heat stroke
What are the signs and symptoms of heat cramps, and what causes them?
Involuntary, painful muscle spasms during or after strenuous exercise
Caused by electrolyte abnormalities like hyponatremia (due to only replenishing water but not electrolytes)
What are the signs and symptoms of heat exhaustion? How will the skin feel?
Sudden dizziness, nausea, headache, profuse sweating, fatigue associated with hypotension, tachycardia, and a low-grade fever
Skin feels pale, cool, and moist -> vasoconstriction due to hypovolemia with sweating
What is the pathogenesis of heat exhaustion?
Extreme sweating leads to inadequately compensated hypovolemia, with slightly elevated body temperature and peripheral vasoconstriction to maintain blood pressure
What is the pathogenesis of heat stroke?
Inability to dissipate heat quickly enough and dehydration leads to loss of sweat.
- > highly elevated body temperature
- > denaturation of proteins / cell membranes with expression of heat shock proteins and amplified acute phase response
- > hsp’s will create septic shock-like response
What are the signs and symptoms of heat stroke?
High core body temp (>104F/40C)
Hot, dry, flushed skin (peripheral vasodilation for convection)
Tachycardia, neurologic symptoms, difficulty breathing
What are the most severe manifestations of heat stroke?
Multiorgan failure and rhabdomyolysis (skeletal muscle lysis)
Does alcohol use affect hyperthermia or hypothermia and why?
Hyperthermia - makes worse -> diuresis contributes to hypovolemia and makes you less likely to notice
Hypothermia - makes worse -> peripheral vasodilation (flushing) will make you lose more heat
Where does focal tissue injury tend to occur in hypothermia, and what is its mechanism?
Peripheral areas with poor collateral circulation, which become ischemic due to peripheral vasoconstriction
(toes, fingers, nose, ears)
-> interstitial fluid crystallizes, proteins denature, and vascular permeability increases due to endothelial cell injury by these crystals.
-> hypercoagulant prothrombotic state results
What is the first manifestation of focal tissue injury in hypothermia, what does this look like, and what can it progress to?
Frostbite -> appears like blisters due to edema in the injured area, which becomes discolored and eventually turns black / loses sensation.
Progresses to gangrene
What is immersion foot and what causes it? What is it most similar to?
Trench foot
- > due to constrictive footwear in damp, unsanitary conditions
- > Vascular, soft tissue, and nerve injury with secondary infections
Most similar to wet gangrene
What is perniosis?
Chilblains - abnormal vascular reactions to cold
How do childblains appear? Why does thishappen?
Appear as small, itchy, swollen, painful lesions which go from red to blue upon rewarming
-> seen in temperate, humid climates due to overdilation / hyperactivity of blood vessels on rewarming (like Reynaud’s phenomenon in reverse)
Why is radiation often given in fractionated doses now?
Allows time for repair of normal cells, but hopefully not cancer cells
What types of tissues are most susceptible to radiation, with respect to cellular proliferation rate, availability of oxygen, and vascularization?
- Rapidly proliferating cells are most vulnerable (GI tract, bone marrow)
- Well-oxygenated tissues are more vulnerable due to oxygen-derived free radicals
- Vascularization predisposes to damage due to acute / chronic effects of radiation on blood vessels
What is the primary effect of radiation on cells?
Results in double-stranded breaks in DNA, which may be recovered in slower growing cells, or lead to apoptosis or carcinogenesis
