Week 13 Notes - Injuries pt. 1 PDF
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Dr M Hossu
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Summary
These notes detail injuries due to physical agents, specifically focusing on temperature-related injuries (cold and heat) and mechanical trauma. It covers localized and generalized effects, including frostnip, frostbite, hypothermia, and burns. The notes also discuss the severity of burns and different mechanisms of injury.
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Injury due to physical agents Temperature o Cold Localized – frostnip and frostbite Generalized - Hypothermia o Heat Localized- Burn injury Generalized – Hyperthermia, fever Mechanical Traum...
Injury due to physical agents Temperature o Cold Localized – frostnip and frostbite Generalized - Hypothermia o Heat Localized- Burn injury Generalized – Hyperthermia, fever Mechanical Trauma Electrical current Radiation [MH] All injuries reflect the effects of basic forms of (physical) energy (mechanical, thermal, electric/electromagnetic, nuclear). Thermal Injuries Injuries due to cold Cold = losing heat (90% through the skin) at high rate →freezing ice crystals o faster in wet environment / water immersion o Complicated by alcohol ingestion (peripheral vasodilator increases rate of heat loss, while subject feels warm) Decreased blood flow AND blood vessel destruction → coagula on, edema, and RBC extravasations Decreased sensation / numbness → lack of awareness about the injury Decreased CNS activity Localized cold injury Frost nip – cold but not frozen o Trench foot / Immersion foot - immersion in cold (but not) freezing water Frostbite – frozen tissue; o Superficial – numb, swollen, red borders; recover in few weeks, o Deep – hardened skin, blisters, blue-gray-black, crust; risk of reperfusion injury Generalized cold injury - hypothermia < 35oC (95oF) especially a problem in the very young and the elderly who are exposed to cold environments. o Low body temperature 36-35 C: peripheral vasoconstriction and shivering, ↗ blood pressure, ↗ heart and respiratory rate o Shelter, dry clothes, sweet warm drinks, high caloric food o Moderate: Core temperatures of less than 32 C/90F →drowsiness, amnesia, confusion →severe lethargy, no more shivering o Core temperatures of less than 28 C /83F →low blood pressure, pulmonary edema, coma and death Dr M Hossu Notes 188 Injuries due to increased heat Localized heat injury (Burns) Incidence o ~ 450,000 seen in medical facilities o hospitalizations ~ 40,000 /year o 3,500 deaths per year (>70% at home) o Children about 30% of burn injuries – mainly due to scalds. Causes o fire/flame (43%), o scalds (34%), o contact with hot objects (9%), o electricity (4%), and chemical agents (3%) Evaluation of burns: Burn Classification - NCBI Bookshelf (nih.gov) o Depth of injury: (based on: appearance, blanching to pressure, pain, and sensation) First degree burns involves the epidermis of the skin only. It appears pink to red, there are no blisters, and it is dry. It is moderately painful. Superficial burns heal without scarring within 5 to 10 days Second degree burns Superficial partial-thickness: involves the superficial dermis. o It appears red with blisters and is wet, and the erythema blanches with pressure. o The pain is severe. o Healing typically occurs within 3 weeks with minimal scarring Deep partial-thickness: involves the deeper dermis. o It appears yellow or white, is dry, and does not blanch with pressure. o There is minimal pain due to a decreased sensation. o Healing occurs in 3 to 8 weeks with scarring present. Third degree burns It appears white or black/brown. The burn is leathery and dry, & there is no blanching with pressure. Minimal to no pain because of decreased sensation. heal by contracture and take greater than 8 weeks. Full-thickness burns require skin grafting. Fourth degree shows charred skin with possible exposed bone. Fifth degree has charred, white skin, and exposed bone. Sixth degree has loss of skin with exposed bone. Dr M Hossu Notes 189 o Surface area (total body surface area TBSA) – rules of nines. Grading system for Burn Injury (American Burn Association) Mechanism: o Local acute changes protein denaturation, disruption in collagen cross-linking, damage to endothelial and epithelial cells o Surrounding tissue: blood vessel occlusion. increased permeability of blood vessels → edema. release of Inflammatory substances (DAMP), ROS, o A zone of coagulation (the area nearest the source of heat) is surrounded by a zone of stasis, further surrounded by a zone of hyperemia at the periphery. o Possible inhalation injury (hot air and possibly chemical damage) o critical in managing burn injuries is to prevent the middle ischemic region from becoming necrotic due to hypoperfusion, edema or infection Complications of thermal injuries o Hypovolemia – shock Dr M Hossu Notes 190 o Generalized edema -→ pulmonary → respiratory insufficiency o Infection (virtually ALL burns are colonized) o Necrosis of surrounding tissue o Formation of eschar = coagulative necrotic tissue, leathery and stiff →compression o Scarring o Peptic ulcers- Curling's ulcers (high quantities of corticosteroids - ↘ mucus) Generalized heat injury Exposure to increased external temperature → Hyperthermia = increased body temperature > 37.5oC (without changing the hypothalamic temperature set-point o o o Therapeutic: ~ 40 C / 104 F for an hour Heat cramps o Loss of water and electrolytes in sweat o Painful spasms of voluntary muscles o Heat-dissipating mechanisms are able to maintain normal core body temperature o Prevented by fluid AND salt replacements Heat exhaustion o most common hyperthermic syndrome o Characterized by weakness, headache, nausea and vertigo followed by collapse o Loss of water leads to hemoconcentration o Vasodilation leads to venous pooling, decreased effective blood volume, decreased cardiac output o Skin is gray and wet, blood pressure may be low but body temperature is normal o Most patients recover when moved into a cool place o Fluid and electrolytes replacement is required Heat stroke o Severe and life threatening condition caused by heat exposure o o Failure of heat regulation, usually the increase in body temperature m/c > 40 C follows cessation of sweating o associated with confusion, delirium and loss of consciousness o Peripheral vasodilation causes peripheral circulatory failure and shock o High mortality rate o No exposure to a hot environment, NO antipyretics Fever ↗ temperature due to ↗ body’s temperature set-point Malignant hyperthermia o An inherited disease of skeletal muscle o Exposure to certain drugs (e.g. general anesthetics) →muscle contractions & increased heat production →↗in body temperature o In absence of this exposure the body temperature is normal Dr M Hossu Notes 191