Week 13 Notes - Injuries pt. 1.pdf

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/90F →drowsiness, amnesia, confusion →severe lethargy, no more shivering o  Core temperatures of less than 28 C /83F →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