Path Lab-Trauma Flashcards
5 types of mechanical injury
Abrasions, contusions, lacerations, incised wounds and puncture wounds
A patient presents with a skin lesion and only the epidermal layer is removed. What type of mechanical injury is this?
Abrasion
A patient presents with a skin lesion that shows extravasation of blood into surrounding tissue. What type of mechanical injury is this?
Contusion
A patient presents with a skin lesion that shows tearing of tissues, jagged edges and intact blood vessels and nerves. What type of mechanical injury is this?
Laceration
A patient presents with a skin lesion that shows tearing of tissues, defined borders and severed blood vessels. What type of mechanical injury is this?
Incised wound
When is a puncture wound termed as penetrating vs. perforating?
Penetrating = entrance wound. Perforating = entrance and exit wound.
What factors determine the clinical significance of a thermal burn injury?
Depth, percentage of body surface, internal injury and promptness of treatment.
A patient presents with a thermal burn confined to the epidermis. What type of burn is this?
Superficial burn
A patient presents with a thermal burn confined to the dermis and epidermis. Its gross appearance is pink and blistery and is very painful. Histology reveals coagulative necrosis and marked exudation. What type of burn is this?
Partial thickness burn. Note that nerve endings are spared and the lesion is very painful.
A patient presents with a thermal burn that affects the subcutaneous tissue and muscle. Its gross appearance is white, dry and the patient cannot feel anything at the wound site. Histologic examination reveals coagulative necrosis and marked exudation. What type of burn is this?
Full-thickness burn. Note that these are anesthetic because full nerves are lost.
Greatest threats to life in patients with thermal burn injuries
Shock, sepsis and respiratory insufficiency
What is responsible for the hypovolemic shock seen in patients with burns that cover at least 20% of body surface?
Fluid rapidly shifts to the interstitial spaces because plasma protein is lost. This results in generalized edema.
How does the resting metabolic rate change in someone with extensive burns?
It increases and the patient loses lots of heat and burns a lot of calories.
Common infections associated with burn injuries due to loss of blood flow and blockade of inflammatory response?
Pseudomonas aeruginosa is most common. S. aureus and Candida may also be involved.
Why might a patient who sustained a burn injury begin to suffocate 24-48 hours after the injury?
Inhalation of Cl, S and NH3 react with water to form alkalis and acids that cause inflammation in the airway that lead to obstruction.
Why might a patient who sustained a burn injury get pneumonitis deeper in the lungs?
Inhalation of NO from burning plastic
What is responsible for the constant itching at the site of injury burn victims feel for years after the injury?
Release of excess neuropeptides like substance P at the injury site results in hypertrophic scarring that itches.
Heat injury that often occurs in athletes due to loss of electrolytes
Heat cramps
Heat injury that often occurs as a result of water depletion and hypovolemia. How do people recover?
Heat exhaustion. Collapse and prostration results in spontaneous recovery.
Heat injury that occurs as a result of thermoregulatory mechanism failure
Heat stroke. Sweating ceases and marked vasodilation causes peripheral pooling of blood which can result in hyperkalemia, tachycardia and arrhythmias.
What is responsible for the necrosis of muscle in people who get heat stroke?
Nitrosylation of the ryanodine receptor type 1 (RYR1)
Why are alcoholics at increased risk for hypothermia
The superficial blood vessels dilate even in cold temperatures and allow heat to escape.
When does loss of consciousness, atrial fibrillation and bradycardia begin in people with hypothermia?
Body temperature of 90 degrees
Direct effects of hypothermia
Cell lysis from high salt concentration due to crystallization of water
What is responsible for the edema, ischemia and hypoxia that occur in hypothermia?
Vasoconstriction and increased vascular permeability cause edema and hypoxia, but are only evident upon rewarming. Ischemia is a result of increased blood viscosity.
Where are you most likely to have an electrical injury that results in tetanic muscle spasm, irreversible clenching, chest wall muscle spasms and asphyxia?
In a home with alternating current electricity.
Where are you most likely to have an electrical injury that results in paralysis of the medullary centers and extensive burns?
High voltage from lightening
How are our cells affected by UV light, infrared light, microwaves and sound waves?
These are all types of non-ionizing radiation and only cause our atoms to vibrate.
How are our cells affected by x-rays, gamma rays, high-energy neutrons, alpha particles and beta particles?
These are all types of ionizing radiation and can directly damage DNA or displace electrons that produce ROS that damage DNA. Cells can then either repair themselves and go on, or they don’t repair themselves and die or don’t repair themselves and become cancerous. Note that alpha particles are most damaging.
Radioactive disintigrations per second
Curie (Ci)
Radioactive energy absorbed by target tissue per unit mass
Gray (Gy) and Rads (1 cGy)
Radioactive energy that depends on the biologic effect of the radiation
Sievert (Sv)
Tissues with highest susceptibility to damage by ionizing radiation
Those that divide rapidly:gonads (leading to sterility), bone marrow (leading to marrow aplasia and anemia), lymphoid tissue (shrinkage of nodes and spleen) and GI mucosa.
What types of tumors will respond poorly to ionizing radiation?
Those with poor blood supply. This is because there is less oxygen around to form ROS and damage DNA.
Vascular changes associated with radiation
Interstitial fibrosis, endothelial cell swelling and vacuolization and hyalinization that can occur years later.
Nuclear changes seen with radiation
Chromosomal changes, clumping and nuclear swelling
How does radiation commonly affect the lungs and salivary glands?
Vascular damage, loss of stem cells and the release of cytokines that promote inflammation stimulates fibroblast proliferation and causes radiation-induced fibrosis. Note that the colorectal and pelvic areas can also be affected this way.
Gram positive cocci that form clusters
Staph aureus.
What are the virulence factors associated with S. aureus?
Clumping factor: binds fibrinogen as a bridge to endothelial cells. Lipase: degrades skin lipids and produces abscesses. Protein A: bind Ig Fc region to escape opsonization. Alpha toxin: depolarizes host cell membranes by forming pores in them. Beta toxin: sphingomyelinase. Delta toxin: Detergent peptide. Gamma toxin: lyses erythrocytes. Leukocidin: lyses leukocytes. Exfoliative A/B toxins: cleaves desmoglein and separates keratinocytes. Superantigen:binds MHC and TCRs to activate T-cells, release cytokines and cause Toxic Shock Syndrome.
A patient presents with hypotension, renal failure, coagulopathy, liver disease, respiratory distress, a generalized erythematous rash and soft tissue necrosis around an abscess on the buttocks. Labs show a gram positive cocci in clusters. What is causing his condition?
Toxic shock syndrome from S. Aureus superantigen.
Focal suppurative inflammation of the skin and subcutaneous tissue in moist, hairy areas like the face, axillae, groin, legs and submammary folds caused by staph infection
Furuncle
How do people typically get staphylococcal lung infection?
Hematogenous spread
A middle aged woman from Florida prints with rapidly spreading erythematous cutaneous swelling on the face. The rash has sharp serpiginous borders and forms a butterfly distribution. Histologic examination shows microabscesses and PMNs. What is your diagnosis?
Erysipelas from strep. pyogenes.
A patient presents with a tough, dirty gray to black superficial membrane on the oropharynx. PMN infiltration is intense. Labs show a gram positive rod with clubbed ends. What is causing his condition? How do you treat him?
C. diphtheria has a phage-encoded A-B toxin that ADP-ribosylates EF-2. You treat him with antitoxin.
A farmer presents with painless, pruritic papules after working with raw hide and wool. The vesicles show striking surrounding edema and black eschar ulcers on ruptured vesicles. Physical exam reveals regional lymphadenopathy. Lab reveals a boxcar shaped gram positive rod. What is your diagnosis?
Bacilllus anthraces that causes cutaneous anthrax.
A patient presents with fever, cough and chest pain about a week after working with raw hid and wool. The next day he has abrupt onset of fever, hypoxia, sweating and meningitis. CXR reveals perihylar pneumonia and mediastinal hemorrhage. LP reveals boxcar shaped gram positive rods. He dies 2 days later. What is causing his condition?
Bacillus anthraces that causes inhalation anthrax.
A patient presents with fever, weight loss and cough for the past 6 months. Screening tests for Tb and malignancy are negative. History reveals diabetes and HIV. Sputum culture reveals a slender gram positive organism with branching filaments and beaded appearance. What is likely causing this patient’s condition?
Nocardia asteroides is found in soil and is an opportunistic infection in patients with HIV and diabetes because they have depressed T-cell immunity. Note that 1/5 of Nocardia asteroides infects the CNS too.
30-year-old male involved in a fatal motorcycle accident. No helmet was worn. The patient died despite aggressive life-saving intervention. A forensic pathologist performed the autopsy on the decedent, which showed numerous external blunt force injuries including a broken left leg. Internal examination identified liver and spleen lacerations, atlanto-occipital joint dislocation, and coup/contrecoup brain contusions. Toxicology results were negative for illicit drugs or alcohol consumption. Cause of death was listed as “Blunt Force Injuries” and manner of death “Accident.” One of his injuries is shown below. What might these injuries indicate?
The facial abrasion may indicate intracranial injury like diffuse axonal injury. The shoulder contusion may indicate the atlanto-occipital dislocation.
A 45-year-old man was a victim of a hit-and-run accident on an isolated road in Delaware . It took three days to find the body along the roadside in a shallow ditch. The decedent did not have proper ID in his wallet. A forensic autopsy was performed on the severely decomposed body. The cause of death was determined to be “Blunt Force Injuries involving the head, torso, and extremities”. “Manner of death “Homicide.” What are the stages of decomposition the body likely went through?
1) Green discoloration due to colonic bacteria denaturing hemoglobin with H2S to produce green biliverdin. 2) Marbling: bacteria move into blood vessels and H2S react with Hgb to form green-purple biliverdin. 3) Putrefaction: bloated abdomen, skin slippage and degloving of hand.
A 49-year-old man was beaten to death by his son after the father refused to give his son cash to support his son’s drug habit. After beating his father on the lower extremities with an iron skillet, he hit his father on the head with the skillet. The father was still conscious and attempted to call for 911 for help. The son then manually strangled him to death. A forensic autopsy was performed. The cause of death was determined to be “Asphyxia by manual strangulation associated with blunt force injuries.” Manner of death “Homicide.” What types of injuries would you expect to find on autopsy?
Contusions, lacerations and conjunctival petechiae from strangulation induces capillary rupture.
Police found this unresponsive 35-year-old male on the kitchen floor after being notified by a neighbor’s compliant of domestic violence. Next to the victim was a blood covered Phillips screwdriver and a kitchen knife having a 6” blade, but with a broken tip. A forensic autopsy is performed by the medical examiner. Tip of the knife was found on x-ray, wedged deep in the heart and sternum. Multiple defense wounds were identified on the back of the hands and arms. The decedent’s girlfriend is in custody after she confessed to murder while in a blind rage after discovering her boyfriend was unfaithful. What will differentiate the stab wounds you see from the incisions you see?
Stab wound are deeper than they are wide. Incisions are wider than they are deep. Neither of them have tissue bridges within them.
35 year old male US Navy Ensign undergoing superficial radiation therapy for pruritis ani et scrota; accidently exposed to several thousand roentgens of radiation at 50KV due to equipment operator error. Five year history of intractable anal and scrotal itching that has not responded to antibiotics, steroids, pinworm treatment or other topical treatments. WBC: 1,200 Platelets: 40,000 HCT: 25%. Why might he be at risk for radiation lymphedema?
Radiation kills lymphocytes and shrinks lymph nodes, which reduces lymph nod drainage.
A 45-year-old postal worker presents to her physician complaining of fever, myalgia, malaise, fatigue, retrosternal pain, and a nonproductive cough. She is diagnosed with a viral URI and sent home with a non- steroidal anti-inflammatory drug and a decongestant. Two days later, she is taken to the local emergency room with high fever, dyspnea, tachypnea, cyanosis, and chest pain. Chest X-ray in the ER demonstrates a widened mediastinum, paratracheal and hilar fullness, and pleural effusions. Peripheral blood smear is shown below. What is your diagnosis?
Note the boxcar-shaped gram positive rods that indicates B. antracis.
Which region of this brain was likely the “coup” region?
The front. The lesion on the back is likely the contra coup lesion.
How might someone have colon problems if they receive radiation for testicular cancer?
A common effect of radiation is colonic stricture.
Late changes after radiation
Skin dyspigmentation/atrophy, pulmonary interstitial fibrosis, lymph node fibrosis, GI fibrosis, adhesions, keloid formation and sterility.
What cells would you expect to see in the alveoli of a patient with inhalation anthrax?
Hemosiderin-laiden macrophages from alveolar hemorrhage.
What gram positive cocci that grows in clusters can cause this?
Staph can cause osteomyelitis in kids.
