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?
A patient presents with a skin lesion that shows extravasation of blood into surrounding tissue. What type of mechanical injury is this?
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?
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?
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?
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 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