AssessmentsBurns: Clinical practice
USMLE® Step 1 style questions USMLE
USMLE® Step 2 style questions USMLE
A 19-year-old woman comes to the clinic because of a rash on her thighs. She has just returned home from her first semester of college for the holidays. She states that she first began to notice the rash when she first went to college and began living in her dorm room. The rash is most prominent after she has been studying on her laptop. The affected skin is mildly itchy and has a "lace-like" pattern.
Which of the following is the most similar to the most likely diagnosis in this patient?
Content Reviewers:Rishi Desai, MD, MPH
The skin is the largest organ of the body, and is made of the epidermis, the dermis, and the hypodermis.
Burns result from exposure of skin cells to an overwhelming amount of energy in the form of heat, causing cellular necrosis.
The degree of injury depends on the temperature, the duration of exposure, and the baseline structural integrity of the skin; which means younger children and elderly individuals are at higher risk of injury, because their skin is relatively weaker.
Okay, burns can be classified based on the cause, or by the depth of injury which corresponds to the severity of the burn.
Burns are most commonly thermal, which can result from scalds, such as hot water, or flames, such as from house-fires.
Less commonly, burns can be electrical, like from exposure to lightning strike or high-voltage electrical current, or from exposure to chemical substances, which can be acidic or alkaline.
Based on depth, burns can be first, second, or third degree.
First degree burns are also called superficial burns, and involve the epidermis only.
A prime example would be a simple sunburn from a day on the beach, which appears red, with no blisters.
Second degree burns are further subclassified into superficial partial thickness burns, which involve the epidermis and the superficial dermis, and deep partial-thickness burns, which involve the epidermis and the deep dermis.
Superficial partial thickness burns appear red and are often blistered, whereas deep partial thickness burns appear red or white, with no blisters.
Third degree burns are full-thickness burns, extending through and destroying the entire dermis.
These appear leather-like with a charred appearance and tense feel.
Usually, third degree burns are surrounded by a rim of second degree burns.
Fourth degree burns extend beyond the dermis, destroying fascia, muscle or bone.
Because third and fourth degree burns destroy the entire skin, they destroy the skin nerve endings, and therefore can feel relatively painless.
Due to their strength and velocity, electrical burns have an entrance and an exit wound, similar to a gunshot. But aside from that, the skin actually looks fine.
However internally, the muscles are injured and even heart can be severely damaged, so don’t let normal skin fool you.
Sadly, in children, specific burn patterns raise suspicion for physical abuse. These include burns with a sharply demarcated edge, small circular burns matching a cigarette tip, or burns in the perineal region matching a pattern that could only be explained if the child was dipped into scalding water.
Management of burns begins at the scene.
First, remove the individual from the source, making sure you don’t expose yourself to electrical current or chemicals.
Additionally, remove all clothing, accessories or jewelry from the individual, as they may be contributing to injury.
On the way to the hospital, cool the injured areas with room-temperature water.
It may be intuitive to use ice or iced-water, but this should be avoided because it can worsen the injury.
At the emergency department, management starts with the ABCs; that is airway, breathing and circulation.
Using a fiberoptic or direct laryngoscope, look for edema and obstruction of the airway.
The decision to intubate is based on the presence of oropharyngeal swelling, stridor and respiratory distress causing hypoxemia. But sometimes, it’s more subtle.
Clinical signs like hoarseness of the voice, facial burns, drooling, soot in the airway, or even singed nasal or facial hairs should encourage you to secure the airway prophylactically, even if the airway isn’t swollen yet or they are not in obvious respiratory distress.
Sometimes it’s too late and the airway has closed, and in that case a surgical cricothyroidotomy is performed. In other words, if the main airway door is closed, you better break in through the window.
Also, If exposure to carbon monoxide is a concern, like in the setting of a closed house-fire, 100 percent oxygen is provided using a non-rebreather mask, and carboxyhemoglobin levels are measured.
Alright, so burns cause a tremendous amount of fluid loss, but it’s not as obvious as the fluid loss seen in diarrhea, vomiting or bleeding.
Burns increase capillary permeability, causing a tremendous amount of fluid to shift from the plasma to the interstitial space, which is called “third-spacing”.
To replace the loss, place two large-bore intravenous lines on an unburnt area of the skin. The amount of fluid to give depends on the total body surface area affected. Importantly, first degree burns are not included in the calculation.
To measure this, the “rule of 9s” is used in adults. This method divides the body into eleven areas, each equal to 9 percent.
The head is 9, each arm is 9, each leg is 18; that is 9 for the anterior aspect and 9 for the posterior aspect.
The chest, abdomen, upper back, and lower back each represent 9 percent. Nine times 11 is 99, so that last 1 percent is the perineum.
Sometimes, the burn areas are patchy, and it can be difficult to ascertain a percentage.
To tackle this issue, the palm can be used to estimate, as the palm approximates 1 percent of a person’s total body surface area.
Because children have larger heads and smaller extremities, the “rule of 9s” cannot be applied to them. Instead, the more complex Lund and Browder chart is used, which takes into account the child’s age. This chart may also be applied to adults.
Alright, once you got the percentage, it’s inserted into the Parkland formula, which calculates how much intravenous Ringer’s lactate the individual should receive.
Ringer’s lactate is used because its composition is closest to the extracellular fluid.
In the first 24 hours, the amount of Ringer’s lactate to give in milliliters is equal to: 4 multiplied by the weight in kilograms, multiplied by the percentage of the total body surface area involved. Half of the number you get is given in the first 8 hours, and the other half is given over the next 16 hours.
Alright, so the adequacy of fluid resuscitation is determined by inserting a Foley catheter and measuring the urine output hourly. In adults, 0.5 milliliters per kilogram per hour is considered adequate, whereas in children 1 milliliter per kilogram per hour is adequate.
The idea behind this strict fluid regimen is Jackson’s burn model, which states that a burn injury is divided into three zones, a central zone of coagulation, which is dead and unsalvageable, a middle zone of stasis, and an outer zone of hyperemia.
Adequate fluid resuscitation may potentially save the zones of stasis and hyperemia from irreversible injury.
Under- or over-resuscitation may result in more tissue injury.
Also, tetanus toxoid should be given if the individual had not received it in the past 5 years.
Tetanus immunoglobulin is added if they haven’t received the primary series during childhood.