The Physiology of Burns

The topic of burns seems like a simple subject. Everyone has probably had a burn at some point. But what if I told you there is a lot more to the process of burns than meets the eye?

Degrees of Burns

Burns are classified in different degrees. For example, a sunburn would most likely result in a first-degree burn. This minor burn is characterized by swollen, inflamed skin. The epidermis is the only part of the skin affected and will typically heal on its own.

If you were to touch a hot pan right off the stove, you could obtain a second-degree burn. These burns are characterized by blisters and swelling as well as a lot of pain. These burns extend through the epidermis and partially through the dermis. These burns should be cleaned and covered to prevent infection.

When individuals are exposed to a severe enough burning process, for example scalding water, they could obtain third-degree burns. This degree of burn extends through the epidermis and dermis. It can destroy nerve endings which interestingly results in less pain for the patient. They are characterized by a white, red or black appearance. Treatment should involve being evaluated at a hospital, ideally a hospital that specializes in treatment of burns.

Fourth degree burns are burns that are deep enough to affect the muscles and bones of the body. They are most likely to occur via electrocution or if a patient were unable to escape a fire. Similarly to third-degree burns, these are characterized by a white or black appearance. Treatment for full-thickness burns involves excision or even amputation.

Cellular Level

What happens in at the cellular level when tissue is burned? If the cells aren't immediately destroyed there is an inflammatory reaction caused by the release of histamine. There is vasodilation as well as increased venous permeability as the affected cells have lost their ability to retain fluid. There is a massive fluid shift from inside the cells to the surrounding area around the cells(also known as the interstitial space). Simply put, the cells are leaking fluid.

Fluid Replacement

Burns can be measured multiple ways but the way I use the most is the "Rule of Nines." It states that certain areas of the body are pre-established as percentages. For example, each of the upper limbs is estimated at 9%.


Above image is referenced from Betts, J. G., Young, K. A., Wise, J. A., Johnson, E., & Poe, B. Anatomy & physiology. Openstax. PG. 206

The Rule of Nines is a helpful tool for estimating TBSA(Total Body Surface Area) affected. I use this tool on the ambulance when I have a patient who has sustained serious burns.

Once I can estimate the TBSA, I can start the fluid replacement portion of treatment for the patient. My only option for fluid replacement at my specific ambulance agency is normal saline 0.9%. Normal saline 0.9% is made up of sodium, chloride and water. Other options are available but not utilized by my current agency for various reasons. For more information on normal saline I have linked an article from the National Library of Medicine

Paramedics used to blindly dump fluid into patients with hopes to start the fluid replacement process as soon as possible but nowadays we have become much more sophisticated and use formulas. There are several formulas for calculating fluid replacement. The Parkland Formula is a well known, widely utilized formula for calculating fluid replacement.

Parkland Formula: 4 mL/kg/%TBSA (3 mL/kg/%TBSA in children) = total amount of crystalloid fluid during first 24 hours.

(TBSA --> Total Body Surface Area)

An article from the National Library of Medicine about fluid replacement with more information about the Parkland Formula is linked here.

Burns can range from minor sunburn to irreversible deep tissue and bone damage. With major burns the body can become dehydrated and have electrolyte imbalances. Treatment involves covering burned site, pain management, temperature regulation and the beginning of the fluid replacement process.


I hope this short discussion about burns helped you to better understand the physiological affects they have on the human body. To address how this topic relates to societal issues I think there is little known about how burns should be treated in our society. I hope that this response will be informative to anyone who was unsure of how to treat burns. There is always more to learn and I look forward to any thoughts, comments or corrections my classmates will come up with.

Questions to my classmates:

  1. What does infection have to do with burns?
  2. Why are renal problems associated with burns?

If anyone is interested in learning more about burns, I have placed all links that I have referenced in the footnotes. The Nation Library of Medicine also has many more resources available on their website.

Betts, J. G., Young, K. A., Wise, J. A., Johnson, E., & Poe, B. Anatomy & physiology. Openstax. PG. 206
Li, H., Sun, S. R., Yap, J. Q., Chen, J. H., & Qian, Q. (2016). 0.9% saline is neither normal nor physiological. Journal of Zhejiang University. Science. B, 17(3), 181–187.
Mehta M, Tudor GJ. Parkland Formula. [Updated 2022 Jul 11]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from:

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