A 25 year old male was brought into the ED after his shirt caught on fire when he accidentally leaned back while sitting near a fireplace. He has partial-thickness burns on his entire back and the posterior aspect of both arms. He weighs 85 kg.

What percentage of his body has been burned?
How would you calculate how much crystalloid he would require in the first 24 hours?
The “Rule of 9s” can be used to estimate the percentage of body surface area (BSA) burned.
The head is 9%, each arm is 9%, the front and back of the thorax are each 18%, and the legs are each 18%. The perineum is 1%.
This patient had involvement of the posterior aspects of both arms, at 4.5% each, and the back (18%) for a total of 27%.
The Parkland formula is used to calculate the total amount of crystalloid solution that needs to be administered over the first 24 hours in patients with second and third degree burns. The first half should be administered over the first 8 hours, and the rest over the next 16 hours.
The formula is: 4mL x body weight in kg x % body surface area (BSA) burned
In this case, it would be 9,180 mL total over 24 hours, with 4,590 mL over the first 8 hours, and the remainder over the next 16 hours.
Although this seems like a large amount of fluid, the burn causes microvascular injury that leads to increased vascular permeability and edema, resulting in decreased intravascular volume.