Behind the Knife ABSITE 2026 - Burns

All right. Welcome back to behind the knife. We're moving on to the burn chapter today. This is very high yield material. We're only going to focus on the stuff that we have seen or heard about being on the test before. All right, Kevin, ready to get started? Yep. Let's do it. All right. So the easy first place to start is the assessment of burns. So how do we classify burns? Yeah. So you have your first, second. third and fourth degree burns. The first degree is superficial, only involving the epidermis. The second degree is partial thickness. It involves the epidermis and part of the dermis. Third degree is the full thickness. It involves the epidermis and the entire dermis. And then the fourth degree is the involvement of bone or muscle. Yep. Perfect. Yeah. So just remember, we talk about it in different ways. So second degree can be divided into superficial partial thickness and deep partial thickness. But for the app site, 1st, degree are probably where you're going to get most of your hits. All right, moving on. So this is probably more important clinically. But what are the

histologically zones of burn injury? Yeah. So you have three of these. You have the zone of hyperemia, which is. increased tissue perfusion, and this tissue may recover. You have the zone of stasis, which is poor tissue perfusion and questionable viability. And then you have the zone of coagulation. This is where the maximum damage has been done and it's irreversible tissue loss. Yeah. And a straightforward burn, you can see this pretty well clinically, and you can also see how these different zones evolve over time. But for the test, just remember the hyperemia, zona stasis and zona coagulation. All right, Kevin. So we're going to have a picture for this in the book. But just in, in general terms, walk me through for an adult. What are the rules of nine? So if I got a patient on the test and I had to calculate the burn percentage to do maybe a resuscitation formula or something like that, how would I walk through that? Okay. Yeah. So focusing on adults, the head is 9%, the upper extremities are 9% each. The

anterior trunk is 18%. The posterior trunk is 18%. The lower extremities are 18% each, and then the genitalia is 1%. All right, let's change. Change to a pediatric patient. So how are they different? Yeah. So for the pediatric patients, the most of it's the same except that the lower extremities are down to 14 percent each of the, and the head and neck is a lot bigger percent. So the head and neck and the lower extremities are the ones that change with the pediatrics. So the head and neck is 18 percent where it was 9 percent in the adults. Then the upper extremities are 9 percent each, which is the same. The anterior and posterior trunk are the same at 18 percent and the lower extremities are 14 percent each. Yep, perfect. And and clinically to another way to really, you could potentially estimate burn size using the patient's palm, the patient's palm, not your palm, which gives you about 1 percent burn. And you can do that in the emergency room or wherever you're seeing burns. Okay, so let's walk through resuscitation. All

right, patient rides your trauma bay after suffering large full thickness burns. How do you determine initial fluid resuscitation? So there are many different ways to do this in practice, but the Parkland is the most tested. And so the Parkland formula is four milliliters per kilogram per percent total body surface area. And then there's also the modified brook formula, which is two milliliters per kilogram per a percent total body surface area. And so for the both formulas which we're giving for burns, you're using these formulas and burns that are greater than 15 to 20 percent TBSA. You're giving the first half of the fluid over the first eight hours, and you're giving the remaining half over the next 16 hours. So for the Parkinforma, for example, which is the most tested four milliliters per kilogram per percent TBSA, you take that full amount, you divide it in half. And then you divide it by eight and that gives your fluid requirements for the first eight hours. And then the rest of it is divided by 16. And that's how much you're going to give over the next 16 hours.

The reason we do, there's many different formulas out there. Like I mentioned but like I said, Parkland and modified Brooke tend to be the ones that are most commonly on the test. All right, Kevin, moving on. So what are we, resuscitation formulas are great, but really what are we monitoring in burn patients? Yeah. So really you want to know what's their urine output. You want to see what their kidney perfusion is. And so for adults, that's 0. 5 milliliters per kilogram per hour. And for children, that's one milliliter per kilogram per hour. Yeah. And for adults, children have a wide range of kilograms you're going to be covering, but for adults, that's usually about 30 to 50 CCS an hour for target urine output. And what's the classic fluid we use for resuscitation? Lactated ringers. Yeah, lactated ringers, most U. S. hospitals, you can use lactated ringers for the initial fluid. But, whatever crystalloid is available, it also can be used if you're, if lactated ringers for some reason is not an option. So what other options can we use in

addition or as rescue therapy? And this is speaking in very broad terms. Yeah, so you have most of the options available, such as albumin, fresh frozen plasma, renal replacement therapy, and then if they're heading down the ARDS pathway, you can use ECMO. Yeah, good. So albumin and fresh frozen plasma have been used as the initial fluid for resuscitation in some burns. They are typically used in most... burn centers at this point as a rescue therapy or an adjunct therapy later on during resuscitation. But just know that they can be used. Albumin is typically used as a rate versus bolus sitting, if they have hypotension, you and use chrysolloid for that. Renal replacement therapy is helpful especially if the patient is, already Diving into renal failure early. It helps with volume management as well as getting those bad humors out. And then these patients are really highly susceptible to ARDS. So this is one population where we're really truly seeing that

early use the ECMO may be beneficial and also patients with severe airway injury in combination with the higher resuscitations. All right. So speaking of airway injury so we have a big burn that comes in, say 80 percent burn. It was a house fire. What additional tests would we need to be to get in this patient, Kevin? Yeah, you want to make sure you're doing a bronchoscopy on all of these patients. Okay, good. And what's it, what are the things that are concerning, especially in a question stem that we may want to consider intubating? Yeah, so if the patient has upper airway stridor, if they have worsening hypoxemia, if they've had a massive volume resuscitation, or they are noted to have vocal cord edema, or soot on the vocal cords. Yeah, exactly. So and just going through it. So let's say. You have damage to the lower airways. What is that caused by? So that's caused by inhaled toxins. Yeah. In reality, it's combination held toxins and potentially heat if it's like severe heat in a house fire in closed space. But you weren't, if they,

that question comes up, they're going to get at, potentially is this injury due to inhaled toxins? That's what they're looking for. All right. So what other considerations that we need to consider patients that are burned in an enclosed space? And these are, pretty highly testable. Yeah. So carbon monoxide poisoning and cyanide poisoning are two things to consider. Yeah. They go hand in hand. If you're thinking about one, you got to think about the other and same thing we're treating. If you're treating one, you got to treat the other. So for specifically for carbon monoxide poisoning, what are the symptoms of severe poisoning? Yeah. So that can be. Seizures or decreased or loss of consciousness from a metabolic perspective, they can have a lactic acidosis or cellular hypoxia. And then from a cardiovascular perspective, they can present with the arrhythmias, myocardial ischemia or injury, right? And these carbon monoxide poisoning, you can get a carboxyhemoglobin off the first ABG you get, it can be a good guide based on the time of injury of how far along they are on that. All right. Just like we talked about, Kevin. So how do you diagnose these

patients? So you really have to expect this in any of your patients within it that come in from an enclosed space. And so carboxyhemoglobin levels can confirm, but they don't correlate well, but it's important to remember that you cannot use standard pulse oximetry in these patients. Yeah. You'll have falsely high readings in those patients. All right. What's the treatment for the majority of carbon monoxide poisoning? High flow, highly concentrated oxygen. Whether awake or intubated. Yeah. And then you want to follow up the serial carboxyhemoglobin measurements to make sure you have the appropriate downtrend. If carboxy carbon monoxide poisoning is, severe, and you're at a center that has that hyperbaric oxygen therapy is also an option for these patients. But usually by the time you can get them to a center that has this, the carboxyhemoglobin has already cleared. All right, moving on to cyanide poisoning how do we treat, the basics of this you're going to see on the test, how do we treat it? Yeah, so you're going to use the cyano kit, right? And, the

hallmark findings for cyanide poisoning usually, like I said, it's combined with carbon monoxide poisoning, but you're going to have those patients with severe lactic acidosis. And that's something that might come up in the question stem that has to make you think of cyanide poisoning. Hydroxychromalamin is a very or cyano kit is a very, It's pretty safe drug to give, especially during resuscitation. So if there's any concern at all and now most pre hospital providers are actually given this moving on. All right. Going on to the, one of the highly tested things about burn is a topical antimicrobial agents and their side effects. All right. So let's just walk through these. Kevin, Bacitracin, what do we use it for? And what are the side effects? Yes, we use it for second degree burns. It gives you gram positive coverage and the side effects include rash and nephrotoxicity. Okay. Mupiricin. So use this for staphylococcal infections and it's not used as a prophylactic agent. Side effects can be irritation. All right. So silver

sulfadiazine or SSD. So you use this for third degree burns and you get gram negative coverage with this. And then the side effects can include neutropenia and thrombocytopenia. Neutropenia, thrombocytopenia. Those are the ones that pop up on tests all the time. All right, moving on to mafenide acetate. So this is also used for third degree burns and it also gives you gram negative coverage and you can use for pseudomonas infections. And what you have to be concerned about here is the metabolic acidosis. Yep. I think mafenhyde acetate MA metabolic acidosis commonly tested. And finally silver nitrate. So once again, you use for third degree burns, it gives you gram positive and negative coverage. And there's quite a few side effects include met hemoglobinemia, hyponatremia, hypochloremia, hypokalemia. Hypocalcemia and staining of the skin. Yep. And just to go back to SSD or Silver Sci-Fi Diaz it's contraindicated in patients with a sulfa allergy. And it's also contra-indicated

and, sorry, excuse me. Going to silver nitrate is contraindicated in patients with G six PD deficiency. All right. So burns are often associated with hypothermia. So this is a good, very good time to talk about mild, moderate and severe hypothermia. So this is something that does come up on the app site. And we'll just walk through what you, what are the definitions of the hypothermia at each level and what are the symptoms of the two. So going on to mild hypothermia, so Kevin, what's the Fahrenheit scale for those and what kind of symptoms would you have with that? Yeah, so this is 90 to 94 degrees and you're going to see shivering and mild mental status changes. Okay for moderate hypothermia, what's the range in symptoms? Yeah. So that's 84 to 89 degrees. And you're going to have agitation, combativeness, muscle spasticity, dilated pupils, and slow respirations. Good. And finally, severe hypothermia.

Yeah, so this is the 70 to 84 degrees. They're going to have a prolonged QRS. They're going to have Osborne waves. They're going to be flaccid comatose and have development of v fib. Yeah, the severe type. So once again, mild is 90 to 94 degrees Fahrenheit. Moderate is 84 to 89 degrees Fahrenheit. and severe is anything less than 84 degrees Fahrenheit. So patient comes in in arrest for hypothermia, Kevin and maybe they got pulled out of a lake or got pulled off the street. What is the, the thing you want to do prior to calling time of death if they've been arrested? Yeah they're not dead until they're warm. Exactly. All right. Moving on to frostbite. We're going to walk through the different degrees of frost, frostbite and what are the characteristics of it. Once again, does come up on the upside occasionally. All right. So first degree frostbite or frostbite, Kevin, what is it? Yeah. So this is the superficial frostbite. It's characterized by numbness and edema and a firm plaque.

Second degree. Yeah. This is partial thickness. You can see milky white blister formation. And the healing skin will be noted to be atrophic. All right. Third degree. Yeah. So this is full thickness hemorrhagic blister formation, and you may have a black eschar and may result in limb or tissue loss. Yeah. And then just to reiterate, third degree is that hemorrhagic blister formation and full thickness injury. And finally, fourth degree. This extends to the bone and it'll be black and mummified tissue at presentation. Okay, good. How do we treat frostbite? So you treat the hypothermia first, you do rapid active rewarming of the tissue in heated water. If there's deeper injuries, it may require debridement. You drain the milky or clear blisters and you leave the hemorrhagic blisters intact. Yep. Once again, drain the milky and clear blisters, leave the hemorrhagic blisters intact. Okay. Going back to Burns. Now we want to talk about different types of graphs. So the

two types of graphs we typically use are full thickness skin graphs and split thickness skin graphs. So what are the pro and pros and cons of using a full thickness skin graph over a split thickness skin graph, Kevin? Yeah. So the full thickness skin graphs are used to cover joints and facial structures. The elastin in the dermis causes more primary contracture immediately after harvest as compared to a split thickness skin graft. Yeah, and then like they're less prone to secondary contracture as well. Anything else? Yeah full thickness skin grafts cannot be meshed to increase the surface area. And the full thickness skin grafts have worse donor site morbidity. Yeah. Or a higher chance of complication potentially. Once again, very, there's many nuances to different types of skin grafts, but this is just high yield stuff. You need to know for the upside. When do I use a, if I'm choosing, if it's over joints and facial structures, otherwise you split thickness for the most part.

Yeah. Ideally any of the cosmetic places or the places where you want you don't want to take the chance on a contracture, a full thickness skin graft is. is helpful. But in many cases you don't have the option to use a lot of full thickness skin grafts. So you have to use split thickness skin graft. But it does have in general has better cosmesis at the end. All right, moving on to the last section before our quick hits what's the classic treatment of severe electro injury? Yeah, so this can cause rhabdomyolysis and myoglobinuria and we'll need to see high volume resuscitation for severe injuries. And also cardiac monitoring. In addition, you need to be monitoring their extremities for compartment syndrome. Yeah, electrical injury can present a very wide range of different types of patients. The ones you're going to probably see on the outside are patients who have a severe electrical injury. So they will need, they're the patients who need high volume resuscitation. We're looking at 100

cc's of urine per hour. Cardiac monitoring is pretty much standard for almost all types of electrical injuries, especially ones that you're going to see on the ab site. And then if it was an extremity that was burnt such as a hand or foot, that patient's going to need monitor for compartment syndrome, especially if they have a severe injury, need a high volume resuscitation, they might swell and they'd be concerned for type of a compartment syndrome going forward. All right. Like I said, quick hits going forward here with burn just to round out some things we did not really touch on to reiterate the really important parts. All right. Number one, Kevin treatment or carbon monoxide poisoning, 100 percent oxygenation with a face mask. Good initial treatment of hydrofluoric acid burns, topical calcium gluconate gel. Okay. Treatment of met hemoglobinemia. Yeah. Methylene blue. All right. How do first and second degree burns heal? These heal from epithelialization and primarily from the hair

follicles. So you get epithelialization either from the wound edges or it might heal primarily from the hair follicles within the wound.