Chapter 21: Burns

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You know, usually when we talk about a medical diagnosis, there's this expectation of precision.

It almost feels like engineering.

Right.

We really prefer things to be binary like that.

Broken or not broken.

Exactly.

Like, you break your arm, the x -ray shows that jagged white line, and the doctor points at the screen and just says, there's the problem, we fixed that bone, and we're done.

It's comforting because the pathology is confined to one specific area.

The rest of the body just carries on as usual.

But then you step into the world of critical care burn management, and suddenly that targeted x -ray approach is completely useless.

You aren't just looking at a localized skin wound.

No, not at all.

You're looking at a physiological landscape that is honestly total systemic chaos.

Yeah.

The internal plumbing of the entire body just collapses.

If you're listening to this right now, maybe you're a nursing student grabbing a coffee prepping for a massive critical care exam.

You already know the stakes.

Today, we're figuring out how to stop that collapse.

We really are.

We're doing a deep dive into Chapter 21, from Introduction to Critical Care Nursing, the seventh edition.

Our mission today is a one -on -one tutoring session, breaking down the physiological cascade of severe burns from cellular destruction all the way to resuscitation.

And we really have to approach this by looking at cause and effect.

Because in the critical care unit, sheer memorization of interventions,

well,

it'll only get you so far.

Right.

You need the actual mechanism.

Exactly.

You have to understand the microscopic why behind what is happening so you can anticipate what the patient's cardiovascular and renal systems are going to do before they actually do it.

I love that approach.

So let's start at ground zero, which is the skin itself, the integumentary system.

It's the largest organ of the body.

And I think we often take for granted that it's not just like a wrapper holding our insides together.

Oh, absolutely not.

It's a highly active defensive barrier.

It's performing constant, vital physiological labor.

Regulating fluid, right?

Yeah.

It regulates massive amounts of fluid loss.

It controls core body heat,

synthesizes vitamin D, and it's your primary shield against environmental infection.

So to understand what happens when it burns, we have to visualize its architecture.

We're looking at two main layers.

Right.

On the surface, you have the thin protective epidermis.

And just beneath that is the much thicker dermis, which is basically the operational hub.

That's where you find the blood vessels, sweat glands, hair follicles, nerve endings.

Yep.

And anchoring all of that is the subcutaneous fat tissue.

So when thermal energy hits that architecture, the temperature and the duration of contact dictate the depth of the burn, which we generally classify as superficial, partial thickness, and full thickness.

But when you look at a severe burn, it's not actually just one uniform wound with a single depth.

It behaves much more like a bull's eye target.

I think that bull's eye visualization is the best way to understand the text's zones of thermal injury.

A burn is incredibly dynamic.

It evolves over time.

Right.

So if you picture the absolute center of that bull's eye, the point of maximum thermal impact, that is the zone of coagulation.

And coagulation in this context means dead tissue, right?

Correct.

The zone of coagulation experiences the greatest heat transfer.

The cells there undergo immediate, irreversible necrosis.

It's completely gone.

Yeah, it's a full thickness injury where the proteins literally denature and coagulate.

Nothing can save the tissue in that center circle.

But the rings radiating outward from that dead center are where the critical care nurse actually goes to work.

So the immediate next ring is the zone of stasis.

Exactly.

And if I'm understanding the pathology correctly, the tissue in this middle ring is severely injured and starved of blood flow, but it isn't dead yet.

So isn't our primary nursing goal to save this zone of stasis from converting into a full thickness burn?

That is the ticking clock of burn care, yes.

The zone of stasis has decreased perfusion, meaning blood flow is sluggish and struggling.

It is potentially salvageable.

However, if that patient doesn't receive aggressive fluid resuscitation, or if they develop severe swelling or an infection, that sluggish blood flow stymes entirely.

So the cells suffocate.

They suffocate, the tissue dies, and that dead zone of coagulation basically expands outward.

Wow.

And just to complete the bullseye, the outermost ring is the zone of hyperamemia, which usually just looks red, has minimal cell injury, and recovers fine on its own.

Right, it recovers spontaneously.

So the entire game is maintaining blood flow to that middle zone of stasis.

But keeping the blood pumping becomes incredibly difficult because of a massive systemic crisis the textbook calls burn shock.

Yeah, the localized burn triggers a localized alarm, but then the whole body panics.

The barrier is destroyed, so the body mounts an explosive systemic inflammatory response.

And this is driven by chemical mediators, right?

Specifically histamine and bradykinin.

Yes.

I want to pause on bradykinin and histamine for a second because we hear those terms constantly in pharmacology.

What are they actually doing to the blood vessels on a microscopic level in a burn patient?

We'll think of them as chemical wedges.

Normally, the endothelial cells that line your blood vessels fit tightly together, keeping the blood and fluid inside the vessel.

Like a sealed pipe.

Exactly.

But when histamine and bradykinin are released in massive quantities, they force those cells to contract and pull apart.

The tight junctions open up, making the capillaries highly permeable.

They form literal gaps in the blood vessel walls.

Massive gaps.

And this leads to a phenomenon known as third spacing.

Intravascular fluid begins pouring out of the blood vessels and into the interstitial space, the tissue between the cells.

But it's not just water leaking out, is it?

No.

Massive protein molecules, particularly albumin, leak through those gaps as well.

And albumin is crucial because it generates oncotic pressure.

It acts like a molecular sponge inside the blood vessels holding the water in.

Right.

So if the albumin escapes into the surrounding tissue, it drags even more fluid out of the cardiovascular system with it.

Which leaves the vascular space severely depleted.

The cellular destruction goes even deeper than that.

Because of the trauma and lack of oxygen,

the actual cell membranes begin to fail.

Oh, wow.

Yeah, the transmembrane electrical potential drops, which shuts down the sodium potassium pumps.

Okay, I remember this from biology.

If the pump fails, sodium floods into the cell.

And in the human body, water always follows sodium.

Always.

So now water is being dragged out of the blood vessels, into the tissues, and then directly inside the cells themselves.

Yep.

The cells blow up like water balloons.

This physiological disaster creates a unique hemodynamic crisis called burn shock.

Which is a lethal combination, right?

Very lethal.

It's a mix of distributive shock, because the body's fluid is distributed into the wrong compartments, and hypovolemic shock, because the actual circulating blood volume inside the vessels has absolutely plummeted.

I always picture it like trying to fill a bucket with a leaky hose.

The patient looks incredibly swollen from the outside.

They have massive tissue edema.

But their actual blood vessels, the internal hose, are bone dry.

But here is what confuses me.

If their blood vessels are practically empty, why doesn't their blood pressure immediately crash to zero on the monitor?

Ah, because the body has a brilliant, but ultimately temporary, compensatory mechanism.

The sympathetic nervous system detects the drop in volume and panics.

So it dumps adrenaline.

Exactly.

Massive amounts of catecholamines, adrenaline, and noradrenaline into the blood stream.

This causes severe vasoconstriction, clamping the blood vessels down incredibly tight, and forces the heart to beat dangerously fast to maintain an artificial blood pressure.

So the heart is running a marathon trying to pump blood that simply isn't there.

It's masking the internal bleed out.

It is entirely a mask.

And while the blood pressure might look deceptively stable for a moment, the organs are starving.

Renal blood flow drops off a cliff.

Which means the kidneys stop filtering.

Right.

Leading to oliguria, dangerously low urine output.

If we don't intervene rapidly, the patient goes into acute renal failure.

Which brings us to the most critical window from the text.

The resuscitative phase.

Covering the first 48 hours post -injury.

This is where we step in.

Yes.

But before we frantically try to refill that leaky hose with IV fluids, we have to fall back on our foundational ADCs.

The primary survey doesn't change just because the skin is burned.

Airway and breathing take absolute precedence.

They have to.

Especially if the burn occurred in an enclosed space, you must immediately suspect an inhalation injury.

You're actively assessing for facial burns, singed nasal hairs, hoarseness, or stridor.

Because airway edema from thermal damage can develop so rapidly, Ralph.

Incredibly rapidly.

If you wait for obvious respiratory distress to intubate, the airway might already be swollen completely shut.

That's terrifying.

But beyond the physical swelling, there's a hidden silent gas exchange killer we have to screen for.

Carbon monoxide, or CO, poisoning.

And a standard pulse oximeter clipped to the patient's finger is incredibly dangerous here, because it will flat out lie to you.

It absolutely will.

It might read 98 % or 100 % oxygen saturation.

The patient might even look flushed and cherry red instead of blue and cyanotic.

But they are actively suffocating at a cellular level.

The mechanism behind that lie is fascinating.

A pulse oximeter works by shining light through the capillary bed to measure the color of the hemoglobin, right?

And normal oxygenated hemoglobin is bright red.

The problem is, carbon monoxide binds to hemoglobin with an affinity 200 times greater than oxygen.

200 times.

Yeah, it brutally kicks the oxygen off the molecule and takes its place.

This creates carboxyhemoglobin, which also happens to be bright cherry red.

So the machine reads the color, assumes the hemoglobin is full of oxygen, and gives a falsely reassuring normal number.

Exactly.

So the strict protocol is to immediately administer 100 % humidified oxygen via a non -rebreather mask or endotracheal tube.

Here's where it gets really interesting, though.

Why do we specifically need 100 % oxygen?

Why isn't regular room air, which is, what, about 21 % oxygen, enough to just flush the carbon monoxide out of their lungs as they breathe naturally?

It all comes down to the half -life of carbon monoxide.

If a poisoned patient is just breathing normal room air, it takes roughly four hours for the carbon monoxide levels in their blood to drop by half.

And four hours of cellular suffocation guarantees severe brain damage or death.

Exactly.

But if we flood their respiratory system with 100 % oxygen, the sheer concentration gradient acts as a competitive drug.

It forcibly unbinds the carbon monoxide, dropping its half -life from four hours down to just 45 to 60 minutes.

Wow.

We are literally weaponizing pure oxygen to evict the poison.

Now, sticking with the mechanics of breathing, there's a terrifying physical restriction that can happen if a patient has full thickness burns that go completely around their torso's circumferential chest burns.

Yes.

Remember that the dead tissue in the zone of coagulation, the escher, turns hard, leathery, and entirely inflexible.

It's essentially a tight suit of armor wrapped around their ribs.

That's a perfect way to describe it.

And as the viable tissue underneath that armor starts to swell with massive edema from the leaky capillaries, the chest is squeezed from the inside out.

The lungs physically do not have the space to expand.

Right.

The patient cannot ventilate, so the only treatment is a bedside escherotomy.

The physician takes a scalpel and cuts deep, lengthwise incisions directly through the burned skin to release the pressure and allow the rib cage to move.

And the most astonishing part of this is that it often doesn't even require local anesthesia because the nerve endings in that full thickness leathery escher are already completely destroyed.

The incision is essentially painless.

It's a brutal looking but instantly life -saving intervention.

It instantly restores the mechanics of breathing.

But once the airway is secure and the lungs can expand, we have to tackle the hypovolemic shock.

We have to perform the math that saves lives.

The fluid resuscitation algorithms, this is where the clinical judgment of a critical care nurse is really tested.

To fix the intravascular volume deficit, we use the Advanced Burn Life Support or ABLS formula.

It calculates exactly how much lactated ringer solution the patient needs in the first 24 hours.

Let's break down the formula from the text.

You take two milliliters of lactated ringers, multiply it by the patient's weight in kilograms, and then multiply that by the percentage of their total body surface area that's burned.

So, two times kilogram times percent TBSA.

But the total volume that equation spits out is not just infused at a steady continuous rate over the 24 hours.

The capillary leak is most severe immediately after the injury, so the fluid delivery has to match that intensity.

The rule is, half of the total calculated volume must be infused in the first eight hours.

And importantly, that is eight hours from the exact time of the burn, not eight hours from when they rolled through the hospital doors.

That's a huge distinction.

It is.

The remaining half is then given over the next 16 hours.

Let's run a real scenario from the chapter's case study to make this math real.

We have a patient, Mrs.

J.

She weighs 65 kilograms, and she suffered a 30 % total body surface area burn.

Using the formula, two milliliters times 65 kilograms times 30.

That gives us a total volume of 3 ,900 milliliters for the first 24 hours.

Right.

So we take that total, 3 ,900, and divide it in half.

That's 1 ,950 milliliters that must go in during the first eight hours.

And if she arrived immediately after the injury, we divide 1 ,950 by eight hours, which means we have to set that IV pump to 243 milliliters per hour.

I mean, I have to push back here, because a normal maintenance IV drip is usually around 75 to 100 milliliters per hour.

Oh, yeah.

We are blasting nearly 250 an hour into this woman.

Won't that sheer volume back up into her heart and drown her lungs and pulmonary edema?

In a healthy patient, absolutely it would.

But in a severe burn patient, the vascular space is essentially a bottomless pit because of those massive gaps between the endothelial cells.

The leaky hose.

Exactly.

The fluid is leaking out almost as fast as you're pumping it in.

The goal isn't to overfill them.

The goal is just to keep enough volume passing through the heart and the kidneys to keep the organs alive until the blood vessels finally seal themselves back up.

Which is why the formula is just a starting point.

Every patient's capillary leak is unique.

We can't just set the pump to 243 an hour and walk away.

We have to constantly perform endpoint monitoring to see if the resuscitation is actually working.

And we already established we cannot trust blood pressure because adrenaline is artificially propping it up.

Urine output is the ultimate source of truth.

It is the gold standard for monitoring fluid resuscitation.

We titrate the IV fluids up or down based strictly on the kidneys.

What's the target?

We want to see a continuous urine output of 30 to 50 milliliters per hour in an adult.

If they're making that much urine, it proves the kidneys are getting enough blood flow.

It's a direct physiological mirror.

If the kidneys are filtering, the heart is pumping which means our leaky hose is full enough.

But there are specific scenarios in the text where the standard 2 milliliter math goes out the window.

If the patient suffered an electrical burn, the formula doubles.

We use 4 milliliters per kilogram instead of 2.

Why do electrical burns demand so much more fluid?

Because the surface of an electrical burn is highly deceptive.

The electrical current travels through the body by taking the path of least resistance, which is typically along blood vessels, nerves, and deep muscle tissue.

So the outside might look fine.

Right.

The patient might only have a tiny entrance wound on their hand and an exit wound on their foot.

But beneath the skin, the current has essentially cooked the deep muscle tissue.

And when deep muscle is destroyed, it triggers rhabdomyolysis.

The muscle cells burst open and release a massive protein called myoglobin into the bloodstream.

Myoglobin is the danger here.

As that heavy, sludgy protein makes its way to the kidneys to be filtered, it physically jams and clogs the delicate renal tubules.

Like pouring wet concrete into a coffee filter?

That's exactly what it's like.

It causes rapid acute kidney injury.

To prevent the kidneys from shutting down, we have to push a significantly higher volume of fluid, the 4 milliliter formula, to forcefully flush that myoglobin out.

And our target urine output jumps, right?

Yes.

From the normal 30 to 50, all the way up to 75 to 100 milliliters per hour.

High pressure flushing to clear the pipes.

That makes perfect sense.

Now, switching to chemical burns, I have an assumption I want to test.

If a patient comes in with a chemical burn from an alkaline substance, like a household oven cleaner or liquor drain opener,

my instinct is that it would be less dangerous than a burn from a severe aphid, like battery acid.

Am I wrong?

It's a very common assumption, but clinically, alkalisers are significantly more destructive.

Really?

Yeah.

Acids generally cause coagulation necrosis.

When an acid hits the skin, it immediately denatures the surface proteins, creating a thick, hard escher.

That hardened tissue actually acts as a protective shield, which physically blocks the acid from penetrating any deeper.

So the acid essentially traps itself on the surface, but how does an alkali behave differently?

Alkalis cause liquefaction necrosis.

Yeah.

Instead of cooking the tissue into a hard shield, the alkaline chemical melts the cell membranes.

It literally turns the tissue into a soupy liquid.

Yeah, because the tissue is liquefied, there is no barrier.

The chemical is free to continue diffusing deeper and deeper into the fat and muscle, causing incredibly extensive ongoing damage.

Liquifaction necrosis.

That is a horrifying visual, but an unforgettable mechanism.

And regardless of whether it's acid or alkali, the immediate intervention is massive, prolonged flushing with water to dilute the agent.

Always flush it.

Right.

There is one more etiology we have to discuss, and it requires the nurse to look past the physiology and evaluate the context of the injury.

We have to be hypervigilant for signs of abuse.

As a critical care nurse, you are a mandated reporter.

You must critically evaluate the burn pattern.

For example, if a child or a dependent elderly patient is brought in with a severe scald burn on their lower legs, and you observe a perfectly straight, clear line of demarcation where the burn stops, and there are absolutely no irregular splash marks and anywhere else.

That perfect line tells a story.

It does.

It indicates an intentional immersion injury.

If it had been an accidental spill, the patient would have thrashed and tried to escape, causing water to splash randomly across the skin.

A straight line means someone forcibly held them down in the scalding water.

Exactly.

Recognizing that pattern is a vital, non -negotiable nursing responsibility.

It is grim, but it saves lives.

Okay, let's take a breath.

We've navigated the chaotic first 48 hours.

We stabilize the airway.

We manage the massive fluid math to support the kidneys.

We flush the chemical agents.

Right around 48 to 72 hours post -injury, a major shift happens.

Yes.

The tight junctions in the capillaries finally heal.

The massive leak seals up.

The fluid that was trapped in the tissues begins shifting back into the blood vessels, and the patient starts having massive diuresis, peeing out all that third -spaced edema.

We are now officially out of the resuscitative phase and into the acute phase.

The clinical focus pivots dramatically here.

The patient has survived the cardiovascular shock, but now the central nervous system realizes the body has massive open wounds that need to be closed.

To rebuild that tissue, the body enters a severe hypermetabolic and catabolic state.

The textbook equates this to running a continuous marathon for months.

Their resting metabolic rate skyrockets to 100 % or even 200 % above normal.

They are burning calories at an astonishing rate.

If we don't aggressively intervene with massive nutritional support, the body will literally cannibalize its own skeletal and cardiac muscle for the energy it needs to heal the skin.

Which means nutrition is an emergency intervention.

We place an enteral feeding tube almost immediately, often within hours of admission, and continuously pump high -calorie, high -protein formulas directly into the gut.

And using the gut also prevents intestinal bacteria from translocating into the bloodstream and causing subsist, right?

Exactly.

We also use pharmacology to fight the muscle wasting, specifically a drug called oxandrolone.

Oxandrolone is an anabolic steroid, right?

Yes.

It directly counters the catabolic breakdown.

It promotes protein synthesis, helping to preserve the patient's lean muscle mass, which fundamentally decreases their healing time and helps get them out of the hospital faster.

While we are fueling the body internally, we also have to protect the open wounds externally.

The text has a great medication table for topical antimicrobials used in wound care.

We need to distinguish two main ones.

Silver sulfateazine, commonly known as sylvidine, and mafenyde acetate, known as sulfamolone.

Right.

They seem similar, but they have very different applications.

It all comes down to penetration.

Okay.

Sylvidine is a fantastic broad -spectrum cream, and its primary advantage is that it is soothing and painless when applied.

However,

its molecular structure prevents it from penetrating through thick escher.

So if you put it on a deep, leathery, full thickness burn, the medication just sits on top.

Exactly.

It never reaches the underlying tissue bed where the bacteria are actually multiplying.

So sylvidine is perfect for superficial or partial thickness burns, but for deep escher, you have to switch to the sulfamolone.

Right.

Sulfamolone easily penetrates thick escher and even a vascular tissue like cartilage, which is why it's the gold standard for deep ear burns, but it comes with a severe drawback.

Because it penetrates so deeply, it reaches the viable, raw nerve endings beneath the burn.

The application of sulfamylon is intensely painful for the patient.

Which perfectly sets up our final acute intervention,

pain management.

A burn injury is agonizing.

There's the constant background pain and the excruciating procedural pain of daily wound abridements.

The undisputed gold standard medication is intravenous morphine.

Yes.

But there is a massive physiological trap here that the book highlights.

During the initial resuscitative phase, when the patient is severely swollen with edema, giving pain medication via an intramuscular or subcutaneous injection is absolutely contraindicated.

Think about the mechanics of the fluid shift we just discussed.

If a nurse injects a dose of morphine into a muscle that is massively engorged with third space fluid, the drug can't reach the vascular system.

It just sits trapped in the edematous tissue.

Right.

The patient gets no pain relief.

So the patient is still screaming in agony.

The nurse thinks, the morphine didn't work, I need to administer another IM dose, and maybe another one an hour later.

None of it works.

But what happens 48 hours later when the capillaries seal up and that fluid shifts back into the bloodstream?

All of those trapped, unobsorbed doses of morphine are suddenly swept into the vascular system at the exact same time.

Oh, wow.

It results in a massive, simultaneous bolus of narcotics, leading to a potentially fatal respiratory arrest.

This is why, in a critical burden patient, you always, always use the IV route.

It guarantees immediate delivery and prevents the fluid trap.

Always use the IV route.

Well, we have covered an incredible amount of physiological ground today.

We started at the microscopic pulling apart of endothelial cells that causes burn shock.

We worked through the aggressive ABLS fluid math to save the kidneys, and we pushed all the way into the metabolic marathon of the acute healing phase.

It is a phenomenal amount of complex information.

But by breaking down the underlying cascade, by understanding how the fluid shifts and why the medications behave the way they do, these nursing interventions become logical extensions of the physiology, rather than just a list of tasks you have to blindly memorize.

I see the connections so clearly now.

Before we sign off, I want to leave you, the listener, with a final provocative thought.

It's based on the text's mention of a technology called Cultured Epidermal Autographs, or CEA.

This is truly the frontier of critical care.

We can now take a tiny biopsy of a patient's unburned skin, a sample roughly the size of a postage stamp.

We sent it to a specialized lab, and over three weeks, they cloned the patient's own keratinocytes, expanding that tissue into fragile sheets thousands of times larger than the original sample.

That's amazing.

Then we graphed that cloned skin right back onto the massive burn wounds.

It is literal science fiction happening in our burn units today, but here is the question for you to ponder.

As you step into the critical care environment, ask yourself, how will these rapidly evolving tissue engineering technologies, which have the potential to close massive wounds in weeks rather than agonizing months,

fundamentally change the entire timeline of that hypermetabolic marathon we just discussed?

If we can restore the barrier faster, how will that change our fluid math and our nutritional demands in the future?

Well, the faster we can convince the central nervous system that the wound is closed, the faster we stop the catabolic muscle wasting.

It is going to rewrite the rule book of burn resuscitation.

It's an incredible thought to carry with you as you hit the books tonight.

The physiological waters of critical care are murky, and the systemic chaos is intimidating, but you now have the conceptual blueprint to navigate it.

From all of us here on The Steep Dive and our last minute lecture team, thank you so much for joining us.

We are wishing you the absolute best of luck on your critical care nursing exam.

You've got this.