POTASSIUM

The electrolyte equivalent of “fuck around and find out.”

This week we're talking about potassium.

Symbol: K⁺

Normal serum range: roughly 3.5–5.0 mmol/L.

That doesn't sound particularly exciting, becasue its not!

Until you realize that moving slightly outside that tiny range can turn a perfectly respectable ECG into something that looks like the monitor was dropped down a flight of stairs.

Potassium is basically the body's emotional-support electrolyte.

Except instead of providing emotional support, it controls resting membrane potential, nerve conduction, skeletal muscle function, and cardiac electrical activity.

So perhaps don't piss it off.

Most of your potassium is hiding.

About 98% of the body's potassium is intracellular.

Only a tiny fraction is hanging around in the extracellular fluid where we're measuring it.

Which means the potassium value on your bloodwork represents a surprisingly small portion of the body's total potassium.

This becomes important because potassium loves moving between compartments.

Insulin?

GET IN THE CELL.

Beta-2 stimulation?

GET IN THE CELL.

Acidosis and various cellular shifts?

Potassium may start moving out.

Cell destruction?

EVERYBODY OUT OF THE FUCKING CELL.

The result is that serum potassium can change dramatically without necessarily representing an equally dramatic change in total-body potassium.

DKA is a beautiful example...and also next weeks episode.

Your patient can be total-body potassium depleted while their serum potassium is normal or elevated.

Because apparently electrolytes enjoy psychological warfare.

When potassium gets too low...

Welcome to hypokalemia.

Maybe they're losing potassium through vomiting or diarrhea.

Maybe they're taking diuretics.

Maybe insulin pushed potassium intracellularly.

Maybe you gave a pile of salbutamol and potassium decided:

“Fine. I'll go inside.”

As potassium falls, patients may develop weakness, cramps, fatigue, and cardiac dysrhythmias. MORE FUCKING DYSRHYTHMIAS!

And your EKG may start dropping hints.

Flattened T waves.

ST depression.

Prominent U waves.

Ectopy.

Eventually, potentially dangerous dysrhythmias.

The heart basically starts sending increasingly aggressive emails titled:

“Per my previous potassium…”

And when potassium gets too high...

Now we're playing hyperkalemia.

Renal failure is a major culprit.

But tissue destruction, medications, metabolic derangements, and other conditions can contribute.

As extracellular potassium rises, cardiac electrophysiology starts changing.

You might see:

Tall, peaked T waves...almost like its an opposite of Hypo....go figure.

Then PR prolongation.

P waves can flatten or disappear.

The QRS can widen, just like your waitline after a holiday dinner.

And in severe toxicity, the ECG may deteriorate toward a sine-wave pattern, ventricular fibrillation, or asystole.

At that point, potassium isn't politely suggesting there's a problem.

Potassium has kicked open the door and yelled:

“EVERYBODY GET THE FUCK OUT.”

Calcium enters the chat.

Here's an important distinction.

In severe hyperkalemia with ECG changes, calcium doesn't remove potassium from the body.

It stabilizes the cardiac membrane.

Think of calcium as the friend who arrives at the bar and says:

“Okay. Nobody do anything stupid while we figure this shit out.”

Then you've got treatments aimed at shifting potassium intracellularly.

Insulin and glucose.

Beta-2 agonists.

Sometimes bicarbonate depending on the clinical circumstances.

And ultimately, the potassium still needs to leave the body.

Because moving the problem from the living room into the bedroom doesn't mean you cleaned the house.

And yes, salbutamol is involved.

Remember our Big Blue Band-Aid episode?

Salbutamol stimulates beta-2 receptors and can promote intracellular potassium movement.

Which means the medication we usually associate with:

“WHEEZE BAD. BLUE PUFFER GOOD.”

also has a role in hyperkalemia management in appropriate protocols and circumstances.

Physiology is fucking delightful.

Why should paramedics care?

Because potassium problems can masquerade as all kinds of other shit.

Weakness.

Fatigue.

Palpitations.

Bradycardia.

Tachycardia.

Syncope.

Altered mental status.

Cardiac arrest.

And sometimes your first major clue is the EKG screaming:

“SOMETHING IS VERY FUCKING WRONG.”

A dialysis patient who missed treatment and is now weak and bradycardic?

Think potassium.

Renal failure with bizarre EKG changes?

Think potassium.

DKA undergoing treatment?

Think potassium.

Unexplained widening QRS with suspicious T-wave changes?

At least invite potassium to the differential diagnosis party.

This week's episode

We're diving into:

• What potassium actually does

• Why the intracellular/extracellular gradient matters

• How potassium contributes to resting membrane potential

• Hypokalemia and why it causes dysrhythmias

• Hyperkalemia and why it can kill

• The ECG progression of potassium abnormalities

• Why calcium protects the myocardium without actually lowering potassium

• How insulin shifts potassium

• Why salbutamol somehow wandered into another episode

• Potassium in DKA

• Renal failure and dialysis patients

• And why K⁺ is arguably the most aggressively important letter on your bloodwork

By the end, hopefully you'll stop looking at potassium as:

“That electrolyte that's supposed to be around four.”

And start looking at it as:

“That tiny positively charged bastard standing between my patient and an extremely uncomfortable cardiac arrest.”

As always, That Paramedic Podcast is educational.

It is not medical direction.

I am not your medical director.

Your partner isn't your medical director.

And the firefighter who once watched a YouTube video about hyperkalemia is definitely not your fucking medical director.

Follow your protocols.

Know your scope.

Treat the patient.

Watch the ECG.

And remember:

Potassium doesn't give a shit how close you are to the hospital.

That Paramedic Podcast

Potassium: The Spicy Little Ion That Controls Your Heart

Come for the peaked T waves. Stay because the QRS is getting suspiciously wide.