Hyperkalemia changes the ECG in a fixed order, and that order is what the exam tests: which change comes first, which one means the level has reached the heart, and what the nurse does about it before anything else. Here is the sequence, the rough potassium level for each step, and the stabilize–shift–eliminate logic that follows.
What are the ECG changes of hyperkalemia, in order?
- Peaked T waves — tall, narrow, symmetric, “tented.” Usually the first change, often from about 5.5–6.5 mEq/L. This is the sign that potassium has reached the myocardium.
- PR prolongation and a flattening P wave — atrial conduction slows, typically from about 6.5 mEq/L.
- Widening QRS — ventricular conduction is now poisoned, commonly past 7 mEq/L. From here the strip can deteriorate in minutes.
- Sine wave — the QRS and T merge into a wide, rolling waveform, usually above 8 mEq/L. This is peri-arrest.
- Ventricular fibrillation or asystole.
The levels are approximate. A chronic dialysis patient can carry a 6.5 with a normal strip; an acute rise can peak the T waves at 5.8. The ECG, not the number, tells you how urgent the patient is — which is why the correct first response to “potassium 6.6 with peaked T waves” is different from the response to “potassium 6.6” alone.
Drag the potassium below and watch the strip walk through every step. Then hang calcium gluconate and watch the strip settle while the potassium does not move.
Try it · drag potassium to 7, then 8
Hyperkalemia simulator
See the whole patient respond.
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Bedside monitor · pattern
Hyperkalemia
High extracellular potassium partially depolarizes cells, progressively poisoning myocardial conduction.
Tall, narrow, symmetric, tented T waves are the FIRST ECG change of hyperkalemia. Seeing them means the level has already reached the heart.
Extracellular volume at baseline. The dashed line marks euvolemia.
What the nurse would notice
Hyperkalemia across body systems
Peaked T waves, long PR, lost P, widening QRS, arrest
Weakness, paresthesias; flaccid paralysis when severe
Nausea, diarrhea, hyperactive bowel sounds, cramping
Oliguria or kidney failure is usually the cause
Teaching model, not a clinical calculator. Patterns show high-yield directional relationships under the stated assumption. Real symptoms, ranges and treatment depend on cause, acuity, comorbidities and local protocols.
Signs & symptoms
Present on this panel. Tap any sign to see which values produce it.
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Now see if it holds up on exam questions
A free practice test puts fluids and electrolytes next to everything else the NCLEX asks, with a rationale on every answer.
What does IV calcium do in hyperkalemia?
It protects the heart. It does not lower the potassium. Calcium raises the firing threshold of the cardiac membrane, restoring the gap between the resting potential the potassium has pushed up and the threshold the cell has to reach. The T waves settle and the QRS narrows within minutes — and the potassium level is exactly what it was. The protection lasts about 30–60 minutes, which is the window everything else has to work in. Calcium gluconate is given IV over a few minutes on the monitor; calcium chloride carries three times the elemental calcium and is usually reserved for a central line.
What is the treatment order for hyperkalemia?
The mnemonic that survives the exam is stabilize, shift, eliminate.
- Stabilize: IV calcium for any ECG change. First, always, because it works in minutes and nothing else does.
- Shift: regular insulin IV with dextrose drives potassium into cells within about 15–30 minutes and lowers the level by roughly 0.5–1 mEq/L; nebulized albuterol does the same by a different route; sodium bicarbonate helps mainly when the patient is acidotic. Shifting hides the potassium — it comes back out in a few hours, so the clock is now running on removal.
- Eliminate: a loop diuretic if the kidneys work, a potassium binder by mouth, or dialysis when they do not. Dialysis is the only fast removal in an anuric patient, and it clears the phosphate, the acid and the fluid in the same session.
What does the nurse monitor?
- Continuous ECG from the first abnormal strip until the potassium is back under 5.5.
- Potassium every one to two hours during treatment, and again a few hours after a shift, because it rebounds.
- Glucose after insulin — the dextrose is there to prevent hypoglycemia, and it does not always succeed.
- The cause: hold ACE inhibitors, ARBs, potassium-sparing diuretics and potassium supplements as ordered; check the kidney function.
What makes hyperkalemia more dangerous than the number suggests?
Low calcium. Calcium is what protects the myocardium from potassium, so a patient with a high potassium and a low calcium — the missed-dialysis patient, the tumor-lysis patient — arrests at a lower potassium than you would expect. That combination makes calcium urgent rather than optional. Acidosis pushes in the same direction, because it keeps shifting potassium out of cells. Both are visible on the simulator: drop the calcium and watch the strip get worse at the same potassium.
Hyperkalemia is one of the six electrolyte relationships the exam keeps returning to. The full lesson, with the questions, is here.
Practise the priority question
Free account, no card. What does the nurse do first? — asked the way the NCLEX asks it, with rationales on every option.
Common questions
What is the first ECG change in hyperkalemia?
Tall, narrow, symmetric peaked T waves, usually appearing from about 5.5–6.5 mEq/L. They are the sign that potassium has reached the heart. Later changes are PR prolongation with a flattening P wave, a widening QRS, and finally a sine wave before arrest.
What does calcium gluconate do for hyperkalemia?
It stabilizes the myocardium by raising the firing threshold, so the ECG settles within minutes — but it does not lower the potassium at all. The protection lasts about 30–60 minutes, during which insulin with dextrose or albuterol shifts potassium into cells and a diuretic, binder or dialysis removes it.
What is the treatment order for hyperkalemia?
Stabilize, shift, eliminate. IV calcium first for any ECG change; then regular insulin with dextrose (or nebulized albuterol, or bicarbonate if acidotic) to shift potassium into cells; then a loop diuretic, a potassium binder, or dialysis to remove it from the body.