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Hyperkalemia

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In one line

·Too much potassium in the blood shrinks the voltage gap heart muscle cells need to beat reliably.

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Normal physiology

·Potassium is packed inside every cell at high concentration — about 140 units inside versus only 4 units outside in the blood. This steep difference creates a voltage gap across the cell membrane, like a charged battery. Heart muscle cells use this gap to fire and then reset after every beat. Your kidneys are the main exit door for potassium: they filter your blood and dump about 90 percent of the potassium you eat each day into your urine. The hormone aldosterone (made by the adrenal glands sitting on top of your kidneys) tells the kidney tubules to grab sodium back and kick potassium out. Blood flow through the kidneys and the amount of sodium delivered to the far end of the tubule also control how much potassium leaves. When this system works, blood potassium stays steady between 3.5 and 5.0 units, and the heart's voltage gap stays wide and safe.

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What goes wrong

·High potassium (Hyperkalemia) happens when potassium piles up in the blood faster than the kidneys can remove it, or when cells burst open and dump their potassium load all at once. The kidneys are the bottleneck: if they fail or if medicines block aldosterone, potassium has nowhere to go. Cell breakdown floods the blood with potassium because cells hold 30 times more potassium than blood does. Either way, the rising blood potassium shrinks the voltage gap across the heart muscle membrane, and the heart's electrical system starts to misfire.

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Hallmark signs

·Often no symptoms at all until the level is dangerously high
·Muscle weakness (especially in the legs and arms)
·Tingling or numbness (paresthesias), especially around the mouth or in the hands and feet
·Heart palpitations (feeling your heart skip, race, or pound)
·Nausea or vomiting
·Slow heart rate (bradycardia)
·Peaked (tall, narrow, tent-shaped) T waves on the EKG
·Widening of the QRS complex on the EKG (the heartbeat spike looks stretched out)

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Red flags · escalate now

·EKG changes (peaked T waves, wide QRS, flat P waves, or any new rhythm problem) — even if the patient feels fine
·Muscle weakness so severe the patient cannot stand or move arms and legs normally
·Heart rate below 50 or above 120, or any irregular, skipped beats
·Potassium level 6.5 mEq/L or higher (immediate treatment needed)
·Sudden chest pain, shortness of breath, or feeling faint (may signal a dangerous heart rhythm about to start)

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Workup

·Serum potassium
·12-lead EKG
·Basic metabolic panel (BMP) or comprehensive metabolic panel (CMP)
·Arterial blood gas (ABG) or venous blood gas (VBG)
·Urine potassium and transtubular potassium gradient (TTKG) if the cause is unclear
·Medication review
·Creatine kinase (CK) if rhabdomyolysis is suspected
·Repeat potassium in 1–2 hours after emergency treatment

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Treatment

·Calcium gluconate 1–2 g IV (or calcium chloride 0.5–1 g IV) over 2–3 minutes
·Regular insulin 10 units IV with dextrose 25 g (one ampule of D50) IV push
·Albuterol 10–20 mg nebulized (or 0.5 mg IV if available)
·Sodium bicarbonate 50–100 mEq IV over 5–10 minutes (only if metabolic acidosis (acid building up in the blood) is present, pH below 7.2)
·Loop diuretic (furosemide 40–80 mg IV, or bumetanide 1–2 mg IV) if the kidneys are still making urine
·Sodium polystyrene sulfonate (Kayexalate) 15–30 g oral or rectal (if the GI tract works and high potassium (hyperkalemia) is not immediately life-threatening)
·Hemodialysis (if potassium is above 6.5 mEq/L with EKG changes, or refractory high potassium (hyperkalemia) that does not respond to medical treatment, or acute kidney injury / end-stage kidney disease with no urine output)

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NCLEX trap

·How the patient feels does NOT tell you if the heart is in danger. The EKG tells you. Even when someone feels perfectly okay, a potassium of 7 mEq/L or higher with EKG changes (like peaked, narrow T waves or a widening QRS) is a heart emergency right now. The heart could stop without warning. Always check the EKG before deciding how fast to move — the EKG shows if the heart membrane is unstable, not symptoms.
·Peaked T waves mean the heart's electrical wiring is in danger. Protect the heart membrane FIRST with calcium gluconate 1–2 grams IV push (it doesn't lower potassium but makes the heart safer for 30–60 minutes by raising the voltage the heart needs to misfire). THEN shift potassium into cells with regular insulin 10 units IV plus dextrose 25 grams IV and albuterol 10–20 mg by nebulizer. Calcium buys you time while you set up the real fixes. Order is: protect heart, shift potassium, eliminate potassium.
·Many patients with high potassium (hyperkalemia) feel absolutely nothing until their heart stops. The EKG catches the danger when symptoms don't. A normal EKG in someone with high potassium is reassuring; an abnormal EKG in anyone with high potassium is a true emergency. Never wait for symptoms to decide if high potassium is serious.
·Potassium-sparing diuretics (like spironolactone, amiloride, eplerenone, triamterene) cause high potassium (hyperkalemia) only when the kidneys can't clear potassium fast enough or when paired with ACE inhibitors, ARBs, or NSAIDs without close monitoring. You can use them safely by checking potassium levels every 1–2 weeks at first and stopping them if levels creep above 5.0–5.5 mEq/L. The medicine itself isn't evil — high potassium happens when the kidney's clearing job breaks or when you stack too many potassium-raising medicines together without watching the levels closely.
·Hemolyzed samples (when red blood cells burst in the tube during draw or handling) leak potassium from inside cells into the liquid part of the blood and give a falsely high reading. ALWAYS redraw the sample carefully before treating for high potassium (hyperkalemia) — use a gentle draw, a larger-bore needle, and avoid squeezing the tube too hard. Treating a fake high reading is one of the easiest high potassium traps to fall into. If the redraw is normal, the patient never had true high potassium.
·Insulin and albuterol push potassium back into cells temporarily — they buy time but do NOT remove potassium from the body. Potassium leaks back out of cells in 4–6 hours. The real cure for high potassium (hyperkalemia) is elimination: the kidneys must clear it in urine (boosted with furosemide 40–80 mg IV if kidneys work) or dialysis must pull it out (if kidneys are broken or the patient makes no urine). Shifting is a bridge to safety, not the fix. You must always follow shifting with elimination.

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