Serum K >5.0 mEq/L; cardiac arrhythmia risk drives urgent intervention.
Also known as: hyperkalemia, high potassium
Overview
Serum potassium concentration >5.0-5.5 mEq/L (varies by lab). Severity: mild 5.5-5.9, moderate 6.0-6.4, severe ≥6.5 or any level with ECG changes. Acuity, EKG changes, and underlying cause determine urgency of intervention.
Epidemiology
Affects ~1-10% of hospitalized patients. Most common in patients with CKD, heart failure, diabetes, and those on RAAS inhibitors, MRAs, or potassium-sparing diuretics.
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Question 1RenalMedium
A 67-year-old man with end-stage renal disease on hemodialysis presents with generalized weakness after missing dialysis. Blood pressure is 88/60 mm Hg and he appears ill. The ECG shows peaked T waves, a widened QRS of 160 ms, and a sine-wave pattern. Serum potassium is 7.8 mEq/L. Which of the following is the most appropriate immediate treatment?
AIV sodium bicarbonate
BOral sodium polystyrene sulfonate
CIV calcium gluconate
DIV amiodarone
EIV furosemide
Reveal answer & full explanation
Correct answer: C — IV calcium gluconate
AIV sodium bicarbonate
BOral sodium polystyrene sulfonate
CIV calcium gluconate✓
DIV amiodarone
EIV furosemide
Why IV calcium gluconate is correct
Severe hyperkalemia (potassium 7.8 mEq/L) with a sine-wave QRS and a widened complex represents peri-arrest cardiac membrane instability that demands immediate stabilization.
IV calcium gluconate antagonizes the membrane effects of hyperkalemia within minutes, restoring the resting membrane potential gradient and preventing degeneration into ventricular fibrillation or asystole.
It does not lower the serum potassium; it buys time while potassium-shifting and potassium-removing therapies are started.
In an end-stage renal disease patient, emergent hemodialysis is the definitive step once the membrane is stabilized.
Why the others are wrong
IV sodium bicarbonate — shifts potassium intracellularly but acts over 15-30 minutes and is unreliable in dialysis-dependent patients; choosing it first is right-problem-wrong-step, addressing the level before stabilizing the membrane.
Oral sodium polystyrene sulfonate — removes potassium through the gut over hours, far too slow for a peri-arrest rhythm; a buzzword-match to 'lower the potassium' that ignores the time course.
IV furosemide — promotes renal potassium excretion, but an anuric end-stage renal disease patient cannot respond, making it ineffective (premature closure on a reflexive diuretic).
IV amiodarone — the wide-complex sine-wave pattern can be mistaken for ventricular tachycardia, but it reflects hyperkalemic depolarization of the cardiac membrane; amiodarone does not reverse that effect, and its conduction-slowing and hypotensive effects are dangerous in a patient whose blood pressure is already 88/60 mm Hg (anchoring on the rhythm instead of the potassium).
Question 2RenalMedium
A 62-year-old man with chronic kidney disease (CKD) stage 3b (eGFR 32) has BP 156/96 and serum potassium 5.6 mEq/L on lisinopril and amlodipine. Repeat potassium in 2 weeks is 5.8 mEq/L and ECG shows peaked T waves. What is the most appropriate immediate management?
AOral sodium zirconium cyclosilicate
BEmergent intermittent hemodialysis
CIV calcium gluconate then insulin-dextrose
DDietary potassium restriction and furosemide
EIntravenous sodium bicarbonate infusion
Reveal answer & full explanation
Correct answer: C — IV calcium gluconate then insulin-dextrose
AOral sodium zirconium cyclosilicate
BEmergent intermittent hemodialysis
CIV calcium gluconate then insulin-dextrose✓
DDietary potassium restriction and furosemide
EIntravenous sodium bicarbonate infusion
Why IV calcium gluconate then insulin-dextrose is correct
Potassium 5.8 mEq/L with ECG changes (peaked T waves) is hyperkalemia that requires urgent treatment
Treatment sequence: (1) IV calcium gluconate for membrane stabilization, acting within minutes; (2) insulin plus dextrose, with or without nebulized albuterol, to shift K+ intracellularly; (3) sodium bicarbonate if metabolic acidosis is present; (4) a potassium binder for elimination, with patiromer or sodium zirconium cyclosilicate now preferred over sodium polystyrene sulfonate
Why the others are wrong
Emergent intermittent hemodialysis — dialysis is reserved for refractory hyperkalemia that does not respond to medical management
Oral sodium zirconium cyclosilicate — a potassium binder that removes K+ through the gut and belongs to the later elimination step; its onset is about an hour and it does not stabilize the cardiac membrane, so it cannot replace IV calcium when peaked T waves are present
Dietary potassium restriction and furosemide — dietary restriction alone is too slow when ECG changes are already present; this approach is appropriate for chronic management but not acute hyperkalemia with ECG changes
Intravenous sodium bicarbonate infusion — tempting because CKD often brings metabolic acidosis and bicarbonate can shift potassium into cells, but its effect is modest and unreliable unless acidosis is documented, and it does not stabilize the cardiac membrane; with peaked T waves the first step is IV calcium, and bicarbonate is only an adjunct when metabolic acidosis is present
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Medications: ACEi (lisinopril, ramipril), ARB (losartan, valsartan), MRA (spironolactone, eplerenone, finerenone), ENaC blockers (amiloride, triamterene, and trimethoprim or pentamidine, which act like amiloride), heparin (inhibits aldosterone synthesis), NSAIDs, beta-blockers, digoxin toxicity (inhibits Na/K-ATPase)
Type 4 RTA (hypoaldosteronism — diabetic nephropathy)
Adrenal insufficiency (Addison disease)
Massive cell breakdown: rhabdomyolysis, tumor lysis syndrome, hemolysis, severe burns
Acidosis (intracellular-extracellular shift)
Insulin deficiency / DKA
Excessive intake (salt substitutes, supplements, transfusion of old blood)
Pathophysiology
Potassium is the major intracellular cation; only 2% extracellular. Hyperkalemia results from impaired renal excretion (CKD, hypoaldosteronism), cellular shifts (acidosis, insulin deficiency, hyperosmolality, beta-blockade, succinylcholine, digoxin toxicity), increased intake/release (rhabdomyolysis, tumor lysis), or pseudohyperkalemia (hemolyzed sample, thrombocytosis, leukocytosis). Elevated extracellular K makes the resting membrane potential less negative (partial depolarization toward threshold). Higher K conductance speeds phase 3 repolarization (peaked T waves, short QT), while partial depolarization inactivates fast Na channels, slowing phase 0 and conduction (PR prolongation, QRS widening, sine wave) and ultimately causing ventricular fibrillation or asystole. IV calcium raises the threshold potential, restoring the gap between resting and threshold potential without lowering K.
Clinical presentation
Symptoms
Often asymptomatic until severe or rapidly developing
Muscle weakness, paralysis (severe; ascending similar to Guillain-Barré)
Paresthesias
Palpitations, lightheadedness
Cardiac arrest (life-threatening)
Signs / physical exam
Often unremarkable physical exam
Bradycardia, irregular rhythm
Hyporeflexia, flaccid paralysis in severe cases
Findings of underlying cause (volume status, signs of CKD, diabetic features)
Classic findings
ECG progression: peaked T waves → PR prolongation → loss of P waves → wide QRS → sine wave pattern → ventricular fibrillation/asystole.
Differential diagnosis
Pseudohyperkalemia — Hemolyzed sample, fist clenching with tourniquet, thrombocytosis, leukocytosis; repeat with non-hemolyzed sample or whole blood K
True hyperkalemia from CKD — Elevated creatinine, known CKD; cumulative effect with ACEi/ARB/MRA
Drug-induced — Recent ACEi/ARB/MRA/TMP-SMX initiation; review medication list
Rhabdomyolysis / tumor lysis — Elevated CK + hyperkalemia + hyperphosphatemia + hypocalcemia + AKI
Type 4 RTA — Hyperkalemia + non-gap metabolic acidosis in diabetic; mild hyperkalemia
DKA — Insulin deficiency shifts K out of cells; total body K is depleted despite hyperkalemia at presentation
Diagnostic workup
Diagnostic criteria
Confirmed serum K >5.0 mEq/L. ECG should be obtained urgently in any K >6.0 or any patient with cardiovascular symptoms or comorbidities.
Labs
BMP — confirm K elevation, assess creatinine and bicarbonate
Repeat sample if hemolysis suspected; whole blood K if pseudohyperkalemia suspected
CBC (high WBC or platelet count may cause pseudohyperkalemia)
ABG — assess for acidosis
CK if rhabdomyolysis suspected
Glucose before insulin-dextrose (low baseline glucose raises hypoglycemia risk)
Urine K and urine creatinine (TTKG historical, less used) to assess renal handling
Cortisol, aldosterone, renin if adrenal insufficiency or hypoaldosteronism suspected
Digoxin level if applicable
Imaging
Generally not indicated for hyperkalemia evaluation itself
Diagnostic algorithm
Treatment
Mechanism
Onset
Duration
Calcium gluconate 1-2 g IV
Stabilizes cardiac membrane (NOT lower K)
1-3 min
30-60 min
Insulin 10 U + D50 25 g IV
Shifts K intracellularly
15-30 min
2-6 h
Albuterol 10-20 mg neb
Beta-2 driven K shift
30 min
2-4 h
Sodium bicarbonate
Shifts K (less effective in CKD)
30-60 min
Hours
Furosemide IV
Renal K excretion
30 min-2 h
Hours
Patiromer / Na zirconium cyclosilicate
Binds K in GI tract
1-7 h
Sustained with daily dosing
Hemodialysis
Definitive K removal
Within minutes of initiation
Until next session
Stepwise treatment of acute hyperkalemia: stabilize → shift → remove.
Treatment
First-line
ECG immediately — guides urgency. ECG changes or K >6.5 → emergency treatment.
STABILIZE MEMBRANE (if ECG changes): IV calcium gluconate 1-2 g over 5-10 min (or calcium chloride 1 g via central line). Onset 1-3 min, duration 30-60 min. Repeat if no ECG improvement. CAUTION in digoxin toxicity — give slowly.
SHIFT K INTO CELLS:
Insulin 10 units IV + dextrose (D50 25 g) — onset 15-30 min, duration 2-6 h
Sodium bicarbonate (if acidotic; less effective in CKD) — 50-100 mEq IV
REMOVE K FROM BODY:
Loop diuretic — furosemide, bumetanide — if kidney function and volume permit
Potassium binder — patiromer (oral, slower onset hours), sodium zirconium cyclosilicate (oral, onset 1 h); in acute hyperkalemia these are adjuncts only, since US labels say not to use them as emergency treatment for life-threatening hyperkalemia because of delayed onset
Sodium polystyrene sulfonate (Kayexalate) — older agent; bowel necrosis risk especially with sorbitol; avoid in postoperative or ileus patients
Hemodialysis — definitive treatment for ESRD or severe refractory hyperkalemia
Long-term prevention in CKD/HF: dietary K restriction, optimize diuretic, chronic potassium binder (patiromer, sodium zirconium cyclosilicate) to enable continued RAAS therapy
Repeat K every 2-4 h until stable
Cardiology consultation if persistent ECG changes or arrhythmia
Recheck K and ECG after each intervention
Complications
Cardiac arrhythmia: bradyarrhythmias, AV block, ventricular fibrillation, asystole
Sudden cardiac death
Muscle weakness/paralysis
Bowel necrosis from Kayexalate (especially with sorbitol)
Hypoglycemia after insulin-dextrose (common, roughly 15-20% of treatments; higher risk with eGFR <30 or dialysis, no diabetes, or pre-treatment glucose <126 mg/dL): check glucose every 30 min for the first 2 h, then hourly until at least 6 h after the dose; consider D10 at 50 mL/h for 5 h if pre-treatment glucose is <126 mg/dL
Discontinuation of beneficial RAAS therapy in heart failure / CKD without binders
PANCE pearls
Order of treatment in severe hyperkalemia: STABILIZE (calcium) → SHIFT (insulin/dextrose, beta-agonist, bicarbonate) → REMOVE (diuretic, binder, dialysis). 'C-BIG-K-Drop' mnemonic.
Calcium gluconate STABILIZES the cardiac membrane but does NOT lower potassium. Calcium chloride has 3× the elemental calcium of gluconate but causes tissue necrosis if extravasated.
Insulin + dextrose temporarily shifts K into cells but does not eliminate it; total body K unchanged.
Kayexalate (SPS) has limited efficacy and notable risk of intestinal necrosis. Patiromer and sodium zirconium cyclosilicate are preferred modern alternatives.
Pseudohyperkalemia clues: hemolyzed sample (mention by lab), discrepancy between serum and plasma K, severe thrombocytosis or leukocytosis. Always confirm before invasive treatment.
In CKD or HF, chronic or recurrent hyperkalemia on ACEi/ARB (without ECG changes) can often be managed with dietary K moderation, diuretics, bicarbonate (if acidotic), or a chronic K binder so RAAS blockade can continue; KDIGO 2024 reduces or stops the ACEi/ARB only if these fail, whereas acute hyperkalemia with ECG changes warrants holding them. Binders enable continuation but have not been shown to improve outcomes.
Images
Hyperkalemia ECG progression — peaked T waves (early) → PR prolongation → QRS widening → sine wave (terminal)
References
KDIGO 2020 — KDIGO Controversies Conference on Potassium Management in Kidney Disease
AHA 2025 — Part 10: Adult and Pediatric Special Circumstances of Resuscitation, 2025 AHA Guidelines for CPR and ECC (Cao et al., Circulation 2025;152(16 Suppl 2):S578-S672)
Lindner et al. 2020 — Acute Hyperkalemia in the Emergency Department: A Summary from a Kidney Disease: Improving Global Outcomes Conference (Lindner et al., Eur J Emerg Med 2020;27(5):329-337)
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