Hyperkalemia

Definition: Serum potassium > 5.5 mEq/L. It is potentially the most rapidly lethal electrolyte disturbance, often clinically silent until life-threatening cardiac arrhythmias develop.

Normal Potassium Homeostasis

~98% of total body K+ is intracellular (primarily in muscle); normal serum K+ is 3.5-5.0 mEq/L.
The kidney is the primary route of excretion - aldosterone drives K+ secretion in the cortical collecting tubule (CCT) via ENaC and ROMK channels.
Transcellular shifts are governed by insulin, catecholamines (beta-2), aldosterone, and acid-base status.

Causes

1. Pseudohyperkalemia (False Elevation)

Traumatic hemolysis during blood draw (most common cause of a "high" lab value)
Myeloproliferative disorders: thrombocytosis or extreme leukocytosis releasing K+ during clot formation in the sample tube

2. Increased K+ Load

Exogenous: IV potassium infusion, inappropriate IV fluids, salt substitutes (KCl), transfusion of stored blood
Endogenous cell breakdown: rhabdomyolysis, crush injuries, burns, hemolysis (mismatched transfusion), tumor lysis syndrome, GI bleeding with intestinal absorption

3. Transcellular Shift (K+ out of cells)

Mechanism	Examples
Metabolic acidosis	H+/K+ exchange - H+ enters cells, K+ exits
Insulin deficiency	Loss of Na-K-ATPase stimulation
Beta-adrenergic blockade	Blocks beta-2 mediated cellular K+ uptake
Digitalis toxicity	Inhibits Na-K-ATPase directly
Hypertonicity/hyperosmolality	Solvent drag, cell shrinkage
Succinylcholine	Membrane depolarization, especially risky in CKD

4. Decreased Renal Excretion (most common cause of sustained hyperkalemia)

Advanced renal failure (CKD/AKI) - any etiology
Hypoaldosteronism:
- Primary adrenal insufficiency (Addison's disease, adrenal hemorrhage)
- Type IV RTA (hyporeninemic hypoaldosteronism) - common in diabetic nephropathy
Drugs impairing renal K+ excretion:
- ACE inhibitors / ARBs (suppress aldosterone)
- Potassium-sparing diuretics (spironolactone, eplerenone, amiloride, triamterene)
- NSAIDs - suppress renin release and reduce GFR
- Trimethoprim, heparin, calcineurin inhibitors
- Finerenone and other MRA class agents

Clinical Manifestations

Most patients are asymptomatic until K+ is significantly elevated.

Cardiac (most dangerous - present when K+ > 7 mEq/L)

Cardiac conduction delay is the most common and most dangerous manifestation. ECG changes progress in this sequence:

ECG progression of hyperkalemia - peaked T waves, QRS widening, sine wave pattern

ECG progression: (Left) Normal. (Center) Peaked T waves and QRS widening. (Right) Sine wave pattern preceding arrest.

Sequential ECG changes:

Symmetrically peaked (tall, narrow, "tented") T waves - first sign, often with shortened QT
Prolonged PR interval
Widening of the QRS complex - ominous
Loss of P wave
Loss of R-wave amplitude / ST depression
Sine wave pattern - QRS merges with T wave
Ventricular fibrillation / Asystole

Key point: A normal ECG does NOT exclude dangerous hyperkalemia. Hypocalcemia, hyponatremia, and acidosis worsen the cardiac effects.

Neuromuscular

Skeletal muscle weakness (generally not seen until K+ > 8 mEq/L)
Ascending paralysis (rare)
Paresthesias

Treatment

Treatment Flowchart

NKF Primer on Kidney Diseases, 8e - emergent vs. non-emergent management

Treatment uses three physiologic strategies in order:

Step 1 - Membrane Stabilization (Immediate, minutes)

Indication: ECG changes present, OR K+ > 6-6.5 mEq/L with symptoms

Agent	Dose	Mechanism	Onset
Calcium gluconate 10%	10 mL IV over 1-2 min; repeat in 3-5 min if no ECG improvement	Raises action potential threshold, stabilizes membrane. Does NOT lower K+	Immediate (~1-2 min)
Calcium chloride 10%	3-5 mL IV via central line	Same; more elemental Ca2+ per ampule; avoid peripherally (causes tissue necrosis)	Immediate

Caution in digoxin toxicity: Calcium potentiates digoxin toxicity - administer slowly over 20-30 min as "calcium sandwich" with sodium bicarbonate.

Step 2 - Transcellular Shift (Temporizing, 15-60 min)

Agent	Dose	Mechanism	Onset
Regular insulin + Dextrose	10 units IV regular insulin + 50 mL D50W (1 amp) bolus, then D5W at 100 mL/h	Activates Na-K-ATPase, drives K+ into cells	15-30 min; peak ~60 min
Nebulized albuterol	20 mg (use concentrated 5 mg/mL form) nebulized over 10 min	Beta-2 stimulation activates Na-K-ATPase	30 min; additive to insulin
Sodium bicarbonate	50-100 mEq IV (if pH < 7.3)	Alkalosis drives K+ into cells; also enhances renal excretion	15-30 min

Note: 20-40% of patients are resistant to albuterol. Never give dextrose without insulin in patients with poor endogenous insulin production - the resulting hyperglycemia can paradoxically worsen hyperkalemia. Monitor glucose closely.

Step 3 - Remove K+ from the Body (Definitive)

Modality	When	Notes
Furosemide (loop diuretic)	Adequate renal function, not hypovolemic	Enhances renal K+ excretion; give by slow infusion (not bolus) due to ototoxicity risk
Sodium polystyrene sulfonate (Kayexalate)	Can wait hours	Na-K exchange resin in colon; onset 1-2 h PO or <30 min rectally; risk of colonic necrosis (especially with sorbitol)
Patiromer	Non-emergent, chronic	Ca2+/K+ exchange in colon; onset ~7 h; constipation, hypomagnesemia; separate from other drugs by 3 h
Sodium zirconium cyclosilicate (ZS-9)	Non-emergent to semi-urgent	Binds K+ in exchange for H+ and Na+; onset ~1 h; entire GI tract
Hemodialysis	Oliguric/anuric or ESKD, life-threatening	Fastest and most reliable K+ removal; definitive treatment in renal failure

Emergent vs. Non-Emergent Algorithm

Emergent (ECG changes, rapid rise, K+ >6.5): Calcium gluconate → Insulin + dextrose + albuterol → Remove (dialysis, diuretics, or bicarb based on context)

Non-Emergent (mild, asymptomatic, no ECG changes):

Exclude pseudohyperkalemia
Dietary K+ restriction, avoid salt substitutes
Discontinue offending drugs (NSAIDs, ACE-I, K+-sparing diuretics)
Loop diuretics if renal function allows
Oral NaHCO3 if metabolic acidosis present
K+-binding agents (patiromer or ZS-9 preferred over SPS for chronic management, especially to allow continued RAAS inhibitor use)

Special Situations

CKD patients: Chronically tolerate K+ slightly above 6 mEq/L but are at high risk with any additional load. Succinylcholine use should be cautious. Furosemide requires higher doses.
Cardiac arrest with unknown cause: Assume hyperkalemia and treat empirically with calcium gluconate while resuscitating.
Digoxin toxicity: Use calcium cautiously (slow infusion); hypomagnesemia co-treatment required.
Post-RAAS inhibitor therapy: Patiromer and ZS-9 allow patients to remain on ACE inhibitors/ARBs/MRAs despite hyperkalemia - important for CKD and heart failure outcomes.

Recent Evidence (PubMed, 2024-2026)

A 2025 network meta-analysis (PMID 40542996) confirmed that novel K+-binding agents (patiromer, ZS-9) reduce hyperkalemia and enable optimization of RAAS inhibitor therapy in CKD and heart failure patients - supporting their use as adjuncts to maintain cardiorenal-protective medications.

Sources: NKF Primer on Kidney Diseases 8e, Morgan & Mikhail's Clinical Anesthesiology 7e, Tintinalli's Emergency Medicine, Rosen's Emergency Medicine, Medical Physiology (Boron & Boulpaep), Brenner & Rector's The Kidney

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