Approach to hyperkalemia
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Approach to Hyperkalemia
Definition and Severity
Hyperkalemia is defined as serum K⁺ ≥5.5 mmol/L, with significant (severe) hyperkalemia at ≥6.0-6.5 mmol/L. It is found in 1.1-10% of hospitalized patients and carries a mortality of 14-41% in severe cases - Brenner and Rector's The Kidney.
Severity classification:
- Mild: 5.5-6.0 mEq/L
- Moderate: 6.0-6.5 mEq/L
- Severe: >6.5 mEq/L (or any level with ECG changes)
Step 1 - Rule Out Pseudohyperkalemia
Before any workup, confirm the result is real. Pseudohyperkalemia occurs with:
- Prolonged tourniquet time or fist clenching during venipuncture
- Thrombocytosis, leukocytosis, or erythrocytosis (in vitro K⁺ release)
- Cooling of blood sample post-venipuncture
- Hereditary pseudohyperkalemia (SLC4A1 mutations causing red cell K⁺ leak)
- Acute anxiety causing respiratory alkalosis with redistribution
If suspected, repeat the sample as a plasma (heparinized) specimen rather than serum. - Harrison's Principles of Internal Medicine 22E
Step 2 - Identify the Cause
Mechanism-Based Classification
A. Increased K⁺ intake (rarely the sole cause unless excretion is impaired)
- Dietary excess, IV potassium supplementation, blood transfusions
B. Transcellular shift (K⁺ out of cells)
| Cause | Mechanism |
|---|---|
| Acidemia (non-anion gap metabolic, respiratory) | H⁺ enters cells, K⁺ exits |
| Insulin deficiency / DKA | Reduced Na⁺/K⁺-ATPase activity |
| Beta-blocker toxicity | Impaired Na⁺/K⁺-ATPase stimulation |
| Succinylcholine | Depolarizes muscle, K⁺ exits via ACh receptors |
| Digoxin overdose | Inhibits Na⁺/K⁺-ATPase in skeletal muscle |
| Hypertonic states (mannitol, hypertonic saline, hypertonic glucose) | Solvent drag effect |
| Fluoride poisoning | Inhibits Na⁺/K⁺-ATPase |
| Cationic amino acids (lysine, arginine, epsilon-aminocaproic acid) | Cation-K⁺ exchange |
| Tissue destruction (rhabdomyolysis, tumor lysis, hemolysis, burns) | Cell lysis releases K⁺ |
Note: Anion-gap acidoses (lactic acidosis, ketoacidosis) do NOT cause hyperkalemia via this mechanism - Harrison's 22E
C. Decreased renal excretion (most common mechanism)
- Acute kidney injury (AKI) or chronic kidney disease (CKD)
- Hypoaldosteronism:
- Primary: Addison disease, bilateral adrenalectomy, adrenal hemorrhage, heparin/LMWH-induced
- Hyporeninemic hypoaldosteronism (Type 4 RTA): diabetic nephropathy, NSAIDs, calcineurin inhibitors
- Drug-induced RAAS blockade: ACEi, ARBs, direct renin inhibitors, aliskiren
- Potassium-sparing diuretics: spironolactone, amiloride, triamterene
- Voltage-dependent defects in K⁺ secretion: obstructive uropathy, sickle cell disease
- Gordon syndrome (pseudohypoaldosteronism type II)
Step 3 - Clinical Features
Symptoms are often absent until hyperkalemia is severe. When present:
- Neuromuscular: weakness, fatigue, ascending paralysis, paresthesias
- Cardiac: palpitations, syncope, cardiac arrest (most dangerous manifestation)
- GI: nausea, vomiting (less specific)
Step 4 - ECG Changes (Sequential with Rising K⁺)
ECG changes may be absent even in severe hyperkalemia - a normal ECG does not exclude dangerous hyperkalemia. However, when present, they follow a rough sequence:
| Serum K⁺ | ECG Change |
|---|---|
| 5.5-6.5 mEq/L | Peaked (tall, narrow, symmetric) T waves - earliest sign |
| 6.5-7.5 mEq/L | PR prolongation, P wave flattening/disappearance |
| 7.0-8.0 mEq/L | QRS widening |
| >8.0 mEq/L | Sine wave pattern, VF, asystole |
- Rosen's Emergency Medicine
ECG: Severe hyperkalemia - QRS widening merging into T wave, absent P waves (pre-treatment):
ECG: Same patient after initial treatment - tall peaked T waves, decreased P wave amplitude:
Hyperkalemia can also present as atropine-resistant bradycardia with or without apparent heart block - Rosen's Emergency Medicine
Step 5 - Diagnostic Workup
- Serum electrolytes, BUN/creatinine - assess renal function
- Glucose, insulin levels - diabetic causes
- Arterial/venous blood gas - acidemia
- Urine K⁺, urine creatinine, urine/serum osmolality
- Transtubular K⁺ gradient (TTKG):
TTKG = (U_K × Serum Osm) / (Serum K⁺ × Urine Osm)
- Normal response to hyperkalemia: TTKG >7-8 (appropriate renal excretion)
- TTKG <3-5 in hyperkalemia = impaired K⁺ secretion (aldosterone deficiency or resistance)
- Plasma aldosterone and renin - to distinguish primary from secondary hypoaldosteronism
- ECG - obtain immediately in any suspected hyperkalemia
Step 6 - Treatment
Treatment is organized into 3 simultaneous stages: - Harrison's 22E, Rosen's Emergency Medicine
Stage 1 - Stabilize the Cardiac Membrane (Immediate)
Indication: ECG changes (especially wide QRS), or K⁺ ≥6.5 mEq/L even without ECG changes
| Agent | Dose | Onset | Duration | Notes |
|---|---|---|---|---|
| Calcium gluconate 10% | 10 mL IV over 2-3 min | 1-3 min | 30-60 min | Preferred for peripheral IV access |
| Calcium chloride 10% | 3-4 mL (or 1g) IV | 1-3 min | 30-60 min | Preferred via central line (tissue necrosis if extravasates); 3x more calcium than gluconate |
- Calcium raises the action potential threshold, restoring the difference between resting and threshold potentials - does NOT lower K⁺
- Repeat dose if no ECG improvement or if improvement recurs
- Caution in digoxin toxicity: hypercalcemia potentiates digoxin cardiotoxicity; if necessary, dilute in 100 mL D5W and infuse over 20-30 min
Stage 2 - Shift K⁺ Into Cells (Rapid, Bridges to Removal)
| Agent | Dose | Onset | Effect | Notes |
|---|---|---|---|---|
| Regular insulin + glucose | 10 units IV + 50 mL D50W (25g glucose) | 10-20 min | Peak 30-60 min, lasts 4-6h; ↓K⁺ ~0.6 mEq/L | Follow with D10W infusion at 50-75 mL/h; monitor glucose closely. Reduce to 5 units if renal dysfunction. Omit glucose if blood glucose ≥200-250 mg/dL |
| Nebulized albuterol | 10-20 mg in 4 mL NS over 10 min (4x bronchodilator dose) | ~30 min | Peak ~90 min; ↓K⁺ 0.5-1 mEq/L | ~20% of ESRD patients are resistant; do NOT use alone without insulin |
| Insulin + albuterol combined | As above | -- | ↓K⁺ ~1.2 mEq/L (additive) | Preferred combination for maximum shift |
| Sodium bicarbonate | 150 mEq in 1L D5W IV infusion | 4-6 h | Modest, delayed | Only useful in metabolic acidosis; do NOT give as undiluted IV bolus (risk of hypernatremia/hypertonicity). No role in acute treatment |
| Normal saline | 100-250 mL IV | -- | Minor | Stimulates Na⁺/K⁺-ATPase; useful in hypovolemic patients; use cautiously in anuric patients |
Stage 3 - Remove K⁺ From the Body (Definitive)
| Method | Agent/Dose | Onset | Notes |
|---|---|---|---|
| Hemodialysis | -- | Rapid | Most effective and reliable; mandatory in cardiac arrest or refractory hyperkalemia; peritoneal dialysis considerably less effective |
| Loop diuretics | Furosemide IV | 30-60 min | Only with intact renal function; combine with saline or isotonic bicarbonate to maintain euvolemia |
| Sodium polystyrene sulfonate (SPS/Kayexalate) | 15-30 g in 33% sorbitol suspension PO/PR | Hours (full effect up to 24h) | Risk of intestinal necrosis (especially post-op, opioid use, reduced motility); avoid when possible |
| Patiromer | 8.4 g PO daily | Hours | Nonabsorbed polymer; exchanges K⁺ for Ca²⁺; side effect: hypomagnesemia; preferred over SPS |
| Sodium zirconium cyclosilicate (SZC) | 10 g PO TID x 48h (acute) | 1-2 h (faster onset than patiromer) | Exchanges Na⁺/H⁺ for K⁺ and NH₄⁺; preferred over SPS |
Patiromer and SZC have replaced SPS as preferred binders in most settings due to their lack of intestinal toxicity - Harrison's 22E. A 2025 systematic review (PMID 40542996) confirms novel potassium binders also allow optimization of RAAS inhibitor therapy in CKD and heart failure.
Summary Algorithm
Suspected Hyperkalemia
↓
1. Obtain ECG + serum K⁺ immediately
↓
ECG changes or K⁺ ≥6.5?
YES → IV Calcium IMMEDIATELY (membrane stabilization)
NO → Proceed to workup + shifts
↓
2. Shift K⁺ into cells:
Insulin 10U IV + D50W 50mL
+ Nebulized albuterol 10-20mg
↓
3. Remove K⁺ from body:
- Adequate urine output? → Furosemide ± saline
- Oral/enteral route available? → Patiromer or SZC
- AKI/ESRD or refractory? → Hemodialysis
↓
4. Find and treat the underlying cause
- Review medications (ACEi/ARB, NSAIDs, K-sparing diuretics)
- Check renal function, aldosterone/renin
- Dietary counseling
Special Considerations
- Succinylcholine is relatively contraindicated in pre-existing hyperkalemia, and absolutely contraindicated in patients with burns, neuromuscular disease, prolonged immobilization, or spinal cord injury (marked upregulation of ACh receptors causes massive K⁺ efflux)
- Digoxin toxicity co-existing with hyperkalemia: use calcium with extreme caution; diluted slow infusion preferred
- ACEi/ARBs causing hyperkalemia: with the availability of patiromer/SZC, these drugs can often be continued at reduced dose rather than discontinued - this is a shift in modern management
- ESRD patients: even modest potassium loads or common medications (beta-blockers, ACEi) can precipitate severe hyperkalemia; maintain low threshold for monitoring and treatment - Rosen's Emergency Medicine
Sources: Harrison's Principles of Internal Medicine 22E (2025); Rosen's Emergency Medicine; Brenner and Rector's The Kidney
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