Hyperkalemia

 

Hyperkalemia

Definition:

• Serum potassium > 5 mEq/L

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Etiology

1. Reduced Renal Excretion

• Acute or chronic kidney disease

• Hypoaldosteronism / hypocortisolism

• Type IV renal tubular acidosis

• Drugs: potassium-sparing diuretics, ACE inhibitors, ARBs, NSAIDs, trimethoprim-sulfamethoxazole

2. Increased Intake

• High-potassium diet

• Potassium-containing IV fluids

3. Extracellular Shift (K+ moves out of cells)

• Acidosis: ↑ extracellular H+ inhibits Na+/H+ antiporter → ↓ Na+ gradient → ↓ Na+/K+-ATPase → ↑ K+

• Insulin deficiency / Hyperglycemia → ↓ intracellular K+

• Drugs: Beta blockers, digoxin, succinylcholine (esp. with burns or muscle trauma)

• Hyperosmolality → water moves out of cells, K+ follows

Mnemonic for causes of K+ shift out of cells:

BAD LOSS – Beta blockers, Acidosis, Digoxin, Lysis (cellular), hyperOsmolality, high Sugar, Succinylcholine

4. Extracellular Release from Cell Lysis

• Rhabdomyolysis

• Tumor lysis syndrome

• Hemolysis

5. Pseudohyperkalemia

• Hemolysis during blood draw (fist clenching, delayed analysis, improper technique)

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Pathophysiology

• ↑ Extracellular K+ → resting membrane potential becomes less negative → ↑ excitability

• Acute changes → prominent clinical effects

• Chronic changes → intracellular compensation occurs

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Clinical Features

 Cardiac: arrhythmias (risk of ventricular fibrillation)

Tall, peaked T waves+– Widened QRS complexes (∼ 140 ms)

• Muscle: weakness, paralysis, paresthesia, ↓ deep tendon reflexes

• GI: nausea, vomiting, diarrhea

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Diagnosis

Laboratory:

• Serum K+ measurement (beware of pseudohyperkalemia)

ECG Changes:

Severity	K+ Level	ECG Findings
Mild	5.5–6.4 mEq/L	Tall, peaked T waves
Moderate	6.5–8.0 mEq/L	QRS widening, flattened P waves, peaked T waves
Severe	>8.0 mEq/L	Severe conduction defects, risk of ventricular fibrillation

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Treatment

1. Hyperkalemic Emergency (with ECG changes)

• Stabilize cardiac membrane: IV calcium gluconate

2. Shift K+ into Cells

• Short-acting insulin + glucose

• Inhaled β2-agonists (SABA)

• Sodium bicarbonate IV (especially in acidosis)

3. Remove K+ from Body

• Cation-exchange resins:

  • Sodium polystyrene sulfonate, sodium zirconium cyclosilicate, patiromer

  • Mechanism: exchange Na+ or Ca2+ for K+ in gut → enhanced excretion

  • Adverse: GI upset, hypokalemia

• Hemodialysis: for end-stage renal failure or oliguria

4. Stop offending drugs

• Discontinue K+-sparing diuretics, ACE inhibitors, ARBs, etc.

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