What is hyperkalemia?

Hyperkalemia: Elevated Serum Potassium

Too much potassium is called hyperkalemia, defined as a serum potassium concentration exceeding 5.0 mEq/L (or 5.0 mmol/L). 1, 2

Definition and Severity Classification

Hyperkalemia is classified by severity based on potassium levels 2, 3:

• Mild hyperkalemia: >5.0 to <5.5 mEq/L 2, 3
• Moderate hyperkalemia: 5.5 to 6.0 mEq/L 2, 3
• Severe hyperkalemia: >6.0 mEq/L 2, 3

The condition can be further categorized as acute, chronic, or recurrent based on onset and frequency of episodes. 1 Chronic or recurrent hyperkalemia specifically refers to potassium levels >5 mEq/L measured repeatedly over a 1-year period. 1

Important Diagnostic Consideration: Pseudohyperkalemia

Pseudohyperkalemia refers to falsely elevated potassium levels in the test tube without actual hyperkalemia in the body. 1 This occurs due to potassium release from blood cells or tissue during sampling and can result from 2, 4:

• Excessive fist clenching during blood collection 4
• Hemolysis during sample collection or processing 1, 4
• Delayed specimen processing 4
• Prolonged tourniquet time 4

If pseudohyperkalemia is suspected, measurement should be repeated with blood sampled appropriately or taken as an arterial sample. 1 The European Society of Cardiology warns against failing to rule out pseudohyperkalemia before initiating treatment. 2, 4

Clinical Significance and Prevalence

Hyperkalemia prevalence varies significantly by population 1, 2:

• 2-4% in the general population 1, 2
• 10-55% in hospitalized patients (depending on the potassium threshold used) 1, 2
• Up to 73% in patients with advanced chronic kidney disease 1, 2
• Up to 40% in patients with chronic heart failure 1

Hyperkalemia is potentially life-threatening because it can cause cardiac arrhythmias leading to cardiac arrest and death. 1, 5 The condition leads to more frequent hospitalizations and increased mortality, especially when stringent monitoring is not performed. 1

Common Causes

Drug-induced hyperkalemia is the most important cause of elevated potassium levels in everyday clinical practice. 6 The most common causative medications include 1, 2:

Medications that decrease potassium excretion:

• Renin-angiotensin-aldosterone system inhibitors (ACE inhibitors, ARBs, mineralocorticoid receptor antagonists) 1, 2
• Potassium-sparing diuretics (spironolactone, triamterene, amiloride) 1, 2
• Beta-blockers 1, 2
• NSAIDs 1, 2
• Calcineurin inhibitors (cyclosporine, tacrolimus) 1, 2
• Trimethoprim-sulfamethoxazole 1, 2
• Heparin 1, 2

Medications that increase potassium intake:

• Potassium supplements 1
• Salt substitutes 1, 2
• Stored blood products 1, 2

High-Risk Populations

Hyperkalemia frequently occurs in patients with cardiovascular diseases (heart failure, arterial hypertension, coronary artery disease), particularly when combined with 1, 2:

• Renal function impairment 1, 2
• Diabetes mellitus 1, 2
• Advanced age 1, 2

The incidence increases with severity of renal impairment and is often iatrogenic, caused by concurrent medications and nutritional/herbal supplements. 1

Clinical Presentation

Hyperkalemia is often asymptomatic and incidentally discovered during routine blood tests, especially in chronic cases. 1, 2 When symptomatic, patients may present with 2, 5:

• Muscle weakness 2
• Paresthesias 2
• Cardiac arrhythmias 2

ECG changes include peaked T waves, flattened P waves, prolonged PR interval, and widened QRS complex. 2, 3, 5 The presence of typical electrocardiographic changes or rapid rise in serum potassium indicates that hyperkalemia is potentially life-threatening. 7