Hyperkalemia Quiz

Understanding Hyperkalemia

Hyperkalemia, an electrolyte imbalance characterized by elevated potassium levels in the blood, is a potentially life-threatening condition. Normal serum potassium levels range from 3.5 to 5.0 mEq/L. Levels above this range can lead to significant cardiac and neuromuscular complications. This guide provides an overview for healthcare students and professionals preparing for exams.

Causes of Hyperkalemia

Hyperkalemia can result from increased potassium intake, decreased potassium excretion, or a shift of potassium from the intracellular to the extracellular space.

• Decreased Excretion: This is the most common cause. Conditions like acute or chronic kidney disease, adrenal insufficiency (Addison’s disease), and the use of certain medications impair the kidneys’ ability to excrete potassium.
• Medications: Several drugs can elevate potassium levels, including ACE inhibitors, angiotensin II receptor blockers (ARBs), potassium-sparing diuretics (e.g., spironolactone), and NSAIDs.
• Cellular Shift: Conditions like metabolic acidosis, insulin deficiency (as in DKA), and tissue breakdown (rhabdomyolysis, tumor lysis syndrome) can cause potassium to move out of cells and into the bloodstream.
• Excessive Intake: While rare in individuals with normal kidney function, excessive intake of potassium supplements or salt substitutes can contribute to hyperkalemia.

Clinical Manifestations and Diagnosis

Symptoms are often nonspecific and may be absent in mild cases. When present, they primarily affect the neuromuscular and cardiovascular systems.

• Neuromuscular: Muscle weakness, fatigue, paresthesias, and in severe cases, ascending paralysis and respiratory failure.
• Cardiovascular: Palpitations, and classic ECG changes. The diagnosis is confirmed by a serum potassium level >5.0 mEq/L.

ECG Changes in Hyperkalemia

The electrocardiogram (ECG) is a crucial diagnostic tool. The progression of ECG changes typically correlates with the severity of hyperkalemia:

1. Mild (5.5-6.5 mEq/L): Peaked T waves (tall and narrow-based).
2. Moderate (6.5-7.5 mEq/L): Prolonged PR interval, loss of P waves.
3. Severe (>7.5 mEq/L): Widening of the QRS complex, which can merge with the T wave to form a sine wave pattern, leading to ventricular fibrillation or asystole.

Emergency Management Strategies

The management approach depends on the severity of hyperkalemia and the presence of ECG changes.

1. Stabilize the Myocardium: If ECG changes are present, intravenous calcium (calcium gluconate or calcium chloride) is administered immediately to antagonize the cardiac membrane effects of potassium. This does not lower serum potassium.
2. Shift Potassium Intracellularly: Insulin (with glucose to prevent hypoglycemia) and beta-2 agonists (like albuterol) are used to drive potassium from the blood into the cells.
3. Remove Potassium from the Body: This is achieved through diuretics (if kidney function is adequate), cation-exchange resins (e.g., sodium polystyrene sulfonate), or, most definitively, hemodialysis.

Distinguishing True Hyperkalemia from Pseudohyperkalemia

Pseudohyperkalemia is a laboratory artifact where the measured serum potassium is falsely elevated. This can occur due to hemolysis during a difficult blood draw, excessive tourniquet time, or conditions like thrombocytosis or leukocytosis. A repeat, carefully drawn sample, often a plasma sample from a heparinized tube, can help clarify the diagnosis.

Long-Term Management

Once the acute episode is resolved, long-term management focuses on addressing the underlying cause. This may involve dietary potassium restriction, adjusting or discontinuing offending medications, and managing chronic conditions like kidney disease or adrenal insufficiency.

This information is intended for exam preparation and educational review. Always consult official clinical guidelines and institutional protocols for patient care.