Hyperkalemia

 

What is hyperkalemia, and why is it a concern?

• Definition: Hyperkalemia is a potentially life-threatening condition caused by the inability of the kidneys to excrete potassium or impaired cellular mechanisms to move potassium from the blood into cells.
• Triggers: Common triggers include medications affecting potassium balance, illnesses, dehydration, and specific syndromes such as hyporeninemic hypoaldosteronism in diabetic nephropathy.
• Risks: Rapid rises in potassium or characteristic EKG changes signal an urgent need for treatment due to the risk of severe arrhythmias.

What initial tests should be conducted for hyperkalemia?

• Tests: Obtain urine potassium, creatinine, and osmolarity to help determine the underlying cause, which guides long-term treatment.

How should patients with ECG changes or rapid potassium rise be managed acutely?

• Calcium Gluconate: Administer IV calcium gluconate to stabilize the myocardium, especially if ECG changes are present.
• Potassium Shifting Agents:
  • Insulin with Glucose: Administer IV insulin (10 units) with glucose to rapidly shift potassium into cells.
  • Beta2 Agonists: Nebulized albuterol can be used to enhance the intracellular shift of potassium, either alone or in combination with insulin.
• Potassium Elimination:
  • Use sodium polystyrene sulfonate (Kayexalate) to bind potassium in the colon, often with IV furosemide to promote renal excretion of potassium.

What causes hyperkalemia?

• Renal Excretion Issues: Chronic renal failure, renal hypoperfusion, or hypoaldosteronism can impair potassium excretion.
• Shift from Intracellular to Extracellular: Acidosis, tissue damage (e.g., rhabdomyolysis, trauma), insulin deficiency, and hyperosmolar states like uncontrolled diabetes contribute to potassium shifts.
• Medications: ACE inhibitors, ARBs, NSAIDs, and potassium-sparing diuretics are common medication-induced causes.

How is pseudohyperkalemia differentiated from true hyperkalemia?

• Diagnosis: Pseudohyperkalemia is caused by laboratory artifacts such as hemolysis during sample collection. Confirm by obtaining a plasma potassium level, which will be normal if pseudohyperkalemia is present.

How should hyperkalemia be acutely managed if it is severe (>6.0 mEq/L) or accompanied by ECG changes?

• First Steps: Administer calcium gluconate to protect against arrhythmias if ECG changes are noted.
• Next Steps: Lower serum potassium acutely with insulin and albuterol. If needed, consider sodium polystyrene sulfonate and loop diuretics to reduce total body potassium.

What long-term management strategies exist for hyperkalemia?

• Diet and Medication Adjustments: Limit dietary potassium and discontinue contributing medications if possible.
• Chronic Therapy for Hyporeninemic Hypoaldosteronism: Use fludrocortisone in patients with recurrent or chronic hyperkalemia due to hyporeninemic hypoaldosteronism.
• Special Populations: Monitor elderly patients closely, as they have an increased risk of hyperkalemia with certain medications, especially ACE inhibitors, ARBs, and NSAIDs.

What are the key medications for acute hyperkalemia management?

• Calcium Gluconate: 10-20 mL of a 10% solution IV over 2-3 minutes; stabilizes the myocardium but does not lower potassium.
• Insulin with Glucose: 10 units of regular insulin IV with 50 mL of 50% glucose; shifts potassium into cells.
• Albuterol: 10-20 mg by nebulizer; enhances cellular uptake of potassium.
• Sodium Polystyrene Sulfonate: 50 g orally or rectally; binds potassium in the gut for elimination.
• Furosemide: 20-40 mg IV to enhance renal excretion of potassium, often combined with saline if volume depleted.