Hyperkalemia Lecture Notes

Introduction

• Definition: Elevated potassium level within the blood.

Causes of Hyperkalemia

1. Reduced Excretion of Potassium

• Kidney-related causes:

  • Acute Kidney Injury (AKI)
  • Chronic Kidney Disease (CKD)
  • Acute on Chronic Kidney Disease
  • Severe oliguria or anuria:
    • Oliguria: < 0.5 cc/kg for ≥6 hours
    • Anuria: No urine output
  • Decreased Glomerular Filtration Rate (GFR)

• Hormone-related causes:

  • Low aldosterone levels:
    • Adrenal gland pathology (zona glomerulosa issue)
    • Conditions causing hypoaldosteronism
  • Drug interactions affecting aldosterone production:
    • NSAIDs: Decrease renin production
    • ACE Inhibitors: Inhibit ACE
    • ARBs: Block angiotensin II receptors
    • Potassium-sparing diuretics (e.g., spironolactone, eplerenone): Block aldosterone receptors

2. Transcellular Shift of Potassium

• Decreased insulin:

  • Diabetes Mellitus (Type 1 and 2)

• Drug interactions:

  • Beta-blockers (especially non-selective)
  • Digoxin: Directly inhibits sodium-potassium ATPase

• Acidosis:

  • Respiratory acidosis: High CO2
  • Metabolic acidosis: Organic acids (lactic, keto acids, etc.)
  • Mechanism: Increased H+ ions push K+ out of cells

• Hyperosmolar states:

  • Hyperglycemic hyperosmolar state
  • Severe dehydration
  • Mechanism: High solute concentration pulls water out of cells, increasing intracellular K+ concentration, causing K+ efflux

• Cell damage and lysis:

  • Severe muscle activity (seizures, crush injuries, extreme exertion)
  • Rhabdomyolysis
  • Tumor Lysis Syndrome
  • Hemolysis: Lysis of red blood cells (e.g., hemolytic anemias)

3. Increased Potassium Intake

• Excess dietary intake
• Potassium supplements
• High potassium IV therapy

4. Pseudo-Hyperkalemia

• Hemolyzed blood sample during venipuncture
• Thrombocytosis: High platelet count

Clinical Manifestations

• General Features:

  • Muscle weakness
  • Decreased urine output (oliguria or anuria)
  • Respiratory distress due to muscle weakness
  • Decreased cardiac contractility
  • Decreased deep tendon reflexes
  • Gastrointestinal: Constipation, vomiting

• Cardiac Symptoms:

  • EKG changes due to decreased cardiac excitability:
    • Peaked T waves
    • Wide QRS complex
    • Prolonged PR interval
    • Flattened or absent P waves
    • Sine wave pattern leading to arrhythmias (e.g., V-fib, asystole)

Diagnosis

• Potassium levels:

  • Diagnosis if K+ > 5 mEq/L

• Rule out Pseudo-Hyperkalemia:

  • Hemolyzed samples: Repeat test, use arterial line
  • Thrombocytosis: Check CBC

• Determine underlying cause:

  • Kidney function tests: GFR, BUN, creatinine, urine output
  • Aldosterone levels: Check if suspected hypoaldosteronism
  • Medication review: Look for use of NSAIDs, ACE inhibitors, ARBs, potassium-sparing diuretics
  • Glucose levels: Check for hyperosmolar states
  • Acidosis: ABG for respiratory/metabolic acidosis
  • Drug levels: Beta-blockers, digoxin
  • Muscle damage: CK, myoglobinuria
  • Tumor Lysis Syndrome: Phosphate, uric acid levels
  • Hemolysis indicators: CBC, LDH, haptoglobin, bilirubin (unconjugated)

Treatment

• Stabilize Cardiac Membranes:

  • Calcium gluconate or calcium chloride

• Shift Potassium into Cells:

  • Insulin + Dextrose (D50)
  • Beta2 agonists (e.g., albuterol)
  • Bicarbonate for acidosis

• Eliminate Potassium:

  • Diuretics (Furosemide, possibly thiazides)
  • Cation-exchange resins (e.g., Kayexalate)

• Dialysis:

  • Consider in refractory cases or in patients with severe kidney impairment

Conclusion

• Treat the underlying cause of hyperkalemia
• If kidney injury, dialysis may be necessary

Mnemonic for Clinical Features

• MURDER:
  • M: Muscle weakness
  • U: Urine output decrease
  • R: Respiratory distress
  • D: Decreased cardiac contractility
  • E: EKG changes
  • R: Reflexes decreased