Lecture: Hyperkalemia

Introduction

• Hyperkalemia: High potassium (K) levels in the blood.
• Normal Range: 3.5 to 5.0 mEq/L.
• Concern: Above 5.0 mEq/L can be dangerous.
• Importance: Potassium is critical for heart and muscle function.

Potassium Regulation

• Conductivity to potassium is crucial for heart function.
• Changes in potassium levels can cause arrhythmias.

Causes of Hyperkalemia

1. Excessive Tissue Release or Transcellular Shifts:
   • Diabetes:
     • High glucose levels cause water to leave cells.
     • Potassium leaks out of cells.
     • Low insulin fails to put potassium back into cells.
   • Hyporeninemic Hypoaldosteronism:
     • Low renin levels reduce aldosterone.
     • Less aldosterone means less potassium excretion.
     • Common in diabetes.
2. Increased Potassium Intake:
   • Salt Substitutes: Contain potassium instead of sodium.
   • Renal Failure: Reduced ability to clear potassium.
3. Adrenal Failure:
   • Addison's Disease: Direct attack on the adrenal cortex.
   • Low aldosterone levels cause potassium accumulation.
   • Symptoms include hypoglycemia, hyponatremia, metabolic acidosis.
4. Potassium-Sparing Diuretics:
   • Examples: Spironolactone, amiloride.
5. Medications:
   • ACE Inhibitors: Affect aldosterone production.
   • Beta Blockers: Affect potassium shifting.
6. Pseudo-Hyperkalemia:
   • High cell counts (e.g., leukocytosis) in a blood sample can lyse and release potassium.
   • Lab tests may show falsely elevated levels.

Manifestations of Hyperkalemia

• Heart Function: Potassium conductance affects depolarization.
• Mechanism:
  • Potassium leaving the cell maintains negative charge inside cells.
  • High serum potassium reduces potassium leaving cells.
  • Leading to depolarization and excitability of cardiac cells.
• ECG Changes:
  • Peaked T-Waves: Initial sign of hyperkalemia.
  • Sinusoidal Waves: Severe hyperkalemia that can lead to cardiac arrest.

Key Points on ECG Changes

1. Peaked T-Waves: First sign of hyperkalemia.
2. Sinusoidal Wave: Severe and emergency state.
3. Progression:
   • Reduced membrane excitability.
   • Increased potassium conductance and accelerated repolarization.
4. Emergency: Hyperkalemia primarily affects cardiac function.

Conclusion

• Hyperkalemia: Serious medical condition affecting potassium levels.
• Next Steps: Treatment and management of hyperkalemia.
• Importance: Quick identification and treatment to prevent severe cardiac events.