What causes hyponatremia and hyperkalemia?

Causes of Hyponatremia and Hyperkalemia

The most common causes of concurrent hyponatremia and hyperkalemia are chronic kidney disease, adrenal insufficiency, and medication effects, particularly from renin-angiotensin-aldosterone system inhibitors. 1

Primary Causes

Renal Dysfunction

• Chronic kidney disease (CKD) is the most common cause of hyperkalemia, as renal potassium excretion is typically maintained until GFR decreases to less than 10-15 mL/min/1.73 m² 1
• Advanced kidney disease leads to impaired potassium excretion and sodium retention, resulting in dilutional hyponatremia 2
• The risk of hyperkalemia increases with worsening CKD stages, though patients with CKD may develop tolerance to higher potassium levels 1

Medication-Induced

• Renin-angiotensin-aldosterone system inhibitors (RAASis) including ACE inhibitors and angiotensin receptor blockers can cause both hyperkalemia and hyponatremia 1
• Potassium-sparing diuretics (e.g., spironolactone, eplerenone, amiloride, triamterene) can cause hyperkalemia while potentially contributing to hyponatremia 1, 3
• NSAIDs can cause sodium retention and impair potassium excretion, particularly in patients with compromised renal function 1, 4
• Beta-blockers can contribute to hyperkalemia by decreasing cellular potassium uptake 4

Endocrine Disorders

• Adrenal insufficiency (Addison's disease) causes both hyponatremia and hyperkalemia due to aldosterone deficiency 1
• Hyporeninemic hypoaldosteronism (type 4 renal tubular acidosis), often seen in diabetic nephropathy, leads to impaired potassium excretion and hyponatremia 4

Heart Failure-Related Mechanisms

• Heart failure activates the renin-angiotensin-aldosterone system and increases vasopressin release, leading to water retention and dilutional hyponatremia 3
• In heart failure patients, hyperkalemia can occur due to:
  • Decreased renal perfusion leading to reduced potassium excretion 1
  • Medication effects, particularly when RAASis are combined with aldosterone antagonists 1
  • Metabolic acidosis, which promotes potassium shift from intracellular to extracellular space 3

Other Causes

• Contrast media administration in patients with advanced kidney disease can cause translocational hyponatremia and hyperkalemia 2
• Urinary diversions (e.g., ileal conduit) can cause electrolyte abnormalities including hyponatremia and hyperkalemia due to reabsorption of urinary electrolytes 5
• Severe tissue injury, rhabdomyolysis, or tumor lysis syndrome can release intracellular potassium while dilutional effects or SIADH can cause hyponatremia 1, 4

Clinical Significance and Monitoring

• The combination of hyponatremia and hyperkalemia significantly increases mortality risk and requires careful monitoring 1, 6
• ECG monitoring is essential as hyperkalemia can cause life-threatening cardiac arrhythmias, with a progressive sequence of changes beginning with peaked T waves and potentially leading to asystolic cardiac arrest 4
• Serum potassium concentrations should be targeted in the 4.0-5.0 mEq/L range to prevent adverse cardiac effects 1
• Both hypokalemia and hyperkalemia can cause alterations in muscle function and cardiac arrhythmias, highlighting the importance of maintaining normal electrolyte balance 1

Management Considerations

• Treatment should address the underlying cause while carefully correcting electrolyte abnormalities 6
• In patients with heart failure, close monitoring of electrolytes is essential, particularly when using diuretics, ACE inhibitors, or aldosterone antagonists 1
• Medication adjustments, dietary modifications, and in severe cases, dialysis may be required to correct these electrolyte abnormalities 4, 6