What are the causes and treatments of hyponatremia and hypokalemia?

Causes and Management of Hyponatremia and Hypokalemia

Causes of Hyponatremia (Low Sodium)

Hyponatremia and hypokalemia often occur together and require prompt identification of underlying causes for effective treatment.

Classification by Volume Status:

1. Hypovolemic Hyponatremia

• Gastrointestinal losses: Vomiting, diarrhea
• Renal losses:
  • Diuretic use (especially thiazides) 1
  • Salt-wasting nephropathies
  • Cerebral salt wasting (CSW) in neurosurgical patients 2
  • Adrenal insufficiency (mineralocorticoid deficiency) 2

2. Euvolemic Hyponatremia

• SIADH (Syndrome of Inappropriate ADH secretion) 2
  • Neurological disorders
  • Malignancies
  • Pulmonary diseases
  • Medications (antidepressants, antipsychotics)
• Beer potomania (excessive beer consumption with poor solute intake) 3
• Primary polydipsia (excessive water intake)

3. Hypervolemic Hyponatremia

• Heart failure 2
• Cirrhosis 2
• Nephrotic syndrome
• Advanced kidney disease

Causes of Hypokalemia (Low Potassium)

1. Decreased Intake

• Malnutrition
• Alcoholism 3

2. Increased Losses

• Gastrointestinal:
  • Vomiting
  • Diarrhea
  • Laxative abuse
• Renal:
  • Diuretics (loop and thiazide) 2, 1
  • Primary hyperaldosteronism
  • Secondary hyperaldosteronism (heart failure, cirrhosis) 2
  • Renal tubular acidosis
  • Magnesium deficiency 3

3. Transcellular Shifts

• Insulin administration
• Beta-adrenergic stimulation
• Alkalosis
• Hypokalemic periodic paralysis

Clinical Manifestations

Hyponatremia

• Mild (130-134 mEq/L): Nausea, headache, weakness 4
• Moderate (125-129 mEq/L): Confusion, lethargy 4
• Severe (<125 mEq/L): Seizures, coma, respiratory arrest 4, 5

Hypokalemia

• Mild (3.0-3.5 mEq/L): Often asymptomatic
• Moderate (2.5-3.0 mEq/L): Weakness, fatigue, constipation
• Severe (<2.5 mEq/L): Cardiac arrhythmias, paralysis, rhabdomyolysis 6

Management

Hyponatremia Management

Severe Symptomatic Hyponatremia (<125 mEq/L with neurological symptoms)

• Administer 3% hypertonic saline to raise sodium by 4-6 mEq/L in first 1-2 hours 4, 5
• Limit correction to <10 mEq/L in first 24 hours to prevent osmotic demyelination syndrome 4

Based on Volume Status:

1. Hypovolemic Hyponatremia:

   • Isotonic saline (0.9% NaCl) 4
   • Treat underlying cause (stop diuretics if appropriate)

2. Euvolemic Hyponatremia:

   • SIADH: Fluid restriction (1-1.5 L/day) 2
   • Consider salt tablets or vaptans in resistant cases 2, 4

3. Hypervolemic Hyponatremia:

   • Fluid restriction (1-2 L/day) 2
   • Sodium restriction (<2 g/day) 2
   • Diuretics with careful monitoring 2
   • Treat underlying condition (heart failure, cirrhosis)

Hypokalemia Management

• Mild to Moderate: Oral potassium supplements (KCl preferred) 7

  • 40-80 mEq/day in divided doses

• Severe (<2.5 mEq/L) or Symptomatic:

  • IV potassium chloride (10-20 mEq/hour with cardiac monitoring) 2
  • Maximum rate: 40 mEq/hour in critical situations with continuous cardiac monitoring

• Concurrent Magnesium Deficiency:

  • Correct magnesium deficiency to enable potassium repletion 3

• Potassium-sparing Strategies:

  • Potassium-sparing diuretics (spironolactone, amiloride, triamterene) 2
  • ACE inhibitors or ARBs
  • Caution: Monitor for hyperkalemia when combining these with potassium supplements 2

Special Considerations

Concurrent Hyponatremia and Hypokalemia

• Severe hypokalemia can impair renal concentrating ability, causing polyuria and worsening hyponatremia 3
• Correction priority: In severe cases of both, address life-threatening abnormalities first, but generally correct potassium before aggressive sodium correction 3

Medication-Induced Electrolyte Disorders

• Diuretics (especially thiazides) can cause both hyponatremia and hypokalemia 1
• NSAIDs can worsen hyponatremia in heart failure patients 2
• Monitor electrolytes closely when starting these medications, especially in high-risk patients

Heart Failure Patients

• Careful balance needed between diuresis for volume control and electrolyte management 2
• Potassium target: 4.5-5.0 mEq/L to prevent arrhythmias 2
• Potassium-sparing diuretics may be beneficial but require monitoring when combined with ACE inhibitors 2

Prevention Strategies

• Regular monitoring of electrolytes in patients on diuretics
• Dietary potassium supplementation in patients at risk
• Appropriate fluid management in hospitalized patients
• Education about adequate sodium and potassium intake in diet