What is the treatment for hyponatremia (low sodium levels)?

Treatment of Hyponatremia

The treatment of hyponatremia should be based on volume status assessment, severity of symptoms, and rate of sodium correction to prevent osmotic demyelination syndrome, with specific therapies tailored to the underlying cause. 1

Classification and Initial Assessment

Hyponatremia is classified based on serum sodium levels:

• Mild: 126-135 mEq/L
• Moderate: 120-125 mEq/L
• Severe: <120 mEq/L 1

Volume status assessment is crucial for determining appropriate treatment:

Volume Status	Clinical Signs	Urine Sodium	Likely Causes
Hypovolemic	Orthostatic hypotension, dry mucous membranes, tachycardia	<20 mEq/L	GI losses, diuretics, cerebral salt wasting, adrenal insufficiency
Euvolemic	No edema, normal vital signs	>20-40 mEq/L	SIADH, hypothyroidism, adrenal insufficiency
Hypervolemic	Edema, ascites, elevated JVP	<20 mEq/L	Heart failure, cirrhosis, renal failure

Treatment Approach by Symptom Severity

Severe Symptomatic Hyponatremia (Seizures, Coma, Respiratory Distress)

• Medical emergency requiring immediate treatment
• Administer 3% hypertonic saline as bolus or continuous infusion
• Target initial correction: 4-6 mEq/L within 1-2 hours to reverse severe symptoms 2
• Maximum correction rate: 8 mEq/L in 24 hours to prevent osmotic demyelination syndrome 1
• Monitor sodium levels every 2 hours initially, then every 4 hours during treatment 1

Moderate or Mild Symptomatic Hyponatremia

Treatment depends on volume status:

1. Hypovolemic Hyponatremia:

   • Isotonic (0.9%) saline infusion to restore volume 1
   • Treat underlying cause (e.g., stop diuretics, replace adrenal hormones)

2. Euvolemic Hyponatremia:

   • Fluid restriction (≤1.0 L/day) 3
   • For SIADH:
     • Salt tablets and fluid restriction as first-line therapy 4
     • Consider tolvaptan (vasopressin receptor antagonist) for short-term treatment (≤30 days) 1, 3
       • Starting dose: 15 mg once daily
       • May increase to 30 mg after 24 hours, then to maximum 60 mg daily as needed 3
     • Urea can be effective and safe alternative 5

3. Hypervolemic Hyponatremia:

   • Treat underlying condition (heart failure, cirrhosis, renal failure) 4
   • Fluid restriction
   • Loop diuretics may be beneficial 6
   • Consider tolvaptan for heart failure or cirrhosis-related hyponatremia 1, 3
   • Albumin infusion for patients with hypoalbuminemia 1

Important Precautions

• Avoid overly rapid correction: Do not exceed 8 mEq/L in 24 hours to prevent osmotic demyelination syndrome 1
• Initiate tolvaptan in hospital setting: Monitor serum sodium closely due to risk of too rapid correction 3
• Avoid fluid restriction in first 24 hours of tolvaptan therapy to prevent overly rapid correction 3
• Monitor frequently: Check sodium levels every 2-4 hours during initial treatment 1
• Tolvaptan contraindications: ADPKD, inability to sense thirst, hypovolemic hyponatremia, anuria, use of strong CYP3A inhibitors 3

Clinical Pearls

• Even mild hyponatremia increases mortality risk and is associated with cognitive impairment, gait disturbances, and increased falls 2
• Untreated severe hyponatremia (<120 mEq/L) has a mortality rate of 25% compared to 9.3% in patients with sodium >120 mEq/L 1
• Tolvaptan has been shown to effectively increase serum sodium levels in clinical trials, with significantly greater increases compared to placebo 3
• Avoid hypotonic fluids in patients with hyponatremia as they can worsen the condition 1
• In diabetic patients with hyperglycemia, correct for glucose-induced hyponatremia before initiating specific therapy 1

By following this structured approach based on volume status and symptom severity, clinicians can effectively manage hyponatremia while minimizing the risk of complications from both the condition itself and its treatment.