What fluids are used to treat hypernatremia?

Treatment of Hypernatremia with Appropriate Fluids

For treating hypernatremia, hypotonic fluids such as 5% dextrose in water (D5W) should be used as the primary intravenous fluid, with the correction rate carefully controlled to prevent neurological complications. 1, 2

Understanding Hypernatremia

Hypernatremia is defined as a serum sodium concentration >144 mEq/L and is classified by severity:

• Mild: 145-150 mEq/L
• Moderate: 151-160 mEq/L
• Severe: >160 mEq/L

This condition typically results from water deficit relative to sodium content, either through pure water loss or inadequate water intake.

Fluid Selection Algorithm

First-line fluid therapy:

• 5% Dextrose in Water (D5W) - Provides free water without adding sodium load 1, 3

Alternative options based on clinical context:

• Hypotonic saline solutions (e.g., 0.45% NaCl) - When some sodium replacement is needed alongside free water
• Lactated Ringer's solution - For patients with concurrent metabolic acidosis requiring correction

Contraindicated fluids:

• Normal saline (0.9% NaCl) - Should be avoided as it has a high renal osmotic load (~300 mOsm/kg H₂O) that can worsen hypernatremia 1

Correction Rate Guidelines

The correction rate is critical to prevent neurological complications:

• Standard patients: Maximum correction of 8 mEq/L in 24 hours 4
• High-risk patients (alcoholism, malnutrition, liver disease): Maximum correction of 4-6 mEq/L in 24 hours 4

Monitoring protocol:

• Check serum sodium every 4-6 hours during active correction 4
• Adjust fluid rate based on sodium levels and clinical response

Special Clinical Scenarios

Nephrogenic Diabetes Insipidus (NDI)

For patients with NDI presenting with hypernatremic dehydration:

• Use D5W for intravenous rehydration 1
• Avoid 0.9% NaCl solutions as they increase renal osmotic load
• Calculate initial fluid rate based on physiological demand:
  • Children: First 10 kg: 100 ml/kg/24h; 10-20 kg: 50 ml/kg/24h; remaining: 20 ml/kg/24h
  • Adults: 25-30 ml/kg/24h 1

Diabetic Emergencies with Hypernatremia

In cases of DKA or HHS with concurrent hypernatremia:

• Initially manage hyperglycemia with insulin per protocol
• Once blood glucose <300 mg/dL, switch to D5W and hypotonic solutions 5
• Consider free water administration via nasogastric tube in severe cases 5

Sodium Overload

For acute hypernatremia due to sodium overload:

• Aggressive correction with D5W is recommended
• Target sodium reduction to ≤160 mEq/L within 8 hours and ≤150 mEq/L within 24 hours for better outcomes 3
• Monitor for hyperglycemia as a treatment-related complication

Pitfalls and Caveats

1. Overly rapid correction can cause cerebral edema and neurological deterioration 6
2. Inadequate monitoring may lead to under or overcorrection
3. Using isotonic fluids like 0.9% NaCl can worsen hypernatremia in most cases 1
4. Ignoring underlying causes (e.g., diabetes insipidus, excessive water loss) will lead to treatment failure

Pediatric Considerations

The American Academy of Pediatrics recommends:

• Isotonic maintenance fluids for most hospitalized children to prevent hyponatremia 1
• However, for correction of established hypernatremia, hypotonic fluids are required 1, 6
• Children are at higher risk for complications from rapid correction, requiring more careful monitoring

By following these guidelines and selecting appropriate hypotonic fluids with careful monitoring of correction rates, hypernatremia can be safely and effectively treated while minimizing the risk of neurological complications.