What is the management for a patient with severe hypernatremia?

Management of Severe Hypernatremia (Sodium 220 mg/dL)

Immediate Correction Strategy

For severe hypernatremia, correction should not exceed 10-15 mmol/L per 24 hours, with a maximum rate of 0.5 mmol/L/hour, using hypotonic fluids as the primary treatment to prevent cerebral edema and seizures. 1

The severity of neurological symptoms depends on both the magnitude and rapidity of onset of hypernatremia 1. A sodium level of 220 mg/dL (approximately 220 mmol/L, assuming you meant mmol/L rather than mg/dL) represents life-threatening hypernatremia requiring ICU-level monitoring 2.

Fluid Selection and Administration

Primary Fluid Choice

• Use 5% dextrose in water (D5W) as the primary rehydration fluid because it delivers no renal osmotic load and allows controlled decrease in plasma osmolality 3
• Avoid isotonic saline (0.9% NaCl) as it delivers excessive osmotic load—requiring 3 liters of urine to excrete the osmotic load from just 1 liter of isotonic fluid, which risks worsening hypernatremia 3
• Alternative hypotonic options include 0.45% NaCl (77 mEq/L sodium) for moderate correction or 0.18% NaCl (31 mEq/L sodium) for more aggressive free water replacement 3

Initial Fluid Administration Rates

• Adults: 25-30 mL/kg/24 hours as the baseline maintenance rate 3
• Children: 100 mL/kg/24 hours for first 10 kg, 50 mL/kg/24 hours for 10-20 kg, and 20 mL/kg/24 hours for remaining weight 3
• High-risk populations (infants, malnourished patients) may benefit from smaller-volume frequent boluses (10 mL/kg) due to reduced cardiac output capacity 3

Critical Correction Rate Guidelines

The maximum safe correction rate is 10-15 mmol/L per 24 hours, with a target of ≤0.5 mmol/L/hour 1. Rapid correction induces cerebral edema, seizures, and neurological injury 1. For chronic hypernatremia (>48 hours duration), correction should generally not exceed 8-10 mmol/L per 24 hours 1.

Monitoring Protocol

• Check serum sodium every 2-4 hours during active correction 2
• Monitor serum electrolytes, glucose, and fluid balance regularly 3
• Serial measurements of serum and urine electrolytes are cornerstone of proper therapy, as formulae do not account for ongoing variable fluid losses 2
• Watch for signs of neurological deterioration during correction 1

Special Considerations

Traumatic Brain Injury Patients

Do not use prolonged induced hypernatremia to control intracranial pressure in severe TBI patients 4, 1. The theoretical beneficial effect requires an intact blood-brain barrier to create an osmotic gradient 4. Rapid regulation of brain cell volume limits effectiveness of prolonged hyperosmolarity, with risk of "rebound" ICP during correction 4, 1. The relationship between serum sodium and ICP is weak 4.

Underlying Cause Management

• Address excessive water loss (diarrhea, vomiting) by replacing ongoing losses 3
• Ensure access to free water for inadequate fluid intake 3
• For nephrogenic diabetes insipidus, ongoing hypotonic fluid administration is required to match excessive free water losses; isotonic fluids worsen hypernatremia 3

Common Pitfalls to Avoid

• Never use isotonic saline in hypernatremic patients with renal concentrating defects, as this exacerbates hypernatremia 3
• Avoid correction faster than 0.5 mmol/L/hour to prevent cerebral edema 1
• Do not regard the patient as a closed system—ongoing fluid losses are highly variable and require serial electrolyte monitoring 2
• Hypernatremia is often iatrogenic in ICU settings due to inadequate free water replacement 2

Associated Complications

Hypernatremia causes brain cell dehydration as water shifts from intracellular to extracellular space, leading to neurological symptoms 1. It is associated with hyperchloremia which may impair renal function 4, 1. Hypernatremic dehydration carries the highest morbidity and mortality rate among dehydration types, primarily related to CNS dysfunction 5.