What intravenous (IV) fluids are used to treat hypernatremia?

Treatment of Hypernatremia

For hypernatremia, administer hypotonic fluids such as 0.45% NaCl (half-normal saline), 0.18% NaCl (quarter-normal saline), or D5W (5% dextrose in water) to replace free water deficit, with the specific choice depending on severity and clinical context. 1, 2

Fluid Selection Algorithm

Primary Hypotonic Options

• 0.45% NaCl (half-normal saline) contains 77 mEq/L sodium with osmolarity ~154 mOsm/L, making it appropriate for moderate hypernatremia correction 1
• 0.18% NaCl (quarter-normal saline) contains ~31 mEq/L sodium, providing more aggressive free water replacement for severe cases 1
• D5W (5% dextrose in water) serves as the primary fluid for free water replacement, particularly useful in hyperglycemic patients already on insulin infusions 2, 3

Critical Contraindication

• Never use isotonic saline (0.9% NaCl) as initial therapy - this will worsen hypernatremia, especially in patients with nephrogenic diabetes insipidus or renal concentrating defects 1, 2

Correction Rate Guidelines

Chronic Hypernatremia (>48 hours)

• Maximum correction: 10-15 mmol/L per 24 hours to prevent cerebral edema, seizures, and permanent neurological injury 2, 4
• Brain cells synthesize intracellular osmolytes over 48 hours to adapt to hyperosmolar conditions - rapid correction causes these cells to swell dangerously 2

Acute Hypernatremia (<24-48 hours)

• Can be corrected more rapidly, up to 1 mmol/L/hour if severely symptomatic 2
• Hemodialysis is an effective option for rapid normalization in acute cases 4

Special Clinical Scenarios

Nephrogenic Diabetes Insipidus

• Requires ongoing hypotonic fluid administration to match excessive free water losses 1, 2
• Consider desmopressin (Minirin) for central diabetes insipidus 4

Severe Burns or Voluminous Diarrhea

• Hypotonic fluids required to match ongoing free water losses 1, 2
• Match fluid composition to losses while providing adequate free water 1

Combined Hyperglycemia and Hypernatremia (DKA/HHS)

• Use D5W and Ringer's lactate as primary fluids 3
• Administer free water via nasogastric tube in addition to IV fluids 2, 3
• Consider IV desmopressin to improve free water deficit 3
• This combination is rare but extremely challenging - selecting correct fluid type is the most critical decision 3

Heart Failure Patients

• Implement fluid restriction (1.5-2 L/day) after initial correction 2
• For persistent severe hypernatremia with cognitive symptoms, consider vasopressin antagonists (tolvaptan, conivaptan) for short-term use 2

Cirrhosis with Hypervolemic Hypernatremia

• Discontinue IV fluids and implement free water restriction rather than aggressive fluid administration 2
• Focus on achieving negative water balance 2

Alternative Route: Sterile Water via Central Line

• Intravenous sterile water can be administered relatively safely via central line when enteral supplementation is not possible (e.g., postoperative patients) 5
• Particularly useful in hyperglycemic patients on insulin infusion where D5W is less ideal 5

Monitoring Requirements

• Check serum sodium, potassium, chloride, and bicarbonate levels regularly during treatment 2
• Assess renal function and urine osmolality 2
• Monitor for signs of cerebral edema if correction is too rapid 2, 4

Common Pitfalls to Avoid

• Correcting chronic hypernatremia too rapidly leads to cerebral edema, seizures, and neurological injury 2
• Using isotonic saline in patients with renal concentrating defects exacerbates hypernatremia 1, 2
• Failing to distinguish acute from chronic hypernatremia - chronic cases require much slower correction 2, 4
• Starting renal replacement therapy without considering sodium concentration - rapid drops must be avoided in chronic hypernatremia 4