What fluids are used to manage hypernatremia?

Hypernatremia Fluid Management

Primary Fluid Selection

For hypernatremia, hypotonic fluids are the cornerstone of treatment, with 0.45% NaCl (half-normal saline), 0.18% NaCl (quarter-normal saline), or D5W (5% dextrose in water) being the primary options depending on severity and clinical context. 1

Specific Hypotonic Fluid 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) provides pure free water replacement and is recommended by the American Academy of Pediatrics for severe hypernatremia 2

Critical Correction Rate Guidelines

The maximum correction rate should not exceed 10-15 mmol/L per 24 hours for chronic hypernatremia (>48 hours duration) to prevent cerebral edema, seizures, and permanent neurological injury. 1, 3

• For acute hypernatremia (<24-48 hours): can correct more rapidly, up to 1 mmol/L/hour if severely symptomatic 1
• For chronic hypernatremia (>48 hours): limit to 8-10 mmol/L per day maximum 3
• Brain cells synthesize intracellular osmolytes over 48 hours to adapt to hyperosmolar conditions; rapid correction causes these cells to swell dangerously 1

Treatment Algorithm Based on Volume Status

Hypovolemic Hypernatremia

• Administer hypotonic fluids (0.45% or 0.18% NaCl) to replace free water deficit 1
• Avoid isotonic saline as initial therapy, especially in nephrogenic diabetes insipidus, as this will worsen hypernatremia 4, 1
• Calculate free water deficit and replace systematically 5

Euvolemic Hypernatremia

• Low salt diet (<6 g/day) and protein restriction (<1 g/kg/day) may be beneficial 1
• Consider desmopressin (Minirin) for diabetes insipidus 3
• Hypotonic fluid replacement as needed 6

Hypervolemic Hypernatremia

• Focus on negative water balance rather than aggressive fluid administration 1
• In cirrhosis: discontinue IV fluids and implement free water restriction 1
• In heart failure: sodium and fluid restriction (limit to ~2 L/day), with stricter restriction for diuretic-resistant or significantly hypernatremic patients 1

Special Clinical Scenarios

Nephrogenic Diabetes Insipidus

• Requires ongoing hypotonic fluid administration to match excessive free water losses 1
• Isotonic fluids will cause or worsen hypernatremia in these patients 4, 1

Severe Burns or Voluminous Diarrhea

• Hypotonic fluids required to keep up with ongoing free water losses 4
• Match fluid composition to losses while providing adequate free water 4

Severe Hypernatremia with Altered Mental Status

• Combine IV hypotonic fluids with free water via nasogastric tube 1
• Target correction rate: 10-15 mmol/L per 24 hours 1
• For acute cases with severe symptoms, hemodialysis is an effective option to rapidly normalize sodium levels 3

Critical Monitoring Requirements

• Assess volume status, neurological symptoms, and vital signs at baseline 1
• Check serum sodium every 2-4 hours during active correction 1
• Monitor hematocrit and blood urea nitrogen to assess hydration status 1
• Calculate fluid and electrolyte balance continuously 1
• Measure urine osmolality and volume to guide therapy 5

Common Pitfalls to Avoid

• Never use isotonic saline in patients with renal concentrating defects - this exacerbates hypernatremia 4, 1
• Never correct chronic hypernatremia faster than 10-15 mmol/L per 24 hours - risks cerebral edema and seizures 1, 3
• Never use lactated Ringer's solution - it is hypotonic (273 mOsm/L) and not studied for hypernatremia treatment 2
• When starting renal replacement therapy in chronic hypernatremia, avoid rapid sodium drops 3