How to manage hypernatremia in a patient receiving D5W?

Management of Severe Hypernatremia (Na 164 mEq/L)

D5W at 50 mL/hr is dangerously slow for correcting severe hypernatremia—you need to calculate the free water deficit and correct it over 48-72 hours, which typically requires significantly higher infusion rates, while monitoring sodium levels every 2-4 hours to ensure correction does not exceed 10-12 mEq/L per 24 hours. 1, 2

Immediate Assessment Required

Before proceeding with treatment, determine:

• Volume status: Is the patient hypovolemic, euvolemic, or hypervolemic? 1
• Cause of hypernatremia: Water loss (diarrhea, vomiting, diabetes insipidus, inadequate water access) versus sodium gain (hypertonic saline administration, salt ingestion)? 1, 2
• Duration: Acute (<24 hours) versus chronic (>24-48 hours)? This determines safe correction rate 1, 2
• Neurologic status: Altered mental status, seizures, or coma indicate severe hypernatremia requiring urgent treatment 1, 2

Calculate Free Water Deficit

Use this formula to determine total water deficit:

• Free water deficit (L) = 0.6 × body weight (kg) × [(current Na ÷ 140) - 1] 1
• For a 70 kg patient with Na 164: 0.6 × 70 × [(164 ÷ 140) - 1] = 7.2 liters deficit

Correction Rate and Fluid Choice

Target correction rate: 10-12 mEq/L per 24 hours maximum 1, 2

• Replace the calculated water deficit over 48-72 hours to avoid cerebral edema from overly rapid correction 1, 2
• Using the example above: 7.2 L ÷ 48 hours = 150 mL/hr minimum (your 50 mL/hr is inadequate)

Fluid selection depends on volume status:

• Hypovolemic patients: Start with isotonic saline (0.9% NaCl) to restore hemodynamic stability, then switch to hypotonic fluid (D5W or 0.45% saline) once blood pressure stabilizes 1, 3
• Euvolemic/hypervolemic patients: Use D5W as primary replacement fluid 1, 2
• Avoid glucose-containing solutions if: Patient has stroke or acute brain injury (glucose worsens neurologic outcomes) 4

Critical Monitoring Protocol

Check serum sodium every 2-4 hours initially 2, 3

• If correction exceeds 0.5 mEq/L per hour (12 mEq/L per 24 hours), slow the infusion rate immediately 1, 2
• Monitor for signs of cerebral edema: worsening mental status, seizures, headache 1, 2
• Check serum osmolality, glucose, and potassium levels 2
• Monitor urine output and osmolality to assess ongoing losses 2

Special Considerations for Extreme Hypernatremia (Na >190 mEq/L)

Extreme hypernatremia carries >60% mortality and requires intensive monitoring 2

• ECG monitoring is essential—extreme hypernatremia causes QT prolongation and fatal ventricular arrhythmias 2
• One case report documented successful rapid correction using isotonic saline in a patient with Na >200 mEq/L, but this contradicts standard recommendations and should not be routine practice 3
• The safer approach remains gradual correction over 48-72 hours despite limited data at these extreme levels 2, 3

Common Pitfalls to Avoid

Do not use hypotonic maintenance fluids (D5 0.3% or 0.45% saline) for routine maintenance in hospitalized patients—these cause iatrogenic hyponatremia in other clinical contexts 4

Do not correct chronic hypernatremia too rapidly—cerebral edema from rapid osmotic shifts can be fatal 1, 2

Do not forget ongoing losses—if the patient has diabetes insipidus, diarrhea, or other ongoing water losses, add these to your replacement calculation 1, 2

Do not use D5W in patients with acute stroke or brain injury—use 0.45% saline instead 4

Addressing Underlying Causes

• Diabetes insipidus: Consider desmopressin (DDAVP) after initial volume resuscitation 5
• Inadequate water access: Ensure free access to water once patient is alert enough to drink safely 5
• Iatrogenic causes: Stop hypertonic saline infusions, review medications causing water loss 2

Adjusted Recommendation for Your Patient

For Na 164 mEq/L, assuming 70 kg patient:

• Calculate deficit: ~7.2 L free water deficit
• Infusion rate: 150-200 mL/hr D5W (if euvolemic/hypervolemic) over 48 hours 1
• If hypovolemic: Start with 0.9% saline bolus, then transition to D5W at calculated rate 1, 3
• Monitor Na every 2-4 hours: Adjust rate to keep correction ≤10-12 mEq/L per 24 hours 1, 2
• Your current 50 mL/hr is insufficient and will take >144 hours to correct the deficit 1