How to correct hypernatremia in a patient with severe hyperglycemia?

Correcting Severe Hypernatremia in Hyperglycemic Crisis

In a patient with sodium 178 mEq/L and glucose 40 mmol/L (720 mg/dL), you must first calculate the corrected sodium to determine the true magnitude of hypernatremia, then address both hyperglycemia and free water deficit simultaneously with insulin therapy and hypotonic fluid replacement.

Calculate Corrected Sodium First

The measured sodium of 178 mEq/L is artificially elevated by the hyperglycemia. For every 100 mg/dL glucose above 100 mg/dL, add 1.6 mEq/L to the measured sodium 1:

• Glucose elevation: 720 - 100 = 620 mg/dL
• Correction factor: (620/100) × 1.6 = 9.9 mEq/L
• Corrected sodium: 178 + 10 = 188 mEq/L

This represents severe, life-threatening hypernatremia requiring urgent intervention 2, 3.

Immediate Management Strategy

Insulin Therapy (First Priority)

Start continuous IV insulin infusion at 0.1 units/kg/h (5-7 units/h in adults) after excluding hypokalemia (K+ >3.3 mEq/L) 1. This will:

• Lower glucose by 50-75 mg/dL per hour 1
• Reverse the osmotic component of hypertonicity 4
• Allow water to redistribute back into cells 4

Critical point: As glucose normalizes, the corrected sodium will reveal the true hypernatremia that requires separate treatment with free water replacement 4, 3.

Fluid Replacement Strategy

Initial fluid choice depends on volume status 1:

• If severely dehydrated/hypotensive: Start with 0.9% NaCl at 15-20 mL/kg/h for the first hour to restore perfusion 1
• Once hemodynamically stable: Switch to hypotonic fluids (0.45% NaCl or D5W) to address the free water deficit 2, 4

For this patient with corrected sodium 188 mEq/L, after initial volume resuscitation, use D5W (5% dextrose in water) as the primary fluid because it delivers no osmotic load and allows controlled reduction of plasma osmolality 2.

Calculate Free Water Deficit

Water deficit = 0.5 × body weight (kg) × [(corrected Na/140) - 1] 4, 3

For a 70 kg patient: 0.5 × 70 × [(188/140) - 1] = 12 liters free water deficit

Critical Correction Rate Guidelines

Maximum sodium reduction: 10-15 mEq/L per 24 hours 5. More rapid correction risks cerebral edema 2, 6.

• Target reduction: 0.4 mEq/L per hour maximum 6
• Check sodium every 2-4 hours during active correction 1
• Adjust fluid rates to avoid exceeding correction limits 2

Specific Fluid Administration Protocol

1. Hours 0-1: 0.9% NaCl at 15-20 mL/kg/h if hypovolemic 1
2. After stabilization: Switch to D5W at 200-300 mL/h 2
3. Add free water via NG tube: 250-500 mL every 4 hours if patient can tolerate 2
4. Consider desmopressin 2-4 mcg IV: If ongoing osmotic diuresis prevents sodium correction 2

Potassium Replacement

Once renal function confirmed and urine output established, add 20-30 mEq/L potassium (2/3 KCl, 1/3 KPO4) to IV fluids 1. Hyperglycemic patients have total body potassium deficits of 3-5 mEq/kg despite normal or elevated initial levels 1.

Monitoring Protocol

• Serum sodium: Every 2 hours initially, then every 4 hours 1
• Glucose: Hourly until <250 mg/dL 1
• Potassium: Every 2-4 hours 1
• Mental status: Continuous assessment for improvement or deterioration 2
• Urine output: Hourly to assess ongoing losses 1

Common Pitfalls to Avoid

• Using only isotonic saline: This will not correct hypernatremia and may worsen it in patients with renal concentrating defects 6
• Correcting too rapidly: Exceeding 10-15 mEq/L per 24 hours risks cerebral edema 5, 2
• Ignoring the corrected sodium: The measured sodium underestimates true hypernatremia in hyperglycemia 1, 4
• Inadequate free water replacement: The combination requires both glucose normalization AND hypotonic fluid administration 2, 4
• Stopping insulin when glucose normalizes: Continue insulin at reduced rates (0.05 units/kg/h) with dextrose-containing fluids until metabolic acidosis resolves 1

Special Considerations for This Presentation

This combination of severe hyperglycemia with hypernatremia (rather than the typical hyponatremia) indicates 2, 3:

• Massive osmotic diuresis with water loss exceeding sodium/potassium losses 4, 3
• Likely impaired thirst mechanism or inability to access water 2
• Higher mortality risk requiring ICU-level monitoring 2
• Need for both components of treatment: insulin for hyperglycemia AND hypotonic fluids for hypernatremia 2, 4