How to correct hypernatremia (elevated sodium levels)?

Correction of Hypernatremia

The correction rate for hypernatremia should be determined by its chronicity, with chronic hypernatremia (>48 hours) corrected at a maximum rate of 8-10 mmol/L per day, while acute hypernatremia (<24 hours) can be corrected more rapidly. 1, 2

Assessment of Hypernatremia

• Hypernatremia is defined as serum sodium concentration >145 mmol/L 2
• Classify hypernatremia based on:
  • Duration: acute (<24-48 hours) vs. chronic (>48 hours) 1
  • Volume status: hypervolemic, hypovolemic, or euvolemic 2
• Determine the underlying cause to guide treatment approach 3

Treatment Algorithm Based on Chronicity

Chronic Hypernatremia (>48 hours)

• Correct sodium at a maximum rate of 8-10 mmol/L per day 1
• Avoid rapid correction to prevent cerebral edema 1
• Calculate free water deficit using formula:
  • Free water deficit (L) = Total body water × [(Current Na⁺/140) - 1] 3
  • Total body water ≈ 0.6 × weight in kg for men; 0.5 × weight in kg for women 3

Acute Hypernatremia (<24 hours)

• Can be corrected more rapidly than chronic hypernatremia 1
• For severe cases, hemodialysis is an effective option for rapid normalization 1
• Recent evidence suggests that rapid correction may not increase mortality or neurological complications in critically ill patients 4

Treatment Based on Volume Status

Hypovolemic Hypernatremia

• First, restore intravascular volume with isotonic (0.9%) saline 3
• Once hemodynamically stable, switch to hypotonic fluids (0.45% saline or 5% dextrose) 3
• Monitor urine output and replace ongoing losses 3

Euvolemic Hypernatremia

• Administer hypotonic fluids (0.45% saline or 5% dextrose) 3
• For diabetes insipidus:
  • Central diabetes insipidus: administer desmopressin (DDAVP) 1
  • Nephrogenic diabetes insipidus: treat underlying cause, consider thiazide diuretics 2

Hypervolemic Hypernatremia

• Restrict sodium intake 2
• Consider loop diuretics with hypotonic fluid replacement 3
• Address underlying cause (e.g., primary hyperaldosteronism) 2

Practical Administration Guidelines

• For IV fluid administration, calculate hourly rate based on desired correction:
  • Hourly rate (mL/hr) = Free water deficit (mL) ÷ Hours to correct 3
• Choose appropriate fluid:
  • 5% Dextrose in water (D5W): Free water only
  • 0.45% NaCl: 50% free water
  • 0.9% NaCl: No free water 3

Monitoring During Correction

• Check serum sodium every 4-6 hours during active correction 5
• Adjust fluid rate based on measured sodium levels 3
• Monitor for signs of cerebral edema (headache, nausea, altered mental status) 1

Common Pitfalls to Avoid

• Correcting chronic hypernatremia too rapidly (>10 mmol/L/day), which can lead to cerebral edema 1
• Failing to identify and treat the underlying cause 3
• Inadequate monitoring during correction 5
• Using isotonic saline alone for hypernatremia correction, which may worsen the condition 3

Special Considerations

• In critically ill patients, recent evidence suggests that rapid correction rates may not increase mortality or neurological complications, but caution is still warranted 4
• Patients with renal failure may require renal replacement therapy for hypernatremia correction 1
• When initiating renal replacement therapy in patients with chronic hypernatremia, use a higher sodium dialysate to avoid rapid drops in sodium concentration 1