What is the management of hypernatremia?

Management of Hypernatremia

The management of hypernatremia should focus on correcting the underlying water deficit while addressing the cause, with correction rates tailored to the acuity of onset to prevent neurological complications. 1, 2

Initial Assessment

• Hypernatremia is defined as serum sodium concentration >145 mmol/L 2
• Classify hypernatremia based on:
  • Volume status: hypovolemic, euvolemic, or hypervolemic 2, 3
  • Duration: acute (<48 hours) or chronic (>48 hours) 2
  • Severity: mild, moderate, or severe 2

Diagnostic Approach

• Exclude pseudohypernatremia and confirm glucose-corrected sodium concentrations 3
• Determine extracellular volume status through physical examination 3
• Measure urine sodium levels and osmolality to identify the cause 3
• Calculate ongoing urinary electrolyte free water clearance 3
• Assess for other associated electrolyte disorders 3

Treatment Based on Volume Status

Hypovolemic Hypernatremia

• Replace both water and sodium deficits 1, 3
• Initially administer isotonic fluids (0.9% saline) to restore hemodynamic stability 1
• Once hemodynamically stable, switch to hypotonic fluids (0.45% saline or 5% dextrose) 1, 3
• Address the underlying cause (e.g., stopping diuretics, treating diarrhea) 1

Euvolemic Hypernatremia

• Replace pure water deficit with hypotonic fluids (D5W or 0.45% saline) 1, 2
• For diabetes insipidus:
  • Central: administer desmopressin (DDAVP) 2, 3
  • Nephrogenic: treat underlying cause, consider thiazide diuretics 2, 3

Hypervolemic Hypernatremia

• Promote renal excretion of excess sodium with loop diuretics 2
• Replace ongoing water losses with hypotonic fluids 2, 3
• Discontinue iatrogenic sources of sodium (e.g., hypertonic saline, sodium bicarbonate) 2

Correction Rate Guidelines

• For acute hypernatremia (<48 hours): correction can be more rapid, aiming for 1 mmol/L/hour 2
• For chronic hypernatremia (>48 hours): correct at a maximum rate of 0.5 mmol/L/hour or 10-12 mmol/L/day 2, 3
• Recent evidence suggests that even rapid correction of hypernatremia in critically ill patients may not be associated with increased risk of adverse neurological outcomes 4

Calculating Water Deficit

• Water deficit (L) = Total body water × [(Current Na⁺/140) - 1] 3
• Total body water = Weight (kg) × 0.6 (for men) or 0.5 (for women) 3
• Account for ongoing losses in the calculation 3

Monitoring During Treatment

• Check serum sodium levels every 2-4 hours initially, then every 4-6 hours once stabilized 3
• Monitor for signs of cerebral edema during correction (headache, nausea, vomiting, altered mental status) 2, 3
• Adjust fluid administration rate based on sodium correction and clinical response 3

Special Considerations

• Elderly patients have decreased total body water and may be more susceptible to hypernatremia 5, 2
• Patients with neurological conditions require careful monitoring during correction 2
• Critically ill patients may have multiple contributing factors to hypernatremia 4, 3

Common Pitfalls to Avoid

• Correcting chronic hypernatremia too rapidly, which can lead to cerebral edema 2
• Failing to account for ongoing losses when calculating replacement needs 3
• Not addressing the underlying cause of hypernatremia 1, 2
• Using hypotonic fluids in patients with uncontrolled diabetes insipidus without addressing the primary disorder 2, 3