What is the treatment for a patient with hypernatremia (elevated sodium level)?

Treatment of Hypernatremia

For hypernatremia, correct the free water deficit using hypotonic fluids (5% dextrose or 0.45% NaCl) at a maximum rate of 10 mmol/L per 24 hours for chronic cases (>48 hours), while addressing the underlying cause. 1, 2

Initial Assessment and Fluid Selection

• Determine the chronicity of hypernatremia - acute (<24-48 hours) versus chronic (>48 hours), as this dictates correction rates 2
• Assess volume status and underlying etiology through medical history, physical examination for signs of dehydration, and urine osmolality measurement 1, 2
• Use hypotonic fluids as primary therapy: 5% dextrose (D5W) is preferred because it delivers no renal osmotic load and allows controlled decrease in plasma osmolality 3
• Alternative hypotonic option: 0.45% NaCl (half-normal saline, containing 77 mEq/L sodium) provides both free water and some sodium replacement 3
• Avoid isotonic saline (0.9% NaCl) in hypernatremic patients, as it delivers excessive osmotic load requiring 3 liters of urine to excrete the osmotic load from just 1 liter of fluid, which risks worsening hypernatremia 3

Critical Correction Rate Guidelines

The single most important safety principle is avoiding overly rapid correction to prevent cerebral edema:

• For chronic hypernatremia (>48 hours): Maximum correction of 8-10 mmol/L per 24 hours 2
• Target correction rate: 0.4 mmol/L per hour or 10 mmol/L per 24 hours 3
• For acute hypernatremia (<24 hours): More rapid correction is permissible, and hemodialysis is an effective option to rapidly normalize serum sodium levels 2

Fluid Administration Rates

Initial fluid administration should be calculated based on physiological maintenance requirements:

• For adults: 25-30 mL/kg per 24 hours 3
• For children: 100 mL/kg/24 hours for first 10 kg, 50 mL/kg/24 hours for 10-20 kg, and 20 mL/kg/24 hours for remaining weight 3
• High-risk populations (infants, malnourished patients): Consider smaller-volume frequent boluses (10 mL/kg) due to reduced cardiac output capacity 3

Special Clinical Scenarios

Diabetes insipidus (central or nephrogenic):

• Administer desmopressin (Minirin) for central diabetes insipidus 2
• For nephrogenic diabetes insipidus, ongoing hypotonic fluid administration is required to match excessive free water losses 3
• Never use isotonic fluids in patients with renal concentrating defects, as this will worsen hypernatremia 3

Patients requiring renal replacement therapy:

• During continuous RRT, hypernatremia can be corrected by adding small pre-calculated amounts of 30% NaCl to dialysate/replacement fluid bags, aiming for a sodium concentration in the fluid that allows safe equilibration 4
• When starting RRT in patients with chronic hypernatremia, avoid rapid drops in sodium concentration 2

Monitoring Requirements

• Close laboratory monitoring is essential during correction 2
• Track daily weights and fluid balance meticulously to monitor effectiveness and adjust as necessary 3
• Monitor for neurological symptoms including confusion, altered mental status, or seizures 1, 2

Addressing Underlying Causes

• Excessive water loss (diarrhea, vomiting): Replace ongoing losses 3
• Inadequate fluid intake: Ensure access to free water, particularly in elderly or mentally handicapped patients with impaired thirst mechanism 1, 5
• Sodium excess (rare): In cases of exogenous salt intake, hypotonic fluid therapy provides free water to correct hypernatremia gradually 5

Prognostic Considerations

• Age and initial sodium concentration are the most important prognostic indicators 5
• Very young patients and those with lesser degrees of hypernatremia have better survival rates 5
• Severe hypernatremia (>200 mEq/L) carries significant mortality risk, though survival is possible with appropriate management 5, 6