What are the management strategies for hypernatremia?

Hypernatremia Management

Initial Assessment and Correction Rate

For hypernatremia, administer hypotonic fluids to replace free water deficit, with a target correction rate of 10-15 mmol/L per 24 hours for chronic cases, while acute hypernatremia can be corrected more rapidly at up to 1 mmol/L/hour if severely symptomatic. 1

The critical first step is determining whether hypernatremia is acute (<48 hours) or chronic (>48 hours), as this dictates correction speed 1, 2. Chronic hypernatremia requires slower correction because brain cells synthesize intracellular osmolytes over 48 hours to adapt to hyperosmolar conditions—rapid correction causes cerebral edema, seizures, and permanent neurological injury 1. Acute hypernatremia lacks this adaptation, allowing faster correction without osmotic demyelination risk 1.

Volume Status Assessment and Fluid Selection

Hypovolemic Hypernatremia

• Never use isotonic saline (0.9% NaCl) as initial therapy, especially in nephrogenic diabetes insipidus, as this worsens hypernatremia 1
• Administer hypotonic fluids: 0.45% NaCl (77 mEq/L sodium, 154 mOsm/L) for moderate cases or 0.18% NaCl (31 mEq/L sodium) for severe cases 1
• D5W (5% dextrose in water) provides pure free water replacement with no osmotic load 1
• Match fluid composition to ongoing losses in severe burns or voluminous diarrhea while providing adequate free water 1

Hypervolemic Hypernatremia

• Focus on achieving negative water balance rather than aggressive fluid administration 1
• In cirrhosis: discontinue IV fluids and implement free water restriction 1
• In heart failure: sodium and fluid restriction, limiting intake to ~2 L/day for most hospitalized patients 1
• Consider stricter fluid restriction for diuretic-resistant or significantly hypernatremic patients 1

Special Clinical Scenarios

Nephrogenic Diabetes Insipidus

• Requires ongoing hypotonic fluid administration to match excessive free water losses 1
• Isotonic saline will cause or worsen hypernatremia in these patients—this is an absolute contraindication 1
• Hypotonic fluids must be administered continuously as maintenance therapy 1

Heart Failure with Persistent Severe Hypernatremia

• Vasopressin antagonists (tolvaptan, conivaptan) may be considered for short-term use when cognitive symptoms present 1
• Combine IV hypotonic fluids with free water via nasogastric tube for severe cases with altered mental status 1
• After initial correction, fluid restriction (1.5-2 L/day) may be needed with careful monitoring 1

Cirrhosis with Hypervolemic Hypernatremia

• Prioritize negative water balance over fluid administration 1
• Close monitoring of serum sodium and fluid status essential 1
• Avoid aggressive fluid therapy that worsens ascites 1

Critical Safety Considerations

Correction Rate Limits

• Chronic hypernatremia: maximum 10-15 mmol/L per 24 hours 1
• Acute symptomatic hypernatremia: up to 1 mmol/L/hour permissible 1
• Slower correction critical because rapid changes cause cerebral edema and seizures 1

Monitoring Requirements

• Assess neurological symptoms, vital signs, and volume status continuously 1
• Measure blood electrolytes and acid-base status frequently 1
• Check hematocrit and blood urea nitrogen to assess hydration 1
• Regular monitoring of serum sodium, potassium, chloride, and bicarbonate during treatment 1
• Assess renal function and urine osmolality 1

Common Pitfalls to Avoid

• Using isotonic saline in patients with renal concentrating defects—this exacerbates hypernatremia 1
• Correcting chronic hypernatremia too rapidly (>10-15 mmol/L/24h)—causes cerebral edema and neurological injury 1
• Using prolonged induced hypernatremia for ICP control in traumatic brain injury—requires intact blood-brain barrier and may worsen cerebral contusions 1
• Ignoring the risk of "rebound" ICP elevation during correction as brain cells synthesize intracellular osmolytes 1
• Failing to monitor for hyperchloremia-associated renal impairment during treatment 1

Specific Populations

Traumatic Brain Injury

• Prolonged induced hypernatremia for ICP control not recommended 1
• Weak relationship between serum sodium and ICP 1
• Risk of rebound ICP elevation during correction 1

Patients with Severe Burns or Diarrhea

• Hypotonic fluids required to match ongoing free water losses 1
• Fluid composition should match losses while providing adequate free water 1