What is the management approach for a general adult patient with severe hypernatremia (elevated sodium level)?

Hypernatremia Management

Immediate Assessment and Fluid Selection

For severe hypernatremia in adults, administer hypotonic fluids such as 0.45% NaCl (half-normal saline) or D5W (5% dextrose in water) to replace free water deficit, and never use isotonic saline as initial therapy as this will worsen hypernatremia. 1

Volume Status Determination

• Assess for hypovolemic hypernatremia by checking vital signs (orthostatic hypotension, tachycardia), skin turgor, mucous membrane moisture, and jugular venous filling 1
• Evaluate for hypervolemic hypernatremia by examining for peripheral edema, ascites, jugular venous distention, and pulmonary congestion 1
• Measure urine osmolality and sodium: inappropriately low urine osmolality (235 mOsm/kg) with low urine sodium suggests impaired renal concentrating ability or inadequate water intake 1

Hypotonic Fluid Options

• 0.45% NaCl (half-normal saline) contains 77 mEq/L sodium with osmolarity ~154 mOsm/L, appropriate for moderate hypernatremia correction 1
• 0.18% NaCl (quarter-normal saline) contains ~31 mEq/L sodium, providing more aggressive free water replacement for severe cases 1
• D5W (5% dextrose in water) delivers no renal osmotic load and allows slow, controlled decrease in plasma osmolality—preferred for primary free water replacement 1

Critical Correction Rate Guidelines

The maximum correction rate is 10-15 mmol/L per 24 hours for chronic hypernatremia (>48 hours duration) to prevent cerebral edema, seizures, and permanent neurological injury. 1

• For acute hypernatremia (<48 hours), correction can proceed more rapidly, up to 1 mmol/L/hour if severely symptomatic 1
• Monitor serum sodium every 2-4 hours initially during active correction, then every 6-12 hours 1
• Corrections faster than 48-72 hours have been associated with increased risk of pontine myelinolysis 1

Treatment Algorithm Based on Volume Status

Hypovolemic Hypernatremia

• Administer hypotonic fluids (0.45% NaCl or D5W) to replace free water deficit 1
• Avoid isotonic saline as initial therapy, especially in patients with nephrogenic diabetes insipidus, as this will worsen hypernatremia 1
• For severe burns or voluminous diarrhea, match fluid composition to ongoing losses while providing adequate free water 1

Hypervolemic Hypernatremia

• In cirrhosis patients: Discontinue intravenous fluid therapy and implement free water restriction, focusing on negative water balance rather than aggressive fluid administration 1
• In heart failure patients: Implement sodium and fluid restriction, limiting fluid intake to around 2 L/day for most hospitalized patients 1
• Consider stricter fluid restriction for diuretic-resistant or significantly hypernatremic patients 1

Euvolemic Hypernatremia

• Implement low salt diet (<6 g/day) and protein restriction (<1 g/kg/day) 1
• Administer hypotonic fluids to replace free water deficit 1

Special Clinical Scenarios

Nephrogenic Diabetes Insipidus

• Never use isotonic saline as this will cause or worsen hypernatremia in patients with renal concentrating defects 1
• Ongoing hypotonic fluid administration is required to match excessive free water losses 1
• Desmopressin should not be used for nephrogenic DI 1

Heart Failure with Persistent Severe Hypernatremia

• Vasopressin antagonists (tolvaptan, conivaptan) may be considered for short-term use in patients with cognitive symptoms 1
• Combine IV hypotonic fluids with free water via nasogastric tube if needed, targeting 10-15 mmol/L correction per 24 hours 1
• Fluid restriction (1.5-2 L/day) may be needed after initial correction 1

Traumatic Brain Injury

• Prolonged induced hypernatremia to control intracranial pressure is not recommended as it requires an intact blood-brain barrier and may worsen cerebral contusions 1
• Risk of "rebound" ICP elevation exists during correction as brain cells synthesize intracellular osmolytes 1

Calculating Free Water Deficit

• Use formula: Desired increase in Na (mmol/L) × (0.5 × ideal body weight in kg) to determine fluid requirements 1
• For adults, initial fluid administration rate is 25-30 mL/kg/24 hours 1
• Adjust based on ongoing losses and clinical response 1

Monitoring Protocol

• Check serum sodium every 2-4 hours initially during active correction 1
• Monitor daily weight, supine and standing vital signs 1
• Track fluid input and output with careful attention to urine output, specific gravity/osmolarity, and urine electrolyte concentrations 1
• Assess renal function and urine osmolality regularly 1
• Monitor for hypernatremia-associated hyperchloremia, which may impair renal function 1

Common Pitfalls to Avoid

• Never use isotonic saline (0.9% NaCl) as initial therapy for hypernatremia, especially in patients with nephrogenic diabetes insipidus or renal concentrating defects 1
• Correcting chronic hypernatremia too rapidly (>10-15 mmol/L per 24 hours) can lead to cerebral edema, seizures, and neurological injury 1
• Inadequate monitoring during correction can result in overcorrection or undercorrection 1
• Failing to identify and treat the underlying cause of hypernatremia 1

High-Risk Populations

Older Adults

• Higher risk for both hypernatremia and complications from correction due to reduced renal function 1
• Cognitive impairment may prevent recognition of thirst or ability to access fluids 1
• Sodium restriction should be cautious in diabetic older adults, as <2,400 mg/day may paradoxically worsen nutritional status 1

Pediatric Patients (Neonates)

• Hypernatremia mostly results from incorrect replacement of transepidermal water loss, inadequate water intake, or excessive sodium intake 1
• Assess infant's intravascular volume and hydration status before treatment 1
• Replace plasma volume first in symptomatic hypovolemia 1