How to manage a patient with hypernatremia?

Management of Hypernatremia

Immediate Assessment and Correction Strategy

For hypernatremia, correct the free water deficit using hypotonic fluids at a rate not exceeding 10-15 mmol/L per 24 hours for chronic cases (>48 hours duration), while addressing the underlying cause. 1, 2

Initial Diagnostic Evaluation

Determine the following critical parameters to guide management:

• Assess volume status through vital signs, body weight, skin turgor, mucous membranes, and presence of edema or ascites 1, 3
• Measure urine osmolality and sodium to differentiate between renal and extrarenal water losses 3
• Check serum glucose to exclude pseudohypernatremia (correct sodium by adding 1.6 mEq/L for each 100 mg/dL glucose >100 mg/dL) 4
• Evaluate for diabetes insipidus if urine osmolality is inappropriately low (<300 mOsm/kg) with polyuria 3
• Monitor hematocrit and blood urea nitrogen to assess hydration status 1

Correction Rate Guidelines

The rate of correction is critically dependent on chronicity:

• Chronic hypernatremia (>48 hours): Reduce sodium by maximum 10-15 mmol/L per 24 hours to prevent cerebral edema 1, 2, 3
• Acute hypernatremia (<24-48 hours): Can correct more rapidly, up to 1 mmol/L/hour if severely symptomatic 1
• Never exceed 8-10 mmol/L per day for chronic hypernatremia to avoid seizures and permanent neurological injury 2, 5

The slower correction for chronic cases is essential because brain cells synthesize intracellular osmolytes over 48 hours to adapt to hyperosmolar conditions—rapid correction causes these cells to swell, leading to cerebral edema 1

Treatment Based on Volume Status

Hypovolemic Hypernatremia

• Administer hypotonic fluids (0.45% NaCl or 0.18% NaCl) to replace free water deficit 1, 6
• Never use isotonic saline as initial therapy, especially in patients with nephrogenic diabetes insipidus, as this worsens hypernatremia 1
• For severe dehydration with altered mental status, combine IV hypotonic fluids with free water via nasogastric tube 1

Euvolemic Hypernatremia

• Replace free water deficit with hypotonic solutions (D5W or 0.45% NaCl) 6, 3
• Low salt diet (<6 g/day) and protein restriction (<1 g/kg/day) may be beneficial 1
• For diabetes insipidus, administer desmopressin (Minirin) 2

Hypervolemic Hypernatremia

• Focus on negative water balance rather than aggressive fluid administration 1
• In cirrhosis patients, discontinue IV fluids and implement free water restriction 1
• In heart failure patients, restrict fluids to 1.5-2 L/day after initial correction 1

Special Population Considerations

Heart Failure Patients

• Limit fluid intake to around 2 L/day for most hospitalized patients 1
• Consider stricter restriction for diuretic-resistant or significantly hypernatremic patients 1
• For persistent severe hypernatremia with cognitive symptoms, vasopressin antagonists (tolvaptan, conivaptan) may be considered for short-term use 1

Cirrhosis Patients

• Evaluate for hypovolemic versus hypervolemic state 1
• Provide fluid resuscitation with hypotonic solutions for hypovolemic hypernatremia 1
• Focus on attaining negative water balance for hypervolemic hypernatremia 1

Nephrogenic Diabetes Insipidus

• Ongoing hypotonic fluid administration required to match excessive free water losses 1
• Isotonic fluids will cause or worsen hypernatremia in these patients 1
• Hypotonic fluids are essential to keep up with ongoing losses 1

Monitoring Requirements

• Check serum sodium every 2-4 hours during active correction 2, 3
• Monitor serum potassium, chloride, bicarbonate, and renal function regularly 1
• Assess urine osmolality to guide ongoing therapy 1
• Track fluid balance meticulously 1

Critical Pitfalls to Avoid

• Never correct chronic hypernatremia too rapidly—this causes cerebral edema, seizures, and permanent neurological injury 1, 5
• Avoid isotonic saline in patients with renal concentrating defects, as this exacerbates hypernatremia 1
• Do not use prolonged induced hypernatremia to control intracranial pressure in traumatic brain injury, as it may worsen cerebral contusions 1
• Be cautious when starting renal replacement therapy in chronic hypernatremia to avoid rapid sodium drops 2

Severe Hypernatremia (>200 mEq/L)

For extremely severe cases, rapid correction may be necessary despite theoretical risks:

• One case report demonstrated successful treatment with isotonic solution for serum sodium >200 mEq/L 7
• Hemodialysis is an effective option for acute hypernatremia (<24 hours) to rapidly normalize sodium levels 2
• Close monitoring is essential given the high mortality risk 5