What is the appropriate treatment approach for a patient with hypernatremia?

Hypernatremia Treatment

Immediate Treatment Approach

For hypernatremia (serum sodium >145 mEq/L), replace the water deficit with hypotonic fluids at a controlled rate, targeting a maximum correction of 8-10 mmol/L per 24 hours for chronic cases to prevent cerebral edema. 1, 2

Diagnostic Steps Before Treatment

• Confirm true hypernatremia by excluding pseudohypernatremia and calculating glucose-corrected sodium (add 1.6 mEq/L for every 100 mg/dL glucose above 100 mg/dL) 1

• Assess volume status through physical examination looking for signs of hypovolemia (orthostatic hypotension, dry mucous membranes, decreased skin turgor) versus hypervolemia (edema, jugular venous distention) 1, 3

• Measure urine osmolality and sodium to determine the mechanism - concentrated urine (>600 mOsm/kg) suggests extrarenal water loss, while dilute urine (<300 mOsm/kg) indicates diabetes insipidus 1, 4

• Determine chronicity - acute hypernatremia (<24-48 hours) can be corrected more rapidly, while chronic hypernatremia (>48 hours) requires slower correction 1, 2

Treatment Algorithm

Step 1: Calculate Water Deficit

• Use the formula: Water deficit (L) = 0.6 × body weight (kg) × [(current Na/140) - 1] for men, or 0.5 × body weight for women 1, 3

• Add ongoing losses including insensible losses (approximately 500-1000 mL/day) and any measured urinary or gastrointestinal losses 1, 5

Step 2: Select Replacement Fluid

• For hypovolemic hypernatremia: Start with 0.45% NaCl (half-normal saline) to address both volume and free water deficits 1, 3

• For euvolemic or hypervolemic hypernatremia: Use 5% dextrose in water (D5W) as it provides pure free water without additional sodium load 1, 2

• Avoid normal saline (0.9% NaCl) in hypernatremia as it contains 154 mEq/L sodium and will worsen the condition 1

Step 3: Determine Correction Rate

• For chronic hypernatremia (>48 hours): Limit correction to 8-10 mmol/L per 24 hours to prevent cerebral edema from rapid osmotic shifts 1, 2, 3

• For acute hypernatremia (<24 hours): More rapid correction is permissible, but still monitor closely with serial sodium measurements every 2-4 hours 2, 4

• Never exceed 0.5 mmol/L per hour as the correction rate in chronic cases 1

Step 4: Calculate Infusion Rate

• Divide the calculated water deficit by 24-48 hours depending on severity and chronicity 1, 3

• Add replacement for ongoing losses to the baseline infusion rate 1, 5

• Monitor serum sodium every 2-4 hours initially, then every 6-8 hours once stable correction is achieved 1, 4

Specific Cause-Based Management

Diabetes Insipidus

• Central diabetes insipidus: Administer desmopressin (DDAVP) 1-2 mcg subcutaneously or 10-20 mcg intranasally, in addition to free water replacement 1, 2

• Nephrogenic diabetes insipidus: Treat underlying cause, ensure adequate free water access, consider thiazide diuretics or amiloride in selected cases 1

Hypervolemic Hypernatremia

• Use loop diuretics (furosemide 20-40 mg IV) to promote sodium excretion while replacing free water with D5W 4, 3

• Monitor for fluid overload and adjust diuretic dosing based on volume status 4

Critically Ill Patients

• Provide meticulous fluid balance management as these patients cannot regulate water intake through thirst 4

• Account for all sources of sodium including medications, IV fluids, and enteral nutrition 4

Critical Monitoring Parameters

• Check serum sodium every 2-4 hours during active correction phase 1, 4

• Assess neurological status frequently - watch for confusion, seizures, or altered mental status indicating too-rapid correction 2, 5

• Monitor urine output and osmolality to assess response to treatment and ongoing losses 1

• Track daily weights and fluid balance meticulously 4

Common Pitfalls to Avoid

• Overcorrection is dangerous - rapid correction of chronic hypernatremia causes cerebral edema with potentially fatal consequences 1, 2, 5

• Undercorrection perpetuates morbidity - inadequate water replacement in hospital-acquired hypernatremia is often iatrogenic and preventable 5, 3

• Failing to account for ongoing losses leads to persistent hypernatremia despite calculated replacement 1, 5

• Using isotonic saline in hypernatremia worsens the condition by providing additional sodium load 1

• Ignoring the underlying cause - always address diabetes insipidus, excessive sodium intake, or impaired water access 1, 5, 3