What are the symptoms and treatment of hypernatremia?

Hypernatremia: Symptoms and Treatment

Clinical Presentation of Hypernatremia

Hypernatremia primarily manifests with central nervous system dysfunction and symptoms related to cellular dehydration. 1, 2

Neurological Symptoms

• Altered mental status ranging from confusion to delirium and coma 2, 3
• Seizures in severe cases 1
• Lethargy and obtundation as sodium levels rise 2
• Irritability and restlessness, particularly in pediatric patients 2
• Muscle weakness and hyperreflexia 2

Other Clinical Features

• Intense thirst (in conscious patients with intact thirst mechanism) 3
• Dry mucous membranes and decreased skin turgor indicating dehydration 4
• Hypotension and tachycardia in hypovolemic states 4
• Fever may be present 2

The severity of symptoms correlates with both the absolute sodium level and the rapidity of development, with acute hypernatremia (developing in <24-48 hours) causing more severe symptoms than chronic hypernatremia. 2, 3

---

Treatment Approach

Step 1: Identify the Underlying Cause

• Assess volume status (hypovolemic, euvolemic, or hypervolemic) through physical examination 4
• Measure urine osmolality and sodium to differentiate renal from extrarenal losses 4
• Check for diabetes insipidus if urine osmolality is inappropriately low (<300 mOsm/kg) 4
• Review medications and assess for excessive sodium intake 1

Step 2: Determine Acuity

• Acute hypernatremia (<24-48 hours): Can be corrected more rapidly 3
• Chronic hypernatremia (>48 hours): Must be corrected slowly at no more than 8-10 mmol/L per 24 hours to prevent cerebral edema 3, 1

Step 3: Calculate Water Deficit

Use the formula: Water deficit (L) = 0.6 × body weight (kg) × [(current Na/140) - 1] 4

Step 4: Select Replacement Fluid

For hypernatremic dehydration, use hypotonic fluids:

• 5% dextrose in water (D5W) is preferred as it delivers no renal osmotic load and allows controlled sodium correction 5
• 0.45% NaCl (half-normal saline) for moderate hypernatremia, providing 77 mEq/L sodium 5
• 0.18% NaCl (quarter-normal saline) for more aggressive free water replacement 5
• Avoid isotonic saline (0.9% NaCl) as it worsens hypernatremia by delivering excessive osmotic load 5

Step 5: Determine Correction Rate

Critical safety guideline: For chronic hypernatremia, reduce sodium by no more than 0.4 mmol/L/hour or 10 mmol/L per 24 hours to prevent cerebral edema. 5, 3

• Initial fluid rate for adults: 25-30 mL/kg/24 hours 5
• Monitor serum sodium every 2-4 hours during active correction 3
• Adjust infusion rate based on sodium response 4

Step 6: Special Considerations

For diabetes insipidus:

• Administer desmopressin (DDAVP) 1-4 mcg subcutaneously or intravenously 3
• Continue hypotonic fluid replacement to match ongoing losses 5

For nephrogenic diabetes insipidus:

• Ongoing hypotonic fluid administration required to match excessive free water losses 5
• Isotonic fluids contraindicated as they exacerbate hypernatremia 5

For acute severe hypernatremia (<24 hours):

• Hemodialysis is an effective option for rapid normalization 3
• Close monitoring essential to avoid overly rapid correction 3

---

Common Pitfalls to Avoid

• Never correct chronic hypernatremia faster than 8-10 mmol/L per 24 hours - this causes cerebral edema 3, 1
• Never use isotonic saline in hypernatremic patients - it worsens the condition by delivering excessive sodium 5
• Never assume adequate thirst mechanism - elderly and neurologically impaired patients may not sense thirst 4
• Inadequate monitoring during correction leads to overcorrection complications 3