Introduction
Hypernatremia is a common electrolyte disorder characterized by elevated sodium levels in the blood, typically above 145 mEq/L. It often indicates water imbalance rather than excessive sodium intake and can have serious health consequences if not recognized early.
- Normal levels : 135–145 mEq/L (milliequivalents per liter)
Community-acquired hypernatremia generally occurs in elderly people who are mentally and physically impaired, often with an acute infection. Patients who develop hypernatremia during the course of hospitalization have an age distribution similar to that of the general hospital population. In both patient groups, hypernatremia is caused by impaired thirst and/or restricted access to water, often exacerbated by pathologic conditions with increased fluid loss.
Causes of Hypernatremia
Hypernatremia usually arises due to water loss, sodium gain, or a combination.
1. Water Loss (Most Common Cause)
- Gastrointestinal: Severe diarrhea, vomiting.
- Renal: Osmotic diuresis (e.g., uncontrolled diabetes mellitus), diuretic use.
- Insensible Loss: Fever, sweating, hyperventilation.
2. Sodium Gain
- Iatrogenic: Excessive sodium bicarbonate or hypertonic saline administration.
- Endocrine: Hyperaldosteronism (rare).
3. Reduced Water Intake
- Elderly or incapacitated patients who cannot access water.
- Neurological disorders causing impaired thirst (e.g., hypothalamic injury).
Symptoms of Hypernatremia
Symptoms depend on severity and rate of sodium elevation.
- Mild (145–150 mEq/L): Thirst, weakness, lethargy.
- Moderate (150–160 mEq/L): Confusion, irritability, muscle twitching.
- Severe (>160 mEq/L): Seizures, coma, intracranial hemorrhage, death.
Clinical Tip: Rapid onset hypernatremia (<48 hours) is more dangerous than chronic (>48 hours) because the brain has less time to adapt.
Diagnosis
Laboratory Tests
- Serum sodium >145 mEq/L.
- Serum osmolality >295 mOsm/kg.
- Urine osmolality helps distinguish renal vs. extrarenal water loss.
History & Physical Exam
- Assess fluid intake/output.
- Look for signs of dehydration: dry mucous membranes, hypotension, tachycardia.
Management of Hypernatremia
Step 1: Identify the Cause
- Correct underlying cause: e.g., stop diuretics, manage diabetes insipidus
Step 2: Correct Fluid Imbalance
- Mild/moderate: Oral or IV hypotonic fluids (0.45% saline).
- Severe: 5% dextrose in water (D5W) IV.
Rate of Correction:
- Chronic hypernatremia: ≤10–12 mEq/L per 24 hours.
- Rapid correction may cause cerebral edema.
Step 3: Monitor
- Check serum sodium every 2–4 hours during correction.
- Monitor neurological status and urine output.
Complications of Untreated Hypernatremia
- Cerebral hemorrhage or edema
- Seizures and permanent neurological damage
- Death in severe cases
Prevention Tips
- Ensure adequate water intake, especially in elderly or sick patients.
- Monitor sodium levels in high-risk patients (ICU, post-surgery, diuretic therapy).
- Treat underlying causes promptly.
Conclusion
Hypernatremia is a potentially life-threatening electrolyte disorder. Early recognition, accurate diagnosis, and careful management of fluid therapy are key to preventing severe complications. Awareness of causes, symptoms, and preventive strategies can significantly improve patient outcomes.