Approach to Hyponatremia begins with understanding that it is defined as serum sodium level less than 135 mEq/L. It is one of the most common electrolyte abnormalities encountered in clinical practice and can present with mild symptoms or life-threatening Acute neurological complications.Classification
Classification
Serum Sodium Levels
- Mild: 130–134 mEq/L
- Moderate: 125–129 mEq/L
- Severe: <125 mEq/L
Stepwise Approach to Hyponatremia
Step 1: Check Serum Osmolality
- Hypotonic hyponatremia (most common)
- Isotonic hyponatremia (pseudohyponatremia)
- Hypertonic hyponatremia (e.g., hyperglycemia)
Step 2: Assess Volume Status
- Hypovolemic
- Euvolemic
- Hypervolemic
Step 3: Urine Sodium & Urine Osmolality
- Urine sodium <20 → Extrarenal loss
- Urine sodium >40 → Renal loss or SIADH
Causes Based on Volume Status
Hypovolemic
- Vomiting
- Diarrhea
- Diuretics
Euvolemic
- SIADH
- Hypothyroidism
- Adrenal insufficiency
Hypervolemic
- Heart failure
- Liver cirrhosis
- Nephrotic syndrome
Clinical Features
- Nausea
- Headache
- Confusion
- Seizures
- Coma
Management Overview
Acute Symptomatic
- 3% hypertonic saline
- Correct slowly (avoid central pontine myelinolysis)
Chronic
- Fluid restriction
- Treat underlying cause
Clinical Gold Points
- Rapid correction → Osmotic demyelination syndrome
- SIADH → Euvolemic hyponatremia
- Always calculate corrected sodium in hyperglycemia