Hyponatremia Management Algorithm

1. Starting Point

Hyponatremia

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2. Step 1: Rule out non-hypotonic causes

• Box: Exclude hyperglycemia and other causes of non-hypotonic hyponatremia
  → Result: Hypotonic hyponatremia

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3. Step 2: Assess severity

Decision: Acute or severe symptoms?

• Yes → Consider immediate treatment with hypertonic saline
• No → Proceed to check Urine osmolality

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4. Step 3: Urine Osmolality

Decision: Urine osmolality

• < 100 mOsm/kg
  → Consider:
  • Primary polydipsia
  • Low solute intake
  • Beer potomania
• ≥ 100 mOsm/kg
  → Proceed to check Urine sodium

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5. Step 4: Urine Sodium

Decision: Urine sodium

• < 30 mmol/L
  → Indicates Low effective arterial blood volume Then check:
  • If ECF expanded, consider:
    • Heart failure
    • Liver cirrhosis
    • Nephrotic syndrome
  • If ECF contracted, consider:
    • Diarrhea and vomiting
    • Third spacing
    • Remote diuretics
• ≥ 30 mmol/L
  → Check if Patient on diuretics?

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6. Step 5: Diuretic use

If Yes:

• Consider diuretics as cause
• Still consider all other causes

If No:

• If ECF contracted, consider:
  • Vomiting
  • 1° adrenal insufficiency
  • Renal salt wasting
  • Cerebral salt wasting
• If ECF normal, consider:
  • SIADH
  • 2° adrenal insufficiency
  • (Hypothyroidism)
• Also consider: Occult diuretics as cause

Source