Blood Transfusion Reactions: Causes, Symptoms, and Nursing Implications (Copy)
SIADH, or Syndrome of Inappropriate Antidiuretic Hormone Secretion, is a common cause of euvolemic hyponatremia and a favorite topic on the USMLE Step 1 and Step 2. This blog breaks it down with easy mnemonics, clear tables, and visuals, so you can lock this in for test day!
💡 What Is SIADH?
SIADH is a condition where there’s excessive ADH secretion regardless of serum osmolality, leading to water retention and dilutional hyponatremia. The key is inappropriate water retention without edema.
📊 Clinical Features of SIADH
| Feature | Description |
|---|---|
| Serum Sodium | ↓ Hyponatremia (<135 mmol/L) |
| Urine Osmolality | ↑ (>100 mOsm/kg) |
| Urine Sodium | ↑ (>40 mmol/L) |
| Volume Status | Euvolemic (no edema) |
🔍 Common Causes of SIADH (Mnemonic: "SIADH")
Small cell lung carcinoma
Infections (pneumonia, TB)
Anti-psychotics & SSRIs
Drugs (e.g., carbamazepine, cyclophosphamide)
Head injury or CNS disorders
🧪 Key Diagnostic Steps
| Step | Test | Expected Result |
|---|---|---|
| 1 | Serum Sodium | <135 mmol/L |
| 2 | Serum Osmolality | <275 mOsm/kg |
| 3 | Urine Sodium | >40 mmol/L |
| 4 | Urine Osmolality | >100 mOsm/kg |
💊 Management of SIADH
Fluid restriction (first-line)
Salt tablets in some cases
Demeclocycline or vasopressin receptor antagonists (vaptans) for chronic cases
Treat underlying cause
🧠 High-Yield Takeaway
If you see hyponatremia + normal volume + high urine osmolality on the USMLE, think SIADH—especially in a patient with cancer or CNS issues.
Frequently Asked Questions (FAQs)
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Aim for 4-6 focused hours, ensuring you incorporate breaks to avoid burnout.
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Practice mindfulness techniques, take practice exams under realistic conditions, and maintain a balanced lifestyle.
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Set short-term goals, seek support from mentors, and reward yourself for small achievements.
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Regular exercise improves focus, reduces stress, and enhances overall mental clarity.
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KOTC offers personalized learning tools, gamification features, and adaptive question banks to help students stay on track without burnout.
