SIADH Flashcards
What is the most common cause of SIADH?
Small cell lung cancer (SCLC) is a major cause due to ectopic ADH secretion.
What medications cause SIADH?
- Cyclophosphamide
- Chlorpropamide
- Carbamazepine
- SSRIs
- MANY more …
What are the most common medications can induce SIADH?
SSRIs, carbamazepine, NSAIDs, vincristine, oxytocin, and cyclophosphamide.
What CNS disorders cause SIADH?
- Trauma
- Stroke
- Infection
What common major infection causes SIADH?
pneumonia
What is the diagnostic criteria for SIADH?
- Hypotonic hyponatremia
- Urine osmolarity greater than 100 mOsm/kg H2O
- Urine sodium greater than 40 mEq/L
What is the preferred first-line treatment for mild-to-moderate SIADH?
- Water restriction (<800 mL/day) with possible inclusion of salt administration.
- Water restriction is the preferred means of correcting mild-to-moderate SIADH.
When is hypertonic saline (3%) used in SIADH?
Used in severe hyponatremia (Na+ <110 mEq/L or neurologic symptoms like seizures or coma).
What is the mechanism of action of demeclocycline in SIADH?
Demeclocycline blocks ADH action in the collecting tubules, increasing free water excretion.
Why is lithium not preferred for SIADH treatment?
Lithium has significant nephrotoxicity and unpredictable response compared to demeclocycline.
How do loop diuretics (e.g., furosemide) help in SIADH?
They decrease urine osmolality by blocking NaCl reabsorption in the loop of Henle, promoting free water excretion.
Why should hypertonic saline be used cautiously in SIADH?
Rapid correction (>8 mEq/L per 24h) can lead to osmotic demyelination syndrome (ODS).
What are the clinical features of SIADH?
Hyponatremia, low serum osmolality, high urine osmolality, high urine sodium (>40 mEq/L), euvolemia.
What is the role of vasopressin receptor antagonists (Vaptans) in SIADH?
Tolvaptan (oral) and conivaptan (IV) block ADH receptors, increasing free water excretion; used for refractory SIADH.
Why are thiazide diuretics contraindicated in SIADH?
Thiazides cause sodium loss greater than water loss, worsening hyponatremia.
What is the educational objective for SIADH treatment?
