Syndrome of inappropriate anti-diuretic hormone SIADH its causes and newest treatment

It means an excessive release of ADH

1. Physiology :

Refer to diabetes insipidus.

2. Etiology :

a. Tumor → oat cell carcinoma.

b. Pulmonary lesion :Legionella pneumonia , T.B.

c. CNS : meningitis, encephalitis & head injuries.

d. Drugs :

cholropropamide,carbamazepine,cyclophosphamide -
3. C / P :

· Increased ADH causes water retention→ water

intoxication → dilutional hyponatremia ( nausea,

vomiting, confusion, headache, convulsions &

coma.)

· No edema because of natriuresis.

4. Investigation :

1. ↓ Na (< 130m.Eq /L )

2. ↓ serum osmolarity(< 270m.osmol/L.) & ↑urine

osmolarity ( > 300 m.osmol/L.)

N.B. : Normal renal , adrenal & thyroid functions.

5. Treatment :

a. Fluid restriction → 800-1000 ml / day.

b. demeclocycline:

i. 600-1200 mg /day → inhibit i action of ADH.

ii. Given to patient unresponsive to fluid restriction.

c. For sever hyponatremia : hypertonic saline 1.8% slowly é

fursemide to treat hyponatremia