SIADH

Question 1

What is SIADH?

Answer 1

TOO MUCH ADH

Continued secretion despite plasma being very dilute leading to retention of water and XS blood volume -> hyponatraemia

Question 2

What are the causes of SIADH?

Answer 2

1. Malignancy - SCLC
2. Neuro - stroke, SAH, inf
3. Drugs - SSRIs, amiodarone, carbamazepine, vincristine, cyclophosphamide

Question 3

what are the clinical features?

Answer 3

• Hyponatraemia sx
• Varied + generic
• Anorexia/nausea + malaise
• weakness and aches
• Confusion
• fits and coma

Question 4

How would u diagnose?

Answer 4

Hyponatraemia
Low serum osmolality
High urine osmolality
if euvolaemic, urine Na >40mmol/L consistent w SIADH

Question 5

How would u distinguish SIADH from salt and water depletion?

Answer 5

Give 1-2L 0.9% saline, serum Na will improve, in SIADH this will not

Question 6

What is the treatment of SIADH?

Answer 6

Rx underlying cause
Restrict fluid intake to 500-1000ml daily to increase Na+ conc + reduce sx
Hypertonic saline (conc w salt) if rlly symptomatic
- ORAL DEMECLOCYCLINE - inhibits action of ADH on kidney
- ORAL TOLVAPTAN - ADH antagonist
- ORAL FUROSEMIDE - if severe + to prevent circulatory overload