Hyponatremia

Question 1

Approach

Answer 1

1. Serum & urine Na & osmolality
2. Determine if:
   - hypertonic hyponatraemia
   - isotonic hyponatraemia
   - hypotonic hyponatraemia
3. Determine Volume Status
4. Determine likely causes
5. Look for red flags

Question 2

Hypertonic Hyponatraemia: Osmolality > 295

Answer 2

Hyperglycaemia

Mannitol

Question 3

Isotonic Hyponatraemia: 275- 295

Answer 3

hyperlipidaemia

Hyper paraproteinaemia- multiple myeloma

Question 4

Hypotonic Hyponatraemia < 275

Answer 4

Hyper volemia
Euvolemic
Hypo volemic

Question 5

Hyper volemic Hyponatraemia

Answer 5

Urine Na > 20
- Chronic Renal failure
- cerebral salt wasting
Urine Na < 20
- CCF
- Liver cirrhosis
- nephrotic syndrome

Question 6

Euvolemic Hyponatraemia

Answer 6

Urine Osmolality > Serum
- SIADH (urine Na > 20)
- Drugs: SSRI, TCA, NSAIDS, Amphetamine
- Hypothyroidism
Urine osmolality < serum
- water intoxication
- beer potomania
- psychogenic polydipsia

Question 7

Hypo volemic Hyponatraemia

Answer 7

Urine Na > 20
- Salt wasting nephropathy ( CRF, Intersitial nephritis, RTA)
- mineralo corticoid deficiency- addisons dz
- diuretics: thiazides
Urince Na < 20
- 3rd space losses (burns, pancreatitis, peritonitis)
- dehydration: V&D, fistula