Metabolic

Question 1

Hypernatraemia

Answer 1

Hypovolaemic
- GI loss
- skin loss
- third space loss
- diuretics

Euvolaemic
- central DI
- nephrogenic DI
- GI/skin loss

Hypervolaemic
- hyperaldosteronism
- Cushing syndrome
- hypertonic saline

Question 2

Hypercalcaemia

Answer 2

Causes:
Malignancy: myeloma, metastatic lesion
Endocrine: Hyperparathyroidism, thyrotoxicosis
Dehydration
Drugs: lithium, thiazides

Signs: bony pain, polyuria, renal calculi, lethargy, confusion, coma, abdominal pain, constipation, nausea, vomiting, arrhythmias

ECG: short QT, Osborn J wave

Treatment:
IV fluids
Pamidronate 90mg IV
Diuretics: frusemide 40mg IV
Stop drugs

Question 3

Hyponatraemia

Answer 3

Chronicity:
Mild 125-135
Moderate 120-125
Severe < 120

If hyponatraemia < 135
- First check serum osmolality
- If isotonic likely pseudohyponatraemia secondary to increased protein
- If hypertonic may be due to hyperglycaemia or mannitol administration
- If hypotonic < 285mosm/L follow the ongoing pathway:

Check volume status:
- If hypovolaemic check urine sodium
- if urine sodium < 10 extrarenal cause
- D+V
- third spacing
- if urine sodium > 20 renal cause
- diuretic use
- addison’s (salt wasting disease)
- If hypervolaemic check urine sodium
- if urine sodium < 10 extrarenal cause
- CHF, cirrhosis
- if urine sodium > 20 renal cause
- Renal failure ? cause
- If euvolaemic check urine osmolality
- If urinary osmolality > 100mOsm/kg
- SIADH
- SSRIs, tramadol, amphetamines
- hypothyroidism
- If urinary osmolality < 100mOsm/kg
- Tea and toast diet
- Beer potomania
- Psychogenic polydipsia