A 67 year old man was started on bendroflumethazaide for HTN 2 weeks ago. He has had D&V for the 2 days. He has dry mucous membranes and decreased skin turgor.
U&Es Na = 129mmol/L K = 3.5 mmol/L Ur = 8.0 mmol/L Cr = 100micromol/L
- What is the abnormality?
- How should this patient be managed?
- Hyponatraemia, which is an appropriate response to hypovolaemia caused by D&V
- Volume replacement with 0.9% saline
What are the causes of hyponatraemia when hypovolaemic?
Diarrhoea
Vomiting
Diuretics
Salt losing nephropathy
in hypovolaemia hyponatraemia there is a loss of salt and water
A 57 year old woman has breathlessness worse on lying flat. Her PMHx includes a NSTEMI. She is on ramipril, bisoprolol, aspirin and simvastatin. She has elevated JVP, bibasal crackles and bilateral leg oedema
U&Es Na = 128mmol/L K = 4.5mmol/L Ur = 8.0mmol/L Cr = 100micromol/L
- What is the abnormality?
- What is the treatment?
- Hyponatraemia caused by hypervolaemia, due to underlying cardiac disease
- Fluid restriction and treat the underlying cause
What are the causes of Hyponatraemia with hypervolaemia?
Cardiac failure
Cirrhosis
Nephrotic syndrome
A 55 year old man has jaundice. He has a past history of excessive alcohol intake. He has multiple spider naevi, shifting dullness and splenomegaly
U&Es: Na = 122mmol/L K = 3.5 mmol/L Ur = 2.0mmol/L Cr = 80micromol/L
- What is the abnormality?
- What is the cause?
- What is the treatment?
- Hyponatraemia caused by hypervolaemia. Excess water causes dilution of Na, causing hyponatraemia when there is hypervolaemia
- Cirrhosis
- Fluid restriction and treat the underlying cause
A 40 year old woman presents with fatigue, weight gain, dry skin and cold intolerance. On examination she looks pale
U&Es: Na = 130mmol/L K = 4.2mmol/L Ur = 5.0mmol/L Cr = 65micromol/L
- What is the abnormality?
- What is the underlying cause?
- What is the treatment?
- Hyponatraemia with euvolaemia - no sign of changes in fluid balance
- Hypothyroidism
- Treat the underlying cause - in this case thyroxine replacement
What are the causes of hyponatraemia with euvolaemia?
Hypothyroidism
Adrenal insufficiency
SIADH
A 45 year old woman presents with dizziness and nausea. On examination she looks tanned and has postural hypotension
U&Es: Na = 128mmol/L K = 5.5mmol/L Ur = 9.0mmol/L Cr = 110micromol/L
- What is the abnormality?
- What is the underlying cause?
- What test would show the underlying cause?
- What is the treatment?
- Hyponatraemia with euvolaemia - no sign of change in fluid balance
- Adrenal insufficiency/Addison’s disease
- Short synacthen test
- Treat the underlying cause - give hydrocortisone and fludrocortisone. Must replace the mineralocorticoid and the glucocorticoid
A 62 year old man has chest pain, cough and weight loss. He looks cachectic. He has a 30 year smoking history
U&Es: Na = 125mmol/L K = 3.5mmol/L Ur = 7.0mmol/L Cr = 85micromol/L
- What is the abnormality?
- What is the likely underlying cause?
- What investigation will show the suspected cause?
- Hyponatraemia with euvolaemia, no sign of a change in fluid balance
- Lung cancer, with an tumour ectopically secreting ADH leading to SIADH
- Plasma and urine osmolality
LOW plasma osmolality but HIGH urine osmolality
What is needed to give a diagnosis of SIADH?
No Hypovolaemia No hypothyroidism No adrenal insufficiency Reduced plasma osmolality AND Increased urine osmolality (>100)
What are the possible causes of SIADH?
CNS pathology Lung pathology Drugs (SSRI, TCA, opiates, PPIs, carbamazepine) Tumours Surgery
A 20 year old man presents with polyuria and polydipsia. On examination he has bitemporal hemianopia
U&Es: Na = 150mmol/L K = 4.0mmol/L Ur = 5.0mmol/L Cr = 70micromol/L
- What is the abnormality?
- What is the underlying cause?
- What causes the bitemporal hemianopia?
- Hypernatraemia
- Diabetes insipidus?
- Likely to be inflammation of the pituitary gland that is causing production of excess vasopressin, causing diabetes insipidus. The pituitary gland is located near the optic chiasm and any enlargement can press on this area affecting the visual fields in this pattern
What are the causes of hypernatraemia?
Unreplaced water loss
- GI losses, sweat losses
- Renal losses: osmotic diuresis, reduced ADH release/action (diabetes insipidus)
Patient cannot control water intake e.g. children, children
What hormone is involved in control of water balance and how does it work?
ADH (Vasopressin) produced by the posterior pituitary. Acts to cause water retention in the collecting ducts of the kidneys, through aquaporin 2 water channels
What investigations should be done if diabetes insipidus is suspected?
- Serum glucose (excluded diabetes mellitus)
- Serum potassium (exclude hypokalaemia)
- Serum calcium (exclude hypercalcaemia)
- Plasma and urine osmolality
- Water deprivation test
A 65 year old man with T2DM and HTN presents with malaise and drowsiness. He is on basal bolus insulin regimen, ramipril, amlodipine, simvastatin and aspirin.
U&Es: Na = 125mmol/L K = 6.5mmol/L Ur = 18mmol/L Cr = 250micromol/L
- What is the main abnormality?
- What could the cause be?
- Hyponatraemia and hyperkalaemia
2. Could be due to any factor that affects the renin-angiotensin system e.g. ACE inhibitor
What are the causes of hyperkalaemia?
- Renal impairment - reduced renal excretion
- Drugs - ACE inhibitors, ARBs, spironolactone
- Low aldosterone - Addison’s disease or type 4 tubular acidosis (low renin, low aldosterone)
- Release from cells - rhabdomyolysis, acidosis
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Calcium homeostasis39
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Forensic Toxicology6
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Potassium handling21
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Electrolyte cases17
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Sodium and Fluid Balance30
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Diabetes cases6
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Adrenal cases12
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Hypoglycaemia29
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Assessment of renal function24
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Assessment of renal function 249
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Clinical Chemistry CPC30
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Diabetes CPC1
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Pituitary16
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EMQ on Enzymes, chemistry16
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EMQ on bugs11
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EMQ on Clinical chemistry8
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Enzymes and Cardiac markers32
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Nutrition18
