GENERAL APPROACH
- intake:
- redistribution:
output:
urinary
non-urinary
-> upper GI
-> mid GI
-> lower GI
-> other – skin, bleeding, sweat, RRT
POTASSIUM
Hyperkalaemia
- intake: oral intake, blood transfusion
- redistribution: acidosis, rhabdomyolysis, tumour lysis
- output:
urinary – RTA type 4, renal failure, adrenal insufficiency, DM, K+ sparring diuretics
Hypokalaemia
- intake: inadequate intake
- redistribution: alkalosis, hypoMg2+, glucose infusion, periodic paralysis, beta-agonists
- output:
urinary – steroids (ex or en), DKA, hyperaldosteronism, Cushings, RTA, diuretics
non-urinary
-> upper GI – vomiting
-> mid GI – fistula
-> lower GI – diarrhoea
-> other – sweat, burns, bleeding, RRT
MAGNESIUM
Hypermagnasaemia
- intake: usually iatrogenic (Mg infusion)
- redistribution:
- output:
urinary – renal failure increases risk of accumulation
Hypomagnasaemia
- intake: TPN, malabsorption, alcoholism
- redistribution: insulin, hungry bone syndrome
- output:
urinary – RTA, diuretics, polyuria from any cause
non-urinary
-> upper GI – NG loss
-> lower GI – diarrhoea
CALCIUM
Hypercalcaemia
- intake: Ca2+, vitamin A or D, hypoMg2+, hypovolaemia, TPN
- redistribution: immobilization, malignancy, hyperparathyroidism, sarcoid, lithium, adrenal insufficiency, endocrine causes (thyrotoxicosis, acromegaly, phaeo)
- output:
urinary – thiazides
Hypocalcaemia
- intake: Ca2+, vitamin D, phenytoin (increased metabolism of vitamin D)
- redistribution: alkalosis, citrate toxicity, hyperphosphataemia, pancreatitis, tumour lysis syndrome, rhabdomyloysis, decreased bone turnover, hypoparathyroidism, drugs (bisphosphonates, PPI’s, SSRI’s, gentamicin)
- output:
urinary – ethylene glycol, cis-platin, protamine, loop diuretics
non-urinary – bleeding, plasmapheresis, citrate RRT
PHOSPHATE
Hyperphosphataemia
- intake:
- redistribution:
- output: urinary
non-urinary
-> upper GI
-> mid GI
-> lower GI
-> other – skin, bleeding, sweat, RRT
Hypophosphataemia
- intake: malnutrition, phosphate binders, vitamin D, malabsorption, TPN
- redistribution: refeeding syndrome, insulin in DKA
- output:
urinary – diuretics, osmotic diuresis, hyperparathyroidism, proximal tubular dysfunction (Fanconi’s syndrome)
non-urinary
-> upper GI
-> mid GI
-> lower GI – diarrhoea
-> other – sweat, burns, sepsis, bleeding
SODIUM
- different to the rest!
- must think of mainly redistribution of H2O
To sort out:
(1) Osmolality
(2) Volume assessment
(3) Where is the H2O being lost from?
HYPOTONIC
Hypovolaemic
- urinary (urinary Na+ high) – diuretics, osmotic diuretics, RTA, salt wasting, mineralocorticoid deficiencies
- non-urinary (urinary Na low)
-> upper GI – vomiting
-> mid GI – pancreatitis, bowel obstruction
-> lower GI – diarrhoea, bowel preparation
-> other – skin, bleeding, sweat
Euvolaemic
-> SIADH (most common)
-> psychogenic polydipsia
-> hypotonic IVF therapy
-> adrenal insufficiency
-> hypothyroidism
Hypervolaemic
-> CHF
-> cirrhosis
-> nephrotic syndrome
-> hypothyroidism
-> pregnancy
-> TURP syndrome
ISOTONIC (pseudohyponatraemia)
- high proteins
- high lipids
HYPERTONIC
- glucose
- mannitol
- sorbitol
- radiocontrast
- advanced renal disease (need to correct osmolality = measured osmolalilty – urea)
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