Biochemistry transition Flashcards
normal potassium range
3.5-5.3mmol/l
2 most important factors determining potassium excretion
GFR and plasma potassium concentration
severe hyperkalaemia
> 7mmol/l
ECG findings of hyperkalaemia
tall tented T waves
widening of QRS complex (reflects altered myocardial contractility)
categorisation of hyperkalaemia
decreased excretion
redistribution out of cells
increased intake
causes of decreased excretion hyperkalaemia
renal failure
hypoaldosteronism (often occurs with ACEi/ARBs)
causes of redistribution hyperkalaemia
potassium release from damaged cells (rhabdomyolysis, trauma, tumour lysis) metabolic acidosis insulin deficiency pseudohyperkalaemia hyperkalaemic periodic paralysis
causes of increased intake hyperkalaemia
oral drugs administered as potassium salts
IV potassium - should not be given faster than 20mmol/hr except in extreme cases
blood products
treatment of hyperkalaemia
Calcium gluconate/calcium chloride
insulin and glucose
dialysis
what is pseudohyperkalaemia
increase in concentration of potassium due to its movement out of cells during or after venesection
most common causes of pseudohyperkalaemia
delay in centrifuging separating plasma/serum from the cells/clot
In-vitro haemolysis
Increase in platelet and/or white cell count
where is most potassium in the body found
intracellularly
most common cause of hyperkalaemia
renal impairment
symptoms of hypercalcaemia
neuro and psych features - lethargy, confusion, irritability, depression
GI - anorexia, abdominal pain, nausea, vomiting, constipation
Renal - thirst, polyuria, renal calculi
cardiac arrhythmias
most common causes of hypercalcaemia `
primary hyperparathyroidism
hypercalcaemia of malignancy
rarer causes of hypercalcaemia
inappropriate dosage of Vit D or metabolites granulomatous disease thyrotoxicosis thiazides immobilisation renal disease calcium therapy diuretic phase of acute renal failure milk alkali syndrome
treatment of hypercalcaemia
urgent if calcium >3.5mmol/l
IV saline
bisphosphonates (pamidronate - inhibits bone resorption)
surgical removal of parathyroid adenoma
features of familial hypocalciuric hypercalcaemia
high calcium with detectable PTH
often misdiagnosed as primary hyperparathyroidism leading to unnecessary surgery
what tests will give a correct assessment of hypercalcaemia severity
serum calcium
albumin concentration
these make up adjusted calcium
clinical features of adrenal hypofunction
lethargy, anorexia, pigmentation of hands/mouth, abdo pain, weight loss, postural hypotension, vomiting, nausea, dehydration
biochemical features of adrenal hypofunction
hyponatraemia, hyperkalaemia, elevated serum urea
diagnostic test for adrenal hypofunction
short synacthen test
causes of isolated aldosterone deficiency
adrenal lesion - 18hydroxylase defect
primary renin deficiency - anephric patients
