potassium

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  • Potassium
    • Hypokalaemia
      • symptoms
        • dyshythmia, constipation, fatigue, muscle wasting, muscle weakness, spasms, paralysis
      • causes
        • low potassium in diet, malnutrition or starvation
        • gastrointestinal loss, diarrhoea, excessive sweating, vomiting, pancreatic fistulae, GI adenoma
        • urinary loss, diuretics such as thiazides, or cisplatin
        • diabetic ketoacidosis from polyuria, and loss of K from tubules
        • hypomagnesaemia, magnesium required for K processing
        • alkalosis causes a shift of K from plasma and IF into cells, rising HCO3 causes excretion of K
        • renal stenosis and tumours of adrenal glands  due to high aldosterone and high BP leading to excessive urinary loss of K
        • defects in renal salt transporters eg Gitelman's
      • difference between spurious and physiological causes
        • spurious
          • when sample has been left for a long time and in warm conditions
          • in acute leukaemia where potassium moves into leukaemia cells
      • treatment of diuretic associated hypokalaemia
        • switch to a potassium sparing diuretic
    • Hyperkalaemia
      • causes
        • spurious
          • inappropriate blood collection technique due to increased venous pressure and leakage of fluid into EC space, fist clenching leads to release of K into circulation, antiseptic can cause haemolysis, EDTA contamination, incorrect order of draw, IV drip contamination, delayed specimen to lab leads to K leakage into EC fluid, low temps give rise to a slowing of the Na-K ATPase/ red blood cell pump so K moves into the cells, too high centrifugation leads to haemolysis
        • physiological
          • ineffective elimination
            • Renal insufficiency, ACE inhibitors, angiotensin receptor blockers, Potassium-sparing diuretics e.g. amiloride/ spironolactone), NSAIDs, immuno-suppressants, cyclosporin, Addison's disease, Aldosterone deficiency, congenital adrenal hyperplasia, familial hypertension with hyperkalaemia
          • excessive release from cells
            • muscle wasting, burns, blood transusion or hemolysis, acidosis, low insulin, beta-blockers, digoxin
          • excessive intake
            • dietary supplements, KCl
          • familial pseudohyperkalaemia
            • dominant inherited red cell trait
      • symptoms
        • Sickness, heart palpitations, muscle weakness, hyperventilation, cardiac arrhythmias or heart failure
      • treatment of diuretic associated hyperkalaemia
        • IV saline accompanied by a loop diuretic (eg, furosemide). Discontinue potassium-sparing diuretics, ACE inhibitors, angiotensin-receptor blockers and other drugs that inhibit renal K excretion.

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