Hypokalaemia/Hyperkalaemia

28/04/2013 by admin | Renal

Hypokalaemia:

  1. Serum potassium <3.5mmol/L
  2. Mostly attributed by diuretic therapy (increased losses from urinary/GI tracts), poor intake (eating disorders), or a shift to the intracellular compartment (insulin use, or familial periodic paralysis).
    1. o GI losses = vomiting and diarrhoea, laxative abuse, villus adenoma of colon.
    2. o Renal losses = diuretics, mineralocorticoid excess (Conn’s syndrome, Cushing’s syndrome, ectopic ACTH, secondary hyperalderosteronism [RAS/HTN/HF]).
    3. o Drugs = insulin, excess beta-adrenergic receptor stimulation (salbutamol).
  3. Clinical features: asymptomatic, weakness, intestinal ileus, decreased renal concentrating ability and polyuria (with compensatory polydipsia), ECG changes (=flattened T, U-waves, tachyarrhythmias).
    1. o When severe (<2mmol/L) = profound skeletal weakness, flaccid paralysis, respiratory failure.
  4. Mx:
    1. o <2.5mmol/L = give IV potassium chloride (as an infusion not exceeding 20mmol/h at a concentration not exceeding 40mmol/L).
    2. o 2.5-3.5mmol/L = give oral replacement therapy at 80-120mmol/d

 

Hyperkalaemia:

  1. Serum potassium >5.5mmol/L
  2. Main cause: renal failure and impaired potassium excretion.
    1. o Others: Addison’s disease (reduced mineralocorticoid), spironolactone use, ACE inhibitor use, or potassium retaining diuretics (amiloride), cell destruction in haemolysis, cytotoxic drug use, rhabdomyolysis. These effects are marked in pts with pre-existing renal failure.
  3. Can be an artefact due to haemolysis of blood sample. If high – REPEAT!
  4. Clinical features: asymptomatic, muscular weakness, ECG changes (=peaked T, QRS widening, prolonged PR interval, loss of P, and a ‘sine-wave’ appearance), cardiac arrest.
  5. Mx:
    1. o Mild hypokalaemia <6mmol/L = oral or IV potassium should be restricted
    2. o Severe hypokalaemia >6.5mmol/L = medical emergency!
  1. Give IV calcium gluconate (10ml at 10% IV): to cardioprotect
  2. IV glucose and insulin (50ml of 50% glucose and 10 units of short-acting insulin): to shift insulin into cells
  3. Calcium resonium: to bind excess potassium
  4. Dialysis: to filter blood. 
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