- Serum potassium <3.5mmol/L
- 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).
- o GI losses = vomiting and diarrhoea, laxative abuse, villus adenoma of colon.
- o Renal losses = diuretics, mineralocorticoid excess (Conn’s syndrome, Cushing’s syndrome, ectopic ACTH, secondary hyperalderosteronism [RAS/HTN/HF]).
- o Drugs = insulin, excess beta-adrenergic receptor stimulation (salbutamol).
- Clinical features: asymptomatic, weakness, intestinal ileus, decreased renal concentrating ability and polyuria (with compensatory polydipsia), ECG changes (=flattened T, U-waves, tachyarrhythmias).
- o When severe (<2mmol/L) = profound skeletal weakness, flaccid paralysis, respiratory failure.
- o <2.5mmol/L = give IV potassium chloride (as an infusion not exceeding 20mmol/h at a concentration not exceeding 40mmol/L).
- o 2.5-3.5mmol/L = give oral replacement therapy at 80-120mmol/d
- Serum potassium >5.5mmol/L
- Main cause: renal failure and impaired potassium excretion.
- 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.
- Can be an artefact due to haemolysis of blood sample. If high – REPEAT!
- Clinical features: asymptomatic, muscular weakness, ECG changes (=peaked T, QRS widening, prolonged PR interval, loss of P, and a ‘sine-wave’ appearance), cardiac arrest.
- o Mild hypokalaemia <6mmol/L = oral or IV potassium should be restricted
- o Severe hypokalaemia >6.5mmol/L = medical emergency!
- Give IV calcium gluconate (10ml at 10% IV): to cardioprotect
- IV glucose and insulin (50ml of 50% glucose and 10 units of short-acting insulin): to shift insulin into cells
- Calcium resonium: to bind excess potassium
- Dialysis: to filter blood.