Serum K over 5.5

Plasma potassium levels are regulated by a number of factors including aldosterone, acid-base balance and insulin levels. Metabolic acidosis is associated with hyperkalaemia as hydrogen and potassium ions compete with each other for exchange with sodium ions across cell membranes and in the distal tubule.

Causes of hyperkalaemia:

• Decreased excretion
  • acute kidney injury
  • drugs*: potassium sparing diuretics, ACE inhibitors, angiotensin 2 receptor blockers, spironolactone, ciclosporin, heparin, amiloride
  • Addison's disease
  • Aldosterone disease
• Redistribution out of cells
  • metabolic acidosis
  • K released from damaged cells
  • Insulin deficiency
• Increased intake
  • Increased fluids, diet, medications (increased usage of K supplementation)
• Pseudohyperkalaemia - Pseudohyperkalemia is the term applied to the clinical situation in which in vitro lysis of cellular contents leads to measurement of a high serum potassium level that does not reflect the true in vivo level.
  • Prolonged tourniquet time, taken from arm recieving infusion

Foods that are high in potassium:

• salt substitutes (i.e. Contain potassium rather than sodium)
• bananas, oranges, kiwi fruit, avocado, spinach, tomatoes
• beta-blockers interfere with potassium transport into cells and can potentially cause hyperkalaemia in renal failure patients - remember beta-agonists, e.g. Salbutamol, are sometimes used as emergency treatment
• *both unfractionated and low-molecular weight heparin can cause hyperkalaemia. This is thought to be caused by inhibition of aldosterone secretion

Investigations

U and Es:

K > 5.5mmol/L

• Mild - 5.5-5.9