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Potassium Balance

Normal 3.5-5mmol/l

Hyperkalaemia

Causes

Input Distribution Excretion
  • Excess K therapy
  • Blood transfusion
  • Rhabdomyolisis
  • burns
  • oncology
  • Cellular (cf insulin)
  • Renal failure
  • Renin-Angiotensin-Aldosterone inhibition (aldosterone promotes Na reabsoprtion at expense of K excretion)
  • ACEi
  • K-sparing diuretics
  • Addison's disease (adrenal insufficiency)

Consequence: VF arrest

  • > 6.5mmok/l needs urgent treatment (leads to arrest - hence used as cardioplegic solution)
  • Symptomatic
  • ECG changes:
    • Tall tented T-waves (T-pot), increased PR
    • Wide QRS
    • Sinusoidal pattern

 

Management

  1. Recheck potassium
  2. Cardiac monitoring
  3. Pharmacological treatment
    • 10ml calcium gluconate (10%) IV over 2 mins (cardioprotection)
    • 20U Insulin + 50ml 50% Dextrose IV (drives potassium into cells)
    • Nebulised salbutamol 2.5mg
    • Calcium resonium 15g/8hours PO
  4. Dialysis (persistently high K / pH <7.2)

Hypokalaemia

Input Distribution Excretion
  • Decreased oral intake / starvation
  • Alkalosis / insulin excess
  • Artefact - sampling from drip arm 
  • GIT losses: vomiting, diarrhoea, fistula
  • Renal losses: Conns, cushings, diuretics, RTA 

 

Management

  1. Replacement 
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