Hypokalaemia

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LogoWarningBox4.pngSevere Hypokalaemia [K+] < 2.5 mmol/l should be treated urgently. Hypokalaemia exacerbates digoxin toxicity. Consult local guidelines on precise emergency management.

Potassium is the major intracellular cation.

  • Hypokalaemia is regarded as a plasma [K+] < 3.5 mmol/l
  • Severe hypokalaemia is regarded as a plasma [K+] < 2.5 mmol/l and should be treated urgently.
  • Hypokalaemia can be as arrhythmogenic as hyperkalaemia.

Comprehensive review in [1]

Contents

Clinical

Symptoms

Symptoms can be non-specific and can be unrecognised.

  • Asymptomatic
  • Weakness
  • Lethargy
  • Reduced tone
  • Tetany
  • Depression

Investigations

Plasma [K+] < 3.5 mmol/l

Hypokalaemia/hypokalaemia ECG will show changes

  • U waves
  • Reduced amplitude T waves

Causes

Treatment

Urgency depends on clinical symptoms, the K+ level and the patient. Approach is to:

  • Eliminate cause
  • Replace Potassium, either i.v. or oral as appropriate
  • Patient may also have a low Magnesium. K+ level will not rise until [Mg] levels has been normalised.

Practical Points

Enough potassium must be given to meet both basal requirements (~1mmol/kg/day) and deficit. As a rough guide, every 1 mmol below the normal range corresponds to a deficiency of 100-200mmol K+.

  1. Oral
    • Sando-K = 12mmol K+ per tablet
    • Kloref = 6.7mmol K+ per tablet
    • Various fruits contain potassium and may be preferrable to the above.[2]
  2. IV therapy
    • through standard fluid bags (usu max. 40mmol per bag)
    • on the general ward, max. 10mmol per hour
    • if central line and cardiac monitoring available, up to 10-20mmol/hour, though such rapid replacement is rarely required.

References