The decision of when to treat and how to treat patients with hypokalaemia must be based on the clinical state of the patient

State of Patient Possible Management
Mild hypokalaemia Dietary supplementation and monitoring
Potassium administration
Magnesium supplementation
Moderate hypokalaemia Potassium administration
Magnesium supplementation
Severe hypokalaemia Intravenous potassium replacement
Magnesium administration
Cardiac arrest Potassium chloride administration
Further investigation Determine cause

Mild/moderate hypokalaemia

Most patients who are asymptomatic with mild hypokalaemia do not require urgent correction (unless cardiac disease is present). Dietary supplementation and monitoring may suffice.

The treatment of hypokalaemia involves potassium administration. The deficit, calculated from serum potasssium, crudely approximates at 0.3 mmol/l for every 100 mmol reduction in body potassium. Thus the deficit is considerable despite small reductions in serum levels. Replacement must be gradual. Magnesium deficiency is associated with potassium depletion and magnesium supplementation facilitates more rapid correction of hypokalaemia. Magnesium levels should be obtained to determine coexistent hypomagnesaemia.

Severe hypokalaemia

In severe hypokalaemia intravenous replacement must be used. This must be rigorously controlled using infusion pumps according to local protocols.

The maximal rate of correction is 20 mmol/h K+. Some authorities recommend that the unstable patient suffering from rhythm disturbances may receive a rapid initial infusion of 2 mmol/min over 10 minutes if cardiac arrest is imminent.

Magnesium administration (5 ml of 50% over 30 minutes) should commence soon after. Never bolus inject potassium and always ensure adequate mixing of the solution occurs before the infusion is started.

Learning bite

  • Potassium replacement requires cardiac monitoring.
  • Take special care in patients with low serum potassium due to transcellular potassium shifts. Rebound hyperkalaemia can occur quickly.

Cardiac arrest

Cardiac arrest due to hypokalaemia may require 20 mmol potassium chloride IV over 2-3 minutes, repeated until potassium is > 4.0 mmol/l. Prompt correction increases the chances of successful defibrillation and may decrease the incidence of post arrest arrhythmias.

Further investigation

Longer term further investigation is directed towards the cause. It may involve measurement of renin, aldosterone and computerised tomography (CT) of adrenal glands.

Learning bite

Mortality in patients with hypokalaemia in hospital is ten fold higher than the general hospitalised population. It is important to detect, monitor and treat the condition correctly.