Management
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.