Hypokalaemia: Difference between revisions

| name = Hypokalaemia

| definition = Serum potassium level < 3.5

|}

Upper gastrointestinal fluids don't contain much potassium, so loss of the fluid itself does not cause severe hypokalaemia. However, the resulting hypovolaemia can cause hyperaldosteronism, which can cause hypokalaemia. Lower gastrointestinal fluids, however, contain much potassium, and so loss of these fluids (usually due to diarrhoea) can cause hypokalaemia.

== Pathomechanism ==

Hypokalaemia causes the resting membrane potential of muscle cells to be lower than normal (that is, more negative, also called ''hyperpolarised''). This makes the membranes harder to excite, which causes weakness.

* In the conducting system of the heart, hypokalaemia paradoxically causes depolarisation by triggering sodium influx into cells. This increases membrane excitability in the conducting system, predisposing to arrhythmia.

* In ventricular cells, hypokalaemia delays ventricular repolarisation

== Clinical features ==

Symptoms are more severe if the drop in serum potassium is rapid than if it is chronic. Mild hypokalaemia is usually asymptomatic. Moderate hypokalaemia can cause muscle weakness, constipation, ileus, and restless legs. Severe hypokalaemia can cause arrhythmia, rhabdomyolysis, and paresis. Hyporeflexia is a possible sign.

A urine potassium of > 20 mmol/L in the setting of hypokalaemia is indicative of renal loss of potassium.

== Management ==

Mild hypokalaemia does not usually require hospitalisation, but moderate, severe, or symptomatic hypokalaemia requires hospitalisation. Severe hypokalaemia requires [[intensive care]]. Severe cases should be continously monitored with ECG. The underlying cause should be adressed if possible. Any concomitant hypomagnesaemia must also be treated, as hypomagnesaemia maintains hypokalaemia.