Symptoms and Arrhythmias

Even severe hypokalaemia may be totally asymptomatic. Symptoms, when they occur, are due to decreased excitability of neuromuscular cardiac function. Muscular weakness, constipation and ileus are common [10].

In patients with pre-existing ischaemic myocardial damage there is an increased incidence of arrhythmias. Severe hypokalaemia, K_(s) < 2.5 mmol/l can cause rhabdomyolysis and when K_(s) < 2.0 mmol/l this can cause ascending paralysis with eventual respiratory arrest.

Patients may present with polyuria and polydipsia due to an impaired ability to concentrate urine.

Learning bite

In patients taking digoxin, hypokalaemia increases the incidence of arrhythmias.

Arrhythmias

Hypokalaemia, especially after acute myocardial infarction (MI), can predispose to VF and VT. Correction of the potassium may be required in such cases for antiarrhythmic drugs to be effective.

Sotalol is more likely to induce arrhythmias, such as torsades, in patients with hypokalaemia.

Learning bite

Arrhythmias are far more likely in patients with heart failure, ventricular hypertrophy and ischaemic heart disease who have abnormal potassium levels.