Overview
Hypokalaemia, or a reduced serum potassium concentration of <3.5mmol/L, is associated with hyperpolarisation of cardiac myocytes. If severe, hypokalaemia causes abnormal ventricular automaticity which may result in ventricular arrhythmias.
Pathogenesis
Causes of Hypokalaemia
- Inadequate intake
- GI loss - vomiting, high NG output, diarrhoea, fistula, laxative abuse
- Renal loss - Conns, Cushings, ectopic ACTH, loop diuretics, osmotic diuresis, corticosteroids, hypomagnesaemia, RTA
- Compartmental shift - alkalaemia, insulin, refeeding, beta agonists
Manifestations
Clinical Features
- Weakness
- Hypotonicity
- Depression
- Constipation
- Ileus
ECG Findings in Hypokalaemia
Moderate to Severe
- PR prolongation
- ST depression
- T wave flattening or inversion
- Prominent U wave (resulting in an apparent prolonged QT interval)
Life-Threatening
- Torsade de pointes
- Ventricular tachycardia
- Ventricular fibrillation
ECG changes are not typically seen until the potassium concentration is <3.0.
Diagnosis
Severity of Hypokalaemia
- Mild - 3.0 - 3.5 mmol/L
- Moderate - 2.5 - 3.0 mmol/L
- Severe - <2.5 mmol/L
Next Page
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------