Disorders of Plasma Potassium Concentration
| Plasma potassiumconcentration (mmol/L) | Classification | Clinical and ECG features |
|---|---|---|
| >6.5 | Severe hyperkalaemia | Often asymptomatic. Muscle weakness may occur. ECG: tall peaked T wave with shortened QT interval → Progressive lengthening of the PR interval and QRS duration → Sine wave QRS pattern → Ventricular standstill or fibrillation. |
| 5.5–6.5 | Moderate hyperkalaemia | May be asymptomatic. |
| 5.0–5.5 | Mild hyperkalaemia | May be asymptomatic. |
| 3.5–5.0 | Normal range | |
| 3.0–3.5 | Mild hypokalaemia | May be asymptomatic. |
| 2.5–3.0 | Moderate hypokalaemia | ECG: arrhythmias may occur, especially in patients with underlying cardiac disorders or taking antiarrhythmic drugs. |
| <2.5 | Severe hypokalaemia | Muscle necrosis may occur. Below 2 mmol/L there may be ascending paralysis, resembling Guillain-Barré syndrome. Ileus. ECG: ST depression, reduced T wave amplitude, increased U wave amplitude. Arrhythmias commonly occur: extrasystoles, atrial fibrillation, atrioventricular block, ventricular tachycardiac and fibrillation. |