Hyperkalemia is an electrolyte abnormality with adverse clinical outcome or death if not treated properly.
Most patients with hyperkalemia slightly over 5 mmol/l are asymptomatic. When present, symptoms are nonspecific and predominantly related to muscular or cardiac function.
Hyperkalemia can result from any of the following reasons, which often occur in combination:
Hyperkalemia = potassium level > 5.5 mmol/l
Moderate hyperkalemia > 6.0 mmol/l
Severe hyperkalemia > 7.0 mmol/l
ECG findings generally correlate with the potassium level, but potentially life-threatening arrhythmias can occur without warning at almost any level of hyperkalemia.
Early ECG changes of hyperkalemia (5.5-6.5mmol/l)
ECG changes if blood potassium is 6.5-8.0 mmol/l
At a serum potassium level higher than 8.0 mmol/l, the ECG shows the following
Sensitivity of ECG changes is not very high - 34-43%, but specificity is about 85%.
!! Suspect hyperkalaemia in any patient with a new bradyarrhythmia or AV block, especially patients with renal failure, on haemodialysis or taking any combination of ACE inhibitors, potassium-sparing diuretics and potassium supplements.
ECG 1 Hyperkalemia 6.5 mmol/l in a patient with chronic renal failure (slight ST elevations in I, II, avL, peaked T waves in I, II, aVF, V2-V6)
ECG 2A Iatrogenic hyperkalemia in a patient with renal failure (wide QRS complexes, ST deviations, peaked waves)
ECG 2B ECG of the same patient after reverting hyperkalemia
The aggressiveness of therapy is directly related to the rapidity with which hyperkalemia has developed, the absolute level of hyperkalemia, and the evidence of cardiotoxicity.