Hyperkalemia

Hyperkalemia is a common electrolyte abnormality that can lead to a variety of ECG changes. In the presence of an elevated potassium with ECG changes most likely related to hyperkalemia, it's important to act fast.

The actual parameters for what constitutes a hyperkalemia can vary by region and institution. Emergency Care BC, for example, suggests rapid treatment for any potassium greater than 6.5 mmol/L, or greater than 5.5 mmol/L with a significant contributor to hyperkalemia (e.g. significant kidney impairment or muscle breakdown).

In the emergency setting, hyperkalemia treatment is largely focused on:

  1. Stabilizing the cardiac membrane - if there are ECG changes, give calcium gluconate (in most cases) or calcium chloride (if pre-arrest).
  2. Shift potassium into the cells - administer dextrose IV and regular insulin. Inhaled beta-agonists (like salbutamol/albuterol) can also be used in conjunction with dextrose and insulin.
  3. Reduce levels of potassium - generally with potassium-excreting diuretics like furosemide.

Use of sodium polystyrene sulfate (Kayexalate) is not indicated in the emergency setting, and there's increasing evidence that the risks of side effects from its use outweighs its benefits. Instead it's more crucicial to deal with the cause of the hyperkalemia in the first place.

Early ECG Changes of Hyperkalemia

Early ECG changes associated with hyperkalemia include a shrinking P wave, prolonged PR interval, prolonged QT interval, and early widening of the QRS complex. The T waves will also be peaked - possibly as tall or taller than the preceding R wave - but narrow.

Worsening ECG Changes of Hyperkalemia

As the hyperkalemia worsens, the QRS complexes will widen and the ventricles will become more and more irritated. This presents as an accelerated idioventricular rhythm.

At very severe levels of hyperkalemia, the QRS complexes will take on this characteristic "sine wave" pattern. These ECG changes are still reversible and decreasing the potassium levels can cause the rhythm to convert back to a sinus rhythm.