Hyperkalemia

Hyperkalemia results in:

1. Inhibition of atrial myocardial depolarization
2. Slowing of heart rate
3. Prolongation of QRS depolarization
4. And may result in ventricular fibrillation or asystole when very severe

The ECG is a poor substitute for serum potassium levels to determine the degree of abnormality.

ECG Findings:

1. From reduction of P wave amplitude and prolongation of PR interval to absence of P waves altogether
2. Increase in QRS duration
3. Increase of QT duration
4. Slowing of heart rate
5. T waves become tall and spiked
6. Decreased R wave amplitude

Etiology:

1. Addison’s Disease (hypoadrenocorticism)
2. Obstructive urinary disease
3. Oliguric, anuric renal disease
4. Acidosis
5. Uncontrolled diabetic ketoacidosis

Treatment:

1. IV fluids, using 0.9% NaCl (if no urinary obstruction)
2. Sodium bicarbonate to correct acidosis
3. Calcium gluconate antagonizes the cardiotoxic effects of potassium
4. IV glucose and insulin may be needed to drive potassium intracellularly
5. Treat the underlying disease

Prognosis: Excellent response to prompt therapy

Comments:

• This disorder must be distinguished from atrial standstill or silent atrium, a diffuse atrial myocardial disorder wherein the atrial tissue is neither capable of initiating an impulse nor being activated (also known as atrioventricular muscular dystrophy). This disorder will not respond to potassium reductive therapy.
• The most specific ECG feature is the absence of P waves. At times these may be difficult to identify in the frontal plane leads. The V leads are usually the best leads to illustrate P waves.