The amount of potassium (K+) in the blood determines the excitability of nerve and muscle cells, including the heart muscle or myocardium. When potassium levels in the blood rise, this reduces the electrical potential and can lead to potentially fatal abnormal heart rhythms.
High serum potassium levels also called hyperkalemia can be life threatening and requires immediate therapy. There are several conditions which can significantly affect serum potassium levels and cause them to rise.
Metabolic acidosis causes an increase in serum pH which has a direct effect on serum levels of potassium. When serum pH drops (metabolic acidosis) serum potassium rises, and potassium shifts from intracellular to extracellular (into the blood).
Another condition that is a common cause of hyperkalemia is end-stage renal disease. When the kidneys fail, they can no longer remove excess potassium, and it accumulates in the blood.
Signs and symptoms of hyperkalemia include weakness, ascending paralysis, and respiratory failure.
There are some ECG signs that may suggest hyperkalemia. Mild hyperkalemia can cause peaked T waves.
As potassium levels continue to rise, you may see flattened p-waves, prolonged PR-interval, and other anomalies. If hyperkalemia is left untreated you may see idioventricular rhythms and a sine-wave pattern. Severe hyperkalemia can lead to asystolic cardiac arrest.
The treatment of hyperkalemia depends on the severity and the patient’s clinical presentation.
For mild hyperkalemia removal of potassium from the body is achieved with diuretics which cause the release of potassium in the urine. One example of a diuretic which does not spare potassium is furosemide.
Resins like Kayexalate can also be used to remove potassium from the body. Kayexalate can be administered orally or by retention enema.
For moderate elevation, potassium can be shifted from the vascular space (serum) to intracellular space using the 3 methods listed below:
- The administration of glucose + insulin (50ml D50 + 10 units regular insulin) can be given over 15 to 30 minutes.
- Nebulized albuterol: 10 to 15 mg nebulized over 15 minutes
- Sodium Bicarbonate: 50 mEq IV over 5 minutes
For severe elevation, both removal of potassium from the body and shifting potassium to the intracellular space is critical. The measures listed above in each category should be utilized. Along with this, Calcium Chloride should be given over 2 to 5 minutes to reduce the effects of high potassium levels on the heart. When hyperkalemia is severe, administration of calcium chloride lowers the risk of ventricular fibrillation.
The table below contains the medications listed above and their most common dosages.