Hyperkalemia is an increased level of potassium in the blood. Potassium ions are present in high concentrations in our cells. In the blood the normal potassium concentration is quite low ranging approximately from 3.5 to 5.3 mmol/L. If the concentration is below normal, we speak about hypokalemia and in higher concentrations about hyperkalemia.
There are numerous causes of elevated potassium; I shall mention the most common and the most clinically important.
Increased potassium intake
Potassium in high concentration is present in some food, for example in stone fruit. Similar condition occurs when administering the patient potassium in form of dietary supplements or intravenous infusions.
Medications increasing levels of potassium
There are many drugs that do not contain potassium but may cause hyperkalemia by influencing the potassium metabolism. This includes for example ACE-inhibitors (antihypertensive agents) and spironolactone (diuretic agent).
Tumor cells multiply rapidly and parts of the tumor mass often succumb to necrosis. Necrotic cells release potassium and this increases its concentration in blood. This is worsened during chemotherapy and radiotherapy when large numbers of tumor cells are destroyed.
The kidneys excrete potassium into the urine, and therefore their impaired function usually causes increase of potassium in the blood. Total renal failure (either acute failure or advanced stages of chronic failure) accompanied with serious hyperkalemia is a clear indication for dialysis. Such patients must avoid excessive potassium intake in periods between dialysis.
High blood sugar
Potassium is closely linked to blood sugar level (glycemia). Without any complicated details, when there is high blood sugar, potassium concentration also increases and vice versa. This occurs in inadequately treated or untreated patients with diabetes.
This endocrine disorder is related to the lack of a human hormone aldosterone produced in adrenal glands. Aldosterone has many effects including blood minerals. It increases sodium blood level and lowers potassium level. Lack of aldosterone in Addison's disease causes hyperkalemia and hyponatremia (low concentration of sodium ion).
Hyperkalemia may be asymptomatic but usually manifests with fatigue, muscle weakness, diarrhea, confusion and certain ECG changes. The patient suffers from bradycardia and severe forms of hyperkalemia may even cause a sudden cardiac arrest.
Blood potassium level can be easily detected from a sample of venous blood and the ECG may show some characteristic findings in serious cases of hyperkalemia. The diagnostic approach should further focus on finding out the cause of hyperkalemia.
We have to withdraw any current medication increasing the potassium level and apply some potassium-lowering drugs and substances (some diuretics such as furosemide, insulin, calcium). The patient must be adequately hydrated to dilute the blood and reduce the potassium concentration. Severe hyperkalemia not responding to conservative therapy may be solved by dialysis.
In praxis it is wise to apply a glucose infusion with insulin and -or apply some calcium intravenously. This can be well combined with a small intravenous dose of a diuretic agent.