What is hyperkalemia?
Hyperkalemia is a common diagnosis. Fortunately, most patients who are diagnosed have mild hyperkalemia (which is usually well tolerated). However, any condition causing even mild hyperkalemia should be treated to prevent progression into more severe hyperkalemia. Extremely high levels of potassium in the blood (severe hyperkalemia) can lead to cardiac arrest and death. When not recognized and treated properly, severe hyperkalemia results in a high mortality rate.
Technically, hyperkalemia means an abnormally elevated level of potassium in the blood. The normal potassium level in the blood is 3.5-5.0 milliequivalents per liter (mEq/L). Potassium levels between 5.1 mEq/L to 6.0 mEq/L reflect mild hyperkalemia. Potassium levels of 6.1 mEq/L to 7.0 mEq/L are moderate hyperkalemia, and levels above 7 mEq/L are severe hyperkalemia.
How does hyperkalemia affect the body?
Potassium is critical for the normal functioning of the muscles, heart, and nerves. It plays an important role in controlling activity of smooth muscle (such as the muscle found in the digestive tract) and skeletal muscle (muscles of the extremities and torso), as well as the muscles of the heart. It is also important for normal transmission of electrical signals throughout the nervous system within the body.
Normal blood levels of potassium are critical for maintaining normal heart electrical rhythm. Both low blood potassium levels (hypokalemia) and high blood potassium levels (hyperkalemia) can lead to abnormal heart rhythms.
The most important clinical effect of hyperkalemia is related to electrical rhythm of the heart. While mild hyperkalemia probably has a limited effect on the heart, moderate hyperkalemia can produce EKG changes (EKG is a reading of theelectrical activity of the heart muscles), and severe hyperkalemia can cause suppression of electrical activity of the heart and can cause the heart to stop beating.
Another important effect of hyperkalemia is interference with functioning of the skeletal muscles. Hyperkalemic periodic paralysis is a rare inherited disorder in which patients can develop sudden onset of hyperkalemia which in turn causes muscle paralysis. The reason for the muscle paralysis is not clearly understood, but it is probably due to hyperkalemia suppressing the electrical activity of the muscle.
What are the symptoms of hyperkalemia?
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Hyperkalemia can be asymptomatic, meaning that it causes no symptoms. Sometimes, patients with hyperkalemia report vague symptoms including:
- muscle weakness, or
- tingling sensations.
More serious symptoms of hyperkalemia include slow heartbeat and weak pulse. Severe hyperkalemia can result in fatal cardiac standstill (heart stoppage). Generally, a slowly rising potassium level (such as with chronic kidney failure) is better tolerated than an abrupt rise in potassium levels. Unless the rise in potassium has been very rapid, symptoms of hyperkalemia are usually not apparent until potassium levels are very high (typically 7.0 mEq/l or higher).
Symptoms may also be present that reflect the underlying medical conditions that are causing the hyperkalemia.
What causes hyperkalemia?
The major causes of hyperkalemia are kidney dysfunction, diseases of the adrenal gland, potassium sifting out of cells into the blood circulation, and medications.
Hyperkalemia and kidney dysfunction
Potassium is normally excreted by the kidneys, so disorders that decrease the function of the kidneys can result in hyperkalemia. These include:
- acute and chronic renal failure,
- lupus nephritis,
- transplant rejection, and
- obstructive diseases of the urinary tract, such as urolithiasis (stones in the urinary tract).
Furthermore, patients with kidney dysfunctions are especially sensitive to medications that can increase blood potassium levels. For example, patients with kidney dysfunctions can develop worsening hyperkalemia when given salt substitutes that contain potassium, potassium supplements (either orally or intravenously), or medications that can increase blood potassium levels. Examples of medications that can increase blood potassium levels include:
- ACE inhibitors,
- nonsteroidal anti-inflammatory drugs (NSAIDs),
- Angiotensin II Receptor Blockers (ARBs), and
- potassium-sparing diuretics
Hypokalemia (low serum potassium)
Low potassium (hypokalemia) refers to a lower than normal potassium level in your bloodstream. Potassium is a chemical (electrolyte) that is critical to the proper functioning of nerve and muscles cells, particularly heart muscle cells.
Normally, your blood potassium level is 3.6 to 5.2 millimoles per liter (mmol/L). A very low potassium level (less than 2.5 mmol/L) can be life-threatening and requires urgent medical attention.
Low potassium (hypokalemia) has many causes. The most common cause is excessive potassium loss in urine due to prescription water or fluid pills (diuretics). Vomiting or diarrhea or both can result in excessive potassium loss from the digestive tract. Only rarely is low potassium caused by not getting enough potassium in your diet.
Causes of potassium loss leading to low potassium include:
- Chronic kidney disease
- Diabetic ketoacidosis
- Diarrhea(causing anal irritation)
- Excessive alcohol use
- Excessive laxative use
- Excessive sweating
- Folic acid deficiency
- Prescription water or fluid pills (diuretics) use
- Primary aldosteronism
- Some antibiotic use
A small drop in potassium level often does not cause symptoms, which may be mild, and may include:
- Feeling of skipped heart beats orpalpitations
- Muscle damage
- Muscle weakness or spasms
- Tingling or numbness
A large drop in potassium level may lead to abnormal heart rhythms, especially in people with heart disease. This can cause you to feel lightheaded or faint. A very low potassium level can even cause your heart to stop.