By Cat Troiano
Monitoring potassium levels is an important step in providing care to patients, particularly those who are taking antihypertensive medications as well as those with kidney disease or gastrointestinal conditions.
What is Potassium?
Potassium is a macromineral that acts as an electrolyte to facilitate communication between nerves and muscles, and transportation of nutrients to cells and of wastes from cells. Potassium plays in essential role in cardiac function. While skeletal muscles, the ones that endure those resistance-training workouts, are voluntary and require the efforts of the exerciser in addition to the biochemical reactions that take place in the body with the onset of physical activity, cardiac muscle is involuntary and must work continuously and efficiently to maintain blood perfusion and sustain life. Potassium aids in ensuring that nerve signals reach all of the body’s muscles, including those heart muscles so that they keep pumping. Potassium, along with sodium, which is another electrolyte, helps to regulate the amount of fluid maintained in and around the cells throughout the body. If a patient is dehydrated, the blood viscosity increases and the blood volume decreases, putting a strain on the heart as is beats faster to pump out the blood into circulation.
How Are Potassium Levels Maintained?
Potassium levels are maintained by aldosterone, which is a hormone that is produced in the adrenal glands. Aldosterone limits urinary sodium excretion from the body. Vasopressin, a hormone that is produced in the pituitary gland, acts as an antidiuretic to reduce urinary water excretion from the body. When the body is at risk for becoming dehydrated, such as when an individual sweats through his or her exercise workout, the adrenal gland and pituitary gland increase their secretions of these hormones in an effort to combat the loss of fluid and sodium as the heart rate and stroke volume increase to deliver more nutrient-rich blood to the active muscle cells. This is a normal metabolic reaction to exercise, and all of these levels return to normal after a workout has concluded. Conversely, when fluid levels become elevated, such as when drinking excessively high volumes of water in one sitting, the proportion of electrolytes becomes diluted, which is a potentially fatal condition known as hypernatremia. However, there are also health conditions that can lead to potassium imbalances, and individuals with these conditions must be closely monitored.
Which Patients Should Have Potassium Levels Monitored?
Patients who are being treated for hypertension should have their potassium levels evaluated periodically. Many of the medications used to treat hypertension act as diuretics, resulting in increased urination. Potassium levels should also be monitored in:
- Patients with kidney disease
- Patients with diabetic ketoacidosis
- Patients who present with muscle weakness
- Patients who present with cardiac arrhythmias
A blood serum potassium level is included as part of a basic metabolic profile as well as of an electrolyte panel. An electrolyte panel evaluates the level of potassium as well as those of sodium, chloride and bicarbonate.
The normal reference range for a blood potassium level 3.5 to 5.0 mEq/L
It is important to note that any ruptured blood cells within the sample collection tube will release potassium into the blood sample, which can result in a falsely elevated result. For this reason, all abnormally high potassium results should prompt a repeat test to verify the result. When initial potassium level tests yield either abnormally high or abnormally low results, ordering an evaluation of urine potassium levels is recommended as well.
The normal reference range for a urine potassium level in an adult patient is 25 to 125 mEq/L
What Does an Elevated Blood Potassium Level Indicate?
An abnormally high blood potassium level is diagnosed as hyperkalemia. The most common cause of hyperkalemia is advanced kidney disease. As the kidneys degenerate, renal insufficiency prevents adequate filtration of excess potassium from the blood to be excreted through urination. Thus, the potassium level in the blood increases as the kidney disease advances.
Other causes of hyperkalemia include:
- Type 1 diabetes
- Addison’s disease, a condition that compromised adrenal gland function
- Rhabdomyolysis, a potentially life-threatening muscle injury that can result in renal failure
- Tissue trauma, such as burns or surgical procedures
- Beta blocker medications
- Angiotensin-converting enzyme inhibitors
- Nonsteroidal anti-inflammatory drugs
- Angiotensin II receptor blockers
- Calcium channel blockers
- Overuse of potassium supplementation
- Some anticoagulant drugs, such as heparin
Signs and symptoms of hyperkalemia include:
- Muscle weakness
- Muscle fatigue
- Decreased appetite
- Cardiac arrhythmias
Treatment for mild to moderate cases of hyperkalemia typically include changing a medication that may be the cause of the condition, discontinuing potassium supplementation, reducing dietary intake of potassium-rich foods or use of medications, including diuretic drugs, insulin or potassium binders to help the body eliminate potassium from the gastrointestinal tract prior to absorption.
What Does a Low Blood Potassium Level Indicate?
An abnormally low blood potassium level is diagnosed as hypokalemia, which tends to occur more commonly in female patients and in older individuals. Causes of hypokalemia include:
- Insulin overdose
- Diabetic ketoacidosis
- Diuretic drugs
- Certain corticosteroid drugs
- Certain antibiotic drugs
- Beta-adrenergic bronchodilators
- Chemotherapy drugs
- excessive alcohol consumption
- Use of laxatives and enemas
- Folic acid deficiency
Signs and symptoms of hypokalemia include:
- muscle weakness
- muscle cramps
- cardiac arrhythmias
Treatment for mild to moderate cases of hypokalemia include treating the underlying cause of diarrhea and vomiting, treating dehydration, discontinuing drugs that may be causing the condition or recommending the increased dietary intake of potassium-rich foods.
Patients whose potassium levels are revealed to be less than 3.0 or greater than 6.0 must pursue immediate care, as such numbers may be life-threatening. Excessively high or low potassium levels can result in cardiac arrhythmias and cardiac arrest. Such cases require intravenous fluid therapy and hospitalization to restore normal electrolyte balances.
Unlike most vitamins, most minerals are found in the body as well as taken in through food. Potassium, as well as sodium, chloride, fluoride and iodide, have a high level of bioavailability, meaning that higher proportions of these minerals are readily absorbed and utilized by the body to carry out their metabolic functions.
Foods that are rich in potassium include:
- Sweet potatoes and potatoes
- Beets and beet greens
- Dried fruits, such as raisins or dried apricots
- Yellowfin tuna
- White beans
The daily adequate intake of potassium for healthy men and healthy nonpregnant, nonbreastfeeding women is 4,700 milligrams.
Testing, and monitoring when necessary, blood potassium levels is a crucial key in preserving critical cardiac, muscle and nerve functions in your patients.