Alternative Names: Potassium - low; Low blood potassium.
The presence of an abnormally small concentration of potassium ions in the circulating blood; occurs in familial periodic paralysis and in potassium depletion due to excessive loss from the gastrointestinal tract or kidneys. The changes of hypokalemia may include vacuolation of renal tubular epithelial cytoplasm with impairment of urinary concentrating power and acidification, flattening of the T wave of the electrocardiogram, and muscle weakness
- Hypokalemic Syndrome.
- Hypopotassemia Syndrome.
- Low Potassium Syndrome.
- Nephritis, Potassium-Losing.
- Potassium Loss Syndrome.
Potassium is one of the body's major ions. Nearly 98% of the body's potassium is intracellular. The ratio of intracellular to extracellular potassium is important in determining the cellular membrane potential. Small changes in the extracellular potassium level can have profound effects on the function of the cardiovascular and neuromuscular systems.
The kidney determines potassium homeostasis, and excess potassium is excreted in the urine.
Hypokalemia is defined as a potassium level less than 3.5 mEq/L.
Hypokalemia is a metabolic imbalance characterized by extremely low potassium levels in the blood. It is a symptom of another disease or condition, or a side effect of diuretic drugs. The body needs potassium for the contraction of muscles (including the heart), and for the functioning of many complicated proteins (enzymes). Potassium is found primarily in the skeletal muscle and bone, and participates with sodium to contribute to the normal flow of body fluids between the cells in the body. The normal concentration of potassium in the body is regulated by the kidneys through the excretion of urine. When the kidneys are functioning normally, the amount of potassium in the diet is sufficient for use by the body and the excess is usually excreted through urine and sweat. Body chemicals and hormones such as aldosterone also regulate potassium balance. Secretion of the hormone insulin, which is normally stimulated by food, prevents a temporary diet-induced Hypokalemia by increasing cell absorption of potassium. When Hypokalemia occurs, there is an imbalance resulting from a dysfunction in this normal process, or the rapid loss of urine or sweat without replacement of sufficient potassium.
Potassium disorders are the most common electrolyte abnormality in clinical practice. Hypokalemia is usually well tolerated in otherwise healthy people, but it can be life threatening when severe. Even mild or moderate hypokalemia increases mortality and morbidity in patients with cardiovascular disease. Hypokalemia is the result of an abrupt shift of potassium from the extra-cellular compartment into cells or more frequently the result of potassium depletion by abnormal losses (digestive or kidney). Medication (diuretics) is the most common cause of hypokalemia. In some cases the diagnosis is not readily apparent. In this setting, measurement of an urinary potassium excretion and assessment of acid-base balance are often helpful. When hypokalemia is identified, the disorder should be treated by treating the underlying cause.
Mild hypokalemia usually has no symptoms.
Moderate hypokalemia symptoms may include:
- Muscle weakness.
- Cramps during exercise.
- Leg discomfort when sitting still.
Severe hypokalemia symptoms may include:
Causes and Risk factors:
- Trouble breathing.
- Abnormal heartbeat (arrhythmia).
Hypokalemia is most commonly caused by the use of diuretics. Diuretics are drugs that increase the excretion of water and salts in the urine. Diuretics are used to treat a number of medical conditions, including hypertension (high blood pressure), congestive heart failure, liver disease, and kidney disease. However, diuretic treatment can have the side effect of producing hypokalemia. In fact, the most common cause of hypokalemia in the elderly is the use of diuretics. The use of furosemide and thiazide, two commonly used diuretic drugs, can lead to hypokalemia. In contrast, spironolactone and triamterene are diuretics that do not provoke hypokalemia.
Other commons causes of hypokalemia are excessive diarrhea or vomiting. Diarrhea and vomiting can be produced by infections of the gastrointestinal tract. Due to a variety of organisms, including bacteria, protozoa, and viruses, diarrhea is a major world health problem. It is responsible for about a quarter of the 10 million infant deaths that occur each year. Although nearly all of these deaths occur in the poorer parts of Asia and Africa, diarrheal diseases are a leading cause of infant death in the United States. Diarrhea results in various abnormalities, such as dehydration (loss in body water), hyponatremia (low sodium level in the blood), and hypokalemia.
Because of the need for potassium to control muscle action, hypokalemia can cause the heart to stop beating. Young infants are especially at risk for death from this cause, especially where severe diarrhea continues for two weeks or longer. Diarrhea due to laxative abuse is an occasional cause of hypokalemia in the adolescent or adult. Enema abuse is a related cause of hypokalemia. Laxative abuse is especially difficult to diagnose and treat, because patients usually deny the practice. Up to 20% of persons complaining of chronic diarrhea practice laxative abuse. Laxative abuse is often part of eating disorders, such as anorexia nervosa or bulimia nervosa. Hypokalemia that occurs with these eating disorders may be life-threatening.
Surprisingly, the potassium loss that accompanies vomiting is only partly due to loss of potassium from the vomit. Vomiting also has the effect of provoking an increase in potassium loss in the urine. Vomiting expels acid from the mouth, and this loss of acid results in alkalization of the blood. (Alkalization of the blood means that the pH of the blood increases slightly.) An increased blood pH has a direct effect on the kidneys. Alkaline blood provokes the kidneys to release excessive amounts of potassium in the urine. So, severe and continual vomiting can cause excessive losses of potassium from the body and hypokalemia.
A third general cause of hypokalemia is prolonged fasting and starvation. In most people, after three weeks of fasting, blood serum potassium levels will decline to below 3.0 mM and result in severe hypokalemia. However, in some persons, serum potassium may be naturally maintained at about 3.0 mM, even after 100 days of fasting. During fasting, muscle is naturally broken down, and the muscle protein is converted to sugar (glucose) to supply to the brain the glucose which is essential for its functioning. Other organs are able to survive with a mixed supply of fat and glucose. The potassium within the muscle cell is released during the gradual process of muscle breakdown that occurs with starvation, and this can help counteract the trend to hypokalemia during starvation. Eating an unbalanced diet does not cause hypokalemia because most foods, such as fruits (especially bananas, oranges, and melons), vegetables, meat, milk, and cheese, are good sources of potassium. Only foods such as butter, margarine, vegetable oil, soda water, jelly beans, and hard candies are extremely poor in potassium.
Alcoholism occasionally results in hypokalemia. About one half of alcoholics hospitalized for withdrawal symptoms experience hypokalemia. The hypokalemia of alcoholics occurs for a variety of reasons, usually poor nutrition, vomiting, and diarrhea. Hypokalemia can also be caused by hyperaldosteronism; Cushing's syndrome; hereditary kidney defects such as Liddle's syndrome, Bartter's syndrome, and Franconi's syndrome; and eating too much licorice.
Hypokalemia can be measured by acquiring a sample of blood, preparing blood serum, and using a potassium sensitive electrode for measuring the concentration of potassium ions. Atomic absorption spectroscopy can also be used to measure the potassium ions. Since hypokalemia results in abnormalities in heart behavior, the electrocardiogram is usually used in the diagnosis of hypokalemia. The diagnosis of the cause of hypokalemia can be helped by measuring the potassium content of the urine. Where urinary potassium is under 25 mmoles per day, it means that the patient has experienced excessive losses of potassium due to diarrhea. The urinary potassium test is useful in cases where the patient is denying the practice of laxative or enema abuse. In contrast, where hypokalemia is due to the use of diuretic drugs, the content of potassium in the urine will be high—over 40 mmoles per day.
- Serum potassium level <3.5 mEq/L (3.5 mmol/L)
- BUN and creatinine level
- Glucose, magnesium, calcium, and/or phosphorus level if coexistent electrolyte disturbances are suspected.
- Consider digoxin level if the patient is on a digitalis preparation; hypokalemia can potentiate digitalis-induced arrhythmias.
- Consider arterial blood gas (ABG): Alkalosis can cause potassium to shift from extracellular to intracellular.
- CT scan of the adrenal glands is indicated if mineralocorticoid excess is evident (rarely needed emergently).
- T-wave flattening or inverted T waves.
- Prominent U wave that appears as QT prolongation.
- ST-segment depression.
- Ventricular arrhythmias (eg, premature ventricular contractions [PVCs], torsade de pointes, ventricular fibrillation).
- Atrial arrhythmias (eg, premature atrial contractions [PACs], atrial fibrillation).
Serum potassium levels above 3.0 mEq/liter are not considered dangerous or of great concern; they can be treated with potassium replacement by mouth. Levels lower than 3.0 mEq/liter may require intravenous replacement. Decisions are patient-specific and depend upon the diagnosis, the circumstances of the illness, and the patient's ability to tolerate fluid and medication by mouth.
Over the short term, with self-limited illnesses like gastroenteritis with vomiting and diarrhea, the body is able to regulate and restore potassium levels on its own. However, if the hypokalemia is severe, or the losses of potassium are predicted to be ongoing, potassium replacement or supplementation may be required.
In those patients taking diuretics, often a small amount of oral potassium may be prescribed since the loss will continue as long as the medication is prescribed. Oral supplements may be in pill or liquid form, and the dosages are measured in mEq. Common doses are 10-20mEq per day. Alternatively, consumption of foods high in potassium may be suggested for replacement. Bananas, apricots, oranges, and tomatoes are high in potassium content. Since potassium is excreted in the kidney, blood tests that monitor kidney function may be ordered to predict and prevent potassium levels from rising too high.
When potassium needs to be given intravenously, it must be given slowly. Potassium is irritating to the vein and must be given at a rate of approximately 10 mEq per hour. As well, infusing potassium too quickly can cause heart irritation and promote potentially dangerous rhythms like ventricular tachycardia.
Medicine and medications:
Oral is the preferred route for potassium repletion because it is easy to administer, safe, inexpensive, and readily absorbed from the GI tract. For patients with mild hypokalemia and minimal symptoms, oral replacement is sufficient. For patients who have severe hypokalemia and are symptomatic, both intravenous and oral replacement are necessary. While intravenous potassium dosages of up to 40 mEq/h have been advocated, patients should receive no more than 20 mEq/h IV to avoid potential deleterious effects on the cardiac conduction system. Potassium solutions should never be given as an intravenous push and should be administered as a dilute solution. Higher concentrations of intravenous potassium are damaging to the smaller peripheral veins.
Potassium chloride, IV.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
- Potassium chloride, oral (Klor-Con, K-Dur).