Hypokalemia is a low level of
potassium
Potassium is a chemical element; it has Symbol (chemistry), symbol K (from Neo-Latin ) and atomic number19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to ...
(K
+) in the
blood serum
Serum () is the fluid and solvent component of blood which does not play a role in clotting. It may be defined as blood plasma without the clotting factors, or as blood with all cells and clotting factors removed. Serum contains all proteins ex ...
.
[ Mild low potassium does not typically cause symptoms.] Symptoms may include feeling tired, leg cramps, weakness
Weakness is a symptom of many different medical conditions. The causes are many and can be divided into conditions that have true or perceived muscle weakness. True muscle weakness is a primary symptom of a variety of skeletal muscle diseases, ...
, and constipation
Constipation is a bowel dysfunction that makes bowel movements infrequent or hard to pass. The Human feces, stool is often hard and dry. Other symptoms may include abdominal pain, bloating, and feeling as if one has not completely passed the ...
.[ Low potassium also increases the risk of an abnormal heart rhythm, which is often too slow and can cause ]cardiac arrest
Cardiac arrest (also known as sudden cardiac arrest CA is when the heart suddenly and unexpectedly stops beating. When the heart stops beating, blood cannot properly Circulatory system, circulate around the body and the blood flow to the ...
.[
Causes of hypokalemia include vomiting, ]diarrhea
Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...
, medications like furosemide
Furosemide, sold under the brand name Lasix among others, is a loop diuretic medication used to treat edema due to heart failure, liver scarring, or kidney disease. Furosemide may also be used for the treatment of high blood pressure. It can ...
and steroid
A steroid is an organic compound with four fused compound, fused rings (designated A, B, C, and D) arranged in a specific molecular configuration.
Steroids have two principal biological functions: as important components of cell membranes t ...
s, dialysis, diabetes insipidus
Diabetes insipidus (DI) is a condition characterized by large amounts of dilute urine and increased thirst. The amount of urine produced can be nearly 20 liters per day. Reduction of fluid has little effect on the concentration of the urine. ...
, hyperaldosteronism, hypomagnesemia
Magnesium deficiency is an electrolyte disturbance in which there is a low level of magnesium in the body. Symptoms include tremor, poor coordination, muscle spasms, loss of appetite, personality changes, and nystagmus. Complications may in ...
, and not enough intake in the diet.[ Normal potassium levels in humans are between 3.5 and 5.0 ]mmol/L
Molar concentration (also called molarity, amount concentration or substance concentration) is the number of moles of solute per liter of solution. Specifically, It is a measure of the concentration of a chemical species, in particular, of a sol ...
(3.5 and 5.0 mEq/L) with levels below 3.5 mmol/L defined as hypokalemia. It is classified as severe when levels are less than 2.5 mmol/L.[ Low levels may also be suspected based on an electrocardiogram (ECG).][ The opposite state is called ]hyperkalemia
Hyperkalemia is an elevated level of potassium (K+) in the blood. Normal potassium levels are between 3.5 and 5.0 mmol/L (3.5 and 5.0 mEq/L) with levels above 5.5mmol/L defined as hyperkalemia. Typically hyperkalemia does not cause symptoms. Oc ...
that means high level of potassium in the blood serum.[
The speed at which potassium should be replaced depends on whether or not there are symptoms or abnormalities on an electrocardiogram.][ Potassium levels that are only slightly below the normal range can be managed with changes in the diet.][ Lower levels of potassium require replacement with supplements either taken by mouth or given ]intravenously
Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutr ...
.[ If given intravenously, potassium is generally replaced at rates of less than 20 mmol/hour.][ Solutions containing high concentrations of potassium (>40 mmol/L) should generally be given using a ]central venous catheter
A central venous catheter (CVC), also known as a central line (c-line), central venous line, or central venous access catheter, is a catheter placed into a large vein. It is a form of venous access. Placement of larger catheters in more centr ...
.[ ]Magnesium
Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...
replacement may also be required.[
Hypokalemia is one of the most common ]water–electrolyte imbalance
Electrolyte imbalance, or water-electrolyte imbalance, is an abnormality in the concentration of electrolytes in the body. Electrolytes play a vital role in maintaining homeostasis in the body. They help to regulate heart and neurological function ...
s.[ It affects about 20% of people admitted to hospital.] The word ''hypokalemia'' comes from ''hypo-'' 'under' + ''kalium'' 'potassium' + ''-emia'' 'blood condition'.
Signs and symptoms
Mild hypokalemia is often without symptoms. Acute potassium depletion through severe dietary restriction leads to hypokalemia and elevation
The elevation of a geographic location (geography), ''location'' is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational equipotenti ...
of blood pressure
Blood pressure (BP) is the pressure of Circulatory system, circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term ...
. Severe hypokalemia, with serum potassium concentrations of 2.5–3 meq/L (Nl: 3.5–5.0 meq/L), may cause muscle weakness
Muscle weakness is a lack of muscle strength. Its causes are many and can be divided into conditions that have either true or perceived muscle weakness. True muscle weakness is a primary symptom of a variety of skeletal muscle diseases, includ ...
, myalgia
Myalgia or muscle pain is a painful sensation evolving from muscle tissue. It is a symptom of many diseases. The most common cause of acute myalgia is the overuse of a muscle or group of muscles; another likely cause is viral infection, espec ...
, tremor, and muscle cramps
A cramp is a sudden, involuntary, painful skeletal muscle contraction or overshortening associated with electrical activity. While generally temporary and non-damaging, they can cause significant pain and a paralysis-like immobility of the affe ...
(owing to disturbed function of skeletal muscle
Skeletal muscle (commonly referred to as muscle) is one of the three types of vertebrate muscle tissue, the others being cardiac muscle and smooth muscle. They are part of the somatic nervous system, voluntary muscular system and typically are a ...
), and constipation
Constipation is a bowel dysfunction that makes bowel movements infrequent or hard to pass. The Human feces, stool is often hard and dry. Other symptoms may include abdominal pain, bloating, and feeling as if one has not completely passed the ...
(from disturbed function of smooth muscle
Smooth muscle is one of the three major types of vertebrate muscle tissue, the others being skeletal and cardiac muscle. It can also be found in invertebrates and is controlled by the autonomic nervous system. It is non- striated, so-called bec ...
). With more severe hypokalemia, flaccid paralysis
Flaccid paralysis is a neurological condition characterized by weakness or paralysis and reduced muscle tone without other obvious cause (e.g., trauma). This abnormal condition may be caused by disease or by trauma affecting the nerves associ ...
and hyporeflexia may result. Reports exist of rhabdomyolysis
Rhabdomyolysis (shortened as rhabdo) is a condition in which damaged skeletal muscle breaks down rapidly. Symptoms may include muscle pains, weakness, vomiting, and confusion. There may be tea-colored urine or an irregular heartbeat. Some o ...
occurring with profound hypokalemia with serum potassium levels less than 2 meq/L. Respiratory depression
Hypoventilation (also known as respiratory depression) occurs when ventilation is inadequate (''hypo'' meaning "below") to perform needed respiratory gas exchange. By definition it causes an increased concentration of carbon dioxide (hypercapni ...
from severe impairment of skeletal muscle function is found in some people. Psychological symptoms associated with severe hypokalemia can include delirium, hallucinations, depression, or psychosis.
Causes
Hypokalemia can result from one or more of these medical
Medicine is the science and Praxis (process), practice of caring for patients, managing the Medical diagnosis, diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment, Palliative care, palliation of their injury or disease, ...
conditions:
Inadequate potassium intake
Not eating
Eating (also known as consuming) is the ingestion of food. In biology, this is typically done to provide a heterotrophic organism with energy and nutrients and to allow for growth. Animals and other heterotrophs must eat in order to survive – ...
a diet with enough potassium-containing foods or fasting can cause the gradual onset of hypokalemia. This is a rare cause and may occur in those with anorexia nervosa
Anorexia nervosa (AN), often referred to simply as anorexia, is an eating disorder characterized by Calorie restriction, food restriction, body image disturbance, fear of gaining weight, and an overpowering desire to be thin.
Individuals wit ...
or those on a ketogenic diet
The ketogenic diet is a high-fat, adequate-protein, low-carbohydrate diet, low-carbohydrate dietary therapy that in conventional medicine is used mainly to treat hard-to-control (refractory) epilepsy in children. The diet forces the body to b ...
. In a short-term study, severely low potassium intake (10 meq/day) led to mild hypokalemia at 9 days (mean serum potassium 3.2 meq/L).
Gastrointestinal or skin loss
A more common cause is excessive loss of potassium, often associated with heavy fluid losses that flush potassium out of the body. Typically, this is a consequence of diarrhea
Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...
, excessive perspiration
Perspiration, also known as sweat, is the fluid secreted by sweat glands in the skin of mammals.
Two types of sweat glands can be found in humans: eccrine glands and Apocrine sweat gland, apocrine glands. The eccrine sweat glands are distribu ...
, losses associated with crush injury
A crush injury is injury by an object that causes compression of the body. This form of injury is rare in normal civilian practice, but common following a natural disaster. Other causes include industrial accidents, road traffic collisions, bui ...
, or surgical procedures. Vomiting
Vomiting (also known as emesis, puking and throwing up) is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose.
Vomiting can be the result of ailments like food poisoning, gastroenteritis, pre ...
can also cause hypokalemia, although not much potassium is lost from the vomitus. Rather, heavy urinary losses of K+ in the setting of post-emetic
Vomiting (also known as emesis, puking and throwing up) is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose.
Vomiting can be the result of ailments like food poisoning, gastroenteritis, preg ...
bicarbonaturia force urinary potassium excretion. (See discussion of alkalosis below.) Other gastrointestinal
The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The tract is the largest of the body's systems, after the cardiovascular system. ...
causes include pancreatic fistulae and the presence of adenoma
An adenoma is a benign tumor of epithelium, epithelial tissue with glandular origin, glandular characteristics, or both. Adenomas can grow from many glandular organ (anatomy), organs, including the adrenal glands, pituitary gland, thyroid, prosta ...
.
Urinary loss
* Certain medications can cause excess potassium loss in the urine. Blood pressure medications such as loop diuretic
Loop diuretics are pharmacological agents that primarily inhibit the Na-K-Cl cotransporter located on the luminal membrane of cells along the thick ascending limb of the loop of Henle. They are often used for the treatment of hypertension and e ...
s (e.g. furosemide
Furosemide, sold under the brand name Lasix among others, is a loop diuretic medication used to treat edema due to heart failure, liver scarring, or kidney disease. Furosemide may also be used for the treatment of high blood pressure. It can ...
) and thiazide diuretics (e.g., hydrochlorothiazide
Hydrochlorothiazide, sold under the brand name Hydrodiuril among others, is a diuretic medication used to treat hypertension and swelling due to fluid build-up. Other uses include treating diabetes insipidus and renal tubular acidosis and t ...
) commonly cause hypokalemia. Other medications such as the antifungal amphotericin B
Amphotericin B is an antifungal medication used for serious fungal infections and leishmaniasis. The fungal infections it is used to treat include mucormycosis, aspergillosis, blastomycosis, candidiasis, coccidioidomycosis, and cryptococ ...
or the cancer drug cisplatin
Cisplatin is a chemical compound with chemical formula, formula ''cis''-. It is a coordination complex of platinum that is used as a chemotherapy medication used to treat a number of cancers. These include testicular cancer, ovarian cancer, c ...
can also cause long-term hypokalemia. Diuretic abuse among athletes and people with eating disorder
An eating disorder is a mental disorder defined by abnormal eating behaviors that adversely affect a person's health, physical or mental health, mental health. These behaviors may include eating too much food or too little food. Types of eatin ...
s may present with hypokalemia due to urinary potassium loss.
* A special case of potassium loss occurs with diabetic ketoacidosis
Diabetic ketoacidosis (DKA) is a potentially life-threatening acute complication of diabetes mellitus. Signs and symptoms may include vomiting, abdominal pain, deep gasping breathing, increased urination, weakness, confusion and occasionally ...
. Hypokalemia is observed with low total body potassium and a low intracellular concentration of potassium. In addition to urinary losses from polyuria
Polyuria () is excessive or an abnormally large production or Frequent urination, passage of urine (greater than 2.5 L or 3 L over 24 hours in adults). Increased production and passage of urine may also be termed as diuresis. Polyuria often appe ...
and volume contraction, also an obligate loss of potassium from kidney tubules occurs as a cationic
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
partner to the negatively charged ketone, β-hydroxybutyrate.
* A low level of magnesium in the blood can also cause hypokalemia. Magnesium
Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...
is required for adequate processing of potassium. This may become evident when hypokalemia persists despite potassium supplementation. Other electrolyte abnormalities may also be present.
* An increase in the pH of the blood (alkalosis) can cause temporary hypokalemia by causing a shift of potassium out of the plasma and interstitial fluid
In cell biology, extracellular fluid (ECF) denotes all body fluid outside the Cell (biology), cells of any multicellular organism. Body water, Total body water in healthy adults is about 50–60% (range 45 to 75%) of total body weight; women ...
s into the urine via a number of interrelated mechanisms.
1) Type B intercalated cells in the collecting duct
The collecting duct system of the kidney consists of a series of tubules and ducts that physically connect nephrons to a minor calyx or directly to the renal pelvis. The collecting duct participates in electrolyte and fluid balance through rea ...
reabsorb H+ and secrete HCO3, while in type A intercalated cells protons are secreted via both H+-K+ATPases and H+ ATP-ases on the apical/luminal surface of the cell. By definition, the H+-K+ATPase reabsorbs one potassium ion into the cell for every proton it secretes into the lumen of the collecting duct of a nephron. In addition, when H+ is expelled from the cell (by H+ATP-ase), cations—in this case potassium—are taken up by the cell in order to maintain electroneutrality (but not through direct exchange as with the H+-K+ATPase). In order to correct the pH during alkalosis, these cells will use these mechanisms to reabsorb great amounts of H+, which will concomitantly increase their intracellular concentrations of potassium. This concentration gradient drives potassium to be secreted across the apical surface of the cell into the tubular lumen through potassium channels (this facilitated diffusion occurs in both Type B intercalated cells and Principal cells in the collecting duct).
2) Metabolic alkalosis is often present in states of volume depletion, such as vomiting, so potassium is also lost via aldosterone
Aldosterone is the main mineralocorticoid steroid hormone produced by the zona glomerulosa of the adrenal cortex in the adrenal gland. It is essential for sodium conservation in the kidney, salivary glands, sweat glands, and colon. It plays ...
-mediated mechanisms.
3) During metabolic alkalosis, the acute rise of plasma HCO3− concentration (caused by vomiting, for example) will exceed the capacity of the renal proximal tubule
The proximal tubule is the segment of the nephron in kidneys which begins from the renal (tubular) pole of the Bowman's capsule to the beginning of loop of Henle. At this location, the glomerular parietal epithelial cells (PECs) lining bowman’s ...
to reabsorb this anion
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
, and potassium will be excreted as an obligate cation
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
partner to the bicarbonate.
* Disease states that lead to abnormally high aldosterone
Aldosterone is the main mineralocorticoid steroid hormone produced by the zona glomerulosa of the adrenal cortex in the adrenal gland. It is essential for sodium conservation in the kidney, salivary glands, sweat glands, and colon. It plays ...
levels can cause hypertension and excessive urinary losses of potassium. These include renal artery stenosis
Renal artery stenosis (RAS) is the narrowing of one or both of the renal arteries, most often caused by atherosclerosis or fibromuscular dysplasia. This narrowing of the renal artery can impede blood flow to the target kidney, resulting in r ...
and tumors
A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...
(generally nonmalignant) of the adrenal glands, e.g., Conn's syndrome (primary hyperaldosteronism). Cushing's syndrome
Cushing's syndrome is a collection of signs and symptoms due to prolonged exposure to glucocorticoids such as cortisol. Signs and symptoms may include high blood pressure, abdominal obesity but with thin arms and legs, reddish stretch marks, ...
can also lead to hypokalemia due to excess cortisol binding the Na+/K+ pump and acting like aldosterone. Hypertension and hypokalemia can also be seen with a deficiency of the 11-beta-hydroxysteroid dehydrogenase type 2 enzyme which allows cortisols to stimulate aldosterone receptors. This deficiency—known as apparent mineralocorticoid excess syndrome—can either be congenital or caused by consumption of glycyrrhizin
Glycyrrhizin (glycyrrhizic acid or glycyrrhizinic acid) is the chief sweet-tasting constituent of ''Glycyrrhiza glabra'' (liquorice) root. Structurally, it is a saponin used as an emulsifier and gel-forming agent in foodstuffs and cosmetics. I ...
, which is contained in extract of licorice
Liquorice (Commonwealth English) or licorice (American English; see spelling differences; ) is the common name of ''Glycyrrhiza glabra'', a flowering plant of the bean family Fabaceae, from the root of which a sweet, aromatic flavouring is ...
, sometimes found in herbal supplements, candies, and chewing tobacco.
* Rare hereditary defects of renal salt transporters, such as Bartter syndrome or Gitelman syndrome, can cause hypokalemia, in a manner similar to that of diuretics. As opposed to disease states of primary excesses of aldosterone, blood pressure is either normal or low in Bartter's or Gitelman's.
Distribution away from extracellular fluid
* In addition to alkalosis, other factors can cause transient shifting of potassium into cells, presumably by stimulation of the Na+/K+ pump. These hormones and medications include insulin
Insulin (, from Latin ''insula'', 'island') is a peptide hormone produced by beta cells of the pancreatic islets encoded in humans by the insulin (''INS)'' gene. It is the main Anabolism, anabolic hormone of the body. It regulates the metabol ...
, epinephrine
Adrenaline, also known as epinephrine, is a hormone and medication which is involved in regulating visceral functions (e.g., respiration). It appears as a white microcrystalline granule. Adrenaline is normally produced by the adrenal glands a ...
, and other beta agonists (e.g. salbutamol
Salbutamol, also known as albuterol and sold under the brand name Ventolin among others, is a medication that opens up the medium and large airways in the lungs. It is a short-acting β2 adrenergic receptor agonist that causes relaxation of ...
or salmeterol), and xanthines
Xanthine ( or , from Ancient Greek for its yellowish-white appearance; archaically xanthic acid; systematic name 3,7-dihydropurine-2,6-dione) is a purine base (genetics), base found in most human body tissues and fluids, as well as in other org ...
(e.g. theophylline
Theophylline, also known as 1,3-dimethylxanthine, is a drug that inhibits phosphodiesterase and blocks adenosine receptors. It is used to treat chronic obstructive pulmonary disease (COPD) and asthma. Its pharmacology is similar to other met ...
). Stimulants
Stimulants (also known as central nervous system stimulants, or psychostimulants, or colloquially as uppers) are a class of drugs that increase alertness. They are used for various purposes, such as enhancing attention, motivation, cognitio ...
(amphetamine
Amphetamine (contracted from Alpha and beta carbon, alpha-methylphenethylamine, methylphenethylamine) is a central nervous system (CNS) stimulant that is used in the treatment of attention deficit hyperactivity disorder (ADHD), narcolepsy, an ...
s, methylphenidate
Methylphenidate, sold under the brand names Ritalin ( ) and Concerta ( ) among others, is a central nervous system (CNS) stimulant used in the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy. It may be taken Oral adm ...
, cocaine
Cocaine is a tropane alkaloid and central nervous system stimulant, derived primarily from the leaves of two South American coca plants, ''Erythroxylum coca'' and ''Erythroxylum novogranatense, E. novogranatense'', which are cultivated a ...
) can also cause hypokalemia by stimulating beta-2 receptors.
* Rare hereditary defects of muscular ion channels and transporters that cause hypokalemic periodic paralysis can precipitate occasional attacks of severe hypokalemia and muscle weakness. These defects cause a heightened sensitivity to the normal changes in potassium produced by catecholamine
A catecholamine (; abbreviated CA), most typically a 3,4-dihydroxyphenethylamine, is a monoamine neurotransmitter, an organic compound that has a catechol (benzene with two hydroxyl side groups next to each other) and a side-chain amine.
Cate ...
s and/or insulin
Insulin (, from Latin ''insula'', 'island') is a peptide hormone produced by beta cells of the pancreatic islets encoded in humans by the insulin (''INS)'' gene. It is the main Anabolism, anabolic hormone of the body. It regulates the metabol ...
and/or thyroid hormone
File:Thyroid_system.svg, upright=1.5, The thyroid system of the thyroid hormones triiodothyronine, T3 and T4
rect 376 268 820 433 Thyroid-stimulating hormone
rect 411 200 849 266 Thyrotropin-releasing hormone
rect 297 168 502 200 Hypothalamus
r ...
, which lead to movement of potassium from the extracellular fluid into the muscle cells.
Other
* A handful of published reports describe individuals with severe hypokalemia related to chronic extreme consumption (4–10 L/day) of cola
Cola is a Carbonation, carbonated soft drink flavored with vanilla, cinnamon, citrus essential oil, oils, and other flavorings. Cola became popular worldwide after the American pharmacist John Stith Pemberton invented Coca-Cola, a trademarked br ...
. The hypokalemia is thought to be from the combination of the diuretic
A diuretic () is any substance that promotes diuresis, the increased production of urine. This includes forced diuresis. A diuretic tablet is sometimes colloquially called a water tablet. There are several categories of diuretics. All diuretics ...
effect of caffeine
Caffeine is a central nervous system (CNS) stimulant of the methylxanthine chemical classification, class and is the most commonly consumed Psychoactive drug, psychoactive substance globally. It is mainly used for its eugeroic (wakefulness pr ...
and copious fluid intake, although it may also be related to diarrhea
Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...
caused by heavy fructose
Fructose (), or fruit sugar, is a Ketose, ketonic monosaccharide, simple sugar found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is one of the three dietary monosaccharides, along with glucose and gal ...
ingestion.
Pseudohypokalemia
* Pseudohypokalemia is a decrease in the amount of potassium that occurs due to excessive uptake of potassium by metabolically active cells in a blood sample after it has been drawn. It is a laboratory artifact that may occur when blood samples remain in warm conditions for several hours before processing, and occasionally in the presence of a very high count of white blood cells (hyperleukocytosis).
Pathophysiology
About 98% of the body's potassium is found inside cells, with the remainder in the extracellular fluid
In cell biology, extracellular fluid (ECF) denotes all body fluid outside the cells of any multicellular organism. Total body water in healthy adults is about 50–60% (range 45 to 75%) of total body weight; women and the obese typically ha ...
including the blood. This concentration gradient
Fick's laws of diffusion describe diffusion and were first posited by Adolf Fick in 1855 on the basis of largely experimental results. They can be used to solve for the diffusion coefficient, . Fick's first law can be used to derive his second ...
is maintained principally by the Na+/K+ pump.
Potassium is essential for many body functions, including muscle
Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...
and nerve
A nerve is an enclosed, cable-like bundle of nerve fibers (called axons). Nerves have historically been considered the basic units of the peripheral nervous system. A nerve provides a common pathway for the Electrochemistry, electrochemical nerv ...
activity. The electrochemical gradient of potassium between the intracellular and extracellular space is essential for nerve function; in particular, potassium is needed to repolarize the cell membrane
The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extr ...
to a resting state after an action potential
An action potential (also known as a nerve impulse or "spike" when in a neuron) is a series of quick changes in voltage across a cell membrane. An action potential occurs when the membrane potential of a specific Cell (biology), cell rapidly ri ...
has passed. Lower potassium levels in the extracellular space cause hyperpolarization of the resting membrane potential. This hyperpolarization is caused by the effect of the altered potassium gradient on resting membrane potential
The relatively static membrane potential of quiescent cells is called the resting membrane potential (or resting voltage), as opposed to the specific dynamic electrochemical phenomena called action potential and graded membrane potential. The re ...
as defined by the Goldman equation. As a result, a greater-than-normal stimulus is required for depolarization of the membrane to initiate an action potential.
In the heart, hypokalemia causes arrhythmias because of less-than-complete recovery from sodium-channel inactivation, making the triggering of an action potential less likely. In addition, the reduced extracellular potassium (paradoxically) inhibits the activity of the IKr potassium current and delays ventricular repolarization. This delayed repolarization may promote reentrant arrhythmias.
Diagnosis
Blood
Normal potassium levels are between 3.5 and 5.0 mmol/L
Molar concentration (also called molarity, amount concentration or substance concentration) is the number of moles of solute per liter of solution. Specifically, It is a measure of the concentration of a chemical species, in particular, of a sol ...
with levels below 3.5 mmol/L (less than 3.5 mEq/L) defined as hypokalemia.[
]
Electrocardiogram
Hypokalemia leads to characteristic ECG
Electrocardiography is the process of producing an electrocardiogram (ECG or EKG), a recording of the heart's electrical activity through repeated cardiac cycles.
It is an electrogram of the heart which is a graph of voltage versus time of ...
changes (PR prolongation, ST-segment and T-wave depression, U-wave formation).
The earliest ECG findings, associated with hypokalemia, are decreased T wave height. Then, ST depressions and T inversions appear as serum potassium levels reduce further. Due to prolonged repolarization of ventricular Purkinje fibers
The Purkinje fibers, named for Jan Evangelista Purkyně, ( ; ; Purkinje tissue or subendocardial branches) are located in the inner ventricular walls of the heart, just beneath the endocardium in a space called the subendocardium. The Purki ...
, prominent U waves occur (usually seen at V2 and V3 leads), frequently superimposed upon T waves, therefore producing the appearance of prolonged QT intervals, when serum potassium levels fall below 3 mEq/L.
Amount
The amount of potassium deficit can be calculated using the following formula:
Meanwhile, the daily body requirement of potassium is calculated by multiplying 1 mmol to body weight in kilograms. Adding potassium deficit and daily potassium requirement would give the total amount of potassium need to be corrected in mmol. Dividing mmol by 13.4 will give the potassium in grams.
Treatment
Treatment includes addressing the cause, such as improving the diet, treating diarrhea
Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...
, or stopping an offending medication. People without a significant source of potassium loss and who show no symptoms of hypokalemia may not require treatment. Acutely, repletion with 10 mEq of potassium is typically expected to raise serum potassium by 0.1 mEq/L immediately after administration. However, for those with chronic hypokalemia, repletion takes time due to tissue redistribution. For example, correction by 1 mEq/L can take more than 1000 mEq of potassium over many days.
Oral potassium supplementation
Mild hypokalemia (>3.0 mEq/L) may be treated by eating potassium-containing foods or by taking potassium chloride supplements in a tablet or syrup form (by mouth supplements). Foods rich in potassium
Potassium is a chemical element; it has Symbol (chemistry), symbol K (from Neo-Latin ) and atomic number19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to ...
include dried fruits (particularly apricot
An apricot (, ) is a fruit, or the tree that bears the fruit, of several species in the genus ''Prunus''.
Usually an apricot is from the species '' P. armeniaca'', but the fruits of the other species in ''Prunus'' sect. ''Armeniaca'' are also ...
s, prune
A prune is a dried plum, most commonly from the European plum (''Prunus domestica'') tree. Not all plum species or varieties can be dried into prunes. Use of the term ''prune'' for fresh plums is obsolete except when applied to varieties of ...
s and figs), nuts, bran
Bran, also known as miller's bran, is the component of a Cereal, cereal grain consisting of the hard layersthe combined aleurone and Fruit anatomy#Pericarp layers, pericarpsurrounding the endosperm. Maize, Corn (maize) bran also includes the p ...
cereals and wheat germ, lima beans
A lima bean (''Phaseolus lunatus''), also commonly known as butter bean, sieva bean, double bean or Madagascar bean, is a legume grown for its edible seeds or beans.
Origin and uses
''Phaseolus lunatus'' is found in Meso- and South America. Tw ...
, molasses
Molasses () is a viscous byproduct, principally obtained from the refining of sugarcane or sugar beet juice into sugar. Molasses varies in the amount of sugar, the method of extraction, and the age of the plant. Sugarcane molasses is usuall ...
, leafy green vegetables, broccoli
Broccoli (''Brassica oleracea'' var. ''italica'') is an edible green plant in the Brassicaceae, cabbage family (family Brassicaceae, genus ''Brassica'') whose large Pseudanthium, flowering head, plant stem, stalk and small associated leafy gre ...
, winter squash
Winter squash is an annual fruit representing several squash species within the genus '' Cucurbita''. Late-growing, less symmetrical, odd-shaped, rough or warty varieties, small to medium in size, but with long-keeping qualities and hard rinds, ...
, beet
The beetroot (British English) or beet (North American English) is the taproot portion of a '' Beta vulgaris'' subsp. ''vulgaris'' plant in the Conditiva Group. The plant is a root vegetable also known as the table beet, garden beet, dinner ...
s, carrot
The carrot ('' Daucus carota'' subsp. ''sativus'') is a root vegetable, typically orange in colour, though heirloom variants including purple, black, red, white, and yellow cultivars exist, all of which are domesticated forms of the wild ...
s, cauliflower
Cauliflower is one of several vegetables cultivated from the species '' Brassica oleracea'' in the genus '' Brassica'', which is in the Brassicaceae (or mustard) family. Cauliflower usually grows with one main stem that carries a large, rou ...
, potato
The potato () is a starchy tuberous vegetable native to the Americas that is consumed as a staple food in many parts of the world. Potatoes are underground stem tubers of the plant ''Solanum tuberosum'', a perennial in the nightshade famil ...
es, avocado
The avocado, alligator pear or avocado pear (''Persea americana'') is an evergreen tree in the laurel family (Lauraceae). It is native to Americas, the Americas and was first domesticated in Mesoamerica more than 5,000 years ago. It was priz ...
s, tomato
The tomato (, ), ''Solanum lycopersicum'', is a plant whose fruit is an edible Berry (botany), berry that is eaten as a vegetable. The tomato is a member of the nightshade family that includes tobacco, potato, and chili peppers. It originate ...
es, coconut water
Coconut water (also coconut juice) is the clear liquid inside young coconuts (fruits of the coconut palm). In early development, it serves as a suspension for the endosperm of the coconut during the nuclear phase of development. As developm ...
, citrus fruits (particularly oranges), cantaloupe
The cantaloupe ( ) is a type of true melon (''Cucumis melo'') with sweet, aromatic, and usually orange flesh. Originally, ''cantaloupe'' refers to the true cantaloupe or European cantaloupe with non- to slightly netted and often ribbed rind. ...
, kiwis, mango
A mango is an edible stone fruit produced by the tropical tree '' Mangifera indica''. It originated from the region between northwestern Myanmar, Bangladesh, and northeastern India. ''M. indica'' has been cultivated in South and Southeast As ...
es, banana
A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large treelike herbaceous flowering plants in the genus '' Musa''. In some countries, cooking bananas are called plantains, distinguishing the ...
s, and red meats.
Eating potassium-rich foods may not be sufficient for correcting low potassium; potassium supplements may be recommended. Potassium contained in foods is almost entirely coupled with phosphate and is thus ineffective in correcting hypokalemia associated with hypochloremia that may occur due to vomiting, diuretic therapy, or nasogastric drainage. Additionally, replacing potassium solely through diet may be costly and result in weight gain due to potentially large amounts of food needed. An effort should also be made to limit dietary sodium intake due to an inverse relationship with serum potassium. Increasing magnesium intake may also be beneficial for similar physiological reasons.
Potassium chloride supplements by mouth have the advantage of containing precise quantities of potassium, but the disadvantages of a taste which may be unpleasant, and the potential for side-effects including nausea
Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. It can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the throat.
Over 30 d ...
and abdominal discomfort. Potassium bicarbonate
Potassium bicarbonate ( IUPAC name: potassium hydrogencarbonate, also known as potassium acid carbonate) is the inorganic compound with the chemical formula KHCO3. It is a white solid.
Production and reactivity
It is manufactured by treating an ...
is preferred when correcting hypokalemia associated with metabolic acidosis
Metabolic acidosis is a serious electrolyte disorder characterized by an imbalance in the body's acid-base balance. Metabolic acidosis has three main root causes: increased acid production, loss of bicarbonate, and a reduced ability of the kidn ...
.
Intravenous potassium replacement
Severe hypokalemia (<3.0 mEq/L) may require intravenous
Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutr ...
supplementation. Typically, a saline solution is used, with 20–40 meq/L KCl per liter over 3–4 hours. Giving IV potassium at faster rates (20–25 meq/hr) may inadvertently expose the heart to a sudden increase in potassium, potentially causing dangerous abnormal heart rhythms such as heart block
Heart block (HB) is a disorder in the heart's rhythm due to a fault in the natural pacemaker. This is caused by an obstruction – a block – in the electrical conduction system of the heart. Sometimes a disorder can be inherited. Despite the ...
or asystole
Asystole (New Latin, from Greek privative a "not, without" + ''systolē'' "contraction") is the absence of ventricular contractions in the context of a lethal heart arrhythmia (in contrast to an induced asystole on a cooled patient on a heart-lun ...
. Faster infusion rates are therefore generally only performed in locations in which the heart rhythm can be continuously monitored such as a critical care unit. When replacing potassium intravenously, particularly when higher concentrations of potassium are used, infusion by a central line is encouraged to avoid the occurrence of a burning sensation at the site of infusion, or the rare occurrence of damage to the vein. When peripheral infusions are necessary, the burning can be reduced by diluting the potassium in larger amounts of fluid, or adding a small dose of lidocaine to the intravenous fluid, although adding lidocaine may increase the likelihood of medical errors. Even in severe hypokalemia, oral supplementation is preferred given its safety profile. Sustained-release formulations should be avoided in acute settings.
Potassium-sparing diuretics
Hypokalemia which is recurrent or resistant to treatment may be amenable to a potassium-sparing diuretic
A diuretic () is any substance that promotes diuresis, the increased production of urine. This includes forced diuresis. A diuretic tablet is sometimes colloquially called a water tablet. There are several categories of diuretics. All diuretics ...
, such as amiloride, triamterene, spironolactone
Spironolactone, sold under the brand name Aldactone among others, is classed as a diuretic medication. It can be used to treat edema, fluid build-up due to hepatic cirrhosis, liver disease or kidney disease. It is also used to reduce risk o ...
, or eplerenone
Eplerenone, marketed under brand name Inspa or Espler, is an aldosterone antagonist used primarily in the treatment of heart failure with reduced ejection fraction (HFrEF), particularly following myocardial infarction. It may also be considered ...
. Concomitant hypomagnesemia will inhibit potassium replacement, as magnesium is a cofactor for potassium uptake.
Popular culture
The plot of the science fiction novel '' Destiny's Road'' by Larry Niven
Laurence van Cott Niven (; born April 30, 1938) is an American science fiction writer. His 1970 novel ''Ringworld'' won the Hugo Award for Best Novel, Hugo, Locus Award, Locus, Ditmar Award, Ditmar, and Nebula Award for Best Novel, Nebula award ...
centers around the setting's scarcity of available potassium, and the resulting deficiency and its effects on the world's colonists and their society.
See also
* Bartter syndrome
* Gitelman syndrome
* Hypokalemic acidosis
* Potassium deficiency (plant disorder)
* Superior mesenteric artery syndrome
Superior mesenteric artery (SMA) syndrome is a gastro-vascular disorder in which the third and final portion of the duodenum is compressed between the abdominal aorta (AA) and the overlying superior mesenteric artery. This rare, potentially li ...
References
Further reading
*
*
External links
Content of Selected Foods per Common Measure, sorted by nutrient content (Potassium)
List of foods rich in potassium (U. Mass. Med.)
National Organization for Rare Disorders: Hypokalemia
{{Authority control
Electrolyte disturbances
Mineral deficiencies
Nephrology
Potassium
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