What is potassium?
Potassium is an essential nutrient and electrolyte required for maintaining fluid and electrolyte balance in the human body.
AdvertisementsPotassium deficiency disease (hypokalemia) is a condition wherein serum potassium (K+) concentration drops below 3.5 mmol/L. Severe deficiency of potassium in the plasma can be fatal.
Potassium deficiency diseases have multifactorial aetiologies and may present multiple causes in the same patient. Apart from poor intake, loss of the mineral through diarrhea, diuresis or vomiting are the primary causes for subnormal potassium levels. Some medications, treatments and genetic mutations are also causative factors for drop in serum K+ levels.
Though potassium homeostasis depends on potassium excretion by kidneys, the skeletal muscles, possessing a huge capacity for potassium exchange, play an important role in short-term potassium homeostasis. The common hypokalemia symptoms include muscle weakness and cramps.
Potassium food sourcesSeveral food source of both animal and plant origins have considerable amounts of potassium. Bananas, avocados, oranges, cantaloupe melons, peaches, baked potatoes, tomatoes, spinach, peas and nuts are good plant sources. Meat products and dairy products also have considerable amounts of potassium. The normal K+ serum level is 3.5-5.0 mmol/L. The recommended dietary allowance for adults is 4700 mg of potassium.
Functions of PotassiumPotassium (K+) is the major cation (positive ion) inside human cells whereas the sodium (Na+) is the major cation outside the cells. A difference in the cell membrane electric potential is caused by the concentration differences of these charged particles. The electric potential created by these ions causes the cell to generate an electrical discharge critical for body functions such as neurotransmission, muscle contraction, and heart beat.
Potassium deficiency disease causesThe causes of low potassium levels are:
- insufficient dietary potassium intake,
- eating disorders (anorexia nervosa and bulimia),
- excessive sweating and dehydration,
- persistent vomiting,
- severe diarrhoea,
- laxative abuse,
- fluid loss due to burns,
- low magnesium levels,
- chronic kidney disease,
- diabetic ketoacidosis,
- oral glucose overload,
- increase in plasma insulin,
- increase in catecholamines levels,
- abnormally high aldosterone levels,
- rare hereditary defects of renal salt transporters,
- renal loss of potassium due to diuretic therapy,
- sudden shift of K+ from plasma to skeletal muscles pool,
- treatment of asthma with injection or inhalation of a beta-adrenoceptor agonist,
- use of certain antibiotics,
- affliction by AIDS,
- alcoholism and
- bariatric surgery.
Potassium deficiency signs and symptomsMild deficiency may be asymptomatic or cause mild symptoms like, muscle weakness and pain, constipation, abdominal bloating, nausea or vomiting, tingling or numb sensation, fatigue and feeling of skipped heart beats or palpitations. A serious drop in serum K+ levels can cause cramp, abnormal heart rhythms (arrhythmia), spasms, fainting, psychosis, delirium, confusion, muscle damage, heart smooth muscle damage, reduced heartbeat, flaccid paralysis, hyporeflexia and cardiac arrest.
Potassium deficiency diagnosisDiagnosis of low K+ serum levels by testing its blood plasma levels. The serum levels of the other electrolytes may also be checked due to their inter-relationship. The status of heart may be checked by an electrocardiogram (ECG) to understand the severity of cardiac involvement. Differential diagnosis may be done to rule out renal tubular acidosis, Cushing's syndrome, and hypocalcemia.
Potassium deficiency diseasesHypokalemia, hypokalemic periodic paralysis and sudden cardiac death are some of the effects of low serum K+ levels. Low dietary intake, severe loss from the body as gastrointestinal loss, skin loss and urinary loss and certain genetic conditions contribute to these electrolyte anomalies.
HypokalemiaHypokalemia, also known as hypopotassemia, is inadequate potassium levels in the blood serum. 98% of the K+ is found inside the cells and the rest 2% is found in the extracellular fluids. The concentration gradient between intracellular and extracellular K+ is maintained principally by the Na+/K+ pump. The normal serum level is 3.5-5.0 mmol/L and the drop below 3.5 mmol/L is hypokalemia. Serum levels falling below 2.5 mmol/L is severe hypokalemia and a serious situation.
Hypokalemic periodic paralysisHypokalemic periodic paralysis is a rare, autosomal dominant genetic disease with disturbed function of ion channel subunits or the proteins that regulate them. The patients have mutations in SCN4A or CACNA1S genes. The patient suffers from fall in serum potassium levels and associated muscle weakness or paralysis. In patients with this genetic mutation, strenuous exercise, high carbohydrate intake, high sodium intake, sudden changes in temperature, noise and flashing lights can induce an attack. Oral potassium supplements may relieve the attack and maintain muscle strength and function.
Sudden cardiac deathSudden cardiac death is death from heart disease within one hour. Electrolyte disturbance, especially disturbed potassium homeostasis, is one among the several triggers promoting arrhythmia (irregular heartbeat), which may lead to death. Patients with cardiovascular diseases such as hypertension, coronary artery disease, heart failure and arrhythmia while being treated with diuretics, beta-adrenoceptor agonists or insulin are at risk of severe hypokalemia or transient reductions in plasma potassium concentration. Keld Kjeldsen concluded in the study 'Hypokalemia and sudden cardiac death' that,
"the more at risk of fatal arrhythmia and sudden cardiac death a patient is, the more attention should be given to the potassium homeostasis."
Potassium deficiency disease treatmentConsidering the severity of symptoms and the level of drop in K+ in serum, the treatment option is selected. Those with mild or moderately low K+ levels (2.5-3.5 mmol/L) are treated with oral replacement. Those with cardiac arrhythmias and other heart ailments with significantly low K+ serum levels (less than 2.5 mmol/L) may require hospital care and IV administration.
The intravenous potassium replacement is done very slowly to stall cardiac problems and the procedure may take several hours. After restoring the K+ serum levels, the causative factor may have to be treated to avoid recurrence of the potassium deficiency disease.
1.Ali Ahmed, Faiez Zannad, Thomas E Love, Jose Tallaj, Mihai Gheorghiade, Olaniyi James Ekundayo, Bertram Pitt. A propensity matched study of the association of low serum potassium levels and mortality in chronic heart failure. Eur Heart J. 2007 Jun; 28(11): 1334–1343.
2.Keld Kjeldsen. Hypokalemia and sudden cardiac death. Exp Clin Cardiol. 2010 Winter; 15(4): e96–e99.