Hypokalemia causes
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Hypokalemia Microchapters |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]; Aditya Govindavarjhulla, M.B.B.S. [3]; Assistant Editor(s)-In-Chief: Jack Khouri
Overview
The etiology of hypokalemia can be quite difficult to diagnose. As a matter of fact, many organ systems are involved in the regulation of potassium level and any derangement to their normal function can cause hypokalemia. Drugs, diarrhea, kidney disease, endocrine diseases and many others are potential culprits.
Causes
Hypokalemia can be the consequence of decreased ingestion, increased losses or transcellular shift from the extracellular to the intracellular compartment.
- Perhaps the most obvious cause is insufficient consumption of potassium (that is, a low-potassium diet). However, without excessive potassium loss from the body, this is a rare cause of hypokalemia. Alcoholism, anorexia nervosa, dental problems and dysphagia can all impair food intake and cause hypokalemia. In the hospital setting, hypokalemia can present in patients on total parenteral nutrition or potassium-free IV fluids.
- Excessive loss of potassium, often associated with excess water loss, which "flushes" potassium out of the body. Typically, this is a consequence of GI losses (vomiting and diarrhea), or excessive perspiration.
- Increased urinary losses:
- Certain medications can accelerate the removal of potassium from the body; including thiazide diuretics, such as hydrochlorothiazide; loop diuretics, such as furosemide; as well as various laxatives. The antifungal amphotericin B has also been associated with hypokalemia.
- A special case of potassium loss occurs with diabetic ketoacidosis. In addition to urinary losses from polyuria and volume contraction, there is also obligate loss of potassium from kidney tubules as a cationic partner to the negatively charged ketone, β-hydroxybutyrate.
- Hypomagnesemia can cause hypokalemia. Magnesium is required for adequate processing of potassium. This may become evident when hypokalemia persists despite potassium supplementation. Other electrolyte abnormalities may also be present.
- Disease states that lead to abnormally high aldosterone levels can cause hypertension and excessive urinary losses of potassium. These include renal artery stenosis and tumors (generally non-malignant) of the adrenal glands. Hypertension and hypokalemia can also be seen with a deficiency of the 11β-hydroxylase enzyme which allows cortisol to stimulate aldosterone receptors. This deficiency can either be congenital or caused by consumption of glycyrrhizin, which is contained in extract of licorice, 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.
- Transcellular potassium shift to the intracellular space:
- Increased extracellular pH (each 0.11 unit increase in pH corresponds to a 0.4 meq/l decrease in potassium level)
- Elevated insulin
- Elevated beta-adrenergic activity (stress, beta-agonist intake, etc)
- 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 catechols and/or insulin and/or thyroid hormone that lead to sudden influx of potassium from the extracellular fluid into the muscle cells.
- Hypothermia
- Thyrotoxicosis
- Theophylline
- Rapid expansion of cell mass (eg, during refeeding after prolonged starvation, when patients with pernicious anemia are treated with vitamin B12 and with tumors having rapid cell turnover)