Hypokalemia overview

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Hypokalemia Microchapters


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Differentiating Hypokalemia from other Diseases

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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]; Aida Javanbakht, M.D. Assistant Editor(s)-In-Chief: Jack Khouri


Low level of potassium (usually below 3.5 mEq/L) in body is called hypokalemia. The condition is also known as potassium deficiency.

Historical Perspective

The prefix hypo- means low and kal refers to kalium, which is Neo-Latin for potassium. The end portion of the word, -emia, means "in the blood" (note, however, that hypokalemia is usually indicative of a systemic potassium deficit).


Potassium is one of the intracellular cation. Any derangement of potassium serum levels can disturb the transmembrane potential and renders excitable cells (nerve and muscle) hyperpolarized and less excitable. However, cardiac cells don't obey this rule and become hyperexcitable. Potassium regulation is essential to maintain a normal activity in cells. Any imparment in potassium serum levels will have severe consequences on several organs especially the heart and the nervous system. Normally, total potassium excretion in stool is low and most ingested potassium is absorbed. The kidney is the main regulator of potassium balance through excretion (the kidney excretes 90-95% of dietary potassium); the gut excretes a minimal amount of dietary potassium (approximately 10%).


The etiology of hypokalemia can be quite difficult to diagnose. Diferent organ systems play role 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. Hypokalemia can be the consequence of decreased ingestion, increased losses (renal, GI or excessive sweating) or transcellular shift from the extracellular to the intracellular compartment. The most common causes are diarrhea, vomiting and diuretic use (mostly loop and thiazide diuretics).


Diagnosis relies on a constellation of findings including:


Past medical history and medication history are so important in finding the reason of hypokalemia (eg hyperthyroidism, hyperaldosteronism, Cushing's disease,etc).


Laboratory findings

Many labs can be helpful. The transtubular potasium gradient (TTKG), urine potassium, sodium, osmolality and chloride levels can help define the etiology of hypokalemia.


The most notable EKG findings in hypokalemia are due to the delayed ventricular repolarization, manifesting as (QT-U) with prominent U waves. The ECG changes of hypokalemia are commonly seen at potassium levels < 3 meq/Li. 90% of the patients with potassium levels <2.7 meq/L have abnormal ECG findings.


The oral route is the safest. There are many oral potassium salts that can be prescribed including potassium chloride (the most popular) and the organic alkalinizing salts that are metabolized to potassium bicarbonate in the body. Severe hypokalemia ca be treated via IV potassium chloride infusion with doses that shouldn't exceed 60 mEq/L unless ECG monitoring is provided. A central line can be used for administration of greater concentrations of potassium chloride.


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