Hypokalemia is a potentially fatal condition in which the body fails to retain sufficient potassium to maintain health. The condition is also known as potassium deficiency. The prefix hypo- means low (contrast with hyper-, meaning high). The middle kal refers to kalium, which is 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). more...
Signs and symptoms
There may be no symptoms at all but severe hypokalemia may cause:
- Muscle weakness
- Disturbed heart rhythm (arrhythmias), leading to ectopic beats
- Serious arrhythmias
- Increased risk of hyponatraemia with resultant confusion and seizures
Hypokalemia can result from a variety of medical conditions:
- Perhaps most obviously, insufficient consumption of potassium (that is, a low-potassium diet) can result in the condition. More commonly, however, hypokalemia occurs due to excessive loss of potassium, often associated with excess water loss, which "flushes" potassium out of the body. Typically, this is a consequence of vomiting and diarrhea.
- Hypomagnesemia can also cause hypokalemia. This is realized as a possibility when hypokalemia persists despite potassium supplementation.
- Certain medications can also accelerate the removal of potassium from the body, including loop diuretics, such as furosemide or bumetanide, as well as various laxatives. The antifungal amphotericin B is also associated with hypokalemia. Often doctors and pharmacists will suggest changes in their patients' diets to compensate for the effects of medication. For instance, recommending that a patient eat a (potassium-rich) banana daily; sometimes, doctors will co-prescribe a potassium supplement when a potassium-depleting drug is prescribed.
Potassium is essential for many body functions, including muscle and nerve activity. Potassium is the principal intracellular cation, with a concentration of about 145 mEq/L, as compared with a normal value of about 4 mEq/L in extracellular fluid, including blood. More than 98% of the body's potassium is intracellular; measuring it from a blood sample is relatively insensitive, with small fluctuations in the blood corresponding to very large changes in the total bodily reservoir of potassium.
The osmotic gradient of potassium between intracellular and extracellular space is essential for nerve function; in particular, potassium is needed to repolarize the cell membrane to a resting state after an action potential has passed. Decreased potassium levels in the extracellular will cause hyperpolarization of the resting membrane potential. As a result, a greater than normal stimulus is required for depolarization of the membrane in order to initiate an action potential.
Potassium is also essential to the normal muscular function, in both voluntary muscle (e.g. the arms and hands) and involuntary muscle (e.g. the heart and intestines). Severe abnormalities in potassium levels can seriously disrupt cardiac function, even to the point of causing cardiac arrest and death.
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