Hypokalemia

 ICD9        = 276.8|

}} Hypokalemia is a potentially fatal condition in which the body fails to retain sufficient potassiumto 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 Latinfor potassium. The end portion of the word, -emia, means 'in the blood' (note, however, that hypokalemia is usually indicative of a systemic potassium deficit).

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 hyponatraemiawith resultant confusionand seizures

Causes

Hypokalemia can result from a variety of medicalconditions:

• Perhaps most obviously, insufficient consumptionof 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 waterloss, which "flushes" potassium out of the body. Typically, this is a consequence of vomitingand diarrhea.

• Hypomagnesemiacan also cause hypokalemia, as magnesium is required for the adequate processing of potassium. This may come to light when hypokalemia persists despite potassium supplementation. Other electrolyte abnormalities may also be present.

• Certain medicationscan also accelerate the removal of potassium from the body, including loop diuretics, such as furosemideor bumetanide, as well as various laxatives. The antifungal amphotericin Bis also associated with hypokalemia. Often doctorsand pharmacistswill suggest changes in their patients' diets to compensate for the effects of medication. For instance, recommending that a patient eat a (potassium-rich) bananadaily; sometimes, doctors will co-prescribea potassium supplement when a potassium-depleting drug is prescribed.

• Extremely high caffeineintake (>40 mg/L blood concentration).

Pathophysiology

Potassium is essential for many body functions, including muscleand nerveactivity. Potassium is the principal intracellularcation, with a concentration of about 145 mEq/L, as compared with a normal value of about 4 mEq/L in extracellularfluid, 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 osmoticgradient of potassium between intracellular and extracellular space is essential for nerve function; in particular, potassium is needed to repolarize the cell membraneto a resting state after an action potentialhas passed. Decreased potassium levels in the extracellular space 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 arrestand death.

Treatment

The most important step in severe hypokalemia is removing the cause, such as treating diarrheaor stopping offending medication.

Mild hypokalemia (>3.0 mmol/L) may be treated with oral potassium chloride supplements (Sando-K®, Slow-K®). As this is often part of a poor nutritional intake, potassium-containing foods may be recommended, such as tomatoes, orangesor bananas.

Severe hypokalemia (<3.0 mmol/L) may require intravenoussupplementation. Typically, salineis used, with 20-40 mmol KCl per liter over 3-4 hours. Giving intravenous potassium at faster rates may predispose to ventricular tachycardiasand requires intensive monitoring.

Difficult or resistant cases of hypokalemia may be amenable to amiloride, a potassium-sparing diuretic, or spironolactone.

Hypokalemia in pets

Cats can develop hypokalemia in old age, but Burmese kittens may be genetically prone to the condition if both parents have a defective gene. Symptoms are: staggering, an inability to keep up head which droops alarmingly and animals have good appetite but fail to gain weight. Treatment is by adding ground potassium tablets to the animal's food.^{[citation needed]}

See also

• Hypomagnesemia
• Potassium deficiency (plant disorder)

Reference

• Kasper DL et al (Eds). Harrison's Principles of Internal Medicine, 16th ed, chapter 41, pages 258-61. ISBN 0071402357.

External link

• Potassium in the human diet
• MedlinePlus Encylopedia000479
• eMedicineemerg/273
• DDB6445de:Hypokaliämie

pt:Hipocaliémia

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Hypokalemia Wikipedia article Hypokalemia.