The Merck Manual of Medical Information--Home Edition
Section 12. Disorders of Nutrition and Metabolism
Chapter 137
High Potassium Levels
Hyperkalemia (high potassium blood level) is a blood potassium concentration higher than 5.0 milliequivalents (mEq) per liter of blood.
In general, a high blood potassium concentration is more dangerous than a low one. A potassium concentration above 5.5 mEq per liter of blood begins to affect the heart's electrical conducting system. If the blood concentration continues to rise, the heart rhythm becomes abnormal and the heart may stop beating.
Hyperkalemia usually results when the kidneys don't excrete enough potassium. Probably the most common cause of mild hyperkalemia is the use of drugs that block the kidneys' excretion of potassium, such as triamterene, spironolactone, and angiotensin converting enzyme inhibitors. Hyperkalemia can also be caused by Addison's disease, in which the adrenal glands don't produce sufficient amounts of the hormones that stimulate the kidneys to excrete potassium. (see page 712 in Chapter 146, Adrenal Gland Disorders) Addison's disease is becoming an increasingly common cause of hyperkalemia, as more people with AIDS develop problems with their adrenal glands.
Partial or complete kidney failure can result in severe hyperkalemia. Thus, people with poor kidney function generally must avoid foods high in potassium.
Hyperkalemia can also result when a large amount of potassium is suddenly released from the reservoir in cells. This might happen if a large amount of muscle tissue is destroyed (as in a crush injury), if a person has a severe burn, or if a person overdoses on crack *******. The rapid influx of potassium into the bloodstream can overwhelm the kidneys' ability to excrete it and result in life-threatening hyperkalemia.
Symptoms
Mild hyperkalemia causes few if any symptoms. Usually, hyperkalemia is first diagnosed in routine blood tests or when a doctor notices changes on an electrocardiogram. Occasionally, symptoms such as an irregular heartbeat occur; an irregular heartbeat may be experienced as palpitations.
Treatment
Immediate treatment is essential when the blood potassium concentration rises above 5 mEq per liter in someone with poor kidney function or above 6 mEq per liter in someone with normal kidney function. Potassium can be removed from the body through the gastrointestinal tract or the kidneys or by dialysis. Potassium can be removed by inducing diarrhea and by swallowing a preparation that contains a potassium-absorbing resin. This resin isn't absorbed from the gastrointestinal tract, so the potassium leaves the body in the stool. If the person's kidneys are functioning, a diuretic can be given to increase potassium excretion.
When treatment is needed even more rapidly, the person may be given an intravenous solution containing calcium, glucose, or insulin. Calcium helps protect the heart from the effects of high potassium, but this effect lasts only a few minutes. Glucose and insulin drive potassium from the blood into cells, thus lowering the blood potassium concentration. If these measures fail or if a person has kidney failure, dialysis may be necessary.
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