Definition of Hyperkalemia:

Hyperkalemia is higher-than-normal levels of potassium in the blood.

Causes, incidence, and risk factors:

Potassium is involved in regulating muscle tissue, and is part of digestion, metabolism, and homeostasis (maintaining a balance between the many electrical and chemical processes of the body).

Hyperkalemia occurs when the level of potassium in the bloodstream is higher than normal. This may be related to an increase in total body potassium or the excess release of potassium from the cells into the bloodstream.

The kidneys normally remove excess potassium from the body. Most cases of hyperkalemia are caused by disorders that reduce the kidneys' ability to get rid of potassium.This may result from disorders such as:

• Acute kidney failure
• Chronic kidney failure
• Glomerulonephritis
• Obstructive uropathy
• Rejection of a kidney transplant

The hormone aldosterone regulates kidney removal of sodium and potassium. Lack of aldosterone can result in hyperkalemia with an increase in total body potassium. Addison's disease is one disorder that causes reduced aldosterone production.

Any time potassium is released from the cells, it may build up in the fluid outside the cells and in the bloodstream. Acidosis leads to the movement of potassium from inside the cells to the fluid outside the cells. Tissue injury can cause the cells to release potassium. Such injury includes:

• Burns
• Disorders that cause blood cells to burst (hemolytic conditions)
• Gastrointestinal bleeding
• Rhabdomyolysis from drugs, alcoholism, coma, or certain infections
• Surgery
• Traumatic injury
• Tumors

If the kidney is working properly, and there is enough aldosterone, tissue trauma alone rarely leads to hyperkalemia. A normally functioning kidney will remove the excess potassium that has been released from the cells.

Increased intake of potassium can cause hyperkalemia if kidney function is poor. Salt substitutes often contain potassium, as do many "low-salt" packaged foods.

Hyperkalemia may be caused by medications, including medications that affect kidney function (potassium sparing diuretics, such as spironolactone, amiloride, or triamterene) and potassium supplements (especially intravenous potassium).