Hyperkalemia
Alternative names:
high potassium; potassium - high
Definition:
A condition caused by higher than normal level of potassium in the bloodstream.
Causes, incidence, and risk factors:
Potassium has many functions in the body. It helps to regulate the activity of all muscle tissue, including smooth muscles (such as the muscles in the intestines), the muscles of the heart, and skeletal muscles. It is part of enzyme reactions used in digestion and metabolism. It is also part of the mechanism (homeostasis) used by the body to maintain a balance between the many electrical and chemical processes of the body.
Almost all (98%) potassium in the body is found inside the cells (intracellular). Only about 2% occurs in the fluids outside of the cells (extracellular ). Potassium can move into and out of cells. Blood tests reflect only the extracellular potassium levels and do not indicate the amount of potassium within the cells. Movement of potassium into or out of cells can change the blood potassium level (serum potassium) when there is no change in the total amount of potassium in the body.
Hyperkalemia occurs when the level of potassium in the bloodstream is higher than normal. This may be related to increase in total body potassium or excessive release of potassium from the cells into the bloodstream.
The kidneys normally excrete excess potassium from the body; therefore, most cases of hyperkalemia are caused by disorders that reduce the kidneys' ability to excrete potassium. Insufficient kidney function may result from disorders including (but not limited to): The hormone aldosterone (see the aldosterone test) regulates kidney excretion 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 accumulate in the extracellular fluid and the bloodstream. Acidosis (acidic condition of the body) results in movement of potassium from inside the cells to the extracellular fluid.
Tissue trauma causes the cells to release potassium into the extracellular fluid. This includes: If kidney function is adequate and sufficient amounts of aldosterone are present, tissue trauma alone rarely results in hyperkalemia. A normally functioning kidney will excrete the excess potassium that has been released from the cells.
Increased intake of potassium may 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).
Hyperkalemia can have serious, potentially life threatening effects on the body. A gradual increase in potassium, as may occur with chronic renal failure, may be better tolerated than a sudden increase. Slightly higher than normal potassium levels may be well tolerated by some persons with chronic renal failure.
|
