High potassium; Hyperkalemia
Hyperkalemia is a condition caused by higher than normal levels 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 - smooth muscles (such as the muscles in the intestines), the muscles of the heart, and skeletal muscles. Potassium is part of the enzyme reactions in digestion and metabolism. It is also part of homeostasis, the mechanism 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):
- Acute kidney failure
- Chronic kidney failure
- Lupus nephritis
- Rejection of a kidney transplant
- Obstructive uropathy
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:
- Traumatic injury
- Gastrointestinal bleeding
- Hemolytic conditions (disorders that cause blood cells to burst)
- Rhabdomyolysis from drug ingestion, alcoholism, coma, or certain infections
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.
Hyperkalemia is often asymptomatic. Occasionally, the following signs or symptoms may be seen:
- Irregular heartbeat (this may be an emergency symptom if prolonged or severe)
- Slow, weak, or absent pulse (emergency symptom)
Signs and tests
- The pulse may be slow or irregular.
- Serum potassium is high.
- ECG may show potentially lethal arrhythmias: o Bradycardia that progressively slows. o Heart block that may become complete heart block. o ventricular fibrillation.
- ECG may show changes indicative of hyperkalemia.
Cardiac arrest (absent heartbeat) may occur at any time during treatment of hyperkalemia. Hospitalization and close monitoring is required.
The goal of acute treatment is to protect the body from the effects of hyperkalemia. This may include protective measures, shift of potassium into the intracellular fluid, and reduction of total body potassium.
Emergency treatment is indicated if the potassium is very high, or if severe symptoms are present, including changes in the ECG.
Intravenous calcium may be given to temporarily counteract the muscular and cardiac effects of hyperkalemia, including cardiac arrhythmias. Intravenous calcium will only counteract symptoms for about 1 hour, so other treatments should begin immediately.
Intravenous glucose and insulin moves potassium from the extracellular fluids back into the cells. This may reverse severe symptoms long enough to allow correction of the cause of the hyperkalemia.
Sodium bicarbonate causes potassium to shift from extracellular to intracellular fluids. It may reverse hyperkalemia caused by acidosis with no other treatment required. Prolonged use of sodium bicarbonate should be avoided because it may cause severe complications.
Diuretic medications cause decrease in total body potassium. They may be prescribed for persons who can tolerate the loss of body fluid that accompanies use of a diuretic.
Cation-exchange resins, such as sodium polystyrene sulfonate (Kayexalate), are medications that bind potassium and cause it to be excreted from the gastrointestinal tract. These medications may be given orally or rectally.
Dialysis may be used to reduce total body potassium levels, especially if kidney function is compromised. Dialysis is indicated when more conservative measures have failed or are inappropriate.
Long-term treatment includes treatment of the cause and associated disorders.
Treatment of chronic renal failure may include dietary potassium restriction. “Loop diuretics” may be prescribed to reduce potassium and fluid levels in persons with chronic renal failure.
Need for potassium supplements and other medications that may cause hyperkalemia should be reviewed by the health care provider. These medications may be stopped, reduced in dose, or substituted by another medication.
Salt substitute, often used by people on a low salt diet, should not be used by those with renal failure or a history of hyperkalemia.
The probable outcome is variable. The disorder may cause deadly complications, or it may be well tolerated by the body.
- Changes in neuromuscular control
- Cardiac arrest
Calling your health care provider
Go to the emergency room or call the local emergency number (such as 911) if symptoms indicating hyperkalemia are present. Emergency symptoms include loss of consciousness, changes in breathing pattern, nausea, weakness and absent or weak heartbeat.
Disorders that may cause hyperkalemia should be treated promptly. Serum potassium should be monitored in persons with these conditions.
Kidney function should be assessed prior to and during administration of potassium supplements. They should not be given unless the urine output and kidney function is adequate.
by Arthur A. Poghosian, M.D.