Hyperkalemia: An Overview of Elevated Blood Potassium Levels

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Hyperkalemia is the medical term for blood potassium levels that are too high. 

Potassium is a chemical element that is essential for life. It is especially important for the normal functioning of organ systems that rely on the transmission of electrical signals—the heart, muscles, and the nerves. In adults, a normal potassium blood level is between 3.5 to 5.5 mEq/L. Potassium levels that are either too low (hypokalemia) or too high can become life-threatening problems.

What Does Potassium Do?

Potassium is one of the most common chemical elements in the body. (The chemical symbol for potassium is K, which is derived from the Latin name “kalium.” This is where we get the terms hyperkalemia and hypokalemia.)

Most potassium in the body exists inside of cells, where its concentration averages 150 mEq/L, or roughly 30 times higher than in the blood. Furthermore, potassium in the body exists in its ionic form (designated K+), which means it has a positive electrical charge.

Potassium plays a critical role in the maintenance and regulation of the electrical gradient between the inside of cells and the outside of cells, which is essential for life. The generation of electrical signals allow the brain and nerves to function and regulate the heart rhythm. These critical electrical signals are produced by the movement of ions (including K+) back and forth across the cell membranes, by means of a complex system of pumps and channels within the membranes.

In order to assure that these electrical signals continue to do their work normally, the blood levels of potassium must be maintained within a limited range.

In addition to its critical role in the maintenance of the body’s electrical signals, potassium is also important in the regulation of blood pressure, vascular tone, the normal function of insulin and various other hormones, gastrointestinal motility, acid-base balance, kidney function, and fluid and electrolyte balance.

Consequences of Hyperkalemia

Elevated potassium blood levels can disrupt the normal functioning of several organ systems, and can become fatal if not treated. Mild hyperkalemia, however, usually produces no symptoms.

As potassium levels become higher, early symptoms tend to be vague and fairly nonspecific—in particular, mild weakness and fatigue are common. If potassium levels approach 7.0 mEq/L, more severe symptoms may develop including dyspneapalpitationschest pain, nausea and vomiting, severe muscle weakness, or even paralysis. At very high blood potassium levels (usually, greater than 8.0 mEq/L), death may ensue from cardiac arrest or respiratory paralysis.

Because hyperkalemia can become quite dangerous, elevated potassium levels must be taken seriously, even if they are not yet producing any symptoms.

What Conditions Cause Hyperkalemia?

There are numerous potential causes of hyperkalemia, but these can be broken down into three major categories:

  • Excessive intake of potassium. With normally functioning kidneys, it is very difficult to develop hyperkalemia simply from ingesting too much potassium in the diet. However, it is possible to drive blood potassium levels too high if large amounts potassium supplements are ingested, especially if some degree of kidney disease is also present, or if drugs are being taken that inhibit potassium excretion.
  • Decreased excretion of potassium. Because the maintenance of normal potassium levels is critical to life, the kidneys have evolved efficient mechanisms for hanging on to potassium to prevent hypokalemia, and also for excreting excess potassium to prevent hyperkalemia. However, with either acute kidney failure or chronic kidney disease, the ability of the kidneys to excrete potassium can often become impaired, and hyperkalemia may ensue.

    Before the days of dialysis, hyperkalemia was a frequent cause of death in people with kidney disease. A decrease in the renal excretion of potassium may also occur with Addison’s disease (failure of the adrenal glands), and with drugs that affect the renin-aldosterone system including ACE inhibitorsangiotensin II receptor blockers, and spironolactone.
  • Movement of potassium from the inside of cells to the outside of cells. Because the concentration of potassium inside of the body’s cells is roughly 30 times higher than it is in the blood, anything that causes potassium to shift from inside the cells to outside the cells can produce hyperkalemia. Acidosis—such as diabetic ketoacidosis—causes potassium to move out of cells, and can produce significant and potentially life-threatening hyperkalemia.

    Tissue damage can also produce a shift of potassium from the inside of cells to the outside of cells, simply by the traumatic disruption cell membranes. Hyperkalemia from tissue damage can occur with any kind of severe trauma, burns, surgery, the rapid destruction of tumor cells, hemolytic anemia, or rhabdomyolysis (destruction of muscle cells, as may occur with heat stroke, or with alcoholic or drug-induced stupor).

How Is Hyperkalemia Diagnosed?

It seems simple enough to diagnose hyperkalemia. By definition, hyperkalemia means a high blood level of potassium—so, simply measure a blood test.

However, things are often not as simple as they ought to be. It is not uncommon for blood levels of potassium to be reported as elevated when they actually are not. This can happen if the red cells in the blood sample rupture in the glass tube, releasing potassium into the sample. It can also happen if, during the blood draw, a very tight tourniquet is used for several minutes while a vein is being sought, especially if fist pumping is also employed to expand the veins.

So, if a high potassium level is found in a person who has no obvious reason to have hyperkalemia, and if there are no symptoms or signs of hyperkalemia, the first thing that ought to be done is to simply repeat the blood test.

While waiting for the results of the blood test, there are other things a doctor can do to assess whether hyperkalemia may be present.

The electrocardiogram (ECG) often shows characteristic changes in a person with true hyperkalemia. These may include a characteristic tall, peaked T wave, a short QT interval, or (with dangerously high potassium levels) disappearance of the P wave, a widening QRS complex and/or bundle branch block. (P waves, T waves, QRS complexes, and the QT interval are all components of the ECG.)

When true hyperkalemia is present, the type and magnitude of these changes on the ECG are usually a reliable indicator of how severe the problem is, and can give the doctor a good estimate of whether a state of emergency may be present.

The other blood tests typically obtained when measuring potassium levels are very likely to show abnormal kidney function in a person with true hyperkalemia, since kidney disease is the most common cause. So, the blood BUN and creatinine levels (which reflect kidney function) are often abnormal.

The presence of any of the other possible causes of hyperkalemia (discussed above)—including the prescription drugs being taken, or a history of recent trauma, alcoholism or drug abuse—can also help the doctor assess the likely accuracy of a blood potassium level.

The bottom line is that, while there may be temporary initial confusion in interpreting the blood test, the diagnosis of true hyperkalemia is generally pretty rapid and straightforward.

How Is Hyperkalemia Treated?

The treatment of hyperkalemia depends on the underlying cause, and whether the blood level of potassium is judged to be an emergency or not.

Is it an emergency? Hyperkalemia is considered an emergency if the changes on the ECG indicate that the high potassium level is significantly affecting the normal transmission of electrical impulses in the heart; in particular, if widening of the QRS complex, or signs of bundle branch block, are seen.

A hyperkalemic emergency is also present if symptoms indicate that the high potassium levels are affecting the function of muscles or nerves, especially if severe muscle weakness or paralysis are present. Hyperkalemia caused by severe tissue damage—trauma or rhabdomyolysis—where continued movement of potassium into the blood is very likely to persist, is also considered an emergency.

If the hyperkalemia is deemed to be an emergency, rapid steps must be taken to counteract the effect of high blood levels of potassium, and to remove excess potassium from the blood. Intravenous calcium is used in these circumstances to immediately counteract the effects of high potassium levels on the cell membranes, and to stabilize the electrical systems of the heart, nerves, and muscles.

Meanwhile, the potassium levels themselves can be reduced by administering insulin and glucose (which has the effect of driving potassium into the cells), by giving patiromer (a non-absorbable polymer that draws potassium into the gut) or Kayexalate (a cation exchange resin which also removes potassium via the gut), by giving potassium-wasting diuretics (such as Lasix or a thiazide) if kidney function is adequate, or by employing dialysis if kidney function is seriously impaired. 

When hyperkalemia is not an emergency, but it is still desirable to take action to bring down the potassium blood levels while treating the underlying cause, diuretics, Kayexalate, or patiromer are typically used.

What is the underlying cause? In addition to employing appropriate treatments to lower blood potassium levels, it is important to identify and treat the problem that produced hyperkalemia in the first place. This step may be obvious (such as treating acute diabetic ketoacidosis, or discontinuing spironolactone), or more challenging (such as diagnosing Addisons’s disease).

It may be necessary to institute chronic hemodialysis to prevent recurrent hyperkalemia in a person with chronic kidney disease, or even perform surgery to decompress damaged, swollen muscle tissue (as in a severe compartment syndrome). It is critical to do whatever it takes to identify the underlying cause, and to assure that there will be no recurrence of hyperkalemia.

A Word From Verywell

Hyperkalemia is a potentially dangerous condition, but it can be successfully remediated. When it occurs it is important to quickly assess the immediate level of danger it is causing, and take appropriate steps to return blood potassium levels to normal. It is also vital to identify the underlying cause, and take the necessary steps to prevent a recurrence of hyperkalemia.

Sources:

Kim HJ, Han SW. Therapeutic Approach to Hyperkalemia. Nephron 2002; 92 Suppl 1:33.

Sterns RH, Rojas M, Bernstein P, Chennupati S. Ion-exchange Resins for the Treatment of Hyperkalemia: are They Safe and Effective? J Am Soc Nephrol 2010; 21:733.

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