Kidney Failure Risk Factor: Serum Bicarbonate

What are bicarbonate and serum bicarbonate?

Bicarbonate is a substance called a base, which the body needs to help keep a normal acid-base (pH) balance. This balance prevents your body from becoming too acid, which can cause many health problems. The lungs and kidneys keep a normal blood pH by removing excess acid.

Serum bicarbonate mostly travels throughout the body as carbon dioxide (CO2), a gas that's dissolved in the blood. That's why the amount of CO2 in your blood is used to measure serum bicarbonate (base), and to therefore check your acid-base balance. If CO2 is too low in your blood, then that means serum bicarbonate (base) is low, and your body has too much acid. Too much acid in the body is called metabolic acidosis.

What causes metabolic acidosis in chronic kidney disease (CKD)?

Healthy kidneys remove acid from the body through urine and they keep the right amount of bicarbonate (base) in the blood. But in CKD, the kidneys can't remove enough acid, which can lead to metabolic acidosis.

The normal level of serum bicarbonate is 22-29 mEq/L. Kidney experts recommend that patients not have their serum bicarbonate levels fall below 22 mEq/L.

What are the signs and symptoms?

Not everyone will have signs or symptoms. However, you may have:

  • Long and deep breaths
  • Fast heartbeat
  • Headache and/or confusion
  • Weakness
  • A feeling of being very tired
  • Vomiting and/or feeling sick to your stomach (nausea)
  • Loss of appetite

If you experience any of these, it's important to let your healthcare team know right away.

What are the health problems from metabolic acidosis in CKD or kidney failure?

  • Increased bone loss (osteoporosis): Metabolic acidosis can cause a loss of bone in your body. This can lead to a higher chance of fractures in important bones like your hips or backbone.
  • Decreased growth in children: Metabolic acidosis prevents the release of growth hormone, which is needed for proper growth.
  • Progression of CKD: As acid builds up, kidney function decreases. And as kidney function decreases, more acid builds up to cause more kidney damage. This makes CKD worse.
  • Muscle loss: Excess acid in the body causes muscles to break down, which is called "muscle wasting."
  • High blood sugar: Excess acid can cause your body to resist the effects of insulin, the hormone in your body that helps keep your blood sugar level from getting too high.
  • Death: Studies have shown a link between metabolic acidosis and an increased risk for death.

Why does a low serum bicarbonate increase the risk of reaching kidney failure?

Studies on thousands of patients with a low serum bicarbonate showed that they reached kidney failure faster than patients with a normal serum bicarbonate. The reasons for this are not very clear, but excess acid may not only harm the kidneys directly, but it may also make diseases like high blood pressure and diabetes worse. These two diseases are the main causes of CKD, so making them worse could make kidney failure happen more quickly. Other diseases that are common in CKD, such as heart disease and gout, are also made worse by metabolic acidosis and can therefore make patients reach kidney failure faster than patients who do not have these diseases.

How is metabolic acidosis treated?

Studies have shown that treatment with sodium bicarbonate (baking soda) or sodium citrate pills, which are base substances, can help keep kidney disease from getting worse. However, you should not take sodium bicarbonate or sodium citrate pills unless your healthcare team recommends them. Another type of treatment that binds excess acid in the bowels is being studied for treating metabolic acidosis. You can discuss these treatment options with your healthcare team.

A diet that includes more plant-based proteins than animal-based proteins, along with a high intake of fruits and vegetables, can also help keep acid levels from rising in the blood. Before making any dietary changes, speak with your healthcare team.

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