Lactic Acidosis: Causes, Symptoms, & Treatments

Key Takeaways

The main underlying cause of lactic acidosis is tissue hypoperfusion or not enough oxygen in the tissue. It can be tissue hypoxia (decreased tissue oxygenation) or hypoxemia (low oxygen levels in the blood).
Symptoms of lactic acidosis may include fruity-smelling breath, fatigue, exhaustion, nausea, vomiting, respiratory compensation (fast and deep breathing), muscle cramps, body aches, abdominal pain, and confusion.
Severe lactic acidosis must be treated immediately in the hospital with intravenous (IV) fluids and oxygen therapy. Treatment after will depend on what causes this build-up of lactic acidosis.

Lactic acidosis is a type of metabolic acidosis where there is a buildup of lactic acid (lactate) in the body, leading to high blood lactate levels. Too much lactic acid can be harmful to many organs in the body. Treatment with IV fluids and oxygen therapy are first given to lower lactic acid levels in the blood. Then, the treatment course will depend on the root cause. Please continue reading to find out what causes lactic acidosis, the symptoms, and how doctors treat lactic acidosis.

What is lactic acid?

Lactic acid, also called lactate, is a natural byproduct of cellular metabolism, specifically produced during anaerobic glycolysis, a process that occurs when the body needs rapid energy without sufficient oxygen. It is formed when the body uses a process known as anaerobic glycolysis during glucose metabolism to break down carbohydrates. This process is used to produce energy quickly during emergencies without using oxygen. Aerobic metabolism, on the other hand, utilizes oxygen and is used to produce a steady supply of energy.

For example, when we need an immediate burst of energy and tissues such as the muscles are deprived of oxygen during excessive exercise, the body uses anaerobic glycolysis. This process leads to lactic acid production as a natural byproduct. The soreness you feel in your skeletal muscles after intense exercise is due to excess acid (lactate) and lack of adequate tissue perfusion.

In healthy individuals, the temporary lactic acidosis caused by excess lactic acid production during intense exercise is quickly cleared by the liver and kidneys. However, lactic acidosis persists if there is consistent over-production of lactic acid or decreased function of the liver or kidneys, leading to reduced clearance of lactic acid from the body. This leads to an increased serum lactate concentration, making the pH of the body acidic.

What is the most common cause of lactic acidosis?

Type A lactic acidosis

There are many causes of lactic acidosis. The main underlying cause is tissue hypoperfusion or inadequate tissue perfusion. It can be tissue hypoxia (decreased tissue oxygenation) or hypoxemia (low oxygen levels in the blood). Regardless, if lactic acidosis is a result of tissues being deprived of oxygen, this is classified as type A lactic acidosis, which generally happens as a result of a severe critical illness.

For example, increased lactate production can occur in critically ill patients with pulmonary disorders, circulatory disorders, cardiogenic, hypovolemic, severe sepsis, carbon monoxide poisoning, and chronic seizures. This is called type A lactic acidosis.

Type B lactic acidosis

Increased serum lactate levels can also occur due to reduced lactate clearance from the body in people with chronic liver disease, kidney disease, cancer, HIV (human immunodeficiency virus)/AIDS (acquired immunodeficiency syndrome), mitochondrial diseases, vitamin B1 (thiamine) deficiency, alcohol use disorder, and diabetic ketoacidosis. This is one subgroup of type B lactic acidosis, specifically classified as type B1.

Certain drugs and toxins can cause elevated lactate levels, for example, carbon monoxide, alcohol, cocaine, cyanide, antiretroviral therapy for HIV, beta-adrenergic inhalers (prescribed for lung conditions like asthma), antibiotics (linezolid induced lactic acidosis), epinephrine used for severe allergic reactions, anesthetics such as propofol, and diabetes medications (metformin-associated lactic acidosis). This is classified as type B2 when lactic acidosis is a result of medication side effects or toxins.

Congenital lactic acidosis can occur due to deficiencies in enzymes needed for lactate metabolism. This is considered type B3. Examples include oxidative phosphorylation deficiency, pyruvate carboxylase deficiency, or pyruvate dehydrogenase deficiency.

Other types of lactic acidosis can occur due to severe infection. This is called D-lactic acidosis. This can lead to increased D-lactate levels. D-lactate is produced by bacteria in the colon that play a role in carbohydrate metabolism. Overgrowth of these bacteria can lead to D-lactic acidosis. The liver and kidneys cannot clear this type of lactate, causing it to accumulate in the body. This complication can often happen in people with short gut syndrome.

Besides comprehensive workups with various types of blood tests, anion gap is a blood test to check the acid-base balance of the blood and potential electrolyte abnormalities. When there is an elevated anion gap, it is called anion gap metabolic acidosis. Otherwise, it is called normal anion gap metabolic acidosis.

What organ does lactic acidosis affect?

Lactic acidosis can affect the heart and cause low cardiac output. Severe lactic acidosis can lead to organ failure and death.

What are the signs and symptoms of lactic acidosis?

Signs and symptoms of lactic acidosis may include fruity-smelling breath, fatigue, exhaustion, nausea, vomiting, respiratory compensation (fast and deep breathing), muscle cramps, abdominal pain, headache, and body aches.

More severe metabolic acidosis (lactic acidosis) can cause drowsiness, delirium, confusion, weakness, lack of coordination, and low urine output.

How do doctors diagnose lactic acidosis?

Doctors can diagnose lactic acidosis with blood tests. The criteria for lactic acidosis diagnosis is a blood lactate level of 4 millimoles per liter (mmol/L) or higher and an arterial pH level below 7.35. Other tests ordered for your healthcare team may include a comprehensive metabolic profile, anion gap test, and arterial blood gas test.

How do you fix lactic acidosis?

Temporary lactic acidosis that occurs, for example, due to overexertion or convulsions, usually clears without specific treatment. You can manage it at home with rest and fluids.

Severe lactic acidosis must be treated in the hospital with intravenous (IV) fluids, oxygen therapy, and other supportive measures to control excess lactate levels.

In the longer term, treatment for lactic acidosis depends on the underlying cause. For example, if renal failure (kidney failure) is the cause, your healthcare providers may recommend renal replacement therapy (dialysis). If you have low oxygen levels due to acute circulatory failure, they will treat this condition on an emergency basis. If no critical illness is present and findings do not suggest low oxygen, healthcare providers will consider an underlying etiology (cause) for type B lactic acidosis, such as toxin exposure.

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