Lactic Acidosis - Causes, Complications, and Treatment

Introduction:

Lactic acid is produced in the body by normal physiologic processes and as a finding in cases of diseases. When the secretion is increased and the clearance is slow, there are clinical complications. The increased levels of lactic acid have severe hemodynamic consequences, which can also lead to death.

The serum lactate level elevation can be considered a therapeutic target and risk marker. The higher the time it takes to normalize serum lactate levels, the more the chances of death are. Hyperlactatemia can occur in the presence of adequate oxygenation and tissue perfusion. In contrast, lactic acidosis occurs in case of inadequate tissue perfusion, abnormal carbohydrate metabolism, and due to consumption of some medicines.

What Are the Causes of Lactic Acidosis?

• Normally lactic acid is produced in excess by about 20 mmol/kg/day, which is metabolized mostly by the liver and the kidney. The liver and kidney have the necessary enzymes to utilize lactate for gluconeogenesis. However, some other tissues can use lactate as a substrate and oxidize it to carbon dioxide and water. The tissues which generally produce excess lactic acid are brain tissues, red cells, skin cells, muscles, and the gastrointestinal tract. In heavy exercises, skeletal muscle produces a high level of lactate which gets normalized due to impaired hepatic metabolism.

• Pyruvate, the end product of the glycolysis cycle, also gets converted into lactate under anaerobic conditions. The excess lactate produced in this process goes to the liver to undergo gluconeogenesis.

• Pathological and persistent lactic acidosis occurs when there is excessive lactate production and the liver's capacity is already exceeded to metabolize it. Some of the conditions which can lead to this condition and lactic acidosis are severe hypovolemia, severe hypotension, sepsis, hypothermia, and cirrhosis.

Some of the medications which can lead to lactic acidosis are:

1. Acetaminophen: It is used to treat mild to moderate pain like headaches, toothaches, menstrual pain, and backaches.

2. Beta-Adrenergic Agonists: These drugs help relax the airways' muscles and improve breathing.

3. HAART (Highly Active Antiretroviral Therapy): This drug regimen treats human deficiency virus type-1 (HIV-1).

4. Biguanides (Metformin): This drug is used to control glucose levels in cases of diabetes.

5. Propofol: It is a short-acting drug that leads to decreased levels of consciousness.

6. Salicylates: Medicines used to treat pain, fever, and inflammation.

7. Some other drugs which can also lead to lactic acidosis are alcohols, cocaine, halothane, valproic acid, and Sulfasalazine.

What Are the Different Levels of Lactate in the Body?

• The normal lactate levels in the body are always less than 2 mmol/L.

• In cases of hyperlactatemia, the lactate levels are between 2 mmol/L and four mmol/L.

• Severe increases in lactate levels range from 4 mmol/L to higher concentrations.

• Lactic acidosis can also be defined as pH less than or equal to 7.3 and lactatemia more than two mmol/L. The partial pressure of carbon dioxide is also reduced or equal to 42 mmHg.

What Are the Complications Caused by Lactic Acidosis?

• The increased levels of lactate lead to chances of organ failure.

• Cases of mild and moderately increased levels affected with sepsis have a high mortality rate of up to 30 days in the hospital.

• Lactic acidosis leads to a reduction in cardiac contractility and hyporesponsiveness by blood vessels to the vasopressin.

• One of the primary causes of metabolic acidosis is shock associated with lactic acidosis. Shock can be defined as a state where there is a shortage of oxygen due to inadequate circulation and delivery by the cells. Metabolic acidosis with a pH less than seven deleteriously affects the hemodynamics and may need supportive care.

What Are the Types of Lactic Acidosis?

Two types of lactic acidosis can occur in the body:

• Type-A Lactic Acidosis: It occurs due to hypoperfusion and hypoxia. Hypoxia is a lack of oxygen, which may happen when consumption and delivery mismatch, resulting in anaerobic glycolysis. The examples of type-A acidosis comprise all the states of shock like cardiogenic, septic, obstructive and hypovolemic.

• Type-B Lactic Acidosis: It is less common than type-A lactic acidosis and has nothing to do with tissue hypoxia or hypoperfusion. However, it also prevents the mitochondria from processing the amount of pyruvate, which then undergoes a lactic acid cycle, and the number of lactate increases in the body. Type B lactic acidosis can occur in conditions such as liver diseases, total parenteral nutrition, thiamine deficiency, mitochondrial myopathy, diabetic ketoacidosis, and ethanol intoxication.

What Are the Symptoms of Lactic Acidosis?

There are no specific symptoms of lactic acidosis, and they depend on the underlying cause. However, patients with lactic acidosis are critically ill and in a shocking state, such as septic, hypovolemic or cardiogenic. An examination may show symptoms of hypotension, oliguria, tachypnea, and altered mental status of the patient. Kussmaul respirations, characterized by deep breathing, can be noticed in cases of lactic acidosis as the body is trying to compensate for metabolic acidosis.

How to Diagnose Lactic Acidosis?

The evaluation of lactate concentration is checked by suspecting serum electrolytes, arterial blood gas analysis, and metabolic acidosis. If the anion gap is elevated, it indicates lactic acidosis. In the absence of unmeasured ions such as lactate, the anion gap is typically between four mEq/L to 12 mEq/L. When there is excess lactate, this value exceeds 12 mEq/L.

How to Treat Lactic Acidosis?

The treatment of lactic acidosis depends on the treatment of the underlying cause of it. For example, if the lactic acidosis is due to mesenteric ischemia, then the treatment of ischemia, that is, surgery may be performed. Similarly, treating the seizure is important in cases of convulsions from a seizure.

Thus the treatment options for lactic acidosis are highly diverse depending on the underlying cause. Lactic acidosis due to drugs can be prevented by replacing or altering the dosages.

Conclusion:

Lactic acidosis is a condition with increased lactate levels due to underlying causes such as shock, lack of oxygen, and anaerobic glycolysis in the body. It can also be caused due to some drugs, such as Acetaminophen. The condition's symptoms include altered mental status, oliguria, and hypotension.