Lactic acidosis definition
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Understanding Lactic Acidosis: Definition and Key Insights
Definition of Lactic Acidosis
Lactic acidosis is a type of metabolic acidosis characterized by an elevated concentration of lactic acid in the blood, leading to a decrease in blood pH. It is defined by a plasma lactate level greater than 5 mmol/L and a systemic pH less than 7.30 . This condition arises when there is an imbalance between the production and clearance of lactate, a byproduct of anaerobic metabolism.
Causes and Types of Lactic Acidosis
Overproduction and Underutilization of Lactate
Lactic acidosis can result from either the overproduction or the underutilization of lactate. Overproduction, also known as Type A lactic acidosis, typically occurs in conditions where tissue oxygenation is impaired, such as in cases of shock, sepsis, or severe hypoxia . This type is often associated with circulatory, pulmonary, or hemoglobin transfer disorders.
Underutilization of lactate, or Type B lactic acidosis, occurs when the body's ability to clear lactate is compromised. This can be due to liver disease, inhibition of gluconeogenesis, or deficiencies in enzymes such as pyruvate dehydrogenase . Type B lactic acidosis can also be caused by certain drugs, toxins, or metabolic disorders .
Clinical Presentation and Diagnosis
Clinically, lactic acidosis presents with signs of metabolic acidosis, including a large anion gap and decreased blood pH . Symptoms may include rapid breathing, confusion, and lethargy. The condition is often identified through blood tests showing elevated lactate levels and decreased pH .
Pathophysiology and Mechanisms
Anaerobic Metabolism and Lactate Production
Lactate is produced during anaerobic respiration when oxygen levels are insufficient for aerobic metabolism. Under normal conditions, lactate is cleared by the liver, kidneys, and skeletal muscles. However, in lactic acidosis, the body's buffering systems are overwhelmed, leading to an accumulation of lactate in the blood .
Role of the Liver and Other Organs
The liver plays a crucial role in lactate clearance through processes such as oxidation and conversion to glucose. Abnormalities in liver function can significantly contribute to the development of lactic acidosis. The kidneys also assist in lactate removal, and renal dysfunction can exacerbate the condition.
Treatment and Prognosis
Addressing the Underlying Cause
The primary approach to treating lactic acidosis is to address the underlying cause of lactate overproduction or underutilization. This may involve improving tissue oxygenation, treating infections, or correcting metabolic imbalances .
Controversial Therapies
The use of sodium bicarbonate to correct acidosis is controversial, as it may increase lactate production and has not been shown to improve survival rates significantly . Alternative treatments, such as dichloroacetate, have shown promise in experimental models but have not demonstrated significant clinical benefits.
Prognosis
The prognosis for lactic acidosis varies depending on the underlying cause and the timeliness of treatment. Mortality rates can be high, particularly in cases associated with severe hypoxia or multi-organ failure. Early recognition and prompt treatment of the underlying causes are critical for improving outcomes .
Conclusion
Lactic acidosis is a complex metabolic disorder resulting from an imbalance in lactate production and clearance. It can be caused by a variety of conditions, both hypoxic and non-hypoxic. Understanding the underlying mechanisms and promptly addressing the root causes are essential for effective management and improving patient outcomes.
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