From the Guidelines
Lactic acidosis is categorized into two types: Type 1, resulting from tissue hypoxia, and Type 2, caused by metabolic derangements, medications, or toxins, with metformin being a common culprit in the latter, as evidenced by recent guidelines 1.
Causes and Classification
Lactic acidosis can be classified into two types based on the underlying cause:
- Type 1 (Type A) lactic acidosis results from tissue hypoxia and inadequate oxygen delivery, commonly seen in conditions like shock, severe anemia, or cardiac arrest.
- Type 2 (Type B) lactic acidosis occurs despite adequate tissue oxygenation and is caused by metabolic derangements, medications, or toxins, with metformin toxicity being a notable example, as it can lead to very high circulating levels and increased risk of lactic acidosis, especially when the estimated glomerular filtration rate (eGFR) is <30 mL/min/1.73 m² 1.
Management and Treatment
Management of lactic acidosis involves:
- Addressing the underlying cause, such as improving oxygen delivery in Type 1 or discontinuing the offending agent in Type 2.
- Supporting organ function and occasionally using bicarbonate therapy for severe acidosis (pH < 7.1).
- In cases of metformin-associated lactic acidosis, hemodialysis may be required in severe cases, as the drug is cleared by kidney filtration and high levels can be toxic 1.
Clinical Presentation and Diagnosis
Both types of lactic acidosis present with similar symptoms, including:
- Tachypnea
- Altered mental status
- Hypotension Laboratory findings show elevated lactate levels (typically >4 mmol/L) and metabolic acidosis with an increased anion gap, highlighting the importance of prompt identification and management to improve outcomes 1.
From the Research
Definition and Classification of Lactic Acidosis
- Lactic acidosis is the most common metabolic acidosis, characterized by the accumulation of lactate in the body 2.
- It can be classified into two main types: type 1 and type 2 lactic acidosis, although the exact classification is not explicitly stated in the provided studies.
- Type 1 lactic acidosis is often associated with tissue hypoxia, while type 2 lactic acidosis is related to other causes, such as underlying diseases or medications 3, 4.
Pathophysiology of Lactic Acidosis
- The liver plays a crucial role in removing lactate and hydrogen ions from the body, and abnormalities in aerobic metabolism can contribute to lactic acidosis 2.
- Tissue hypoxia and epinephrine-induced stimulation of aerobic glycolysis are two main mechanisms that contribute to lactic acid accumulation in sepsis and low-flow states 5.
- The cellular injury associated with lactic acidosis is partly due to the activation of NHE1, a cell-membrane Na(+)/H(+) exchanger 5.
Clinical Significance and Treatment of Lactic Acidosis
- Elevated lactate levels in critically ill patients have important implications for morbidity and mortality 6.
- Prompt recognition and treatment of the underlying causes of lactic acidosis remain the cornerstone of treatment 2, 5.
- Eliminating the triggering conditions, such as sepsis or low-flow states, is the most effective therapy for lactic acidosis 5.
- Other treatments, such as sodium bicarbonate administration, hyperventilation, and infusion of calcium, may be considered, but their effectiveness is still being researched 5.