What are the types of lactic acidosis?

From the Guidelines

Lactic acidosis is classified into two main types: Type A and Type B, with Type B further divided into subtypes B1, B2, and B3, and the management of each type requires a distinct approach to address the underlying cause and prevent morbidity and mortality.

Types of Lactic Acidosis

• Type A lactic acidosis occurs due to tissue hypoxia and inadequate oxygen delivery, commonly seen in conditions like shock, severe anemia, carbon monoxide poisoning, and cardiac arrest, as noted in various studies 1.
• Type B lactic acidosis occurs without tissue hypoxia and is further divided into three subtypes:
  • B1 (associated with diseases like diabetes, liver failure, and malignancies) 1.
  • B2 (caused by medications or toxins such as metformin, alcohols, salicylates, and nucleoside reverse transcriptase inhibitors) 1.
  • B3 (related to inborn errors of metabolism) 1.

Clinical Management

The distinction between these types is crucial for clinical management, as Type A requires addressing the underlying oxygen delivery problem, while Type B management focuses on removing the offending agent or treating the underlying condition, as emphasized in recent guidelines 1. Regardless of type, severe lactic acidosis may require supportive care including intravenous fluids, vasopressors if needed, and in some cases, bicarbonate therapy for severe acidemia, though this remains controversial and should be guided by the most recent and highest quality evidence 1.

Recent Evidence

A recent study published in 2021 in The Lancet Diabetes and Endocrinology 1 highlights the importance of careful management of metformin in patients with diabetes, particularly in those with renal impairment, to prevent lactic acidosis. Another study published in 2019 in Circulation 1 discusses the use of metformin in patients with heart failure and diabetes, emphasizing its benefits and potential risks. These studies, along with others 1, underscore the complexity of lactic acidosis management and the need for a tailored approach based on the underlying cause and individual patient factors.

From the Research

Types of Lactic Acidosis

Lactic acidosis is classified into two major types based on pathophysiology:

• Type A: results from tissue hypoxia and/or hypoperfusion 2, 3, 4
• Type B: results from deranged metabolic activity in the cells in the absence of hypoxia/hypoperfusion 2, 3, 4, 5, 6

Characteristics of Type A Lactic Acidosis

• Caused by the lack of oxygen (tissue hypoxia or hypoperfusion) 3, 4
• Impaired cellular respiration leads to lower pH level and increased production of lactate 4
• More common than type B lactic acidosis 2

Characteristics of Type B Lactic Acidosis

• Relatively rare 4
• Occasionally found in patients with hematological malignancies, such as leukemia or lymphoma 4, 6
• Can be caused by drug-induced metabolic abnormalities, such as excessive use of long-acting beta agonists 5
• May be overlooked due to clinicians' poor awareness 5