From the Guidelines
Type B lactic acidosis is a metabolic condition characterized by elevated blood lactate levels without evidence of tissue hypoxia or hypoperfusion, often caused by medications such as metformin, particularly in patients with renal impairment, and requires management focused on treating the underlying cause rather than the acidosis itself.
Causes and Mechanisms
- Type B lactic acidosis develops when oxygen delivery is adequate but lactate production increases or clearance decreases due to other mechanisms.
- Common causes include medications (metformin, nucleoside reverse transcriptase inhibitors), malignancies (especially lymphomas and leukemias), liver disease, thiamine deficiency, and certain inborn errors of metabolism.
- Specific medications like metformin can cause this condition through inhibition of mitochondrial function, as noted in studies such as 1 and 1.
Management and Treatment
- Management focuses on treating the underlying cause rather than the acidosis itself.
- For medication-induced cases, discontinuation of the offending drug is essential, as seen in the context of metformin use in patients with renal impairment 1.
- In malignancy-related cases, treating the cancer is paramount.
- Supportive care with intravenous fluids and close monitoring of acid-base status is important during treatment, as generally recommended in clinical practice guidelines.
Clinical Considerations
- Understanding the distinction between Type A and B lactic acidosis is crucial for proper diagnosis and management, as the treatment approaches differ significantly based on the underlying pathophysiology.
- The risk of lactic acidosis with metformin use, particularly in patients with renal impairment, should be carefully considered, as highlighted in studies such as 1.
- Recent guidelines, such as those from 1, provide updated recommendations on the use of metformin in patients with diabetes, emphasizing its benefits while also acknowledging the need for caution in certain patient populations.
From the FDA Drug Label
There have been postmarketing cases of metformin-associated lactic acidosis, including fatal cases. Metformin associated lactic acidosis was characterized by elevated blood lactate concentrations (>5 mmol/L), anion gap acidosis (without evidence of ketonuria or ketonemia), and an increased lactate: pyruvate ratio;
Type B lactic acidosis is not explicitly defined in the provided drug label. The label discusses metformin-associated lactic acidosis, but does not provide a specific definition for type B lactic acidosis 2.
From the Research
Definition and Characteristics of Type B Lactic Acidosis
- Type B lactic acidosis is a distinct form of metabolic acidosis characterized by low blood pH (≤ 7.35) accompanied by accumulation of lactate (blood concentration ≥ 5 mmol/L) 3.
- It is a rare complication of non-tissue perfusion abnormalities caused by solid tumors or hematologic malignancies 4.
- Type B lactic acidosis occurs in the absence of tissue hypoxia, unlike Type A, which is caused by the lack of oxygen (tissue hypoxia or hypoperfusion) 3, 5.
Causes and Associations of Type B Lactic Acidosis
- Type B lactic acidosis is occasionally found in patients with hematological malignancies, such as leukemia or lymphoma 3.
- It has also been associated with drugs like metformin, linezolid, and nucleoside reverse-transcriptase inhibitors in patients with HIV 6.
- Venlafaxine overdose has been reported as a cause of type B lactic acidosis 6.
- The Warburg effect, which is characterized by a high metabolic rate dominated by glycolysis in rapidly growing malignant tumors, is thought to be a cause of lactic acidosis and/or hypoglycemia in some cases 4.
- Hematologic malignancies, such as diffuse large B-cell lymphoma and Burkitt's lymphoma, have been reported as causes of type B lactic acidosis 4, 7.
Clinical Presentation and Prognosis of Type B Lactic Acidosis
- Type B lactic acidosis can present with severe metabolic acidosis, elevated lactate levels, and hypoglycemia 4, 7.
- The prognosis of lactic acidosis in patients with malignant tumors is very poor 4.
- Effective chemotherapy seems to be the only hope for survival in some cases 4.
- Patients presenting with elevated lactic acid levels need to be thoroughly worked up for all potential causes, including occult high-grade malignancies 5, 7.