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Defining
the Syndrome
| •
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Metabolic
acidosis (pH < 7.25) |
| •
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Blood
lactate > 5 mmol/L |
| •
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Type
A: Anaerobic |
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-
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Tissue
hypoxia
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| •
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Type
B: Aerobic |
|
-
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Malignancy,
glycogen storage diseases, certain myopathies, mitochondrial
toxicity |
| •
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Lactate
level > 9 mmol/L |
|
-
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Widespread
energy deficits contribute to organ failure |
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-
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Mortality
exceeds 75% |
•
Clinically, the syndrome is defined as metabolic acidosis, specifically
a pH < 7.25, accompanied by a blood lactate level of >5 mmol/L.
• Lactic acidosis may be either Type A or Type B. Anaerobic Type
A is associated with tissue hypoxia. Type B is associated with malignancy,
glycogen storage diseases, certain myopathies, and mitochondrial toxicity.
• It is this mitochondrial toxicity that accounts for Type B
lactic acidosis in patients with HIV infection. Nucleoside reverse
transcriptase inhibitors (NRTIs) inhibit mitochondrial DNA replication,
resulting in liver damage.
• When blood lactate levels exceed 9 mmol/L, wide-spread energy
deficits contribute to organ failure, with a mortality rate greater
than 75%. Anion gap is often, but not always, elevated in patients
with lactic acidosis.1,2
References:
1. Chattha G, Arieff AI, Cummings C, Tierney LM Jr. Lactic acidosis
complicating the acquired immunodeficiency syndrome. Annals Intern
Med. 1993;118:37-9.
2. Parrillo JE and Bone RC, eds. Critical Care Medicine: Principles
of Diagnosis and Management. St. Louis, MO:Mosby; 1995;1090.
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