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The appearance of blood in a tube from a peripheral blood draw can give a clue to disease. A specimen may demonstrate lipemia (see Fig. 25.62), which is defined as visible turbidity in serum samples due to lipoprotein particles, specifically chylomicrons. The most common cause of lipemia is hypertriglyceridemia.
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Methemoglobinemia results in a deep brown color of a peripheral blood draw due to the reduced oxygen-carrying capacity of methemoglobin. The most common cause is drug or toxin exposure. Medications notorious for causing methemoglobinemia include benzocaine, dapsone, amyl nitrite, sulfonamides, chloroquine, metoclopramide, and nitroprusside.
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Management and Disposition
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Patients with hypertriglyceridemia typically come to the emergency department because of consequences of the disease such as acute pancreatitis, myocardial infarction, or stroke.
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Treatment of methemoglobinemia is intravenous methylene blue.
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The most common cause of endogenous laboratory interference after hemolysis is lipemia.
Methemoglobin levels of 15% to 30% will cause cyanosis and brown blood.
Methylene blue, the antidote for methemoglobinemia, can cause methemoglobinemia.