Extrinsic Nonimmune Hemolytic Anemias

Published on 04/03/2015 by admin

Filed under Hematology, Oncology and Palliative Medicine

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Chapter 17 Extrinsic Nonimmune Hemolytic Anemias

Elizabeth A. Price, Stanley S. Schrier

Differential Diagnosis of Extrinsic Nonimmune Hemolytic Anemias

There is no simple approach to the differential diagnosis of hemolysis caused by extrinsic nonimmune hemolytic anemia. The physician must pay close attention to the clinical finding. Useful clues come from a determination of whether RBC breakdown is predominantly extravascular or intravascular, but most important in the analysis is the observation of RBC morphology, which can focus the differential diagnosis. Unhelpful terms such as aniso and poik should be discarded. RBCs are spherocytic, stomatocytic, fragmented, echinocytic, acanthocytic, spurred, or bite cells or can be mixtures of these types.

Reduction of Dangerous Methemoglobin Levels

Levels of methemoglobin in excess of 20% to 30% can be dangerous, but they can be easily treated with methylene blue (1-2 mg/kg) infused intravenously over 5 minutes as 0.1 to 0.2 mL/kg of a 1% solution. In the presence of a functioning, intact NADPH–methemoglobin reductase system, methylene blue is reduced to leukomethylene blue, which reduces methemoglobin to hemoglobin.

Agents that Cause Oxidative Hemolysis

Therapeutic agents

Nitrofurantoin (Furadantin)
Sulfasalazine (Azulfidine)
p-Aminosalicylic acid
Phenazopyridine (Pyridium)
Phenacetin
Dapsone and other sulfones
Primaquine

Recreational drugs

Isobutyl nitrate
Amyl nitrite

Miscellaneous agents

Naphthalene mothballs
Paraquat
Hydrogen peroxide

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Chapter 17 Extrinsic Nonimmune Hemolytic Anemias

Elizabeth A. Price, Stanley S. Schrier

Differential Diagnosis of Extrinsic Nonimmune Hemolytic Anemias

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