A patient with Eisenmenger syndrome may develop erythrocytosis to compensate for hypoxemia associated with pulmonary hypertension and a right-to-left shunt through a congenital heart defect. Therapy for the erythrocytosis may be required in certain clinical situations.


Patient selection: Eisenmenger syndrome and erythrocytosis (hematocrit > 55%)

Clinical Situation


dehydration secondary to poor oral intake, diarrhea, diuresis, burn, fever and/or diaphoresis


non-cardiac surgery

isovolumic phlebotomy before surgery and prevention of any hypovolemia

symptoms of hyperviscosity and microcytic indices (low MCV) associated with iron deficiency

correction of iron deficiency, with close monitoring for sudden worsening of hyperviscosity symptoms, which may require isovolumic phlebotomy

symptoms of hyperviscosity and normocytic indices (normal MCV)

isovolumic phlebotomy



• Isovolumic phlebotomy = removal of a unit/pint of whole blood (500 mL) with replacement of an equal volume of normal saline, fresh frozen plasma, salt-free albumin or dextran solution.

• The goal of phlebotomy before surgery is to reduce the hematocrit to <= 65%. The goal of phlebotomy for hyperviscosity is to reduce symptoms rather than to achieve a target hematocrit.

• Symptoms of hyperviscosity may include visual disturbances, headache, dizziness, or subtle neurologic abnormalities.

• Microcytic red blood cells are less deformable than larger red blood cells and so are associated with a higher whole blood viscosity.

• Iron replacement in an iron deficient patient may be followed by increased erythropoiesis, resulting in increased hyperviscosity.

• A patient with microcytosis associated with thalassemia would not benefit from the iron replacement unless there was mixed thalassemia and iron deficiency.


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