Acute Hemodynamic Effects of Red Cell Volume Reduction in Polycythemia of Cyanotic Congenital Heart Disease

Abstract

Acute reduction in red cell volume (RCV) without significant alterations of blood volume in 22 patients with severe polycythemia secondary to cyanotic congenital heart disease resulted in a decrease in peripheral vascular resistance and an increase in stroke volume, systemic blood flow (SBF), and systemic oxygen transport. These changes are probably related to the decreased blood viscosity and yield shear stress associated with lower red cell concentrations. Hypervolemia in hypoxic polycythemia should be maintained in order to sustain an adequate SBF. In contrast to acute phlebotomy which may be expected to decrease blood oxygen content and SBF, the replacement of whole blood with plasma or 5% albumin is shown to result in an increased systemic blood flow and oxygen delivery.

Polycythemia vera: myths, mechanisms, and management

“…Finally, the effectiveness of venesection in relieving symptoms due to an elevated red cell mass has been repeatedly documented in patients with secondary forms of erythrocytosis. [304][305][306][307] Iron deficiency and whole blood viscosity…”

Risk of stroke in adults with cyanotic congenital heart disease.

“…17 It is well to bear in mind, however, that in cyanotic iron-deficient infants and young children, the cerebrovascular occlusive events are venous, not arterial,9'10 and during the erythrocytotic phase of polycythemia rubra vera, treatment with phlebotomy alone is associated with a statistically significant increase in the risk of thrombotic complications including cerebral infarction, a risk that increased in parallel with the frequency of phlebotomy. 6 Golde et all8 cautioned against using hematocrit levels per se as the criterion for phlebotomy in patients with secondary erythrocytosis.…”

Hydroxyurea therapy for management of secondary erythrocytosis in cyanotic congenital heart disease

“…First, the myelosuppressive effect of hydroxyurea can be titrated to sufficiently decrease the red cell count and thus lower the hematocrit, while avoiding toxicity such as significant neutropenia or thrombocytopenia. A lower hematocrit directly reduces the blood viscosity and improves perfusion and oxygen delivery to the tissues [1,3,5,6]. Second, hydroxyurea also induces macrocytosis with increased MCV and MCH while preserving the MCHC.…”

“…However, this approach can have serious consequences including inadequate oxygen delivery and symptomatic hypoxemia, as well as effects from acute changes in blood volume and viscosity, which may paradoxically increase the risk of stroke or other end organ damage independent of the hematocrit [5,6]. Repeated phlebotomy may result in iron deficiency leading to increased rigidity within red cells, which further increases the risk of symptomatic hyperviscosity [7][8][9][10][11].…”