Increased blood viscosity in patients with cyanotic congenital heart disease and iron deficiency

Abstract

I~I YPERVISCO SITY RESULTING FROM POLYCYTHEMIA has been reported frequently in children with cyanotic congenital heart disease. '-~ These patients are at high risk to develop cerebrovascular complications, if polycythemia is accompanied by iron deficiency and microcytosis? -; Iron-deficient microcytic red blood Cells from rabbits and rats were found to be less deformable than normal RBCs? ' To our knowledge rheologic studies on iron-deficient microcytic human RBCs have been reported in only two patients and demonstrate decreased filterability of RBCs in one case ~~ and increased viscosity in the other? The present study was undertaken to evaluate the effect of microcytosis on the viscosity of RBCs suspended in plasma or in albumin solution at a hematocrit of 60%. At this hematocrit, which is often observed in children with cyanotic heart disease, small changes in theologic properties of RBCs markedly influence blood viscosity. H PATIENTS AND METHODS Fifty-nine infants and children (age 6 months to 12 years) with various types of cyanotic congenital heart disease were studied with informed consent of the patient and/or parents. Five milliliters of venous blood were collected in plastic tubes containing powdered EDTA for the viscosity studies and 1 ml in tubes without anticoagulant for the determination of serum iron and total ironbinding capacity. The anticoagulated blood was centrifuged at 2,000 g. Plasma and buffy coat were removed separately. The RBCs were resuspended in the removed autologous plasma and in 1% albumin in NaCl-phosphate buffer solution (osmolality 300 m0sm/1; pH 7.40) at hematocrits of 60 _+ 1%. Hematocrit was measured in duplicate by the microhematocrit method. The values were not corrected for trapped plasma. Studies in our laboratory have shown that plasma trapping between the centrifuged RBCs is about 2% when RBCs are normo- or macrocytic and