Relationship of cerebrovascular symptoms to blood viscosity in a patient with iron deficiency and cyanotic heart disease

Abstract

Iron deficiency predisposes children with cyanotic forms of congenital cardiac disease to cerebrovascular accidents. We studied the contribution of blood viscosity (η) to the cerebrovascular symptoms of an iron deficient adolescent girl with a complete form of transposition of the great vessels. At clinical presentation, blood η was elevated and greater than expected for the hematocrit (HCT) level. An isovolemic, isohematocrit exchange transfusion with iron sufficient blood decreased blood η, rendered η appropriate for HCT level, and stopped cerebrovascular symptoms within hours. Hemoglobin (HB), HCT, chromium 51 red cell mass, pulse, blood pressure and blood gases were unaffected by treatment. Cerebrovascular symptoms returned while blood iron deficiency persisted as blood η again increased beyond that expected for HCT; the anomalous η and symptoms were reversed by isovolemic plasma hemodilution. A comparable magnitude of blood η was well tolerated after blood iron sufficiency was attained and η was appropriate for HCT. The anomalous flow behavior of iron deficient blood was temporally associated with the central nervous system manifestations of polycythemic cyanotic heart disease in our patient.