Subarachnoid Hemorrhage in a Young Child With Sickle Cell Disease: Is Transcranial Doppler Helpful?: In Reply

The observation of Ross et al provides a serendipitous insight into the possible effects of transfusion and subarachnoid hemorrhage (SAH) on cerebral blood flow velocities (CBFVs) in children with sickle cell disease (SCD). Their patient, an 8-year-old girl with hemoglobin SS, had abnormally high transcranial Doppler (TCD) velocities of the bilateral middle cerebral arteries (204 cm/second on the left and 220 cm/second on the right) before blood transfusion for acute chest syndrome. CBFV is inversely proportional to hematocrit,1 so worsening anemia may have been partially responsible for the elevation. Increases in metabolic requirements of the brain, such as with a fever or hypoxia, also increase CBFV as the brain increases blood flow to meet metabolic demands.2 However, although not seen on angiography, the degree of elevation suggests that other processes, such as fixed stenosis or vasoconstriction, may have also contributed. Elevated velocity was associated with hemorrhagic stroke …