Background: Sickle cell disease (SCD) is the most common cause of stroke in children. Impairment of vasodilatory capacity reflecting reduced cerebrovascular reserve was previously shown in adults with SCD and might play a role in the pathophysiology of stroke in such patients. We assessed the hypothesis that children with SCD would also have a higher frequency of impaired cerebral vasoreactivity when compared to healthy age-matched subjects.
Patients and Methods: Patients were selected from the pediatric outpatient clinic of the Department of Hematology at our University Hospital. All those patients with SCD disease (diagnosis confirmed by hemoglobin electrophoresis on cellulose acetate) without a history of symptomatic stroke aged 10 to 18 years old were evaluated. Healthy children of similar age and gender were also studied. Transcranial Doppler (TCD) was performed in all patients and controls subjects, with breath-holding maneuver and calculation of the breath-holding index (BHI) to assess cerebral vasoreactivity. The BHI was obtained by dividing the percentage increase in mean flow velocity occurring during breath holding by the length of time (seconds) subjects hold their breath after a normal inspiration. BHI was considered abnormal if < 0.69.
Results: TCD was performed in 42 patients (mean age 12.7 +/-2.2 years) and 20 controls (mean age 13.90 +/-3.04 years). Blood flow velocities were higher in patients with SCD than in healthy volunteers in all arteries evaluated (p<0.01). Cerebral blood flow velocities were negatively correlated with hemoglobin levels (p<0.05). BHI values in patients with SCD were significantly lower than in control subjects (1.27 +/-0.65 versus 1.74 +/- 0.15, p=0.01 at left and 1.16 +/- 0.45 versus 1.61 +/- 0.11, p<0.01 at right). BHI was abnormal in 19% of the patients and none of the healthy controls (p=0.04).
Conclusions: In conclusion, children with SCD may have impaired cerebral vasoreactivity, with low BHI values suggesting a reduced autoregulation capacity in these patients.