Abstract TMP10: Children With Sickle Cell Anemia Have Impaired Cerebrovascular Reactivity

Abstract

Introduction: Sickle Cell Anemia (SCA) causes lower hemoglobin, leading to increased cerebral blood flow (CBF) to maintain cerebral oxygen metabolism (CMRO 2 ). Although CBF rises in childhood to meet higher CMRO 2 demands, further compensatory increases in CBF in children with SCA may tap into a limited hemodynamic reserve, increasing risk for infarct. Cerebrovascular reactivity (CVR) reflects hemodynamic reserve by measuring the vasculature’s response to vasoactive stimuli, particularly in the gray matter (GM). We hypothesized that children with SCA have lower GM CVR, regardless of CMRO 2 . Methods: We used magnetic resonance imaging of children with and without SCA to collect pseudocontinuous arterial spin labeling (pCASL) for CBF, asymmetric spin echo for oxygen extraction fraction (OEF) and blood oxygen level dependent (BOLD) data correlated with hypercapnic challenges for CVR. Lab draws confirmed Hemoglobin (Hb) values. CMRO 2 was calculated as CBF x OEF x Arterial Oxygen Content (1.36 x Hb x SpO 2 ). Continuous variable differences between groups were analyzed using the Mann-Whitney U test, and categorical variables using the Fisher’s exact test. Linear regression assessed the relationship between CVR and Hb. Reported significant relationships survived multiple comparisons correction. Results: A total of 35 participants, ages 8–22 years had quality CVR data [9 SCA subjects (5 male) and 26 controls (9 male)]. Of these, 8 SCA and 20 controls had adequate quality metabolic data. The groups are matched by age (p=0.56) and sex (p=0.43). Children with SCA had higher GM CBF (62.0 v 49.3 mL/100g/min; p=0.03), but similar GM CMRO 2 (1.81 v 1.42 mL/100g/min; p=0.07) than controls. GM CVR was significantly lower in SCA than controls (0.17 v 0.27 %/mmHg; p=0.0003). Lower CVR was associated with lower Hb (Figure) after adjusting for age and sex (p <0.0001). Conclusion: Lower GM CVR in children with SCA indicates a lower hemodynamic reserve, likely related to the degree of anemia.