Correlation of the middle cerebral artery blood flow velocity with age and Haemoglobin values of children with Sickle cell anaemia in Uyo

Abstract

Introduction: Sickle cell anaemia (SCA) occurs in 1-3% of the Nigerian population. It is the most common cause of stroke in children. The time-averaged mean of the maximum velocity (TAMMV) in the Middle cerebral arteries (MCA) measured by transcranial Doppler (TCD) ultrasonography can estimate the risk of stroke in SCA children. Some clinical factors associated with abnormal TAMMV flows and first stroke (infarctive) in children with SCA are age and low haemoglobin.

Aim: To determine the association between TAMMV of the middle cerebral artery (MCA) in patients with SCA with their age and haemoglobin values and compare it with age and sex-matched children with Haemoglobin AA (HbAA) genotype.

Method: This was a comparative cross-sectional descriptive study conducted among 40 confirmed HbSS patients in steady state and a comparison group of 40 healthy HbAA age and sex-matched children. Demographic and medical data were obtained using a structured proforma. Haemoglobin concentration was estimated for all participants. TCD ultrasound was performed for all participants using the Stroke Prevention Trial in Sickle Cell Anaemia (STOP) protocol. Data was analysed in Statistical Package for Social Science version 22.0 (SPSS Inc., IL, USA).

Results: The mean and standard deviation (Mean±SD) age of HbSS patients was 9.1 ± 4.4 years. The majority (42.5%) of the HbSS children were in the 10-14 years age group. The HbSS patients had a consistently lower mean Hb than the HBAA participants across all age groups and this was statistically significant. (p=<0.001, <0.001, <0.001 and 0.001 respectively).

There was a significant difference in mean MCA velocity between HbSS and HbAA in the age groups above 5 years. (p <0.001). In addition, a significantly moderate positive correlation was observed between the Right MCA velocity and age in the HbSS population (r = 0.451, p = 0.004). While a significant negative correlation was observed between the measured TAMMV of the right MCA and the haemoglobin concentration in both the HbSS and HbAA groups (r = -0.490, p = 0.002) and (r = -0.600, p <0.001).

Conclusion: Our study has observed a positive correlation between age and MCA TAMMV and a negative correlation between Hb concentration and TAMMV in SCA children. The maintenance of adequate Hb in children with SCA is important in reducing the development of abnormal TAMMV velocities which carries a significant risk of stroke.