Clinical correlates of steady-state oxyhaemoglobin desaturation in children who have sickle cell disease

Abstract

Individuals with sickle cell disease (SCD) may have oxyhaemoglobin desaturation during the steady-state, the causes of which are incompletely known. We studied a cohort of 585 children who have sickle cell anaemia (SS), sickle beta0-thalassaemia (Sbeta0), sickle-haemoglobin C disease (SC), or sickle beta+-thalassaemia (Sbeta+) to determine the relationships between steady-state oxyhaemoglobin saturation (SpO2) and SCD genotype, age, gender, steady-state haemoglobin (Hb) and reticulocyte count, and rate of acute chest syndrome (ACS). The SS/Sbeta0 group (n = 390) had lower mean SpO2 than the SC/Sbeta+ group (n = 195) (96.3% vs. 98.7%, P < 0.001). Among SS/Sbeta0 subjects, a decrease in steady-state SpO2 correlated with a decrease in Hb, an increase in reticulocytes, older age and male gender. These correlations were not found in the SC/Sbeta+ group. Prior ACS did not correlate with steady-state SpO2. A multivariate model explained 45% of the variability in SpO2, but only 5% of the variation in SpO2 was explained by Hb. We conclude that steady-state desaturation is common in individuals with SCD, but it appears to be unrelated to prior episodes of ACS and largely unexplained by chronic anaemia.

Figures

Fig 1

Histograms of steady-state oxyhaemoglobin saturation, SpO2 by sickle cell disease genotype. Panel (A) depicts subjects with either sickle cell anaemia or sickle β0-thalassaemia. Panel (B) depicts subjects with either sickle-haemoglobin C or sickle β+-thalassaemia.

Fig 2

Bivariate correlations between steady-state oxyhaemoglobin saturation (SpO2) and other variables by sickle cell disease genotypes. Panel (A) shows the correlation between Hb (Hgb) and SpO2 among sickle cell anaemia (SS, grey circles) and sickle β0-thalassaemia (Sβ0, black squares) subjects. Panel (B) shows the correlation between Hb (Hgb) and SpO2 among sickle-haemoglobin C (grey circles) and sickle β+-thalassaemia (Sβ+, black squares) subjects. Panel (C) illustrates the correlation between SpO2 and age among SS and Sβ0 subjects. Panel (D) depicts the lack of correlation between SpO2 and rate of acute chest syndrome among SS and Sβ0 subjects.