Oxygen Desaturation at Rest and after Exercise in Pediatric Sickle Cell Disease Patients: Correlations with Hemolysis and Elevated Tricuspid Regurgitant Jet Velocity.

Background. As a part of a multicenter, observational study in determining the prevalence and risk factors of elevated tricuspid regurgitant jet velocity (TRV) in children, oxygen desaturation correlated with TRV. We further investigated the risk factors and clinical associations of oxygen desaturation at rest and after execrcise in children at steady state. Methods. 310 children and adolescents with sickle cell disease were studied under basal conditions. Pulse oximetry was determined at rest and after a six minute walk test. The relationships of oxygen saturation at rest and desaturation during exercise to the available clinical and laboratory variables were investigated. Results. Among 300 patients with available baseline oxygen saturations, 30 (10%) had saturation <95 percent, 129 (43%) had saturation of 95–98 percent, and 141 (47%) had saturation >98 percent. Twenty-three (9%) of 244 patients had >3 percentage point reduction in oxygen saturation during a six minute walk; the median (interquartile range) baseline saturation was 96 (95– 99) percent among these patients versus 98 (97–100) percent among those with less or no reduction in saturation during the walk (P = 0.0009). Hemoglobin (p<0.0001), creatinine (p=0.014) and total lung capacity (p=0.042) were also lower in patients with declines in saturations >3 percentage points during the walk while a hemolytic index (p<0.0001), tricuspid regurgitant jet velocity (p=0.030), pulmonary insufficiency end diastolic velocity (PIEDV) (p=0.019), left ventricular mass index (LVMI) (p=0.0006) and left ventricular internal diameter z score (LVIDD z score) (p=0.0001) were higher. In 3 separate logistic regression models (clinical variables, echocardiographic parameters, and pulmonary function testing), lower hemoglobin, hemolytic index, PIEDV, LVIDD z score, and low TLC were independent predictors of six-minute-walk desaturation of >3 percentage points. Conclusion. Markers of hemolysis, low hemoglobin, PIEDV, LVMI, LVIDD z score, lower TLC, and elevated TRV velocities are associated with ≥3% reduction in oxygen desaturation during six minute walk in children and adolescents with sickle cell disease. A high degree of oxygen desaturation during the six minute walk in sickle cell disease patients might serve as an early biomarker for pulmonary hypertension. Exercise induced changes in oxygen saturation in sickle cell disease children may provide insight into the development of pulmonary hypertension as adults.