Daytime and Nocturnal Hypoxemia Are Related With Hemolysis In Adults With Sickle Cell Disease

Different studies had shown that nocturnal hypoxemia is associated with clinical complications in children with sickle cell disease (SCD), and, more recently, iron availability was related with nocturnal oxymetry in these children. However, there are few studies about this subject in adults with SCD, despite the fact that nocturnal hypoxemia occurred in 60% of the patients. We aimed to evaluate daytime and overnight hypoxia and its influence on clinical and laboratorial parameters in adults with SCD.

82 steady state patients with SCD followed at Anemia Out-Patient Clinic from Escola Paulista de Medicina/UNIFESP were invited to this study. This study was approved by Ethical Committee, and all patients agreed in participate. The daytime oximetry (SpO₂) utilized was the mean of at least 3 measurements by pulse oximeter during regular appointments at the out-patient clinic. The nocturnal oximetry data (basal SpO₂ and mean nocturnal SpO₂) were obtained during polysomnography (PSG). Besides clinical evaluation, routine laboratory tests performed near the realization of the PSG were analyzed. The data was analyzed by parametric and non-parametric tests, with α=5%.

The median (range) age was 28 (18-69) years, and 44 (54%) were female. Moderate sleep apnea was diagnosed in 11% of the patients. The mean of SpO₂ obtained for each measurement was: daytime SpO₂: 95.1±4.3, basal SpO₂: 94.3±3.5, and mean nocturnal SpO₂: 93.3±3.6; with statistical significance between daytime and basal SpO₂ (X²=17.0; p<0.001) and between daytime and mean nocturnal SpO₂ (X²=10.3; p=0.001). The percentage of patients with hypoxemia (SpO₂ ≤ 90%) varied according with the measurement: 14.1% at daytime SpO₂, 13.7% at basal SpO₂, and 20.0% at mean nocturnal SpO₂. However, 55% of the patients achieved hypoxemia level during PSG. Association between daytime SpO₂ and previous stroke was observed (X²=4.0; p=0.04). Patients with daytime and basal SpO2 ≤ 90% had higher lactate dehydrogenase (LDH) (634.3±114.9 and 538.0±198.3) compared to the ones with SpO2>90% (384.0±171.6 and 375.7±171.9; p<0.001 and p=0.02, respectively). Reticulocyte count was more elevated in patients with SpO₂ ≤ 90% (daytime SpO₂: 277,639.2±96,108.4; basal SpO₂: 290,722.9±87,791.2 and mean nocturnal SpO₂: 260,582.1±83,532.8) when compared to the ones with SpO₂ >90% (185,537.3±90,445.7; 188,432.2±101,277.1 and 189,194.1±104,478.8; p=0.01; p=0.01 and p=0.03, respectively). No correlation was found within iron and SpO₂.

Daytime and nocturnal hypoxemia showed effect on hemolytic markers in adults with SCD. Daytime SpO₂ presented an association with previous stroke and considering that it was also observed an association between daytime and nocturnal SpO₂, we suggest that daytime SpO₂determination should be monitored in each appointment and can be used as a predictor of SCD severity

Supported by CAPES/SUS and AFIP.

No relevant conflicts of interest to declare.