Preoperative Hemoglobin Level, Oxygen Saturation and Postoperative Outcomes in Children With Cyanotic Congenital Heart Disease: A Propensity-Score Matching Analysis

Abstract

Background: The optimal preoperative hemoglobin (Hb) level is difficult to define in children with cyanotic congenital heart disease (CHD) due to hypoxemia-induced secondary erythrocytosis. This retrospective study integrated preoperative Hb and pulse oxygen saturation (SpO2) using the product of Hb × SpO2 to predict postoperative outcomes in children with cyanotic CHD. Patients and Methods: Children aged <18 years undergoing cardiac surgery with cyanotic CHD were included. The cutoff value of Hb × SpO2 was the age-adjusted lower limit of normal Hb (aaHb) in healthy children. The main outcomes were in-hospital death and the composite outcome of severe postoperative events. Multivariate logistic regression analysis and propensity score matching analysis were used to adjust for important confounders. Results: The presence of preoperative Hb × SpO2 < aaHb was observed in 21.6% of cyanotic children (n = 777). Children with Hb × SpO2 < aaHb had higher in-hospital mortality (12.5% vs. 4.6%, P < 0.001) and composite outcome incidence (69.6% vs. 32.3%, P < 0.001) than those with Hb × SpO2 ≥ aaHb. After propensity score matching, 141 pairs of children were successfully matched. Multivariate analysis showed that preoperative Hb × SpO2 < aaHb was significantly associated with the composite outcome in the entire population (odds ratio = 4.092, 95% confidence interval = 2.748–6.095, P < 0.001) and the matched cohorts (odds ratio = 2.277, 95% confidence interval = 1.366–3.795, P = 0.002). Conclusion: Our results suggest that a preoperative Hb × SpO2 value below the lower limit of normal hemoglobin is a prognostic factor in cyanotic children undergoing cardiac surgery and is a potential criterion to evaluate preoperative anemia in this population.