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Direct relationship of fetal carboxyhemoglobin with hemolysis in alloimmunized pregnancies
J A Widness1, L S Lowe, D K Stevenson
1Department of Pediatrics, University of Iowa, Iowa City 52242-1083.
Insights
Elevated fetal carboxyhemoglobin (HbCO) levels indicate accelerated hemolysis in fetuses with erythrocyte alloimmunization. This finding correlates with disease severity and bilirubin levels, offering a new diagnostic marker.
Area of Science:
- Perinatal Medicine
- Hematology
- Toxicology
Background:
- Carbon monoxide (CO) is a heme degradation byproduct.
- Placental CO diffusion is limited, making fetal CO levels a potential indicator of hemolysis.
Purpose of the Study:
- To investigate the correlation between fetal carboxyhemoglobin (HbCO) levels and the severity of hemolytic disease in fetuses.
- To assess HbCO as a potential biomarker for accelerated hemolysis.
Main Methods:
- Fetal blood was collected via cordocentesis.
- Carboxyhemoglobin (HbCO) levels were measured using gas chromatography.
- HbCO and bilirubin levels were compared between control fetuses and those with hemolytic disease.
Main Results:
- Fetuses with hemolytic disease exhibited significantly higher HbCO levels compared to controls.
- Fetal HbCO levels showed a strong positive correlation with bilirubin and an inverse correlation with hemoglobin concentrations.
- Maternal HbCO levels did not differ between groups, indicating fetal-specific changes.
Conclusions:
- Elevated fetal HbCO levels in non-smoking mothers with erythrocyte alloimmunization are indicative of accelerated hemolysis.
- HbCO serves as a valuable marker for assessing the severity of fetal hemolytic disease.
- Further research can explore HbCO's role in managing alloimmune conditions.
Abstract:
Because carbon monoxide (CO) is a byproduct of heme degradation and because placental diffusing capacity of CO is limited, we hypothesized that the concentration of CO transported in fetal blood as carboxyhemoglobin (HbCO) would correlate with the severity of fetal hemolytic disease. Fetal blood was obtained by cordocentesis and HbCO was measured by gas chromatography. The two primary study groups included control fetuses (n = 26) and fetuses of Coombs-positive mothers before in utero transfusion (n = 15). Compared with controls, fetuses with hemolytic disease had higher HbCO levels (0.0111 +/- 0.0014 versus 0.0159 +/- 0.0072 fraction of total Hb, mean +/- SD, p < 0.002). In contrast, HbCO levels in simultaneously sampled maternal blood samples were not different in the control and alloimmune groups [0.0110 +/- 0.0025 (n = 20) versus 0.0115 +/- 0.0021 (n = 11)]. There was a significant inverse correlation observed between fetal HbCO and Hb concentrations in the group with hemolytic disease (r = -0.73, p < 0.002) but not in controls. In fetuses with hemolytic disease, HbCO and bilirubin were highly correlated (r = 0.88, p < 0.0001). Data from four anemic fetuses who were Coombs negative, three of whom had no evidence of hemolysis, indicated normal HbCO and normal plasma bilirubin levels. A fourth fetus with anemia had viral sepsis and elevated HbCO and plasma bilirubin levels. We conclude that elevated HbCO levels detected in fetuses of nonsmoking mothers with erythrocyte alloimmunization are likely the result of accelerated hemolysis.