In PPHN, blood type may affect efficacy of inhaled nitric oxide
Infants with blood type O responded better to therapy than other types
Infants with persistent pulmonary hypertension of the newborn (PPHN) who have blood type O responded better to inhaled nitric oxide (iNO) vasodilator therapy than those with other blood types, a small study reported.
PPHN newborns with blood type A showed a similar response to type O newborns, while the lowest response, during or after treatment, was in newborns with blood type B.
The findings may explain why some infants fail to respond to iNO therapy.
The study, “Correlation of ABO blood groups with treatment response and efficacy in infants with persistent pulmonary hypertension of the newborn treated with inhaled nitric oxide,” was published in BMC Pregnancy and Childbirth.
Before birth, the mother supplies oxygen to the fetus through the umbilical cord. At birth, separating the baby from the placenta by clamping the umbilical cord requires a rapid switch to pulmonary gas exchange. Pulmonary vascular resistance, the resistance of lung blood vessels to blood flow, must decrease rapidly so pulmonary blood flow can increase. In PPHN, the pulmonary arteries don’t open wide enough, restricting oxygen and blood flow.
iNO, a vasodilator gas, is a routine treatment for PPHN. It works by relaxing and widening blood vessels, which lowers blood pressure. Data from several clinical trials indicate only about half of infants respond to iNO therapy, however.
Studies in adults suggested iNO responses were associated with ABO blood groups — a human blood classification system based on the presence or absence of certain protein-linked sugars on the surface of red blood cells. Blood types are classified as A, B, O, and AB.
Researchers in China investigated whether ABO blood groups affected iNO therapy’s effectiveness in infants with PPHN.
Effect of blood type on iNO therapy analyzed
They collected data on 90 infants diagnosed with PPHM who received iNO therapy alone. Among them, 24 (26.7%) were blood type A, 20 (22.2%) were type B, 39 (43.3%) were type O, and 7 (7.8%) were AB, who were excluded from further study because of the small sample size.
A response to iNO was defined as a greater than 20% increase in the PaO2/FiO2 ratio (P/F), a measure of a person’s respiratory efficiency, which is used as a clinical indicator of hypoxemia (low oxygen in the blood). Increased P/F values generally reflect better lung function and higher blood oxygenation.
After 72 hours of treatment, the response rate to iNO therapy significantly differed among the three groups. The response was the highest in the type O (74.4%) and type A (75%) groups and lowest in the type B group (35%).
Similar results were found after the end of the treatment regimen, with a higher response in the type O (87.2%) and type A groups (79.2%) compared with type B (50%).
An efficacy analysis found no significant differences in blood oxygenation among the three groups before and during treatment, as assessed with P/F and an oxygenation index (OI), a measure of how well lungs are oxygenating blood.
After treatment was stopped, the OI was significantly lower (better) across all three groups. The P/F was significantly higher (better) in the type O group than the other two.
Pairwise comparisons showed significantly higher oxygenation after iNO treatment in those with blood type O than types A and B, with similar results between A and B.
“Our results elucidate a correlation between ABO blood groups and responses to iNO therapy in infants with PPHN,” the researchers wrote. “Specifically, infants with blood type O responded most readily to iNO therapy, with the highest efficacy, among the infants with blood types A, B, and O.”