In the initial 48 hours of life, measurement of end-tidal carbon monoxide (ETCO) concentrations can be used to predict hemolytic hyperbilirubinemia, which can be reported among neonates with hemolytic disease of the fetus and newborn (HDFN), according to findings from a prospective study conducted at the Shenzhen Maternity and Child Healthcare Hospital, Shenzhen, Guangdong, China, and published in the Journal of Perinatology.
It is well-recognized that neonatal hemolysis is a key contributor to severe hyperbilirubinemia within one to two weeks following birth and anemia within three months following birth. Neonatal hemolysis is responsible for between 25.0% and 29.9% of all reported causes of kernicterus, in which bilirubin-associated neurologic damage is observed.
The researchers sought to establish whether measuring ETCO concentrations twice prior to 48 hours after birth among neonates at risk for development of hyperbilirubinemia would help identify those deemed at an elevated risk for hyperbilirubinemia, as well as to distinguish between hemolytic and nonhemolytic causes of the disorder.
The current study was conducted between August 2022 and December 2022. Parents of babies born at >35 weeks’ gestational age who weighed >2000 grams were contacted to see if they were at risk for hemolytic disease because of either blood group incompatibility or glucose 6-phosphate dehydrogenase (G6PD) deficiency.
Read more about HDFN signs and symptoms
Neonates who fulfilled criteria for being at-risk of hyperbilirubinemia participated in the study. Routine measurements of bilirubin and 10-day follow-up were used to categorize the infants in one of the following three categories:
- Normal (ie, no hyperbilirubinemia; all bilirubin values <95th percentile of Bhutani nomogram)
- Symptoms of hemolytic hyperbilirubinemia (ie, bilirubin values ≥95th percentile, positive direct antiglobulin test, elevated reticulocyte counts, or presence of G6PD activity)
- Presence of nonhemolytic hyperbilirubinemia
A total of 386 newborns were enrolled in the study. Among the participants, 83% (321 of 386) of them did not develop hyperbilirubinemia, whereas 17% (17 of 386) of them did develop the disorder. Of these 65 infants, 29 were considered to have hemolytic hyperbilirubinemia and 36 had nonhemolytic hyperbilirubinemia.
Results of the study showed that high ETCO concentrations were statistically significantly associated with being in the hemolytic hyperbilirubinemia group vs the nonhemolytic hyperbilirubinemia group. First-day ETCO concentrations were associated with bilirubin levels and reticulocyte counts (r =0.896 vs r =0.878, respectively). The specificity and the sensitivity for predicting hyperbilirubinemia were excellent (95% and 83%, respectively).
“Newborns with higher ETCO [concentrations] within 48 hours after birth should be monitored more closely to prevent the occurrence of severe hyperbilirubinemia or even kernicterus,” the authors emphasized. “[I]n jaundice monitoring, we should not ignore the clinical symptoms to exclude other [sources] that can cause hyperbilirubinemia[,] such as infection and intracranial hemorrhage.”
