title: Carboxyhemoglobin - the forgotten parameter of neonatal hyperbilirubinemia.
abstract: BACKGROUND
  Neonatal hyperbilirubinemia is influenced by a wide variety of factors, one of which is hemolysis. Serious hyperbilirubinemia may lead to a kernicterus with detrimental neurologic sequelae. Patients suffering from hemolytic disease have a higher risk of developing kernicterus. Carbon monoxide (CO), a byproduct of hemolysis or heme degradation, was described by Sjöstrand in the 1960s. It is transported as carboxyhemoglobin (COHb) and exhaled through the lungs. We were interested in a potential correlation between COHb and total serum bilirubin (TSB) and the time course of both parameters.
  
  
  METHODS
  We used a point of care (POC) blood gas analyzer and did a retrospective analysis of bilirubin and COHb data collected over a 60-day period.
  
  
  RESULTS
  An arbitrary cut-off point set at 2% COHb identified four patients with hemolytic disease of different origins who required phototherapy. In one patient with atypical hemolytic uremic syndrome (aHUS), COHb preceded the rise in bilirubin by about 2 days. Despite this displacement, there was a moderately good correlation of COHb with TSB levels <15 mg/dL (257 μmol/L) (r2: 0.80) and direct bilirubin (r2: 0.78) in the first patient. For all the four patients and all time points the correlation was slightly lower (r2: 0.59).
  
  
  CONCLUSIONS
  COHb might be useful as a marker for high hemoglobin turnover to allow an earlier identification of newborns at risk to a rapid rise in bilirubin.
authors.affiliation: .
authors.forename: Douggl G N
authors.initials: DGN
authors.lastname: Bailey
authors.affiliation: .
authors.forename: Hans
authors.initials: H
authors.lastname: Fuchs
authors.affiliation: .
authors.forename: Roland
authors.initials: R
authors.lastname: Hentschel
mesh_terms: D001663:Bilirubin / Q000378:metabolism*; D015415:Biomarkers / Q000097:blood; D002263:Carboxyhemoglobin / Q000378:metabolism*; D006801:Humans; D006932:Hyperbilirubinemia / Q000097:blood*; D007231:Infant, Newborn; D012189:Retrospective Studies
chemical_list: D015415:Biomarkers; D002263:Carboxyhemoglobin; D001663:Bilirubin
keywords: Carbon monoxide; carboxyhemoglobin; hemolysis; neonatal hyperbilirubinemia; point of care testing