End-tidal carbon monoxide is predictive for neonatal non-hemolytic hyperbilirubinemia

The aim of the present study was to evaluate the value of an end-tidal carbon monoxide corrected for inhaled carbon monoxide concentration (ETCOc) at the early neonatal period. The value would be useful for predicting subsequent hyperbilirubinemia in non-hemolytic full-term infants.

The ETCOc levels were measured every 6 h during the first 72 h of life in healthy, full-term, non-hemolytic, newborn Japanese infants using a breath carbon monoxide analyzer. The ETCOc levels in hyperbilirubinemic infants were compared with those in non-hyperbilirubinemic infants. Hyperbilirubinemia was defined as the level of the peak total serum bilirubin concentration (TBC) greater than or equal to 257 micromol/L (15.0 mg/dL). The ETCOc measurement for predicting subsequent hyperbilirubinemia was evaluated with a receiver-operating characteristic (ROC) curve.

Fifty-one infants were enrolled in the study. Seven of the 51 infants developed hyperbilirubinemia. The ETCOc levels in non-hyperbilirubinemic infants were decreased in the first 72 h after birth. However, those in the hyperbilirubinemic infants were not decreased significantly, and were higher than those in non-hyperbilirubinemic infants at 42, 48, 54 and 66 h of age. The ETCOc level at 42 h of age was the most predictive of subsequent hyperbilirubinemia by ROC analysis. At the cut-off level of 1.8 microL/L (p.p.m.), the sensitivity, the specificity, the positive predictive value and negative predictive value were 86, 80, 40 and 97%, respectively.

Increased ETCOc level in the early neonatal period is associated with subsequent hyperbilirubinemia, even in infants without hemolytic disease. The ETCOc measurement may be useful as a screening test for predicting hyperbilirubinemia without hemolytic diseases.