End tidal carbon monoxide and significant hemolysis

The American Academy of Pediatrics identified significant hemolysis as a significant neurotoxic risk factor for newborns with jaundice in its 2022 guideline for managing hyperbilirubinemia. The guideline recommends starting phototherapy at a lower level than otherwise if significant hemolysis is present. Currently, the optimal way to measure hemolysis is by determining an infant's level of end-tidal carbon monoxide corrected for ambient carbon monoxide (ETCOc). However, it is unclear what the optimal ETCOc level is for determining significant hemolysis. Given the differences in ETCOc levels among infants of different backgrounds, the most reasonable conclusion would be for each unit to determine the mean ± standard deviation ETCOc level of an inclusive group of 200-500 infants in their unit. Each unit could then decide whether to use the 95th, 75th, or some other percentile value as their unit's indicator of significant hemolysis.