Endogenous production of carbon monoxide in normal and erythroblastotic newborn infants

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Abstract
The endogenous production of carbon monoxide (˙VCO) in newborn infants was measured by serial determinations of blood carboxyhemoglobin during rebreathing in a closed system. Mean ˙VCO in nine full-term infants was 13.7 ±3.6 μl CO/kg per hr (SD), and in four erythroblastotic infants ˙VCO ranged from 37 to 154 μl CO/kg per hr preceding exchange transfusion. Mean red cell life-span (MLS) and total bilirubin production were calculated from ˙VCO. MLS in normal newborns was 88 ±15 days (SD), and bilirubin production was 8.5 ±2.3 mg/kg per 24 hr. This is more than twice the amount of bilirubin normally produced in the adult per kilogram of body weight. Normal infants achieved a net excretion of bilirubin of at least 5.6 ±2.3 mg/kg per 24 hr (SD) as calculated from the bilirubin production and the measured rise in serum bilirubin concentration. The measurement of ˙VCO should prove valuable in the study of red blood cell survival and bilirubin metabolism in the newborn infant.