Reduction of neonatal blood eliminates the error induced by oxygen saturation in the spectrophotometric measurement of carboxyhaemoglobin.

Blood carboxyhaemoglobin (COHb) is a sensitive index of haemolysis and has been used in assessing the cause of different types of neonatal jaundice. Although the introduction of automated spectrophotometry provides rapid and accurate measurement in adult blood, in neonates oxygenated foetal haemoglobin (HbF) is thought to interfere with COHb measurement. In an attempt to eliminate this problem, the haemoglobin in neonatal blood was reduced with sodium dithionite. Cord blood from 50 infants was measured before and after reduction using an IL-282 co-oximeter; COHb levels fell after reduction. A significant positive correlation was found between apparent COHb% and oxygenation of cord blood. In contrast, no significant correlation was found between these parameters in adult blood where COHb values remained the same or rose slightly after reduction. In 20 healthy non-icteric neonates the mean reduced blood COHb value was not significantly different from the mean COHb value of 23 healthy non-smoking adults. We suggest that COHb in neonatal blood can be simply and accurately measured by the IL-282 co-oximeter provided that the blood is fully reduced.