Endogenous formation of carbon monoxide in newborn infants. V. On the relation between the carboxyhaemoglobin concentration and the haemoglobin catabolism calculated from simultaneous determinations of carbon monoxide elimination and total haemoglobin

The role of haemolysis in neonatal hyperbilirubinaemia as reflected in carboxyhaemoglobin levels

Carboxyhaemoglobin levels were measured in 250 consecutive, normal, term newborns and in a group of 75 severely jaundiced infants in an effort to assess the role of haemolysis in non-specific neonatal hyperbilirubinaemia--"Physiologic jaundice"-as well as in severe jaundice of various etiologies. In normal newborns a significant correlation (r=0.3293, p less than 0.001) was found between third-day carboxyhaemoglobin and serum bilirubin levels. Significant correlations were also found between the cord and third day values for carboxyhaemoglobin (infants of non-smoking mothers) for reticulocyte count, and for serum bilirubin. Third day haemoglobin showed no correlation with any of the other parameters including cord haemoglobin. Of the infants with third day carboxyhaemoglobin up to 0.75%, 1.7% had third day serum bilirubin values above 16.0 mg/100 ml. The corresponding percentage for the infants with carboxyhaemoglobin above 0.75% was 6.1%. It is concluded that increased rates of haemolysis due to as yet unspecified caused play an important role in the non-specific hyperbilirubinaemia of normal term newborns. As expected, high levels of carboxyhaemoglobin were found in infants with severe jaundice due to Rhesus and ABO haemolytic disease and glucose-6-phosphate dehydrogenase deficiency but also in jaundiced prematures and in Greek infants with severe jaundice of unknown cause.

Smoking during pregnancy and its effects on the fetus

The smoking habits of a group of pregnant women have been recorded and related to the level of carboxyhaemoglobin (COHb) in the circulating blood. Simultaneous maternal and fetal COHb levels at delivery were estimated and on average the fetal levels were 1.8 times greater than the related maternal level. Samples of fetal blood were exposed to carbon monoxide in vitro and an appreciable shift to the left of the haemoglobin dissociation curve was demonstrated. Cigarette smoking during pregnancy diminishes the oxygen carrying capacity of both fetal and maternal blood, affects maternal oxygenation by increased pulmonary venous admixture and diminishes the oxygen available to the fetus at the tissue level by its effect on fetal oxyhaemoglobin dissociation.