Association of neonatal respiratory distress with birth asphyxia and deficiency of red cell mass in premature infants.

Red cell mass (RCM) was estimated using 125I-labelled human serum albumin in 128 premature infants born after 26 to 36 weeks gestation. Infants of three different gestational periods (26--29, 30--32, and 33--36 weeks) with respiratory distress (RD) averaged lower one-minute Apgar scores and lower RCM than infants without RD (P less than 0.05). The incidence of RD was significantly (P less than 0.05) higher in infants with Apgar scores below 6 and in infants with RCM of less than 35 ml/kg than in the infants with greater values. The highest incidence of RD and the highest mortality rate were found in the infants with low Apgar scores and low RCM values. Prematures with similar Apgar scores showed a higher incidence of RD when RCM was low, and infants with similar RCM showed a higher incidence of RD when Apgar scores were low. Our results suggest that both birth asphyxia and deficiency of red cell mass interfere with postnatal cardio-respiratory adaptation. In high-risk premature infants, erythrocytes should be transfused when the venous haematocrit is below 0.459