Objective: Respiratory distress syndrome (RDS) is a frequently seen acute respiratory disorder in the newborn infants. Since the original description of deficiency of the pulmonary surfactant in premature neonates by Avery in 1959, RDS has most commonly been attributed to developmental immaturity of surfactant production. But in clinical practice it has been found that there was RDS in term and late-term neonates. Many of them were recognized as transient tachypnea at the beginning, they were diagnosed as RDS until respiratory distress and the typical radiological signs were demonstrated. The purpose of this study was to investigate the clinical characteristics of RDS of term and late-term neonates.
Methods: All neonates admitted to the neonatal intensive care unit of the Children's Hospital, Zhejiang University School of Medicine between May, 2005 and May, 2007 on the basis of RDS were analyzed. RDS was diagnosed when respiratory distress and the typical radiological signs were documented. Patients were grouped into preterm group (Group 1, gestational age < 35 w, n = 103) and term and late-term group (Group 2, gestational age > or = 35 w, n = 74).
Results: In Group 1, 76 preterm infants were male, the mean gestational age was 31.1 w, the mean Apgar score at 1 min was 7.6, the mean birth weight was 1702 g, 56 cases were vaginally delivered and 47 were delivered through Cesarean section. Only one was delivered via elective Cesarean section before onset of labor. A total of 88 patients needed mechanical ventilation (MV), the time for beginning MV was 8.7 h (1 - 72 h), and lasted for 4.3 d (0.5 - 29 d). The oxygenation index (OI) was 11.9 (10.00 - 52.63) and PaO2/PAO2 was 0.29 (0.03 - 0.98). Four patients had an OI > 40. A total of 28 patients were treated with pulmonary surfactant (PS), and 11 of the 28 underwent MV, the OI before and 2 h, 8 - 12 h and 20 - 24 h after using PS were 10.5, 5.4, 3.4, and 4.3, respectively (P < 0.01). A total of 33 patients in Group 1 had intracranial hemorrhage, 4 patients had pneumothorax, 4 patients had persistent pulmonary hypertension of the newborn (PPHN) and 15 patients had ventilator associated pneumonia (VAP). In Group 2, 54 infants were male, the mean gestational age was 37 w, the mean Apgar score at 1 min was 8.5, the mean birth weight was 2789 g, 8 cases were vaginally delivered, 66 were delivered through Cesarean section and 59 were delivered via elective Cesarean section before onset of labor. A total of 63 patients needed MV, the time for beginning MV was 27.8 h (1 - 72 h, compared to Group 1, P < 0.01), and lasted for 3.7 d (0.5 - 13.5 d). The OI was 19.70 (10.00 - 56.67, compared to Group 1, P < 0.01) and PaO2/PAO2 was 0.16 (0.017 - 0.470, compared to Group 1, P < 0.01). Seven patients had an OI > 40. A total of 8 patients were treated with PS and 7 of them had MV, the OI before and 2 h, 8 - 12 h and 20 - 24 h after using PS were 11.2, 7.6, 7.5, and 7.6 (the last two compared to group 1, P < 0.01, respectively). A total of 16 patients had pneumothorax, 10 patients had intracranial hemorrhage, 16 patients had PPHN and 7 patients had VAP.
Conclusion: Most of the term and late-term neonates who developed RDS were delivered through cesarean section before onset of labor. They underwent MV later. The oxygenation was worse than RDS in preterm infants. PS did not have the same effect as seen in preterm infants. They had more pneumothorax and PPHN.