406 - Evaluation of Thoracic Fluid Content as an Early Diagnostic Indicator of Transient Tachypnea of the Newborn in Full Term Neonates with Respiratory Distress

Publication Number: 1389.406

Yi-Li Hung, Cathay General Hospital, Taipei, Taipei, Taiwan (Republic of China); Wu-Shiun Hsieh, Department of Pediatrics, Cathay General Hospital, Taipei, Taiwan, Taipei City, Taipei, Taiwan (Republic of China); Chung-Min M. Shen, Cathay General Hospital, Taipei, Taipei, Taiwan (Republic of China)

Background: Respiratory distress (RD) is among the most common causes of neonatal intensive care unit (NICU) admission. Differential diagnoses include transient tachypnea of the newborn (TTN), congenital pneumonia, pneumothorax, and meconium aspiration syndrome (MAS). TTN resulting from delayed clearance of fetal lung fluid, often presents as early RD but is difficult to distinguish from other causes immediately after birth in full term neonates. Electrical cardiometry (EC) is a noninvasive method that measures cardiac output and thoracic fluid content (TFC). Because TTN is characterized by pulmonary fluid retention, we hypothesized that TFC might be a potential diagnostic marker in TTN.

Objective: This study aimed to determine whether TFC can help differentiate TTN from other etiologies of RD in full term neonates.

Design/Methods: This prospective study enrolled full-term neonates admitted to the NICU with RD within 6 hours after birth from Jan. through Dec. 2024. Neonates with major congenital anomalies were excluded. EC monitoring was performed daily using four surface electrodes to measure TFC and hemodynamic parameters. Based on clinical and radiographic findings, infants were classified into TTN and non-TTN groups. TFC values were compared between groups, and receiver operating characteristic analysis was used to evaluate the diagnostic performance of TFC for identifying TTN.

Results: 89 full-term neonates were enrolled, including 53 males (59.6%), with a mean gestational age of 38.8 ± 0.9 weeks and mean birth weight of 3,027 ± 358 g. Forty infants were diagnosed with TTN, and 49 with other causes of RD (18 congenital pneumonia, 11 MAS, 8 pneumothorax). Perinatal characteristics, including gestational age, birth weight, sex, and maternal conditions, did not differ between groups. Neonates with TTN had significantly higher TFC on postnatal day (PND) 1 compared with the non-TTN group (35.15 ± 13.87 vs 28.40 ± 5.98 mL/kg; p = 0.07). A PND1 TFC > 25.5 mL/kg predicted TTN with 88.9% sensitivity and 38.6% specificity (AUC = 0.75). TFC declined > 25% by PND2 further discriminated TTN from non-TTN (sensitivity 33.3%, specificity 88.6%). TFC values decreased over time as respiratory symptoms resolved. No significant differences in cardiac output or stroke volume were observed between groups.

Conclusion(s): Thoracic fluid content was higher in full term neonates with TTN compared to other causes of RD. TFC may serve as an early diagnostic indicator for prompt identification of TTN and reducing unnecessary interventions and timely management.