332 - Partial pressure of carbon dioxide (PaCO2) level and severe intraventricular hemorrhage (IVH) in preterm infants on nasal continuous positive airway pressure (CPAP) in the first 72 hours of life

Publication Number: 332.5899

Divya Nagarajan, University of Texas Southwestern Medical School, Dallas, TX, United States; L. Steven Brown, Parkland Health, Dallas, TX, United States; Patti J. Burchfield, University of Texas Southwestern Medical School, Dallas, TX, United States; Venkatakrishna Kakkilaya, UT Southwestern Medical Center, Dallas, TX, United States; Marina Santos Oren, University of Texas Southwestern Medical School, Dallas, TX, United States

Background: The association between hyper and hypocapnia with a higher incidence of severe IVH in preterm infants receiving mechanical ventilation is well established. Permissive hypercapnia is a viable alternative for extreme preterm neonates and decreased need for ventilation at 36 weeks compared to normocapnia. Increasingly, preterm infants are admitted to the neonatal intensive care unit (NICU) on CPAP. CPAP failure can occur due to elevated PaCO2 levels. There is limited data on the safety of hypo and hypercarbia in preterm infants primarily maintained on CPAP.

Objective: To determine if different levels of maximum PaCO2 in the first 72 hours of life in preterm neonates admitted to the NICU on CPAP are associated with severe IVH.

Design/Methods: This is a single-center retrospective study of infants < 32 weeks admitted to the NICU on CPAP between 1/1/2021 and 12/1/2023 at Parkland Hospital in Dallas, TX. Infants with severe congenital malformations were excluded. Serial PaCO2 levels within 72 hours of life were analyzed. The cohort of infants was divided into three groups based on maximum PaCO2 levels: Hypocapnia ( < 35mmHg), Normocapnia (35-60mmHg), and Hypercapnia (>60 mmHg). Severe IVH (Grade 3/4) and periventricular leukomalacia (PVL) were defined based on head ultrasound (US) findings using standard definitions. Baseline maternal and neonatal characteristics, cord gases, respiratory support details, and significant neonatal outcomes were collected. Chi-square testing was used to compare categorical variables, and median was compared with rank sum test amongst groups.

Results: Overall, 412 infants met the inclusion criteria and 407 had PaCO2 data available (Figure 1). A total of 1164 PaCO2 levels were analyzed. Hypercapnia was observed in 30% of infants (122), normocapnia in 65% (266), and hypocapnia in 5% (19). There was no difference in severe IVH between infants with Hypocapnia, Normocapnia, or Hypercapnia. Compared to infants in the normocapnia group, Infants in the hypercapnia group had lower birth weight (BW), GA, exposure to antenatal steroids, and 1- and 5-minute Apgar scores. They also had higher rates of CPAP failure, NIPPV, and surfactant treatment (table 1). Hypercapnia was significantly associated with PVL (p=0.02) and death (p=0.03); however, this was not statistically significant when adjusted for GA (table 2).

Conclusion(s): Hypocapnia (PaCO2 < 35mmHg) or hypercapnia (PaCO2>60mmHg) were not associated with severe IVH in preterm infants with RDS supported with CPAP. Larger trials are needed to evaluate the incidence, safety and effects of permissive hypercapnia in infants on CPAP.

Table 1: Comparison of Baseline Characteristics, Respiratory Support, and Outcomes in 407 Infants < 32 Weeks with RDS Admitted on CPAP with Hypocapnia, Normocapnia and Hypercapnia
*Median (25th, 75th)
*n (%) comparison using Chi-square test and Median (25th, 75th) compared with Rank sum test
Abbreviations: BW = Birth Weight; GA = Gestational Age; PPROM = Premature Prolonged Rupture of Membranes; NIPPV = Non-Invasive Positive Pressure Ventilation; CPAP = Continuous Positive Airway Pressure; BPD = Bronchopulmonary Dysplasia; PDA = Patent Ductus Arteriosus; NEC = Necrotizing Enterocolitis.

Table 2: Comparison of Neurological Outcomes Between Groups of 407 Infants < 32 Weeks with RDS on CPAP with Hypocapnia, Normocapnia and Hypercapnia.
*n (%) comparison using Chi-square test
** Adjusted for GA
Abbreviations: RDS = Respiratory Distress Syndrome; CPAP = Continuous Positive Airway Pressure; IVH = Intra-ventricular Hemorrhage; PVL = Periventricular leukomalacia

Figure 1: Study Flow Diagram