Pulmonary Function at Hospital Discharge in Preterm Infants Randomized to a Single Rescue Course of Antenatal Steroids

Abstract

Objective: To compare the pulmonary function, measured at birth and at hospital discharge, of infants whose mothers had been randomized to a single rescue course of antenatal steroids versus those whose mothers had been randomized to placebo.

Study design: This study involved follow-up at hospital discharge of subjects of a randomized, double-blinded trial. In the original trial, pregnant women at ≥14 days after their initial course of antenatal steroids and <34 weeks' gestation were randomized to rescue antenatal steroids (44 mothers, 56 infants) or placebo (41 mothers, 57 infants). Passive respiratory compliance (Crs), passive respiratory resistance, and functional residual capacity were measured in all infants at birth and again at discharge to evaluate changes in pulmonary mechanics over time. Statistical analyses were based on intention to treat.

Results: We previously reported that compared with infants in the placebo group, infants in the rescue antenatal steroids group had a higher mean Crs value measured within 72 hours of birth (1.21 vs 1.01 mL/cm H₂O/kg; P < .05). Here we show that the Crs benefit in the antenatal steroids group was sustained until discharge. Infants in the placebo group demonstrated improvement in Crs such that by discharge, there was no difference in mean Crs between the rescue antenatal steroids and placebo groups (1.18 vs 1.22 mL/cm H₂O/kg).

Conclusions: Rescue antenatal steroids significantly increased Crs measured within 72 hours of birth, and this increase was sustained until hospital discharge. Preterm infants in the placebo group demonstrated a decreased initial Crs compared with the rescue antenatal steroids group, but achieved a comparable Crs by the time of discharge.

Trial registration: ClinicalTrials.gov: NCT00669383.

Keywords: betamethasone; functional residual capacity; lung trajectory; passive respiratory compliance; passive respiratory resistance; premature infants; pulmonary function tests; rescue antenatal steroids.

Figure 1

CONSORT flow diagram of study participants. Number of initial and discharge pulmonary function tests differs slightly within each group due to some measurements not meeting standard international guidelines. PFTs not meeting standard international guidelines for acceptable measurements were not included in the analysis.

Figure 2

Comparison of A, Crs, B, FRC, C, and Rrs at birth and discharge for infants in the entire cohort (left side of panels) and for the subset born ≤34 completed weeks’ gestation (right side of panels). ** p value <0.05. Crs is given in mL/cm H₂0/kg, FRC in mL/kg, and Rrs in cm H₂0/mL/sec. Error bars represent standard error.