Objective: Dexamethasone improves respiratory status in some preterm infants with
lung disease. Dexamethasone increases heart rate variability, which decreases the
heart rate characteristics index (HRCi), a sepsis risk score that reflects inflammation.
Respiratory improvement can be measured by the ability to wean support, quantified
by a respiratory severity score (RSS). We hypothesized that HRCi and RSS early in
dexamethasone treatment are associated with respiratory improvement marked by successful
extubation.
Study Design: We retrospectively reviewed NICU patients born at <32 weeks gestational
age (GA) admitted from 2012-2022 who received >3 days of dexamethasone for lung disease
while on mechanical ventilation. Daily mean FiO2, HRCi, and RSS (Mean Airway Pressure
x FiO2) were calculated for the dexamethasone start day and two days before and after.
Successful extubation was defined as occurring during the dexamethasone course without
reintubation within 7 days. We compared variables between infants with and without
successful extubation.
Results: A total of 65 infants (mean GA 25±1 weeks) were included. HRCi, FiO2, and
RSS significantly decreased by Day 3 of dexamethasone. Successful extubation (n=38)
was associated with higher postmenstrual age (PMA), lower FiO2 and RSS, and being
on conventional rather than high-frequency ventilation (all p<0.05). Multivariable
analysis found that RSS and PMA, but not HRCi, predicted successful extubation.
Conclusion: Dexamethasone treatment decreased the HRCi, but this was not associated
with extubation success. Higher PMA and lower respiratory support were associated
with successful extubation during dexamethasone treatment.
