Predicting dexamethasone-associated extubation success in preterm infants.

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.