Despite treatment with AS and surfactant (S), many VLBW infants require D therapy. AS have been shown to be synergistic with S. We hypothesized that“priming” with AS may also enhance the response of a VLBW infant to postnatal D. We reviewed AS treatment in an ongoing randomized study examining the effect of two dosing regimes of D (7 day weaning courses, starting at 0.5 mg/kg/day vs 0.2 mg/kg/day) on FRC in intubated VLBW infants< 1000 g at 7 to 14 days of age. We defined treatment with AS as two 12 mg doses of betamethasone with the first dose being at least 24 hours before, but within 7 days of delivery. The control group had no exposure to AS. 17 infants(mean BW= 795g; GA= 25.6 wks; 65% white; 47% female; 59% getting 0.5 mg course of D) had received AS, while 26 infants (mean BW= 806g; GA= 26.2 wks; 54% white; 50% female; 50% getting 0.5 mg course of D) were controls. The AS group got an average of 1.9 doses of S vs 3.1 for the controls (p=0.01). At start of D therapy, there was no significant difference between the 2 groups in mean airway pressure (8.0 vs 6.9 cm H2O) or FiO2(47% vs 43%). Pulmonary function testing was done prior to D, and on days 2,5, and 7. FRC was measured with the nitrogen washout technique(SensorMedics 2600). At least 2 FRC measures were required with a coefficient of variation <10%. Despite comparable PRE FRC, the AS group had a significantly higher FRC on days 2, 5, and 7 of D when compared to controls. The AS group had a better clinical course, with significantly less retreatment with D and less infants on O2 at 36 weeks of corrected chronological age. This initial data indicates that AS coupled with S may allow enhanced response to postnatal D in intubated VLBW infants. This may be due to enhanced structural and / or biochemical maturation afforded by AS. Table

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