INCREASES IN FUNCTIONAL RESIDUAL CAPACITY (FRC) AT TWO DIFFERENT DOSES OF DEXAMETHASONE IN VERY LOW BIRTH WEIGHT (VLBW) INFANTS: A DOUBLE-BLIND, RANDOMIZED TRIAL. † 1359

Abstract

We have reported a one week weaning course of 0.5 mg dexamethasone (DEX) in VLBW ventilator dependent infants 7 - 14 days of age to significantly improve pulmonary compliance (as well as subsequent CLD) when compared to controls(Pediatrics 1995; 95: 584-90). The effect of two different dose regimes of DEX on lung volume in VLBW infants at risk for CLD has not been reported. As part of an ongoing study, we measured FRC and static pulmonary mechanics (PM) in 21 infants ≤ 1000 g ventilator dependent at 7 - 14 days with a randomized, double-blind study design. Ten infants (mean BW=785 g, GA=25.7 wks, 70% male, 50% Caucasian, FIO2 at entry = 0.48, mean airway pressure (MAP) = 7.1 cmH2O) received high dose DEX (0.5mg/kg/day × 3 days; 0.25 mg/kg/day × 3 days; 0.1 mg/kg/day × 1 day) while 11 infants (mean BW=714 g, GA=25.5 wks, 64% male, 45% Caucasian, FIO2 at entry = 0.48, MAP=8.2 cm H2O received low dose DEX (0.2 mg/kg/day × 3 days; 0.1 mg/kg/day × 4 days). FRC and PM were measured at similar ventilator settings before and on days 2, 5, and 7 of DEX. FRC was measured with the nitrogen washout technique. A minimum of 2 measurements were performed with the neonate supine and quiet. Only consistent tracings initiated at end expiration and without evidence of leak were accepted. A study was acceptable if the measurements had a coefficient of variation < 10%. Respiratory compliance (Crs) was measured using the single breath occlusion technique (SensorMedics 2600). FRC is shown as ml/kg and Crs as ml/cm H2O/kg. Both groups had a significant decrease in FIO2 and MAP by day 7 of therapy (p<0.05). Although the increase is more gradual in the low dose DEX group, both high and low dose DEX had significant increases in FRC and Crs by day 7. However, the high dose DEX group had a 129% increase in FRC, while low dose DEX increased FRC by 43% (p<0.05). We speculate that this statistically significant increase in FRC with high DEX versus low DEX will also prove to be clinically significant, and supports a short course of the high dose as more effective than the low dose for infants at risk for CLD.Table