SURFACTANT PHOSPHATIDYLCHOLINE COMPOSITION DURING DEXAMETHASONE TREATMENT IN CHRONIC LUNG-DISEASE

Objectives - To determine whether dexamethasone 'matures' the phosphat idylcholine (PC) composition of broncheoalveolar fluid in infants at h igh risk of neonatal chronic lung disease (CLD), either by increasing the proportion of dipalmitoylphosphatidylcholine (DPPC), expressed as a percentage of total PC (%DPPC), or by increasing the ratio of DPPC t o palmitoyloleoylphosphatidylcholine (DPPC:POPC ratio). Design - Doubl e blind, placebo controlled. Setting and patients - Sixteen infants <3 2 weeks' gestation, <1250 g birth weight who were dependent on mechani cal ventilation and requiring a fractional inspired oxygen of >0.30 at 12 days of chronological age. Intervention - Randomisation to receive a two week reducing course of dexamethasone base at an initial dose o f 0.2 mg/kg three times a day, or equivalent volumes of normal saline, starting at 14 days. Eight infants were randomised into each group. B roncheoalveolar lavage was performed serially throughout the study per iod or until extubation. PC composition of the fluid was analysed by h igh performance liquid chromatography. Outcome measures - The %DPPC an d the DPPC:POPC ratios were calculated for individual infants for days -1 and 0 combined, days 1 and 3 combined, and days 5 and 7 combined. Analysis of covariance was used to analyse the results. Results - The DPPC:POPC ratio was significantly less in the treated group than the p lacebo group on days 1 and 3, and not greater as the hypothesis stated . Three out of five infants treated with dexamethasone and for whom da ta were available showed a substantial rise in DPPC:POPC ratio on days 5/7, compared with the placebo group, but overall these changes were not statistically significant. Conclusions - The data do not support t he hypothesis that dexamethasone's action in producing a clinical impr ovement within the first 72 hours of treatment for neonatal CLD is by the 'maturation' of pulmonary surfactant PC.