INTRODUCTION
Bronchopulmonary dysplasia (BPD) or neonatal chronic lung disease (CLD)
represents a common and complex cardiorespiratory morbidity that affects
preterm infants. Despite advances in care, the prevalence of BPD has
remained constant due to increased survival of extremely low gestational
age newborns (ELGAN).1 It is estimated that 45% of
ELGANs are diagnosed with BPD. Pathologically, BPD is characterized by
abnormal lung development and lung injury with varying degrees of
disrupted alveolarization, vascular remodeling, inflammatory cell
proliferation and pulmonary edema. Lung morbidity associated with BPD
increases the risks for prolonged oxygen and respiratory support
requirements, pulmonary hypertension, impaired growth, and poor
neurodevelopmental outcomes. As such, the prevalence of BPD represents
an essential indicator for benchmarking the quality of neonatal
care.2
Management of BPD includes strategies to avoid invasive mechanical
ventilation together with aggressive pharmacologic and nutritional
interventions. While limiting mechanical ventilation and enhancing
caloric intake have been shown to improve outcomes in BPD patients, the
long-term benefits of medications such as steroids and diuretics for BPD
remain uncertain. In ELGANs with BPD who require increased intravenous
or enteral intake to ensure metabolic requirements, diuretics are used
very commonly to improve pulmonary function despite limited data
regarding their-long term efficacy and safety.3-5 In
the short term, they improve pulmonary function by decreasing
interstitial pulmonary fluid, which can contribute to increased lung
compliance, decreased airway resistance, and subsequently decreased
respiratory support.6-10 Despite these improvements in
pulmonary mechanics, a series of 2011 Cochrane reviews did not
demonstrate long-term benefits, so routine diuretic use for infants with
active or developing chronic lung disease was not
recommended.11,12 In contrast, a more recent
retrospective study of over 37,000 premature infants, approximately half
of whom had received furosemide, found that for every 10% increase in
furosemide exposure-days, there was a 4.6% decrease in the incidence of
BPD.3
Recent advances in lung ultrasound (LUS) diagnosis of neonatal diseases
offer more sensitive detection of pulmonary edema regardless of its
cause.13 Excess water outside of pulmonary blood
vessels can be quantified using LUS by the finding of “B-lines”. In
animal studies, the number of B-lines has been directly correlated with
the severity of pulmonary edema.14 Studies in neonates
with congenital heart disease with pulmonary overflow have found LUS to
be a useful tool to assess pulmonary edema.15 Similar
findings have been reported in infants with pulmonary edema caused by
patent ductus arteriosus.16
Our primary objective was to quantify and compare pulmonary edema before
and after initiation of diuretic therapy for infants with evolving CLD
using LUS. The secondary objective was to assess changes in respiratory
support parameters during the week after initiation of diuretics.