Abstract 1145 Poster Session IV, Tuesday, 5/4 (poster 327)

Aim: To describe the relationship between ductal shunting, estimated pulmonary blood flow (PBF) and pulmonary haemorrhage (PH) in very preterm infants.

Methods: 126 babies born before 30 weeks (median gestation 27w, 23-29w) had echocardiograms at 5, 12, 24 and 48 hours of age. Measures included right (RVO) and left ventricular output (LVO), superior vena cava (SVC) flow and colour Doppler diameter of any ductal shunt (as a semi-quantitative measure of shunt size). PBF was estimated from the sum of RVO and ductal shunt flow. Ductal shunt flow was estimated as LVO minus systemic blood flow (SVC flow × 2.77). This estimate is based on LVO being the sum of systemic blood flow and ductal shunt flow, and also that systemic blood flow can be estimated from SVC flow which is on average 36% of total systemic blood flow. PH was defined as blood stained fluid aspirated from the trachea with respiratory deterioration and xray and/or autopsy evidence of PH.

Results: Twelve babies (9.5%) had a PH at a mean age of 38 hrs (14-55). Nine had frank blood aspirated and 3 had blood stained fluid. Median increase in oxygenation index after PH was 8.9 (1-33). Compared to the rest of the cohort, these 12 babies were less likely to have had antenatal steroids (59% vs. 90%, p=0.008), were less mature (26 weeks vs. 27 weeks, p=0.03), more had a patent ductus arteriosus (PDA) requiring medical closure (92% vs. 23%, p=0.0001) and more had grade 3 or 4 IVH (42% vs. 6%, p=0.0002).

At the 5 hour echocardiogram, the babies with PH had significantly larger diameter ducts (2.1 mm vs. 1.6mm, p=0.0002) but similar PBF (218 ml/kg/min vs. 197 ml/kg/min, p=0.15) compared to the rest of the cohort. At the echocardiogram closest to the PH, (within 3 hrs in 8 babies and 9-20h before the PH in the other 4) 11 of the 12 babies (92%) had a significant PDA over 1.6mm in diameter (median 2.0mm, 0.7-2.4) and the median PBF was 362 ml/kg/min (210-598). In the 8 babies scanned within 3 hrs of the PH, the median PBF was 362 mls/kg/min (304-576). These measures were significantly higher than that found in the rest of the cohort in the same time period where the median duct diameter was 0.5mm (0-2.9) and the median PBF was 237 ml/kg/min (107-569), p<0.0006 for both.

Conclusions: PH in very preterm babies is strongly associated with significant ductal shunting and high estimated pulmonary blood flow. Medical closure of ducts failing to constrict spontaneously within the first few postnatal hours should reduce the risk of PH.