Hemodynamically significant PDA: An echocardiographic and clinical assessment of incidence, natural history, and outcome in very low birth weight infants maintained in negative fluid balance

Fifty very low birth weight (VLBW) infants (750-1500 g, 27-33 weeks gestational age) were assigned at random to one of two groups of negative fluid balance and underwent prospective clinical and echocardiographic examinations during the first month of life. The purpose was to determine: (a) the effect of fluid restriction on the incidence of ductal shunting, (b) the reliability of the physical examination in diagnosing significant ductal shunting, and (c) the relationship between significant ductal shunting and outcome in such infants. None of the infants had manipulations to close the ductus during the first week of life. Using routine structural and functional echocardiographic indices as criteria for the diagnosis of hemodynamically significant ductal shunting (hsPDA), we found that the two fluid-balance groups (8%-10% weight loss vs 13%-15% weight loss) did not significantly differ in incidence of hsPDA, duration of ventilation, or development of BPD. These two groups were then combined for further analysis: 32 (64%) of 50 VLBW infants had hsPDA during the first week of life. The group of infants with hsPDA did not differ significantly from that without hsPDA in birth weight or gestational age, but had a significantly lower Apgar score (P<0.04) and was significantly more likely to require ventilator support for RDS (P<0.01). Although when present a typical ductal murmur was specific for the development of significant ductal shunting, no murmur was heard in 21 (66%) of 32 infants with early hsPDA. Of the infants requiring ventilator support for RDS, the group with early hsPDA needed ventilation for 13.8±9.4 days, significantly longer than the group without early hsPDA (3.2±2.6 days, P<0.001), and had a higher incidence of BPD and death than the group without early hsPDA (P<0.04). In our study of a large group of prospectively identified VLBW infants, we did not find that significant ductal shunting was altered by more stringent fluid restriction, but we did find that such shunting was frequently inapparent clinically, and was associated with significantly increased morbidity and mortality.