30% of preemies who are over 32 weeks GA, and 60% who are under 28 weeks GA have a PDA.
Ligating a symptomatic PDA in a fragile premature infant can have substantial (but usually transient) unwanted hemodynamic consequences. The sudden ligation of the PDA causes an instantaneous rise in afterload, resulting from the obliteration of the the pop-off circuit into the low resistance pulmonary circulation, and an associated drop in preload. This sudden change may not be tolerated well by preemies, most likely due to underlying cardiac dysfunction. So how can we predict which infant is going to fare worse after ligation?
Moin et al, in a study that evaluated 100 premature infants who underwent PDA ligation, noted that 32% of preemies required vasopressor support (either starting pressors or increasing the dose of preexisting pressor support) within 72 hours of PDA ligation. Risk factors associated with need for vasopressor support were a lower gestational age (25 vs 26 weeks), lower birth weight (714 vs 870 grams), and relatively high ventilatory support (RIS>6).
Additionally, those infants who required pressor support after ligation had an increased risk of death before 36 week adjusted gestational age.
The authors cautioned that the study had several limitations by virtue of it's design and that further studies are needed to confirm their observations.
References:
Moin F et al. Risk factors predicting vasopressor use after patent ductus arteriosus ligation. American Journal of Perinatology;20(6)2003:313-320
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