Patent Ductus Arteriosus

Incidence of PDA Closure of PDA in term infants: 50% by 24 hours 90% by 48 hours 100% by 72 hours Closure of PDA >30 weeks gestation: 11% remain open after 4 days Closure of PDA < 30 weeks gestation: 65% remain open after 4 days

Regulation of Ductal Closure Functional closure of lumen: Occurs within hours after birth due to smooth muscle constriction Anatomic occlusion of lumen: Occurs days after birth due to intimal thickening and loss of smooth muscle cells

Factors regulating Ductal Relaxation Increased pulmonary vascular pressure Vasodilator prostaglandins: PGE1 Nitric oxide

Post-natal factors regulating Ductal Closure Increased Pa02 Decreased PVR Decreased circulatory concentrations of PGE1 Decreased PGE1 receptors in ductal wall Increased cortisol concentrations Cortisol decreases the sensativity of the ductus to vasodilating effects of PGE.

Factors Restricting Ductal Closure in Preemies Decreased intrinsic smooth muscle tone Higher circulating PGE1 concentrations Increased sensitivity to vasodilatory effects of PGE1 and NO

Hemodynamic and Pulmonary Consequences of PDA Left to right shunt: increased pulmonary venous pressure, increased pulmonary edema Decreased blood flow to skin, bone, muscle, GI tract, and kidneys Rapid increase in pulmonary blood flow leading to pulmonary hemorrhage (risk of surfactant administration)

Treatment Indocin prophlaxis Treatment indocin: closure in 85% patients Surgical ligation

Complications of PDA BPD NEC Feeding intolerance

Risks of Indocin Use Decreased mesenteric, renal, and cerebral blood flow Oliguria, dilutional hyponatremia Isolated intestinal perforation (increased risk when combined with postnatal steroids) NEC?

Contraindications to Indocin Use NEC Renal failure Bleeding disorders and severe thrombocytopenia Hemodynamically insignificant PDA

Clinical diagnosis Systolic heart murmur, though may be absent Hyperdynamic precordium Bounding peripheral pulses Wide pulse pressure Worsening respiratory status

Indocin Prophylaxis Decreases symptomatic PDA and the need for surgical ligation Decreases Grade III and IV IVH No change in short or long term mortality No difference in rates of NEC Long term neurodevelopmental outcome is not adversely affected