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eFigure 32-1
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Diagram of neonatal transitional circulation.

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  • Fetal circulation (parallel) in transition to complete adult circulation (series)
  • Is essentially a complete adult circulation in series, but with PDA and patent foramen ovale
  • Potential for shunting exists, determined by relation between SVR and PVR
  • Determinants of SVR
    • Intrinsic autoregulatory mechanisms
    • Environmental temperature
    • Radiant warmer–induced vasodilation
  • Determinants of PVR
    • Alveolar hypoxia
    • Reduced total pulmonary vascular bed
    • Sensitization of pulmonary vascular bed by sustained asphyxia

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  • Prenatally, ductus arteriosus (DA) is a vascular connection between the main pulmonary artery (occasionally proximal LPA) and the aorta, diverting blood from pulmonary to systemic circulation.
  • Postnatally, the vasa vasorum to the DA constrict, leading to necrosis of the medial muscular layer → ductal closure.
  • In preterm infants, the DA wall thickness is proportionately less than in term infants, allowing passive diffusion of nutrients from the ductal lumen to the medial muscular layer, even after constriction of the vasa vasorum → higher rate of ductal patency.
  • DA closed in 50% of full-term infants by 24 h, 90% by 48 h, >99% by 96 h.
  • Incidence in term infants: ∼0.02%–0.04% (10% of all CHD in term infants).
    • Incidence in preterm infants: ∼45% of infants <1750 g, ∼80% of infants <1000 g.
    • Increased in: prematurity, hyaline membrane deficiency, asphyxia, high altitude, CHD, increased fluid administration
    • Decreased in: antenatal steroids, intrauterine growth restriction, prolonged rupture of membranes
  • Spontaneous closure of PDA occurs in 38%–85% of babies <1500 g and in 25%–34% of those <1000 g.

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Medical

Surgical

Complications

Transient or permanent renal impairment

Thoracic duct trauma resulting in chylous effusion

Heme-positive stools, ? association with necrotizing enterocolitis (NEC)

Nerve damage resulting in vocal cord paralysis

Impaired platelet function

Surgical site infection

Thrombocytopenia

Postoperative hypotension and circulatory insufficiency

Contraindications

Serum creatinine >1.8 mg/dL

Uncontrolled bleeding diathesis

Platelet count <60,000

Ductal-dependent cardiac disease

Bleeding diathesis

NEC

Duct-dependent cardiac lesions

Sepsis

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Clinical Manifestations

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  • Large PDA can be diagnosed relatively accurately based on clinical findings.
  • Small PDA usually requires an echocardiogram with Doppler, because findings may be similar to pulmonary disease or sepsis.
  • Clinical findings of moderate to large PDA:
    • Hypotension
    • Murmur (Continuous, “machinery”-like, may be intermittent)
    • Heart failure (Poor feeding, apnea, respiratory failure)
    • Wide pulse pressure (>25 mm Hg)
    • Hyperdynamic precordium
    • Bounding pulses (± Palmar pulses, prominent pedal pulses)
    • Respiratory compromise (Increased ventilator support or inability to wean ventilatory support)

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Diagnosis

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  • CXR
    • May be normal, or may see pulmonary edema or cardiomegaly (compare films serially)
  • Echocardiography with Doppler
    • Findings associated with hemodynamically significant PDA include:
      • Ductal diameter >1.5 mm
      • Predominantly left-to-right shunt
      • Disturbed diastolic flow in MPA
      • Reversal of end-diastolic flow in postductal aorta
      • Left atrial/left ventricular enlargement
  • Electrocardiography (no specific findings exist for PDA)
    • May be normal, or may see LVH, BVH, or LAE

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Complications

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  • Pulmonary edema
  • Heart failure
  • Pulmonary hypertension
  • Septic emboli (from ...

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