Patent Ductus Arteriosus (PDA)

Pathophysiology & Presentation

• Failure of the ductus arteriosus to close after birth, leading to a left-to-right shunt from the aorta to the pulmonary artery.
• Hemodynamically Significant PDA (hsPDA) triad: Pulmonary overcirculation, systemic hypoperfusion, and left heart volume overload.
• Clinical signs: Systolic or continuous machinery murmur (best heard at upper left sternal border), hyperactive precordium, bounding peripheral pulses (due to wide pulse pressure).
• Respiratory implications: Increased mechanical ventilation requirements, pulmonary edema, failure to successfully extubate.
• Systemic implications: Decreased cerebral, splanchnic (risk of NEC), and renal blood flow (oliguria).

Diagnostic Criteria (Echocardiography)

• Gold Standard: Complete 2D and Doppler Echocardiogram to confirm hsPDA and rule out ductal-dependent congenital heart disease.
• Ductal diameter: Usually considered significant if > 1.5 mm in extreme preemies.
• Left-to-right flow: Unrestricted (pulsatile) transductal flow with low velocity (< 1.5 m/s) indicates unrestrictive large communication.
• Left atrial-to-aortic root (LA:Ao) ratio > 1.5 indicates substantial left atrial volume overload.
• Retrograde/Reversed diastolic flow clearly visible in the descending aorta or superior mesenteric artery (SMA) is a hallmark of systemic organ steal.

Pharmacologic Closure Protocols (Dosages per Neofax)

• Contraindications to NSAIDs: Active bleeding (IVH, GI), severe thrombocytopenia (<50k), oliguria (UOP < 1 ml/kg/hr) or elevated Creatinine, suspected/confirmed NEC.
• Indomethacin protocol: 3 doses given IV every 12-24 hours. Dosing depends on age at first dose (<48hr: 0.2mg/kg then 0.1mg/kg then 0.1mg/kg; 2-7 days: 0.2, 0.2, 0.2; >7 days: 0.2, 0.25, 0.25).
• Ibuprofen Lysine protocol (preferred for lesser renal toxicity): IV only. Initial dose 10 mg/kg, followed by 5 mg/kg at 24 and 48 hours.
• Acetaminophen (Paracetamol) parmacotherapy (emerging alternative): 15 mg/kg IV or PO every 6 hours for 3 to 7 days.
• Monitor strict I&O and daily BUN/Creatinine during NSAID treatment.

Conservative & Procedural Management

• Conservative measures: Fluid restriction (usually 120-130 mL/kg/day MAX), optimize hematocrit (>35%) to improve oxygen carrying capacity, utilize PEEP to limit pulmonary edema.
• Diuretics (Furosemide): Use cautiously; routine use is not recommended as it stimulates renal prostaglandin synthesis and may keep PDA open.
• Surgical Ligation: Indicated only if medical therapy fails or is strictly contraindicated, and infant cannot be weaned from ventilation.
• Percutaneous Catheter Closure (e.g., Piccolo occluder) is now FDA-approved as an alternative to surgical ligation in infants >700 grams.

Diagnostic & Management Algorithm

• PDA Closure Logic: [START] Murmur, wide pulse pressure -> [EVALUATE] Echo reveals significant PDA -> [DECISION] Symptomatic? -> [YES] Indomethacin/Ibuprofen/Paracetamol -> [NO] Conservative fluid restriction

References

1. Mitra S, Florella R, et al. Treatment of patent ductus arteriosus in preterm infants: a systematic review and meta-analysis. JAMA. 2018.
2. Benitz WE; AAP Committee on Fetus and Newborn. Patent Ductus Arteriosus in Preterm Infants. Pediatrics 2016.