Cardiovascular System
Transition and the ductus arteriosus
Functional ductal closure occurs in 24-72 hours; anatomic closure takes weeks. A hemodynamically significant PDA causes a systolic murmur, bounding pulses, wide pulse pressure, pulmonary edema, and worsening respiratory status. Treat when significant with ibuprofen, indomethacin, or acetaminophen; avoid indomethacin with renal failure, NEC, or thrombocytopenia.
Ductal-dependent lesions
Prostaglandin E1 (0.01-0.05 mcg/kg/min) keeps the ductus open in ductal-dependent pulmonary lesions (tetralogy of Fallot, pulmonary atresia) and systemic lesions (hypoplastic left heart, coarctation, interrupted aortic arch). Apnea is a common side effect, so be ready to support ventilation. In ductal-dependent systemic flow, closing the PDA can cause shock.
Shock and blood pressure
Hypotension is defined by gestational age and postnatal age percentiles, not a single number. Assess perfusion, lactate, urine output, and acid-base status. Give volume 10 mL/kg, then dopamine 5-10 mcg/kg/min, epinephrine, or hydrocortisone for refractory hypotension.
Worked example
A 2-day-old has pink upper extremities, blue lower extremities, weak femoral pulses, and a 28 mmHg systolic blood-pressure difference between right arm and leg. Reasoning: differential cyanosis plus an upper-lower BP gradient suggests coarctation or interrupted aortic arch. Start PGE1, obtain echocardiography, avoid high oxygen, and arrange transfer.
Traps
- Missing four-limb blood pressures and pre/postductal saturations.
- Closing a PDA before excluding ductal-dependent anatomy.
- Attributing a murmur to normal transition when pulses are bounding.
- Using a single BP threshold for all gestational ages.