The preterm infant who stops weaning — a haemodynamically significant PDA

Clinical information for the examiner

Setting: Tertiary NICU, day 5 of life. The infant is ventilated on volume-targeted ventilation (PIP 16, PEEP 5, rate 30, FiO₂ 0.42) for respiratory distress syndrome; antenatal steroids were given and one dose of surfactant administered at birth. The creatinine has risen from 78 to 102 µmol/L. ^[13]

On your arrival:

• Heart rate 158, SpO₂ 92%, blood pressure 52/24 (mean 34), widened pulse pressure 28. ^[13]
• Pulses bounding at the brachial and femoral arteries; precordium hyperdynamic. ^[13]
• Soft systolic murmur at the upper left sternal border. ^[13]
• Urine output 0.8 mL/kg/h (was 2.5). ^[13]

Functional echocardiogram (provided): structurally normal heart; duct diameter 2.1 mm with left-to-right flow; left atrial-to-aortic root ratio 1.7; diastolic flow reversal in the descending aorta; increased left ventricular output. ^[13]