Duct-dependent congenital heart disease: Viva

Branch 1: Recognising the time-critical problem

The candidate should immediately recognise that this baby has cyanosis unresponsive to 100 percent oxygen in a neonate who was well at discharge and collapsed on day 4. This is the classic presentation of duct-dependent congenital heart disease, specifically a duct-dependent pulmonary circulation where blood cannot reach the lungs once the ductus arteriosus has closed. The saturation of 70 percent that does not improve with oxygen is the key discriminator from a pulmonary cause, and the absence of a murmur does not exclude critical congenital heart disease because many severe obstructive lesions generate no turbulent flow. ^[1]

The candidate should state that the single most urgent intervention is to start prostaglandin E1 (alprostadil) at 0.01 to 0.05 micrograms per kilogram per minute intravenously, without waiting for the echocardiogram. The rationale is that the closed ductus arteriosus was the only route for blood to reach the lungs, and reopening it restores pulmonary blood flow and improves the saturation. The first priorities are airway, breathing, and circulation, an intravenous line, and a bedside glucose, followed by the prostaglandin infusion the moment the suspicion is raised. ^[1]