Congenital heart disease presenting in the newborn — structured clinical encounter

Station brief (candidate)

You are the paediatric registrar. A term infant who passed the pulse-oximetry screen and was well at discharge returns on day 3 with poor feeding, mottled cool peripheries, tachypnoea, weak femoral pulses and a capillary gas showing a metabolic acidosis. The team asks you to make the bedside diagnosis, deliver the immediate resuscitation, arrange the investigations, and speak with the parents. You have 12 minutes with the team and 5 minutes for examiner discussion. [6]

Information available on request

• Term infant, normal vaginal delivery, no risk factors for sepsis; passed the pulse-oximetry screen at 24 hours and was well at discharge on day 2. [1]
• On day 3: poor feeding, lethargy, mottled cool peripheries, capillary refill 4 seconds, tachypnoea but clear lungs, weak femoral pulses. [6]
• Capillary gas: pH 7.18, base excess minus 10, lactate elevated; glucose and ionised calcium normal. [6]
• Antenatal anomaly scan was reported as normal. [10]

Tasks

1. State the most likely diagnosis category and the bedside features that support it. [6]
2. Deliver the immediate first-hour resuscitation, naming the key drug, its dose and the principle governing its timing. [9]
3. Outline the bedside assessment and first-line investigations, and explain why the definitive test does not delay treatment. [9]
4. Communicate the situation and the safety-net to the parents in plain language. [7]

Marking anchors

Must-hit

• Recognises a duct-dependent obstructive lesion — coarctation or interrupted aortic arch until proven otherwise — from the day-three collapse, weak femoral pulses and metabolic acidosis, in a baby previously well while the duct was open. [6]
• Starts prostaglandin E1 (alprostadil) 0.01 to 0.05 mcg/kg/min intravenously before echocardiography, stating that the echo confirms but does not treat; stabilises the ABCs, corrects metabolic derangements, and gives empiric antibiotics covering sepsis. [9]
• Anticipates prostaglandin-induced apnoea and readies intubation, with a low threshold for elective intubation before retrieval. [9]

Merit

• Performs simultaneous right brachial and femoral pulse palpation, four-limb blood pressure, pre/post-ductal oximetry, and orders a chest radiograph and urgent echocardiography in parallel with treatment, not after it. [9]
• Counsels the parents in plain language: the ductus was keeping the baby well; its closure caused the collapse; screening catches most but not all lesions; the plan is to reopen the duct and transfer to a cardiac centre. [7]
• Places the case in context: pulse-oximetry screening has a sensitivity of about 76 percent, so left-heart obstruction and some transpositions are missed — a passed screen never excludes congenital heart disease. [2] [7]

Fail

• Treats the collapse as sepsis alone, with fluids and antibiotics and no prostaglandin, while the duct closes irreversibly. [6]
• Waits for the echocardiogram before starting prostaglandin, delaying the one treatment that can restore perfusion. [9]
• Is falsely reassured by the passed screen and the normal antenatal scan, and fails to escalate. [7]