Neonatal CDH: Stabilization

What the Examiner Is Testing

This case tests the fundamental CDH principle: surgery does not fix pulmonary hypertension, stabilization does. The examiner wants to hear you push back on the surgeon and articulate specific gentle ventilation targets — not just "low pressures." Bag-mask ventilation is contraindicated, and you need to explain why.

The Board Trap

The trap is agreeing to go to the OR immediately because the surgeon is standing there waiting. Premature surgery on a CDH neonate with uncontrolled pulmonary hypertension dramatically increases mortality — the pulmonary hypertensive crisis triggered by the surgical stress can be fatal. The second trap is bag-mask ventilation, which distends the stomach and herniated bowel, further compressing the hypoplastic lungs.

Walk-Through: How This Case Plays Out

Examiner: The baby's saturations are 70% on bag-mask ventilation. The surgeon wants the OR now. What do you say?

Me: I would say no to the OR. CDH is not a surgical emergency at this moment — it's a medical one. The first thing I'm doing is intubating to stop the bag-mask ventilation, which is distending the herniated bowel and compressing whatever lung tissue this baby has. After intubation, this baby goes to the NICU, not the OR. Surgery before pulmonary hypertension is stabilized increases mortality significantly.

Examiner: What are your ventilator targets once intubated?

Me: I would use gentle ventilation: peak inspiratory pressure below 25 cmH2O, tidal volumes 4-6 mL/kg, respiratory rate around 40-60. I'm targeting pre-ductal saturations of 85 to 95% — not 100%. Permissive hypercapnia, PaCO2 in the range of 45 to 55, is acceptable. I'm avoiding barotrauma — these lungs are hypoplastic and will rupture if I'm aggressive. The goal is to keep the lungs open enough to oxygenate without damaging them.

Examiner: The baby's pre-ductal sat is 82% and post-ductal is 65%. What does that tell you?

Me: Pre-ductal sat 82% with post-ductal 65% means right-to-left shunting at the ductus arteriosus — there's significant pulmonary hypertension driving deoxygenated blood from the PA into the descending aorta. That's consistent with what I expect in CDH. I'd start inhaled nitric oxide at 20 ppm to selectively reduce PVR. I'd avoid any stimulation that increases pulmonary arterial pressure: pain, cold, loud noise, acidosis, hypoxia.

Examiner: After 36 hours of stabilization, the pre-ductal sat is 92% and the pulmonary hypertension is improving. The surgeon wants to go to the OR now. Do you agree?

Me: Yes — now I'd agree. The pulmonary hypertension has responded and the baby has demonstrated some pulmonary reserve. I'd proceed with TIVA for the repair, keep iNO running throughout, maintain the same gentle ventilation targets in the OR, and be ready for a pulmonary hypertensive crisis during surgical manipulation.

Key Phrases That Score Points

• "Bag-mask ventilation is contraindicated — stop it immediately and intubate."
• "CDH is not a surgical emergency until the pulmonary hypertension is controlled."
• "PIP below 25 cmH2O, permissive hypercapnia PaCO2 45-55 — I'm protecting against barotrauma."
• "Inhaled nitric oxide 20 ppm for selective pulmonary vasodilation without systemic hypotension."
• "Pre-ductal versus post-ductal gradient confirms ductal-level right-to-left shunting — that's the PH I'm treating."

Why This Case Appears on the Boards

CDH tests your ability to hold off surgical urgency when medical stabilization is the correct priority. It's also a pure neonatal physiology test — the pulmonary hypertension, ductal shunting, and gentle ventilation strategy require precise technical knowledge beyond general pediatric principles.