RESPIRATORY CONDITIONS
Persistent Pulmonary Hypertension of the Newborn
A practical guide for paediatric registrars · Failure of the normal circulatory transition (PPHN)
OUT OF PROPORTION
TO THE LUNGS
Sustained high PVR
The pulmonary vasculature fails to relax at birth, so pulmonary vascular resistance stays near fetal levels. The core defect.
Right-to-left shunting
High PVR drives blood right-to-left across the ductus arteriosus and foramen ovale, bypassing the lungs.
Hypoxaemia & acidosis (vicious cycle)
Shunting causes profound hypoxaemia; hypoxia and acidosis raise PVR further, worsening the shunt.
Differential cyanosis
A ductal right-to-left shunt makes pre-ductal (right arm) SpO₂ higher than post-ductal (legs) by >10%.
Labile circulation
RV pressure overload and poor output make the circulation very labile - it deteriorates with agitation and handling.
CLINICAL FINDINGS
- Term/post-term infant, often with a precipitant (MAS, sepsis, asphyxia, CDH)
- Marked cyanosis and hypoxaemia, often out of proportion to the chest findings and CXR
- Labile saturations - marked desaturation with handling or agitation
- Pre/post-ductal SpO₂ difference >10% (differential cyanosis)
- Loud single S2, prominent RV impulse, ± tricuspid regurgitation murmur
- Poor perfusion and hypotension if severe
INVESTIGATIONS
- Simultaneous pre- and post-ductal SpO₂ - a gap >10% supports PPHN
- Echocardiography - the key test: confirms raised pressures and R-to-L/bidirectional shunt, assesses RV, and excludes congenital heart disease
- Blood gas: hypoxaemia ± respiratory/metabolic acidosis
- Oxygenation index (OI) = FiO₂ × mean airway pressure × 100 / PaO₂ - grades severity
- CXR: often clear or reflects the underlying disease
- Sepsis screen, glucose, calcium, lactate
COMPLICATIONS & RED FLAGS
- Refractory hypoxaemia → iNO / ECMO
- Air leak, especially with high ventilation pressures
- Systemic hypotension, low cardiac output, shock
- Survivors: risk of neurodevelopmental impairment (arrange follow-up)
- Red flags: rising OI, widening pre/post-ductal gap, profound lability, hypotension - escalate early and call NETS
Chest X-ray / echo
The CXR is often clear or simply reflects the underlying disease (MAS, RDS, pneumonia, CDH) - clear lungs with severe, labile hypoxaemia is itself a clue. PPHN is confirmed on echocardiography (right-to-left or bidirectional shunt at the duct/foramen ovale, raised RV pressure, and exclusion of structural heart disease), not on the film.
MANAGEMENT
Gentle, minimal-handling care that breaks the vicious cycle - optimise oxygenation and pressure, treat the cause, and escalate to iNO/ECMO.
Supportive & Gentle
- NICU/SCN; minimal handling, cluster cares, sedation ± analgesia (agitation worsens shunting)
- Maintain pre-ductal SpO₂ ~91-95%; avoid both hypoxia and hyperoxia (oxidative injury raises PVR)
- Correct acidosis, hypoglycaemia, hypocalcaemia; maintain normothermia
- Optimise lung recruitment; HFOV for severe lung disease or air leak; avoid over-distension
Circulatory Support
- Maintain systemic BP > pulmonary pressure to reduce R-to-L shunt (volume, inotropes/vasopressors)
- Support cardiac output - e.g. dobutamine, milrinone, noradrenaline per unit protocol
- Treat the underlying cause - antibiotics for sepsis, surfactant for parenchymal disease
Vasodilators & Escalation
- iNO - selective pulmonary vasodilator; start for OI ≥20-25 once echo excludes CHD
- Adjuncts (sildenafil, milrinone) in some units
- ECMO for refractory disease failing maximal therapy - refer early, call NETS
- Avoid: hyperoxia, acidosis, agitation and over-ventilation
- Minimal handling, clustered cares and a quiet, dim environment - stimulation, cold, pain and suction trigger desaturation.
- Pre- and post-ductal SpO2; maintain normothermia and comfort/sedation.
- Watch for labile saturations; have escalation and iNO plans ready.
- Support parents - a frightening, labile picture.
How do you interpret pre/post-ductal saturations - and why does a normal gap not exclude PPHN?
Why must congenital heart disease be excluded by echo before starting iNO?
How does the oxygenation index guide escalation to iNO and ECMO?
Why do hyperoxia, acidosis and agitation each worsen PPHN?
Take-home message: PPHN is sustained high pulmonary vascular resistance causing right-to-left shunting and severe, labile hypoxaemia in the term or near-term infant. Diagnosis is by echocardiography (excluding CHD), guided by pre/post-ductal saturations and the oxygenation index. Management is gentle, minimal-handling supportive care with good oxygenation, systemic BP support and treating the cause, escalating to iNO and ECMO for refractory disease - while strictly avoiding hyperoxia, acidosis and agitation.
For educational purposes only. Always align management to current ANZCOR/NRP guidelines and your local SCN/NICU or NETS protocols.