🫁 Chapter 53: Pulmonary Hypertension and Crisis

PAH · PVR · RV Failure · Inhaled NO · Epoprostenol · Sildenafil · Milrinone · PHC Prevention

🫁 Pulmonary Hypertension: Mean PAP ≥25 mmHg · PVR >3 Wood Units

📊 Definition & Pathophysiology
PAH = mean PAP ≥25 mmHg, PAWP <15, PVR >3 WU. RV failure is major determinant of mortality. Factors increasing PVR: hypoxia, acidosis, hypothermia, pain/agitation, atelectasis, overdistension.
🩸 Pulmonary Hypertensive Crisis (PHC)
Sudden increase in PVR → RV failure → decreased LV filling → hypotension, desaturation, bradycardia, arrest. Precipitated by hypoxia, acidosis, suctioning, pain, extubation, infection.
💊 Inhaled Pulmonary Vasodilators
• iNO (inhaled nitric oxide) 20 ppm — selective pulmonary vasodilator, no systemic hypotension
• Inhaled epoprostenol (prostacyclin) — cost-effective alternative to iNO
💉 Systemic Therapies
• Milrinone: inodilator + lusitropy, reduces PVR (but may cause systemic hypotension)
• Sildenafil (PDE5 inhibitor): 0.3-1 mg/kg PO/IV, inhibits cGMP breakdown
• Prostacyclin analogues: IV epoprostenol, treprostinil
• Endothelin receptor antagonists: bosentan (chronic)
⚠️ Crisis Management
1. 100% O2, intubate if needed
2. Correct acidosis (NaHCO3)
3. Deep sedation/paralysis to prevent agitation
4. iNO 20 ppm or inhaled epoprostenol
5. Milrinone or dobutamine for RV inotropy
6. Noradrenaline for systemic hypotension (maintain coronary perfusion)
📋 RV Failure Support
• Maintain preload (avoid hypovolaemia)
• Avoid hypocarbia (cerebral vasoconstriction) and hypercarbia (acidosis)
• Optimal lung volume (FRC) — avoid atelectasis and overdistension
• ECMO for refractory PHC
⚠️ PHC Precipitants (Box 53.1): Hypoxia, Acidosis, Pain/Agitation, Fever, Infection, Arrhythmias, Atelectasis/Pulmonary overdistension, Trauma/Surgery, Acute chest syndrome.

🩺 Step-by-Step: Pulmonary Hypertension & Crisis Management

1
Identify high-risk PHT patient
Congenital heart disease (post-repair of VSD/AVSD, truncus), PPHN, connective tissue disease, family history. Precipitating factors: hypoxia, acidosis, pain, suctioning, fever, extubation.
2
Prevent pulmonary hypertensive crisis
• Maintain SpO2 >92% (avoid hypoxia)
• Maintain pH >7.35 (avoid acidosis)
• Deep sedation/analgesia before noxious stimuli (suctioning, line placement)
• Avoid hyperventilation (cerebral vasoconstriction) and hypoventilation (hypercapnia)
• Maintain normothermia
3
Recognise PHC — medical emergency!
Sudden hypotension + desaturation → bradycardia → cardiac arrest. Immediate action required.
4
Immediate crisis management
• 100% O2, bag-mask ventilation, intubate if not already intubated
• Correct acidosis: NaHCO3 1-2 mEq/kg IV
• Deep sedation + neuromuscular blockade (prevent agitation)
• Inhaled nitric oxide (iNO) 20 ppm or inhaled epoprostenol
5
Maintain systemic BP and RV function
• Noradrenaline or vasopressin for hypotension (maintain coronary perfusion)
• Milrinone or dobutamine for RV inotropy (reduce PVR, improve CO)
• Avoid pure vasodilators that lower SVR (nitroprusside, nitroglycerin)
6
Optimise ventilation
Target FRC: PEEP 5-8 cm H2O (avoid atelectasis and overdistension). Permissive hypercapnia acceptable as long as pH >7.25.
7
Refractory PHC → ECMO
VA-ECMO unloads the RV, provides gas exchange, buys time for recovery. Indicated if crisis persists despite maximal therapy.