Pulmonary Hypertensive Crisis

Pulmonary hypertensive crisis is an acute rise in pulmonary vascular resistance producing right ventricular failure, low cardiac output, systemic hypotension, hypoxaemia and sometimes cardiac arrest, in patients with pulmonary hypertension. It occurs in pulmonary arterial hypertension, congenital heart disease, after cardiac surgery and in neonates (persistent pulmonary hypertension).

Epidemiology. Pulmonary arterial hypertension affects about 15 to 50 people in a million. Crisis is a leading cause of death, and perioperative mortality in affected patients is about 5 to 15%.

Triggers. Hypoxia, hypercapnia, acidosis, pain, agitation, tracheal suction, anaesthesia induction, infection, arrhythmia (atrial flutter or fibrillation), volume overload or depletion, interruption of pulmonary vasodilator therapy, pulmonary embolism and pregnancy or delivery.

Pathophysiology. Raised pulmonary vascular resistance increases right ventricular afterload, wall tension and oxygen demand, while perfusion falls from systemic hypotension. Right ventricular ischaemia, septal shift and reduced left ventricular filling cause collapse in a vicious cycle. Right to left shunting through a foramen ovale or defect worsens hypoxaemia.

Presentation is sudden breathlessness, syncope, chest pain, hypotension, tachycardia, cyanosis, raised jugular venous pressure, loud second heart sound, tricuspid regurgitation, hepatomegaly and oliguria. Under anaesthesia, pulmonary artery pressure rises, central venous pressure rises and systemic pressure falls.

Red flags.

• Syncope, hypotension or rising lactate.
• Systemic pressure falling toward pulmonary artery pressure.
• Arrhythmia or cardiac arrest.

Echocardiography (dilated right ventricle, septal flattening, reduced tricuspid annular plane systolic excursion, estimated pulmonary pressure, pericardial effusion). ECG (right axis, strain, arrhythmia). Arterial gas, lactate, natriuretic peptide, troponin, liver tests and creatinine. Look for triggers: infection, pulmonary embolism, arrhythmia and drug interruption.

Differential diagnosis. Massive pulmonary embolism, right ventricular infarction, tamponade, sepsis, hypovolaemia and left heart failure.

Admit to intensive care. Treat the trigger, restore pulmonary vasodilator therapy and avoid further rises in resistance.

Oxygen and ventilation. Oxygen to saturation over 94%, avoid hypoxia and hypercapnia. If intubation is needed, use a very experienced operator, ketamine or etomidate for induction, and avoid high PEEP and large tidal volumes. Keep PaCO2 at 4.0 to 4.5 kPa (30 to 35 mmHg) and pH over 7.4.

Pulmonary vasodilators.

• Inhaled nitric oxide 10 to 40 ppm, or nebulised epoprostenol 50 nanogram/kg/min (maintain dose, do not stop abruptly).
• IV epoprostenol starting at 2 nanogram/kg/min and increasing by 1 to 2 nanogram/kg/min every 15 to 30 minutes as tolerated, or treprostinil IV or SC. Monitor hypotension, flushing and headache.
• Sildenafil 10 mg IV every 8 hours (0.25 to 0.5 mg/kg every 6 to 8 hours in children), or enteral 20 mg three times daily.

Right ventricular support.

• Noradrenaline 0.05 to 0.5 microgram/kg/min to maintain systemic pressure higher than pulmonary pressure (mean arterial pressure over 65 mmHg).
• Vasopressin 0.01 to 0.04 units/min, which increases systemic resistance without raising pulmonary resistance.
• Dobutamine 2.5 to 10 microgram/kg/min or milrinone 0.25 to 0.5 microgram/kg/min (watch hypotension) for low output.

Volume. Aim for a central venous pressure of 8 to 12 mmHg. Give small boluses (250 mL) if volume depleted, and diurese (furosemide 40 mg IV, infusion 5 to 20 mg/h) if overloaded.

Rhythm. Restore sinus rhythm quickly: cardioversion for unstable atrial arrhythmia. Amiodarone 150 mg IV over 10 minutes then 1 mg/min, and avoid negative inotropes such as diltiazem or beta blockers.

Rescue. Venoarterial ECMO as a bridge to recovery or transplant, balloon atrial septostomy in selected cases, and urgent transplant evaluation.

Anticoagulation and infection. Treat pulmonary embolism with anticoagulation (and lysis for high risk), and treat infection early.

Monitoring. Arterial and central venous pressure, echocardiography, lactate, urine output, oxygen saturation and drug delivery lines (no interruptions).

Referral and escalation. Pulmonary hypertension centre early. Cardiac intensive care and ECMO team.

Special groups. In pregnancy, mortality is high, and multidisciplinary management with early delivery planning is needed. In neonates, treat persistent pulmonary hypertension with inhaled nitric oxide 20 ppm and ventilation.