Pulmonary Atresia

Keep the duct open - Where pulmonary blood flow is duct-dependent, a continuous prostaglandin E1 infusion holds the ductus open by direct vasodilation of ductal smooth muscle, and it runs until echocardiography confirms a reliable non-ductal source. Do not let it lapse for a line change, a transport, or a pump swap.

Know where the lung blood comes from - Before induction, read the echo and cath data for ventricular function, patency and gradient across the shunt, estimated pulmonary and systemic blood flow, and whether aortopulmonary collaterals are present. Which conduit is feeding the lungs drives the whole anesthetic.

Balance the circulations - Target an SaO2 of 75% to 80%, corresponding to a PaO2 of roughly 40 to 50 mm Hg. Titrate FiO2 down to reach it — 40% to 60% is typical, even for preoxygenation — and allow mild hypercarbia (PaCO2 45 to 55 mm Hg) with deliberate hypoventilation. Hold FRC with tidal volumes of 8 to 12 mL/kg and 3 to 5 cm H2O of PEEP so atelectasis does not add intrapulmonary shunt.

High sats are a warning, not a win - Saturations above target mean pulmonary overcirculation stealing from systemic flow: peripheral hypoperfusion now, and pulmonary hypertension if it persists. Saturations below target mean pulmonary undercirculation. Cyanosis here does not improve with 100% oxygen — a failed hyperoxia test is expected, so do not chase the number with FiO2.

Protect the shunt - If pulmonary blood flow falls far enough, stasis can thrombose a Blalock-Taussig or central shunt, abolishing pulmonary blood flow and causing rapid, catastrophic collapse that needs VA ECMO until flow is re-established. Maintain diastolic pressure: it feeds both the shunt and the coronaries, which are already losing ground to diastolic runoff into the pulmonary circulation.

Drug choices - Fentanyl barely touches contractility or SVR and slightly lowers PVR at high dose. Etomidate and dexmedetomidine have minimal effect on contractility, PVR, or SVR. Ketamine raises SVR without affecting PVR and is reasonable with good ventricular function. Propofol drops SVR and depresses the myocardium, and the fall in output can steal from pulmonary blood flow. Volatiles cut cardiac output dose-dependently through SVR — sevoflurane is preferred and kept low. Skip nitrous oxide, which markedly increases PVR.

Preload and fasting - Cardiac output is preload-dependent and sudden afterload swings are not tolerated, so minimize fasting hours and keep maintenance fluids running. Anxiety and pain provoke unpredictable rises in pulmonary and systemic resistance, so blunt the stress response early.

Hematocrit near 40% - Oxygen delivery in these patients is heavily hemoglobin-dependent. A hematocrit around 40% supports peripheral oxygen delivery when saturations are deliberately low.

Debubble everything - Right-to-left shunting is obligatory in PA-IVS and present across the VSD in PA-VSD, so a venous bubble becomes a systemic embolus. Clear air from every line, stopcock, and syringe.

Where the arterial line goes - An upper extremity arterial line may be unreliable on the side of a Blalock-Taussig shunt because of subclavian runoff, and a patent ductus produces a pre- versus post-ductal discrepancy. Know the shunt side and the ductal anatomy before choosing a site.

Right ventricular dependent coronary circulation - In PA-IVS, progressive coronary stenosis can leave segments of myocardium perfused from the hypertensive right ventricle through RV-to-coronary fistulae, and it carries a poor prognosis. New low cardiac output in one of these patients should make you think myocardial ischemia first.

Emergence - Positive pressure ventilation has real hemodynamic consequences here, so weigh early extubation against the cost of pain, hypoventilation, and hypercarbia from residual anesthetic. Fentanyl and dexmedetomidine ease emergence with the least disturbance to a balanced circulation.

Endocarditis prophylaxis - For six months after surgical repair of the cardiac defect.

Pulmonary atresia is complete obstruction of the right ventricular outflow — the pulmonary valve, often along with the trunk, is atretic, so no blood leaves the right ventricle for the lungs. It comes in two anatomic families. With a ventricular septal defect (PA-VSD, in the tetralogy spectrum) there is a large VSD and an overriding aorta, and the lungs are fed by major aortopulmonary collateral arteries (MAPCAs) arising from the thoracic or abdominal aorta, subclavian, internal mammary, or intercostal arteries, usually stenosed at both ends. With an intact ventricular septum (PA-IVS, under 1% of congenital heart disease) the right ventricle is hypertensive and often hypoplastic with an abnormal tricuspid valve, systemic output depends on obligatory right-to-left shunting across the atrial septum, and RV-to-coronary connections can progress to right ventricular dependent coronary circulation.

Either way, pulmonary blood flow comes from something other than the right ventricle — the ductus arteriosus, MAPCAs, or a surgical shunt. Ductal closure is the lethal event.