Aortic Atresia

The duct is the systemic circulation - Every drop of systemic and coronary flow crosses the ductus arteriosus. Prostaglandin E1 goes up as soon as the diagnosis is suspected and before the duct closes. Untreated, aortic atresia accounts for about 25% of cardiac-related neonatal deaths, with cyanosis appearing around day 2 and heart failure around day 2.5 in roughly 60%.

Balance Qp:Qs — do not chase a normal saturation - Ventricular output is split between lungs and body, and an SpO2 of 75 to 80% is the rough surrogate of a balanced circulation. A higher number means the lungs are stealing from the systemic side and the gut, kidneys and coronaries are under-perfused; a lower number means pulmonary under-circulation. Target a PaO2 of 40 to 50 mmHg and move FiO2 to hold it there.

Ventilation is your vasoactive drug - FiO2 of 40 to 60% is the usual working range. Lowering FiO2 and letting PaCO2 rise to 45 to 55 mmHg by deliberate hypoventilation both raise PVR and push flow back to the body. Tidal volume of 8 to 12 mL/kg with PEEP of 3 to 5 keeps atelectasis from shifting the balance on its own.

Induction agents, sorted by what they do to the balance - Fentanyl has minimal effect on contractility and SVR and slightly lowers PVR at high dose; etomidate and dexmedetomidine have minimal effect on contractility, PVR and SVR. Ketamine raises SVR and leaves PVR unchanged, which suits the child with preserved ventricular function. Propofol drops SVR and depresses the myocardium, and the resulting fall in cardiac output lets pulmonary flow steal from the systemic side. Nitrous oxide markedly raises PVR. IV induction is generally preferred; inhalational induction earns its place when the struggle for access would itself destabilize the child.

Preload dependent, afterload intolerant - Cardiac output depends on preload and tolerates sudden afterload change badly. Minimize fasting hours and keep maintenance fluids running. Aim for a hematocrit around 40% — in a fully mixed circulation, oxygen delivery rides on carrying capacity.

Keep the child calm - Anxiety and pain drive unpredictable swings in both PVR and SVR in a ventricle with no reserve. Premedicate rather than fight an IV in a screaming neonate.

Preop data that changes the plan - Echo and catheterization define ventricular function, patency of and gradient across the shunt, estimated pulmonary and systemic blood flows, and aortopulmonary collaterals. Crackles or pulmonary edema on exam mean pulmonary over-circulation. Around 6% have an intact or restrictive atrial septum and need emergent septostomy or stenting — that child is not a routine case.

Your arterial line may be lying to you - A PDA makes pre- and post-ductal pressures and saturations disagree, so know which limb the catheter and the pulse oximeter are in before you act on the number. An upper-extremity line is also unreliable on the side of a Blalock-Taussig shunt because of subclavian runoff.

Know which repair pathway the patient is on - A hypoplastic left ventricle goes down the univentricular route: Norwood, then bidirectional Glenn, then Fontan. With an adequate left ventricle and a VSD, biventricular repair is possible via the Yasui procedure, or a Norwood followed by a staged Rastelli. The physiology differs completely between stages, so establish where the patient sits before planning anything.

Watch the shunt, not just the numbers - Where pulmonary blood flow depends on a central or Blalock-Taussig shunt, letting flow fall far enough allows shunt thrombosis. That means a complete loss of pulmonary blood flow and rapid, catastrophic collapse requiring VA ECMO until flow is re-established.

Extubation is a hemodynamic decision - Positive pressure ventilation raises intrathoracic pressure with real hemodynamic consequences here, so weigh early extubation against the stress of inadequate analgesia and the hypercapnia of a narcotized spontaneous effort. Fentanyl and dexmedetomidine ease emergence with the least disturbance to the balanced circulation.

Aortic atresia is congenital fusion of the aortic valve cusps, leaving no antegrade flow out of the left ventricle. It sits at the far end of the left ventricular outflow tract malformation spectrum, and total aortic valvular atresia is best understood as the most advanced form of hypoplastic left heart syndrome (HLHS).

The left ventricle is small and thick-walled, the right ventricle is dilated, the mitral valve is small or itself atretic, and the ascending aorta and arch are hypoplastic. Pulmonary venous return crosses to the right heart through a patent foramen ovale or atrial septal defect, and the right ventricle pumps fully mixed blood into the pulmonary artery and, through the ductus arteriosus, into the descending aorta. The whole systemic circulation is duct-dependent — including the coronaries, which fill retrograde through the hypoplastic ascending aorta. Once the duct closes it is uniformly fatal.