Transposition of the Great Arteries (TGA)

Mixing is what keeps them alive - Before repair, oxygenation depends on intercirculatory mixing, not on how much oxygen you deliver. Prostaglandin E1 holds the ductus open and a balloon atrial septostomy enlarges a restrictive atrial communication. Give PGE1 its own dedicated IV access and run it until bypass.

Pre-bypass hemodynamic goals - Maintain cardiac output through heart rate, contractility, and preload, targeting saturations above 75%. Avoid rises in PVR and falls in SVR — both cut pulmonary blood flow and therefore reduce mixing.

FiO2 is a blunt instrument - Up-titrating FiO2 is reasonable when desaturation does not respond to volume or ventilation adjustment, but high FiO2 increases pulmonary flow at the expense of systemic flow.

Reverse differential cyanosis - In TGA the preductal saturation can read lower than the postductal one. Place pre- and post-ductal pulse oximeters so you can actually see it, and use a 5-lead ECG.

Immature myocardium has no reserve - Neonatal myocardium is sensitive to anesthetic myocardial depression, and inotropic support is often needed before bypass.

Debubble everything - Obligatory intracardiac mixing means a venous bubble becomes an arterial embolism. Put bubble filters on the lines and purge meticulously.

Post-bypass in the neonate - The goal is adequate output while avoiding left atrial and pulmonary hypertension. Do not over-volume the newly systemic left ventricle — overdistension raises LA pressure and can compress the reimplanted coronaries. Post-repair echo must confirm coronary perfusion, since the coronary buttons were excised and reimplanted.

Expect to bleed after an arterial switch - Extensive suture lines, long bypass time, and an immature coagulation system make severe post-bypass bleeding the rule. Have product available and ready.

What an arterial switch leaves the adult - The ASO restores normal great-vessel arrangement and gives a series circulation with the left ventricle as the systemic ventricle, and long-term survival is above 90%. The residua to look for are coronary artery obstruction, neoaortic insufficiency, and pulmonary stenosis — so a baseline ECG and the most recent echo of coronary flow, aortic valve, and outflow gradients are the pre-op documents that matter.

What an atrial switch leaves the adult - Mustard and Senning baffles redirect flow at the atrial level and leave a systemic right ventricle. Expect right ventricular failure, arrhythmias, tricuspid valve dysfunction, and baffle-related obstruction or leak, plus a real risk of sudden death. Review the baseline ECG, the rhythm and device history, and the most recent echo of systemic RV function and baffle patency before induction.

Neurodevelopment in the school-age child - Children repaired by arterial switch have a higher rate of neurodevelopmental impairment and ADHD, and many need special education services. Plan premedication and separation accordingly.

Congenitally corrected TGA is a separate problem - Levo-TGA, also called congenitally corrected TGA, is non-cyanotic and presents late with systemic right ventricular failure — see that entry rather than applying d-TGA physiology to it.

In transposition of the great arteries (TGA) the conotruncal septum fails to spiral during development, so the aorta arises from the right ventricle and the pulmonary trunk from the left. In the common dextro form (d-TGA) there is atrioventricular concordance with ventriculo-arterial discordance: deoxygenated blood returns to the right heart and goes straight back out the aorta, while oxygenated blood returns to the left heart and goes straight back to the lungs. The circulations run in parallel rather than in series, which is fatal without mixing between them.

Mixing occurs through a PDA, a PFO or ASD, a VSD (about 45% of patients), or bronchopulmonary collaterals; an unrestrictive atrial-level shunt is the best of them. When the ductus and foramen close and there is no VSD, the neonate develops severe hypoxemia, lactic acidosis, and shock.