Hypoplastic Left Heart Syndrome (HLHS)

Ductal patency is the whole plan - Systemic and coronary perfusion run retrograde through the duct. Prostaglandin E1 starts at 0.05 to 0.1 mcg/kg/min and is titrated down to 0.02 mcg/kg/min once patency is confirmed; use the lowest effective dose, since PGE1 causes respiratory depression and hypotension. Never let the infusion lapse in transport or on the way into the room.

Don't chase a normal saturation - Balanced circulation is a Qp:Qs near 1:1, and 75% to 85% is the target, not a problem to fix. A climbing saturation means pulmonary blood flow is stealing from the systemic circulation, and the infant shows it as poor perfusion, acidosis, and a low diastolic pressure.

High FiO2 is a pulmonary vasodilator - Oxygen drops PVR and floods the lungs at the body's expense. Preoxygenate with 40% to 60% rather than 100%, and titrate FiO2 to a SaO2 of 75% to 80%, which corresponds to a PaO2 of roughly 40 to 50 mmHg. Sub-ambient FiO2 of 15% to 19% is used in some centers to raise PVR deliberately.

Hyperventilation does the same damage - Hypocarbia drops PVR and worsens the steal. Ventilate to a PCO2 around 45 to 50 mmHg; mild hypercapnia is the friend here. Correct metabolic acidosis with sodium bicarbonate, since acidosis raises PVR and depresses the ventricle.

Check the atrial septum before induction - The echo report should say whether the foramen ovale is restrictive or the septum intact. A restrictive septum means the left atrium cannot decompress, drives an irreversible rise in PVR, and sends the infant to the cath lab for balloon atrial septostomy.

Debubble every line - Mixing at the atrial level sends any venous air straight to the systemic and cerebral circulation. Filter and purge lines, stopcocks, and syringes.

Carry the oxygen rather than the flow - Keep the hematocrit at 40% to 45%. Raising oxygen-carrying capacity improves delivery without demanding more pulmonary blood flow.

Drug choices that respect the physiology - Fentanyl has minimal effect on contractility and SVR. Etomidate and dexmedetomidine barely move contractility, PVR, or SVR. Ketamine raises SVR and leaves PVR alone, so it suits a ventricle still contracting well. Propofol drops SVR and depresses the myocardium, and the fall in cardiac output steals from pulmonary flow. Skip nitrous oxide, which markedly raises PVR. If inhalational induction is needed for access, sevoflurane cuts cardiac output the least - bring the concentration down as soon as the airway is secure.

Monitoring - Invasive arterial pressure, CVP, and regional tissue oximetry alongside standard monitors. With a patent duct, preductal and postductal probes read differently, so decide which segment you want before siting them. Hold diastolic pressure up for coronary filling and avoid tachycardia, which raises demand while shortening the time to meet it.

Preload and stress - Cardiac output is preload dependent and the ventricle tolerates sudden afterload swings badly. Minimize fasting hours and continue maintenance fluid. Pain and anxiety move PVR and SVR unpredictably, so stay ahead of stimulation.

Know which stage the child is in - Three palliations: Norwood or hybrid in the first week, hemi-Fontan or bidirectional Glenn around six months, and completion Fontan at two to three years. The physiology and the ventilation goals change completely at each step - see the Fontan Circulation entry for management once the circuit is complete.

Related lesions and genetics - Total aortic valve atresia sits at the severe end of this same spectrum; see the Aortic Atresia entry. Send genetic testing, since HLHS travels with Turner, DiGeorge, and Down syndromes, and a chromosomal abnormality predicts higher morbidity, longer stay, and higher mortality after surgery.

Hypoplastic left heart syndrome (HLHS) is underdevelopment of the left-sided structures - mitral valve, left ventricle, aortic valve, ascending aorta, and aortic arch. It affects about 1 in 5,000 neonates and roughly 3% of congenital heart disease, yet causes 23% of cardiac deaths in the first week of life. Aortic valve stenosis is the usual driver: obstructed outflow in utero raises afterload and cuts flow through the ventricle, so it never grows.

After birth the left ventricle does no useful work. The right ventricle supplies both circulations in parallel rather than in series, and the whole systemic bed - coronaries included - fills retrograde through the ductus arteriosus. Pulmonary venous blood must cross the atrial septum to reach the right heart, so everything mixes and saturation sits at 75% to 85%. Close the duct or restrict the septum and collapse follows fast.