Managing Infants and Children With Congenital Heart Disease

Managing Infants and Children with Congenital Heart Disease

In order to successfully manage an infant with congenital heart disease,
whether for cardiac or noncardiac surgery, there are essential questions
that the clinician must answer.

1. What are the flow characteristics of blood in the infant’s heart?
Where does the deoxygenated blood come from and where does
it go?
Example: In patients with Truncus Arteriosus, blood returns from the
body to the right atrium and then leaves the heart through a large
common vessel that feeds the pulmonary and the systemic
circulation.

2. Which ventricle is the most affected? Which ventricle supplies blood
flow to the pulmonary circulation? Which to the systemic
circulation?
Example: Patients with hypoplastic left heart do not have an
effective left ventricle. In these cases, the right ventricle pumps
blood to the systemic and the pulmonary circulation.

3. Is the pulmonary blood flow normal? Is the pulmonary resistance
elevated?
Example: Infants with a large VSD will have significant increases in
pulmonary blood flow producing a clinical picture of pulmonary
congestion.

4. Are there abnormal communications between the pulmonary
circulation and the systemic circulation?
Example: Infants with ASDs have an abnormal communication
between the right and the left side of the heart. The predominant
flow of blood is usually left to right unless pulmonary vascular
resistance is significantly elevated.

5. Are the valves normal? Are they competent as valves? Do they
obstruct the flow of blood?
Example: Congenital aortic stenosis obstructs the flow of blood out
of the left heart.

6. Is there a normal rhythm?
Example: Infants with WPW can develop supraventricular
tachycardia producing failure if it is allowed to continue.

Further characterization of congenital heart disease can be
accomplished by clinically placing the lesion in one of four categories:
1. Cyanotic with normal blood flow,  2. Cyanotic with decreased
pulmonary blood flow, 3. Acyanotic with increased pulmonary blood
flow, and,  4. Acyanotic with obstructed pulmonary blood flow.

Examples of these categories:

Cyanotic with normal pulmonary blood flow: Single ventricle lesion and
double outlet right ventricle after a Fontan procedure; Transposition of
the great vessels (TGA) after a atrial septectomy

Cyanotic with decreased pulmonary blood flow: Tetralogy of Fallot
after a BT shunt; TGA after BTS

Acyanotic with increased pulmonary blood flow: ASD, VSD, PDA,
Aorto-Pulmonary Window

Acyanotic with obstructed pulmonary blood flow: Pulmonic stenosis,
Aortic stenosis, Hypoplastic left heart syndrome, Coarctation of the
aorta.

Infants with congenital heart disease suffer from abnormal anatomic
variations as well as the usual issues that characterize the transition from
fetal to neonatal life. Their metabolism demands a high heart rate, the left
ventricle has immature muscle elements and there are anatomic
communications that, while physiologically established, are not
anatomically complete – PFO, PDA.
With this as background, the management of infants with congenital
disease, repaired or not must give consideration to the conditions that are
present during the operative procedure; conditions that relate to the
anesthetics that are being given as well as the conditions that are
created by the surgeon and the surgical procedure.
A reasonable example of how complex the management becomes
relates to the patient who was born with a double outlet right ventricle
and has been repaired with a Fontan procedure.  This surgical procedure,
the Fontan, was developed in the early 1970’s and has been modified
many times since the original description. It is used for many patients with
single ventricle physiology, including hypoplastic left heart syndrome. In
this procedure venous blood is returned to the pulmonary circulation
through a conduit that has no pumping function. Usually, the SVC and the
 IVC are connected to the right pulmonary artery, the IVC through a baffle
created through the right atrial wall. A small defect is left in the baffle to
decompress the right heart and this produces some systemic
desaturation.
Patients that have had a Fontan are dependent on the central venous
pressure for filling of the pulmonary circulation and are every sensitive to
elevations in pulmonary vascular resistance. Increased intraabdominal
pressure, produced by laparoscopy, can reduce venous return as can
increased ventilating pressures.  Hypoxemia and hypercarbia can elevate
pulmonary vascular resistance. Either of these will reduce blood flow to
the right side of the heart and subsequently cardiac output. As an aside,
cannulation of the right internal jugular vein is contraindicated because of
the risk of thrombosis.
Thus, evaluation of the anatomical conditions as well as the physiological
conditions that have been created by palliative procedures must be
considered in managing these infants. Communication with the patient’s
cardiologist prior to taking a child to the operating room aids
immeasurably in defining the clinical conditions that the anesthesia care
provider will be presented with. By understanding the anatomy and the
physiology, the astute clinician can plan for common eventualities and
avoid most disasters.
Rae Brown, M.D.