Third Stage of Univentricle Hearts (Fontan Procedure)
The Fontan procedure is the third and last stage of the palliation
procedure for UVH. The procedure is performed to divert the remaining
systemic venous blood from the inferior vena cava to the pulmonary
artery (Figure 5 ). This procedure is usually performed at
around 1 to 5 years of age when restriction of patient activity is
becoming problematic and size of the pulmonary arteries are sufficient
to allow for a low PVR.13 The classic Fontan technique
include creating an atriopulmonary anastomosis is made by isolating the
right atrial chamber by closing the atrial septal defect and connecting
the hypoplastic tricuspid valve to the inferior vena cava. Afterwards,
the right atrial appendage would be anastomosed to the right pulmonary
artery. It was later understood that better streaming the blood flow in
the systemic venous pathway to the lungs could improve the patients’
hemodynamics. By doing so, complications related to progressive atrial
dilation could be avoided. The operation was subsequently modified to
what is known as the lateral tunnel technique. The right atrium was
baffled with an intra-atrial patch, and the superior vena cava was
sutured directly to the right pulmonary artery.13 The
most recent modification of the Fontan procedure consisted of replacing
the intra-atrial routing of the venous blood by inserting an
extracardiac conduit between the inferior vena cava and the right
pulmonary artery.14 The advantages of using an
extracardiac conduit include avoiding multiple suture lines in the
atrium that might serve as a substrate for reentrant
tachycardias.15
Our criteria in selecting candidates that can be safely staged and are
eligible for the Fontan procedure to ensure a high probability of
success include a mean pulmonary artery pressure of less than 15 mmHg,
pulmonary artery resistance index of less than 4 Wood
units/m2, confluent pulmonary arteries with the
diameter of the branches according to the patient’s bodyweight in the
half size, systemic ventricular end-diastolic pressure of less than 15
mmHg, the absence of severe atrioventricular valve regurgitation unless
it can be repaired or replaced, good systemic ventricular function, and
the patient’s age should be more than three years.
The patient is usually positioned in a semi-Fowler position after the
procedure to improve blood flow from the upper body to the right atrium.
Early ambulation after surgery also increases venous return and cardiac
output. Early extubation will also improve pulmonary blood flow and
systemic oxygen delivery, provided that spontaneous breathing provides
enough oxygenation and CO2 removal.16The optimal target for oxygen saturation after the Fontan Procedure is
95%. Low positive end-expiratory pressure and low mean airway pressure
are ideal if the patient still needs ventilator support.
Regarding anticoagulant management, we start the patient on heparin as
soon as possible. If there is no evidence of bleeding, heparin is
administrated at an initial dose of 5-10 IU/kg/hour and titrated until
the therapeutic level is achieved, indicated by a prothrombotic time of
60-80 seconds. In addition, we usually start the patient on 0,2
mg/kg/day of warfarin after extubation, where it is titrated every three
days until therapeutic level is achieved, indicated by an international
normalized ratio (INR) of 2.0-3.0.