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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3683_Библиотеки_им_академика_М_И_Перельмана
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Injury to the Recurrent Laryngeal Nerve
The vagus and recurrent laryngeal nerves are identified so that they are not inadvertently divided or traumatized.
Division of the Smaller Arch
The smaller of the two arches should be divided, otherwise a pseudocoarctation may develop. Therefore, both
arches are dissected and the smaller one is identified. As a precaution, blood pressure cuffs should be placed on
one leg and both arms and a trial occlusion of the smaller arch should be carried out to confirm the absence of a
pressure gradient before dividing it.
Aortopexy
Some advocate tacking the suture line of the descending aorta toward the lateral chest wall fascia so as to open
up the area of the ring “like a book” and thereby prevent postoperative impingement or scar.
PULMONARY ARTERY SLING
A pulmonary artery sling results when the left pulmonary artery arises from the right pulmonary artery and passes
leftward between the trachea and esophagus to reach the hilum of the left lung. The ligamentum arteriosum
extends from the superior aspect of the main pulmonary artery to the undersurface of the aortic arch. This
creates a vascular ring that constricts the trachea but not the esophagus (Fig. 17.4). Hypoplasia of the distal
trachea, with or without complete cartilaginous rings, is present in approximately 50% of these patients.
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FIG. 17.3 Stepwise technique for division and oversewing ends of the left anterior arch.
Incision
Although this lesion can theoretically be approached through a left thoracotomy and repaired without the use of
cardiopulmonary bypass, stenosis and occlusion of the left pulmonary artery have been seen with this technique.
Most surgeons prefer a median sternotomy with cardiopulmonary bypass, especially if tracheal reconstruction is
anticipated.
Median Sternotomy Technique
A standard median sternotomy incision is performed, and cardiopulmonary bypass is instituted with an ascending
aortic cannula and single straight venous cannula in the
right atrium. The procedure is carried out with the heart beating.
FIG. 17.4 Pulmonary artery sling. Note the origin of the left pulmonary artery from the right pulmonary artery and
its course behind the trachea.
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FIG. 17.5 Correction of a pulmonary artery sling. Note the division and reimplantation of the left pulmonary artery
onto the main pulmonary artery in front of the trachea.
The ductus or ligamentum arteriosum is doubly ligated and divided. The main, right, and left pulmonary arteries
are extensively mobilized. With the aorta retracted leftward, the origin of the left pulmonary artery is identified and
dissected free of the back of the trachea. The left pulmonary artery can now be detached from the main
pulmonary artery and brought anterior to the trachea. The resultant opening in the distal main pulmonary artery
is oversewn with a 6-0 Prolene running suture. The left pulmonary artery is reimplanted more proximally on the
main pulmonary artery, using care to not twist or kink the left pulmonary artery. A generous arteriotomy is made
at the appropriate site on the distal main pulmonary artery and the left pulmonary artery is trimmed obliquely to
match this opening. The anastomosis is completed with a running 6-0 Prolene suture (Fig. 17.5). In certain
circumstances, this may require an additional left pulmonary arterioplasty if the left pulmonary artery is
hypoplastic.
FIG. 17.6 Pulmonary artery sling with a stenotic distal trachea. The left pulmonary artery can be brought
anteriorly between the divided ends of the trachea.
FIG. 17.7 Low/posterior insertion of the LPA.
If a stenotic segment of the trachea is present, the trachea may be transected, allowing the left pulmonary
artery to be brought anterior to the trachea through the space between the two divided ends of the trachea (Fig.
17.6). Subsequently, the stenotic portion of the trachea is resected and the two ends are reanastomosed;
occasionally, a full “slide” tracheoplasty is required for long-segment tracheal stenosis. The lie of the left
pulmonary artery must be assessed, and if kinking or stretching is noted, the left pulmonary artery should be
detached and reanastomosed more proximally on the main pulmonary artery.
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When implanting the left pulmonary artery, it is important to place the anastomosis somewhat posteriorly and
inferiorly along the main pulmonary artery; this reduces the chance of stenosis or issues of angulation at the
anastomosis (Fig. 17.7).
18
Systemic Pulmonary Shunting
Because most congenital heart defects are managed by total correction, shunting procedures are now performed
in select patient populations. Systemic to pulmonary artery shunts offer excellent palliation in patients with
anatomically complex cardiac anomalies, in whom definitive repair is best delayed. They are also indicated as a
source of controlled pulmonary blood flow in the initial management of neonates with single-ventricle anatomy.
A common application of the systemic to pulmonary artery shunt is in the neonate with a ductal-dependent
pulmonary circulation. The ability to keep the ductus arteriosus patent with an infusion of prostaglandin E1 allows
these patients to be stabilized and undergo surgery on a semiurgent basis in an unhurried manner.
TYPES OF SHUNTS
The Blalock-Taussig shunt was introduced in 1945. Classically, it consists of anastomosing the subclavian artery
to the pulmonary artery on the side opposite the aortic arch. However, with some technical modifications, the
subclavian artery can be anastomosed to the pulmonary artery on the same side as the aortic arch.
Other shunting procedures were subsequently introduced. They include the Potts shunt (descending aorta to the
left pulmonary artery), Waterston shunt (ascending aorta to the right pulmonary artery), central shunt (interposing
a graft between the ascending aorta and the main pulmonary artery), and the modified Blalock-Taussig shunt
(interposing a Gore-Tex tube graft between the subclavian or innominate artery and the right or left pulmonary
artery).
The Potts shunt was abandoned because it was cumbersome to perform, difficult to close, and could cause high
flow and the early development of pulmonary vascular disease. The Waterston shunt lost favor because of the
high incidence of injury to the pulmonary artery and the difficulty in controlling the amount of flow through the
shunt. The classical Blalock-Taussig shunt is rarely used. Currently, some surgeons perform a central shunt or
modified Blalock-Taussig shunt through a median sternotomy with the belief that the relative disadvantage of this
approach requiring a redo sternotomy and dissection of adhesions for the next procedure is outweighed by the
superior exposure and ability to place the patient on cardiopulmonary bypass should hemodynamic instability
occur. Others prefer performing the operation off bypass through a lateral thoracotomy, rendering the
subsequent completion operation one that is performed through a primary median sternotomy.
MODIFIED BLALOCK-TAUSSIG SHUNT WITH GORE-TEX TUBE GRAFT
INTERPOSITION
Interposition of a Gore-Tex tube graft between the subclavian or innominate artery and the right or left pulmonary
artery is the most commonly performed shunt procedure. With either sternotomy or thoracotomy, it should be
remembered that the lumen of the subclavian or innominate artery is the limiting factor to the volume of flow. In
neonates, a 3.5- or 4-mm graft is used; for older infants, a 5-mm graft is usually selected.
Median Sternotomy Approach
This approach has several advantages. The pulmonary end of the shunt can be placed more centrally,
potentially allowing better and more uniform growth of both pulmonary arteries. The ductus arteriosus can be
occluded at the conclusion of the procedure, preventing excessive pulmonary circulation in the early
postoperative period. The ductus arteriosus can be ligated when a left thoracotomy approach is used but can
rarely be accessed through a right thoracotomy. Finally, if the patient becomes unstable, cardiopulmonary
bypass can be quickly initiated through a median sternotomy.
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Incision
A standard median sternotomy with resection of the thymus is used.
Technique
After opening the pericardium, traction sutures are placed on the pericardial edges. The aorta and pulmonary
arteries are dissected free using scissors or electrocautery on a low setting. Downward traction on the main
pulmonary artery allows the ductus arteriosus to be identified and encircled with a tie or cleaned free of
surrounding tissues in preparation for later metal clip closure. The innominate artery is dissected to allow
application of a C-clamp. The right pulmonary artery is then dissected away from the posterior aspects of the
ascending aorta and superior vena cava. It is mobilized circumferentially and the right upper lobe branch is
identified.
Use of Heparin
If the shunt is being performed without cardiopulmonary bypass, light systemic heparinization (50 units/kg) is
administered just before the clamp is applied to the innominate artery.
The Gore-Tex graft is trimmed obliquely. A fine vascular C-clamp is applied to the innominate artery so that the
inferior aspect of the artery is centered in the excluded portion (Fig. 18.1). The handle of the clamp is then raised
to position the inferior edge of the innominate artery anteriorly. A longitudinal incision is made in the artery, and a
fine adventitial suture is placed on the superior edge of the arteriotomy to keep the lumen open. The
anastomosis is completed with Prolene suture (Fig 18.2).
FIG. 18.1 Modified Blalock-Taussig shunt through a sternotomy: Placing a side-biting clamp on the innominate
artery and rotating it to expose the inferior aspect of the artery. A vein retractor under the innominate vein
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improves exposure.
With the other end of the graft occluded, the vascular clamp on the innominate artery is carefully removed and
the anastomosis is checked for leaks. The length of the Gore-Tex graft is measured to just reach the superior
aspect of the proximal right pulmonary artery. The graft is divided transversely at this site after placing a fine
straight vascular clamp on the graft just below the innominate anastomosis. The right pulmonary artery is
grasped with a fine C-clamp so that the cranial aspect is in the middle of the clamp. The clamp is then rotated so
that a longitudinal incision can be made on the superior edge of the pulmonary artery. The arterial opening
should be approximately two-third of the diameter of the graft lumen as the pulmonary artery stretches. The
anastomosis is completed with a 7-0 Prolene (Fig. 18.3). The clamps are removed and hemostasis confirmed.
Centrally Located Shunt
The median sternotomy approach allows the pulmonary artery end of the shunt to be placed more centrally. The
aorta must be mobilized and retracted leftward with a traction suture on the right side of the aorta, a vein
retractor, or the back of the C-clamp itself (Fig. 18.3).
Coronary Ischemia
Care must be taken when applying traction to the aorta to prevent compression or kinking of the coronary
arteries. If any electrocardiographic changes are noted or hemodynamic instability occurs, the traction suture,
retractor, or clamp must be repositioned immediately.
Pulmonary Flooding
When the shunt is opened and flow through it confirmed, the ductus arteriosus, if present, should be occluded to
prevent pulmonary overcirculation. Too much pulmonary blood flow may lead to systemic hypoperfusion and an
inadequate diastolic blood pressure, resulting in coronary ischemia.
Hemodynamic Instability with Right Pulmonary Artery Clamping
Before incising the pulmonary artery, hemodynamic stability and systemic oxygenation with the C-clamp in place
should be assessed. The clamp may interfere with ductal flow, and reapplying it more distally on the right
pulmonary artery may rectify the problem. However, if desaturation or hemodynamic compromise persists after
repositioning the clamp, the patient should be placed on cardiopulmonary bypass for support during this
anastomosis.
Incorrect Length of the Tube Graft
Tension on the anastomosis owing to too short a tube graft may cause suture line bleeding and an upward pull
on the
pulmonary artery, which can lead to distortion or stenosis of the proximal right pulmonary artery. A graft that is
too long may kink, thereby compromising flow through the graft.
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FIG. 18.2 Modified Blalock-Taussig shunt through a sternotomy: The end-to-side anastomosis of a Gore-Tex
tube graft to the innominate artery. The inferior suture line is completed first.
FIG. 18.3 Modified Blalock-Taussig shunt through a sternotomy: Completing the pulmonary artery anastomosis.
The side-biting clamp has been placed so that the cranial edge of the right pulmonary artery is exposed.
If pericardial reapproximation is desired, a Gore-Tex pericardial membrane should be used in lieu of direct
pericardial approximation since minor changes in mediastinal structures can cause compression and thrombosis
of the shunt. A small chest tube is placed in the anterior mediastinum before a standard sternotomy closure is
performed.
Modified Right Blalock-Taussig Shunt
It may be preferable to place an interposition Gore-Tex tube graft between the innominate/subclavian and
pulmonary arteries through a thoracotomy incision. Some surgeons prefer a thoracotomy approach for the initial
shunt. In this case, a right-sided shunt may be used because it is easier to take down. The technique is
essentially the same for both sides. The following description pertains specifically to the right side.
Incision
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