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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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FIG. 9.53 Positioning a slightly long vein graft behind the left atrial appendage with a piece of Surgicel.
Twist of the Graft
Every precaution should be taken to ensure the proper lie of the graft without any twisting along its length, which
may occur particularly with vein grafts at the back of the heart (Fig. 9.54). In rare cases, when this occurs, the
proximal
anastomosis must be redone. If for any reason this is not feasible, the vein graft may be divided and
reanastomosed after being untwisted. Some surgeons prefer to mark the vein graft with a methylene blue stripe
to prevent this complication.
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FIG. 9.54 Twisting of a vein graft.
The vein end is tailored to have a large, wide, hood-shaped opening (Fig. 9.13). This can be accomplished by
dividing the vein approximately 30 degrees obliquely with respect to its length and then extending the incision
generously downward at the heel to create a vein graft opening that is at least 20% larger than the aortic
opening.
Mismatch between the Vein Graft and Aortic Opening
The circumference of the vein graft must be at least 20% larger than the aortic opening; otherwise, the vein
stretches out flat and compromises the lumen (Fig. 9.55).
If the vein caliber is small, the aortic opening should be limited to a narrow slit corresponding to the incision
at the heel of the graft.
If the aortic opening is inadvertently made too large, the opening can be narrowed to the appropriate
diameter with a purse-string 4-0 Prolene suture (Fig. 9.56).
With a no. 11 blade, a 3- to 4-mm slit-like incision is made at a precise site for each proximal anastomosis. The
opening is dilated slightly with the tip of a fine forceps. A disposable punch is introduced into the slit-like opening,
and a circular part of the aortic wall, 4.0 to 4.8 mm in diameter, is removed (Fig. 9.57).
FIG. 9.55 The hood of a vein graft is flattened owing to too large an aortic opening.
FIG. 9.56 Narrowing too large an aortic opening with a purse-string suture.
FIG. 9.57 Creating aortic opening with a disposable punch.
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Intimal Wall Detachment
The introduction of the punch into the aortic lumen must be performed meticulously to avoid intimal detachment,
which could lead to subsequent dissection of the aorta. When the aortic wall is thick and calcified, the separated
segment of the aortic wall should be included in the suturing process.
FIG. 9.58 Correct orientation of a proximal vein graft to the left anterior descending or diagonal coronary artery.
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FIG. 9.59 Incorrect orientation of a proximal vein graft leading to kinking by the pulmonary artery. A: A graft to
the left anterior descending artery. B: A graft to the right coronary artery.
Technique for Proximal Anastomosis
The lie of the LAD or diagonal vein grafts should take a deep concave course to join the aorta in an oblique
manner at the 2 o'clock position at the anastomotic site (Fig. 9.58). Positioning this graft with the heel of the
anastomosis between the 3 and 5 o'clock positions may result in kinking of the graft by the pulmonary artery
when the heart is full (Fig. 9.59).
The ramus and obtuse marginal grafts join the aorta horizontally at the 3 o'clock position. The distal right vein
graft takes a course along the atrioventricular groove and joins the ascending aorta at the 6 to 7 o'clock position,
and the posterior descending artery grafts take a course lateral to the atrium and join the aorta at approximately
the 8 o'clock position. The right-sided grafts are anastomosed to the anterior right lateral aspect of the aorta
relatively high on the aorta (Fig. 9.60). This prevents the graft from being kinked by the superior vena cava or the
right ventricular outflow tract (Fig. 9.59B). Under special circumstances, the left-sided grafts can be passed
behind the aorta through the transverse sinus and be anastomosed to the right side of the aorta (Fig. 9.61). The
latter technique is particularly useful when there is calcification of the left side of the ascending aorta or when the
vein is short. Nevertheless, this technique predisposes the vein graft to possible twisting behind the aorta and
makes control of any bleeding from a side branch difficult.
FIG. 9.60 Correct placement and orientation of the proximal vein grafts.
The surgeon must always anticipate the possibility that the patient may require aortic valve replacement at
some time in the future. Therefore, the proximal anastomoses should be placed high on the aorta to allow a
subsequent aortotomy to be made without interfering with the proximal graft sites.
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The proximal anastomosis is started with a 30-in. long 5-0 or 6-0 Prolene double-armed suture. The precise lie
and course of direction of the vein graft are envisioned. The first stitch is passed from the inside of the graft to
the outside and then passed from the outside to the inside of the aorta in a counterclockwise direction (Fig.
9.62). After three to five rounds of suturing, the graft is lowered into position, and the needle is clamped (Fig.
9.63). The needle at the other end of the suture is now passed in a backhand manner, from the inside to the
outside of the aorta (Fig. 9.64), followed by outside to inside of the vein graft in a clockwise direction (Fig. 9.65).
This over-and-over
suturing is continued to meet the other arm of the suture (Fig. 9.66). When all the proximal anastomoses are
completed, the vein grafts are each occluded with atraumatic bulldog clamps. The perfusion pressure is
temporarily reduced, and the aortic clamp is removed. Blood is allowed to distend the vein grafts and to leak
through the anastomoses (Fig. 9.67). This maneuver displaces air, allows the vein graft to assume its hood
shape, and prevents purse-string constriction of the anastomosis. The suture ends are now tied securely.
Normal perfusion pressure is resumed when all sutures have been tied.
FIG. 9.61 Routing a graft through the transverse sinus.
FIG. 9.62 Stepwise technique for a proximal anastomosis.
FIG. 9.63 Stepwise technique for a proximal anastomosis.
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FIG. 9.64 Stepwise technique for a proximal anastomosis.
FIG. 9.65 Stepwise technique for a proximal anastomosis.
FIG. 9.66 Stepwise technique for a proximal anastomosis.
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FIG. 9.67 Stepwise technique for a proximal anastomosis.
Calcified Aorta
Placement of proximal anastomoses should be on the normal aortic wall. Calcific sites should be avoided.
However, aortic walls are sometimes very diseased and at times calcified. Often, “toothpaste” material is
squeezed out of the aortotomy site; at other times, there are calcific plaques within the aortotomy. The edges of
the aortotomy should be free of any debris. It is cleaned with a dry gauze, and the aortic clamp is loosened
slightly to allow blood to gush out of the aortotomy and wash away any debris or particles.
Technical points to ensure good proximal anastomoses include tailoring a generous opening in the proximal vein
because the aortic wall is not pliable. In addition, deep bites of all the layers of the aortic wall must be taken.
Epiaortic Ultrasonographic Scan
Atherosclerotic changes of the aorta are very common in elderly patients. Epiaortic ultrasonographic scanning
can be used to detect localized atheromatous areas that may not be detectable by digital palpation. At times, the
aorta may be so diseased that proximal vein grafts may have to be placed on the innominate artery. A totally
calcified lead pipe aorta may have to be replaced (see Chapter 8).
Free Internal Thoracic and Radial Arterial Grafts
If a free internal thoracic or radial arterial graft is used, a small aortic opening must be made. Unless the aortic
wall is fairly thin, it may be preferable to anastomose the proximal arterial conduit to a vein graft hood or to a
patch of vein or pericardium that has already been sewn to an aortic opening.
Marking of Proximal Anastomoses
To facilitate angiographic location of the proximal anastomoses in the future, some surgeons incorporate a
radiopaque ring into the proximal suture line.
Aortic Wall Adventitial Tissue
In preparing the site for proximal anastomosis, adventitial tissue on the aortic wall should be incorporated in
the suturing process. This is particularly important in elderly patients with delicate aortic walls. The
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adventitial tissue acts as “natural” pledgets, providing a secure anastomosis and adding strength to the
aortic wall.
OFF-PUMP CORONARY ARTERY BYPASS GRAFTING
Traditionally, coronary artery bypass grafting has relied on the aid of cardiopulmonary bypass to obtain a
bloodless and stationary operating field. However, despite the many advances made, blood contact with the
artificial surfaces of the cardiopulmonary bypass circuit continues to produce a well-documented diffuse
inflammatory response that affects multiple organ systems and is responsible for much of the noncardiac
morbidity after open-heart surgery. Off-pump coronary bypass grafting has been associated with decreased
transfusion requirements, and may be a preferred strategy in high-risk patients with cerebrovascular disease or
aortic calcific disease.
Relative Contraindication to Off-Pump Surgery
Patients who have had recent myocardial infarction with impaired left ventricles and patients with dilated
ventricles are not ideal candidates for off-pump bypass procedures. Similarly, in patients with more than mild
mitral insufficiency, grafting the branches of the circumflex coronary artery may cause hemodynamic instability.
These patients may be best managed by performing the revascularization procedure on the beating heart with
cardiopulmonary support. The aorta is not clamped and cardioplegia is not administered. The heart is kept
empty, providing optimum myocardial protection and hemodynamic stability.
Anesthetic Considerations
The main goal of anesthesia management is to maintain hemodynamic stability during the various manipulations
of the heart during off-pump coronary surgery. Ideally, an oximetric pulmonary artery catheter is used to
continuously measure mixed venous oxygen saturation and cardiac output. Transesophageal echocardiography
may have limited value when the heart is displaced to a vertical position. The key to avoiding emergent
conversion to cardiopulmonary bypass is to be proactive, rather than reactive, in optimizing surgical conditions to
prevent hypotension and low cardiac output. Intravascular volume should be replenished because the most
common cause of low blood pressure is decreased venous return with positioning of the heart. Hemoglobin level,
electrolytes, acid-base status, and arterial blood gases should be maintained within a normal range. Although
inotropic support may be necessary, it is kept to a minimum to prevent tachycardia, which can interfere with
optimal suture placement and increase myocardial oxygen consumption. Most important, continuous
communication is needed between the operating surgeon and the anesthesiologist.
Positioning the Heart
The most critical aspect of off-pump coronary bypass surgery is the positioning of the heart to expose the target
vessel adequately without hemodynamic compromise. This can be accomplished through strategic placement of
four deep pericardial sutures (Fig. 9.68) and appropriately placing the patient in various positions. The first
pericardial suture is placed above the left inferior pulmonary vein well below the phrenic nerve, the second near
the inferior vena cava, and the last two equidistant in a line drawn between the first two sutures. Rommel
tourniquets are used to avoid abrasions on the epicardium by the pericardial sutures. By sequentially increasing
the tension on each suture from the pulmonary vein to the inferior vena cava, coupled with steep Trendelenburg
positioning of the
operating table rotated toward the surgeon, the heart can be lifted out of the pericardial sac to expose the LAD
and diagonal target vessels. Generally, lifting the heart to a vertical position is relatively well tolerated.
Commercially available apical suction devices (Fig. 9.69) can be used to lift the heart vertically so that the lateral
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