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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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In patients who are diabetic or have peripheral vascular disease and are prone to poor wound healing, multiple
skin incisions are made, leaving intervening bridges of skin intact. This allows better closure of the wound and
minimizes ischemic changes along the skin edges (Fig. 9.5A).
Wound Healing
A wound in the lower leg tends to heal slowly; this is of particular significance in the elderly diabetic patient with
peripheral vascular disease. Meticulous handling of tissues and careful wound closure are mandatory.
It is perhaps preferable not to harvest veins from the lower legs of elderly patients with diabetes or
peripheral vascular disease.
When both greater saphenous veins have been stripped for varicosities or removed for previous bypass
procedures, a search should be made for one or both lesser saphenous systems. Often, an adequate segment of
vein can be procured. In these cases, the patient should be prepared and draped in such a manner that the back
of the legs can be exposed.
FIG. 9.6 Excluding a localized varicosity.
Varicosities
Saphenous veins with varicosities should be avoided. The walls of these vessels are dilated and abnormal, and
the large caliber predisposes to lower flow velocity and possibly early graft thrombosis and occlusion.
Localized Varicosities
Localized varicosities can be detected along the vein wall when it is being gently distended. They may be
partially excluded by the application of metal clips on the redundant tissue parallel to the vein wall (Fig. 9.6).
Intimal Injury
The vein must never be pulled or stretched to facilitate dissection. The intimal layer is very delicate and may
tear, giving rise to the formation of a nidus for platelet aggregation and possible subsequent early occlusion of
the graft (Fig. 9.7A). This is more likely to occur when multiple skin incisions are made and the vein has to be
harvested from beneath the skin bridges.
Overdistention of the Vein
The vein graft should be gently distended; any excessive pressure can result in intimal tear and disruption.
Devices are commercially available to prevent the intraluminal pressure from exceeding 150 mm Hg.
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FIG. 9.7 A: Pulling or stretching vein injures the intima. B: Gentle retraction with an elastic band.
FIG. 9.8 Ligating or clipping vein branches.
Avulsion Injury
Stretching of the vein may also result in avulsion injury owing to tension on small side branches. These tears on
the vein wall can be oversewn with 7-0 or 8-0 Prolene sutures to ensure adequate hemostasis; however, the
vein integrity remains disrupted.
The vein can be gently retracted by means of elastic vessel bands whenever necessary (Fig. 9.7B).
The side branches are identified and ligated; alternatively, they can be occluded with metal clips and then
divided (Fig. 9.8).
Branch Stump
The branches should be ligated or clamped approximately 1 mm from the vein wall to minimize the presence of a
stump, which may predispose to thrombus formation and early graft occlusion (Fig. 9.9A). Any stump can easily
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be eliminated by application of a fine metal clip behind the tie, parallel with the vein wall (Fig. 9.9B).
Graft Narrowing
Conversely, the tie or metal clip should never occlude part of the vein wall itself. This gives rise to localized
constriction (Fig. 9.9C). The tie or clip should be gently removed. Applying pressure with a heavy needle driver
on the closed loop of the metal clip will separate the two ends and facilitate its removal. The tie or metal clip is
replaced or reapplied appropriately.
Adventitial Constriction
The adventitial tissue may at times be caught in the tie around one of the branches, creating a localized
constriction. The adventitial band should be carefully divided with Potts scissors (Fig. 9.10).
When an adequate segment of vein is dissected free, it is divided at each end and removed. The vein stumps in
the groin and the ankle are securely ligated.
Skin Closure
The leg wound is closed in layers with absorbable sutures. In the groin region or where the wound is deep, an
extra layer of closure may be necessary. The skin is closed with fine absorbable suture material in a subcuticular
manner.
FIG. 9.9 A: Leaving excess stump on a vein branch. B: A metal clip eliminates stump. C: A clip constricting vein.
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FIG. 9.10 Dividing the adventitial band to relieve constriction.
Wound Drainage
If the wound is deep or continues to ooze blood, closed-system drainage for 24 hours should be used. This
prevents hematoma formation and possible infection.
Wound Infection
Patients with diabetes and patients with peripheral vascular disease are at increased risk of this complication.
Therefore, the wound must be closed atraumatically and without leaving any dead space. Absolute hemostasis
must be achieved before closure is begun. The subcuticular skin closure may be reinforced with deeply placed,
interrupted horizontal mattress monofilament sutures that are left in place until satisfactory healing has been
completed, usually for at least 2 to 3 weeks.
Regardless of harvest technique, an olive-tipped cannula is introduced into the distal end of the vein. The vein is
gently distended with autologous heparinized blood. Any avulsed branches are identified and securely ligated
with 4-0 silk or oversewn with 7-0 or 8-0 Prolene sutures, taking all the aforementioned precautions into
consideration (Fig. 9.11).
Suturing the Vein Wall
At times, the wall of the vein itself at the site of the avulsion of its branches requires suture closure; this can be
accomplished by taking longitudinal bites of the vein wall with 7-0 or 8-0 Prolene when it is being distended.
Transverse suturing gives rise to localized constriction (Fig. 9.12).
The end of the vein is then cut, avoiding any intimal valvular remnant, and trimmed so that is has a smooth,
hood-shaped orifice for anastomosis to the coronary artery (Fig. 9.13).
Vein End
If the caliber of the vein is small, the opening may be further enlarged by incising the vein orifice at the heel.
Valvulotome Injury
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Some surgeons have advocated the use of a valvulotome to cut away the valve leaflets in the saphenous veins.
Although this appears to be useful at times, it may create buttonhole defects in the vein wall. Therefore, if the
device is used, great caution must be exercised. We do not routinely remove the valve leaflets unless they are
located at the anastomotic sites.
Lower Versus Upper Leg Veins
Traditionally, the vein procured from the lower leg conforms more to the caliber of the coronary arteries, has few
if any valves, and can withstand higher intraluminal pressure. It is therefore more suitable for bypass grafting of
the smaller coronary arteries. However, the normal arterialization process and intimal hyperplasia may result in
higher early graft closure of small saphenous vein conduit. Despite all its advantages, the proximal end of a
narrow-caliber vein graft may be too small for a standard aortic anastomosis. The proximal anastomosis will have
to be carried out to a smaller aortic opening rather than a regular punched-out hole.
FIG. 9.11 Gently distending a vein.
FIG. 9.12 Transverse closure of an avulsed branch leads to constriction of a vein.
CORONARY ARTERY BYPASS GRAFTING WITH CARDIOPULMONARY
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BYPASS
Although many approaches have been used in the last decade for coronary artery bypass surgery, including
limited thoracotomy incisions and techniques, a median sternotomy is considered the incision of choice in most
cases today. Although off-pump coronary artery bypass grafting is a valuable technique in selected cases,
cardiopulmonary bypass is used in majority of coronary revascularization cases.
Venous drainage is accomplished through a single atriocaval cannula in most patients undergoing coronary
artery bypass surgery. Bicaval cannulation is used when concomitant procedures necessitating an opening into
the right side of the heart are indicated. Oxygenated blood is returned to the patient by direct cannulation of the
ascending aorta. In rare instances when aortic cannulation is not feasible because of an ascending aortic
aneurysm or extensive aortic wall calcification, the femoral or axillary arterial route is chosen instead (see
Chapter 2).
FIG. 9.13 Trimming the end of a vein to create a hood.
Venting of the left side of the heart through the right superior pulmonary vein or through the pulmonary artery has
been used, but it is unnecessary in most instances (see Chapter 4). In rare instances, when reoperative surgery
for a single bypass to the circumflex coronary artery is needed, a left thoracotomy is an alternate approach. In
such cases, cardiopulmonary bypass is achieved by both femoral artery and femoral vein cannulation (see
technique described in Chapter 2).
Myocardial Preservation
Cold blood cardioplegia is infused into the aortic root to achieve cardioplegic arrest of the heart initially and
repeated every 10 to 15 minutes during the cross-clamp time. Additional cardioplegic solution is infused directly
into the vein graft after the distal anastomosis is completed. Core cooling to 34°C and topical cold or iced saline
supplement myocardial protection. Critical proximal disease of major coronary arteries may interfere with the
uniform distribution of cardioplegia and prevent complete cardioplegic arrest of the myocardium. Retrograde
cardioplegic perfusion through a coronary sinus catheter is a useful adjunct for optimal myocardial protection
during coronary revascularization (see Chapter 3).
In patients with acute coronary occlusion and impending infarction, the culprit vessel is grafted first to allow
cardioplegic solution to be delivered through the vein graft to the involved myocardial territory.
Retrograde administration of cardioplegia may be particularly useful when arterial conduits are used
because cardioplegia cannot be delivered through the graft.
Patients undergoing redo coronary artery bypass procedures with patent but diseased vein grafts are at risk
of embolization of graft debris into the distal coronary artery bed. In these cases, retrograde cardioplegia is
indicated.
When patent in situ arterial grafts are present, antegrade cardioplegia will not reach the myocardium that
these grafts supply. The patent grafts must first be identified and temporarily occluded with an atraumatic small
bulldog clamp. Retrograde blood cardioplegia can then be administered effectively.
FIG. 9.14 A: A stroker blade is used to expose coronary artery. B: A poker blade is used to incise the anterior
wall of a coronary artery.
Cardioplegic solutions containing high potassium must never be infused directly into the vein grafts because
this may cause injury to the vein wall intima.
General Principles of Arteriotomy
On cardiopulmonary bypass with a quiet, decompressed heart, the coronary arteries are digitally palpated for
evidence of disease and calcification. An appropriate site for arteriotomy is selected. This site should be, as
much as possible, free of any gross disease. The epicardium overlying the coronary artery is incised and spread
sideways with a special knife, a stroker blade (e.g., Beaver Mini-Blade A6400, Fig. 9.14A). This allows better
inspection of the coronary artery wall. After the exact site of arteriotomy has been established, a poker blade
(e.g., Beaver Micro-Sharp Blade A7513) is used to incise the anterior wall of the coronary artery (Fig. 9.14B).
The surgeon must memorize the precise anatomy of the coronary arteries as depicted in the angiogram so
that the bypass graft is placed distal to the site of obstruction of the coronary artery.
Placement of the Arteriotomy
Care must be taken to perform the arteriotomy in the midline of the coronary artery. An oblique incision results in
distortion of the artery at the heel or toe of the anastomosis. If an attempt is made to correct the direction of the
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arteriotomy, a flap of arterial wall is created. This leads to a less than perfect anastomosis (Fig. 9.15).
Injury to the Posterior Arterial Wall
Special precautions must be taken not to damage the posterior wall of the coronary artery. This can happen if
the
angle of the blade is perpendicular to the vessel. The angle should always be approximately 45 degrees with
respect to the coronary artery (Fig. 9.16). If the posterior wall has been incised through the adventitia by the
blade, it should be approximated with a fine suture of 8-0 Prolene tied on the outside of the vessel (Fig. 9.17).
FIG. 9.15 Oblique arteriotomy and attempted correction create a flap of arterial wall.
FIG. 9.16 Perpendicular angle of a blade damages the posterior wall of a coronary artery.
Calcified, Nonpliable Arterial Wall
Sometimes the arterial wall is inflexible and heavily calcified, making it impossible to tailor a satisfactory
arteriotomy to perform a functioning anastomosis. A button of anterior wall is removed at the arteriotomy site. The
technique essentially entails the removal of a triangular segment of anterior arterial wall from the site of the
anastomosis. The calcified arterial wall would otherwise restrict the lumen of the graft anastomosis (Fig. 9.18).
FIG. 9.17 Incision through the posterior wall of a coronary is repaired with a suture tied outside the vessel.
FIG. 9.18 Removing a triangular segment from a calcified coronary artery.
The arteriotomy is then enlarged both proximally and distally (Fig. 9.19). A special modification of Potts scissors
is available to enlarge a coronary artery in particularly difficult locations. The diameter of the coronary artery
lumen as well as the presence of distal obstructive plaques may be
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evaluated by gently inserting calibrated probes through the arteriotomy site (Fig. 9.20).
FIG. 9.19 Enlarging an arteriotomy with Potts scissors.
FIG. 9.20 Calibrating the lumen of a coronary artery with a probe.
Distal Obstructive Plaque
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