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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_612_Библиотеки_им_академика_М_И_Перельмана
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FIGURE 5.8. End-to-side anastomosis using continuous
(running) sutures. An elliptical opening is created on the
recipient vessel wall, and the end of the donor vessel is
anastomosed to this opening. The end-to-side technique
maintains distal flow in the recipient vessel and is
frequently performed when there is a donor and recipient
vessel diameter mismatch. (From Yap LH, Butler CE.
Chapter 8: principles of microsurgery. In: Thorne CH,
Bartlett SP, eds. Grabb and Smith’s Plastic Surgery, 6th
ed. Lippincott Williams & Wilkins; 2006:66-72, Figures 8.1-
8.8.)
Prior to the anastomosis, the surgeon should ensure that the table
height is appropriate, so that their elbows are comfortably bent to
allow their forearms and wrists to rest on the patient to lessen any
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tremor, as opposed to having both hands free-floating. The
microinstruments should be grasped at some comfortable point
between midway and the tip of the instruments. As in most surgeries,
the microneedle should be positioned in the needle driver at the
center point of the needle, with the needle directed at a slight
anterior angle. The microsurgeon should cleanly intubate the vessel
to provide a landing zone for the needle through the vessel wall
(Figure 5.9). The needle tip is then positioned at a 90° angle to the
vessel wall and upon entering the vessel lumen, the tip should be
clearly visible and the needle rotated so as to follow the curve of the
needle. Full-thickness sutures provide intimal continuity and less
subendothelial collagen exposure, resulting in less thrombus
formation and highest rate of patency.29 Sutures should be evenly
spaced from each other and at the same distance from the vessel
edge.
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FIGURE 5.9 Forceps countertraction to facilitate needle
placement and penetration. A. In select cases, partially
open blunt jeweler’s forceps tips are placed into the vessel
lumen to evert the vessel wall, avoid inclusion of the back
wall in sutures, and provide countertraction for needle
penetration. Extreme care must be taken to avoid
traumatizing the vessel intima; some microsurgeons avoid
this technique for this reason. B. When the needle is
passed from inside the vessel lumen to outside the lumen,
it is often useful to use the tips of the forceps to provide
countertraction on the adventitial surface of the vessel to
facilitate needle penetration. (From Yap LH, Butler CE.
Chapter 8: principles of microsurgery. In: Thorne CH,
Bartlett SP, eds. Grabb and Smith’s Plastic Surgery, 6th
ed. Lippincott Williams & Wilkins; 2006:66-72, Figures 8.1-
8.8.)
Upon completion of the anastomoses, the double-opposing clamp
is removed, followed by the venous clamp to restore outflow and
finally the more proximal recipient arterial clam. Topical lidocaine or
papaverine can be used to reduce spasm and the flap is irrigated
with warm saline. Typically, the pedicle instantaneously becomes
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visibly pulsatile. In breast reconstruction, the superficial vein should
be assessed for distention—an overly distended or plump superficial
vein during the flap harvest or following anastomosis may signify a
superficial dominant flap system that would benefit from a second
vein anastomosis using the superficial vein.
The Acland test is a useful test to assess patency of the venous
anastomosis. Two jeweler’s forceps are placed directly side by side
and used to occlude the recipient vein distal to the anastomosis. The
more downstream jeweler’s forceps is used to milk blood distally for
2 to 3 mm but remains nearly occlusive, while the proximal forceps is
then released. An immediate filling of that vein segment indicates a
patent anastomosis (Figure 5.10).
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FIGURE 5.10. Use of the Acland test to confirm
antegrade vascular flow through an anastomosis. A. The
direction of blood flow is indicated by the arrow. B. Two
jeweler’s forceps are used to gently occlude the vessel
distal to the venous anastomosis. C. Blood is milked out of
the vessel between the two forceps by gently sliding the
distal forceps along the vessel without injuring it. This
results in a segment of collapsed vessel between the
proximal and distal forceps. D. Releasing the proximal
forceps allows the collapsed vessel segment to be filled by
antegrade flow if the anastomosis is patent. The distal
forceps prevent retrograde filling of the collapsed segment.
This test should be performed sparingly to minimize
potential trauma to the vessel intima. (From Yap LH, Butler
CE. Chapter 8: principles of microsurgery. In: Thorne CH,
Bartlett SP, eds. Grabb and Smith’s Plastic Surgery, 6th
ed. Lippincott Williams & Wilkins; 2006:66-72, Figures 8.1-
8.8.)
The flap is then checked for bright red bleeding and any excessive
bleeding is cauterized with Bovie electrocautery. SPY-PHI
angiography is another tool used to not only assess perfusion of the
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flap but also help guide any trimming of less well-perfused areas
(Figure 5.11). Once the microsurgeon is pleased with the perfusion
of the flap, inset of the flap can begin.
FIGURE 5.11 Myocutaneous vertical rectus abdominis
muscle flap. A. Following dissection. B. SPY Portable
Handheld Imaging (SPY-PHI) angiography demonstrating
adequate perfusion of the flap following transfer for softtissue coverage of the lower extremity. The distal
tip/portion of the flap (screen left) may benefit from
excision given the darkened appearance on SPY-PHI.
Interposition Grafts
When it is not possible to perform a tension-free primary
anastomosis of the donor and recipient vessels, an autogenous
interposition vein graft may be used. Synthetic grafts are not used
given the associated high risk of thrombosis. Interposition grafts are
less commonly employed in breast reconstruction but more
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commonly in H&N and extremity reconstruction. The greater and
lesser saphenous vein grafts are the most common conduits used,
the latter being of slightly smaller vessel diameter. For upper
extremity revascularization or replantation, grafts can be harvested
from the wrist or feet. Regardless of the site, the diameter of the graft
should approximate the donor and recipient vessel luminal
diameters. It is important to orient the vein grafts with a marker or
clip so that the surgeon knows the direction of blood flow in relation
to the valves. Vein grafts should be harvested longer than the
desired length to accommodate for contraction. Although arterial
grafts can be used, vein grafts are preferred and a neointima is
formed by ingrowth of smooth muscle cells from the recipient vessel
and the wall thickens.
Flap Inset/Securing
Inset of the flap should be tensionless and when in doubt, can be
delayed until several days later. Drains are used both in the donor
site and under the flap, but are positioned well away from the pedicle
and perforators to avoid injury upon pulling the drains or inadvertent
suction. Joints should be immobilized if near a flap, and if a splint or
external fixator is being used, care should be taken to not obscure
the flap for subsequent monitoring.
POSTOPERATIVE MANAGEMENT
The strive for success in microsurgery does not cease at the end of
an operation. Postoperatively, any potential for external compression
should be avoided. Deep venous thrombosis prophylaxis is routine
and pain control is optimized to allow for early mobility when
possible. Urine output monitoring is used to gauge adequate fluid
resuscitation, and when no longer needed for monitoring, the urinary
catheter is discontinued. In cases of limb salvage, the extremity
should be elevated, and placed on a “kickstand” in the case of heel
flaps. Dangling protocol and plans for rehabilitation are clearly
delineated with the patient, family, and nursing staff.
Monitoring
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Despite the innumerable adjuncts for postoperative flap monitoring,
nothing supersedes clinical assessment. When possible, a skin
paddle is left clearly visible and an external doppler signal should be
identified and marked with a 5-0 prolene suture. Clinical evaluation
includes an assessment of flap color, capillary refill, temperature,
and skin tone/swelling. If a skin paddle or cutaneous component to
the flap is not possible, or an additional monitoring device is desired,
the implantable Cook-Swartz doppler has long been a trusted tool for
free tissue monitoring. Ideally, the cuff monitor should be placed
distal to the arterial anastomosis and care should be taken to ensure
that the cuff is not wrapped too tight around the vessel. The wire
from the implantable doppler should also be positioned to minimize
the potential for extrinsic compression on the anastomosis, pedicle,
or perforators. For digit replantation, pulse oximetry and surface
temperature are helpful to monitor tissue perfusion. Near-infrared
spectroscopy tissue oximetry technology (ViOptix T. Ox Tissue
Oximeter, ViOptix, Freemont, CA) may allow detection of vascular
compromise even before conventional clinical symptoms are present
and can be monitoring. The device measures the scatter and
absorption of near-infrared light by hemoglobin, the principal
chromophore in the skin. This method of monitoring can also be
linked to a smart phone to allow for flap monitoring from home.
Regardless of the method used for monitoring, a final assessment of
flap perfusion should be performed before and after extubation and
certainly prior to leaving the operating room.
Those transferring the patient should be aware of baseline
vascular perfusion of the flap as well as the method and frequency of
monitoring. Patients are typically monitored in an intensive care or
step-down unit with telemetry capabilities and to allow for the
frequent nursing assessments, up to every 1 hour for the first 24 to
48 hours, because flap compromise is most common within this time
period. In keeping with early vascular surgery teachings, early flap
loss is oftentimes technical and either related to perforator/pedicle
injury or kinking, and anastomotic issues. Early detection of
impending flap failure and expeditious return to the operating room is
successful in salvaging an ailing free flap the majority of the time.
30
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Anticoagulation
The concern surrounding the use of anticoagulation perioperatively
is the potential increased risk of bleeding, with no proven effect on
preventing thrombosis or flap failure.31 Hematomas increase the risk
of vascular compromise from compression on the pedicle. Lowmolecular-weight dextran is no longer recommended because of the
associated systemic morbidity.32 Aspirin and low-dose heparin, as
opposed to higher therapeutic dosing, may not significantly increase
the risk of bleeding and are reliable postoperative anticoagulation
agents.
33,34
Unless a patient has a medical condition such as cardiac disease
that warrants a lower threshold for blood transfusions, restrictive
transfusion strategy (Hg level <7 g/dL or clinically symptomatic)
reduces associated morbidity and hospital costs.
35
FLAP TAKE BACK
Success in microsurgery depends on many factors, undoubtedly
surgical technique being most important. This includes flap
dissection and harvest when performing free tissue transfer, recipient
vessels preparation, the setup and execution of the anastomoses,
and the inset of the flap. Special care should be taken when handling
the pedicle and recipient vessels and when performing the
anastomosis. Damaged vessel endothelium is highly thrombogenic,
resulting in platelet adhesion, secretion of prothrombotic factors, and
the recruitment of additional platelets. Additional clot burden ensues
with the conversion of fibrinogen to fibrin, and when large enough, a
mechanical obstruction of the vessel lumen occurs.
Inevitably, all reconstructive microsurgeons will face a situation of
vascular compromise or flap loss. Time from detection of
compromise to return to the operating room is critical and any delay
reduces the likelihood of salvage.36 The most common causes of
early reexploration following microvascular reconstruction is pedicle
thrombosis followed by bleeding/hematoma.36 Arterial thrombosis is
less common than venous thrombosis and when detected late, has a
higher risk of ultimate flap failure. Clinical exam may shed light on
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the cause for the thrombosis: a pale flap likely indicates an arterial
issue, whereas a swollen and congested flap foreshadows a venous
problem. When redoing either an arterial or venous anastomosis,
length discrepancy between the artery and vein may warrant use of
a vein graft to avoid kinking of the pedicle. Therefore, for any take
back, it is worthwhile to discuss the potential for a vein graft with the
patient and family as part of the informed consent, as well as
potential donor sites for the vein. The patient must also be counseled
regarding the potential for total flap loss despite salvage attempts.
Alternative reconstructive options that may include another free flap
should be reviewed. The potential use of chemical thrombolysis or
systemic heparin should be discussed specific to the increased risk
of bleeding. All of the above should be thoroughly documented.
During the take back, the flap is carefully elevated, keeping in
mind the location of the perforators/pedicle. Any compressive
hematoma should be evacuated and sources of bleeding identified
and ligated or cauterized. A hematoma and venous congestion often
present concurrently, and therefore the source of bleeding will not be
controlled until venous outflow is reestablished. The field should be
copiously irrigated with heparinized saline and warm irrigation to
evacuate clot and to help facilitate tissue plane dissection.
The pedicle lie should be assessed for kinking or twisting and this
may have occurred during the setup of the microvascular
anastomoses. Once the pedicle orientation is deemed appropriate, it
should be palpated to assess for thrombosis and the anastomoses
should be evaluated for patency. If thrombosis is detected, it is likely
that the surgeon will have to use a combination of the following:
balloon thrombectomy, intravascular irrigation with heparin,
anastomotic revision with or without vein grafting, and thrombolysis.
If the pedicle distal to the anastomosis is healthy and uninvolved,
a single-vessel clamp should be applied to prevent distal migration of
the thrombus. A single-vessel clamp should be placed on the healthy
proximal internal mammary artery. The anastomosis of concern is
sharply excised and examined for technical obstruction (ie, backwall
suture) or clot. Subsequently, a manual milking technique with
microvascular jeweler’s forceps is applied to dislodge the thrombus.
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