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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3781_Библиотеки_им_академика_М_И_Перельмана
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20 Descending Thoracic andThoracoabdominal Aortic Aneurysms
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Open Repair
Preoperative Planning
• Open aortic repair requires careful preoperative assessment of the anatomy and
planning of the anticipated procedure.
• Based on extent of repair, clamp sites and circulatory support strategy should be
determined.
• Branch vessel anatomy (including large intercostal/lumbar vessels) should be
carefully noted, and method of revascularization should be determined.
• Spinal cord protection (detailed below).
• Operative plan should be communicated with the anesthesia team preoperatively,
and further, intraoperative close communication should be maintained.
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Physiologic Evaluation
Given the signicant physiologic stress for patients undergoing open surgical repair,
preoperative evaluation of patient’s ability to tolerate surgery should be carefully
determined including:
• Overall functional status of a patient.
• Cardiac evaluation with an echocardiogram or stress test, and if necessary, coronary
angiography, given that these patients are often elderly with atherosclerotic disease.
• Pulmonary function tests as chronic obstructive pulmonary disease is often prevalent and is a major risk factor for increased rate of complications and mortality
after TAAA repair.
• Assessment for chronic renal insufciency should be conducted with routine lab
work, specically glomerular ltration rate, and if necessary, duplex ultrasonography or cross-sectional imaging. Like COPD, pre-existing renal dysfunction
increases risk of mortality after TAAA repair.
Operative Steps
An open extent II thoracoabdominal aortic aneurysm repair is described here.
DTAA repair is less extensive and requires a thoracotomy without the abdominal
component.
Anesthesia andPositioning
• Before initiation of anesthesia, a prophylactic cerebrospinal uid drainage catheter can be considered depending on the extent of repair.
• Lung isolation is achieved either with a double lumen endotracheal tube or using
a bronchial blocker. Isolated ventilation of the right lung with collapse of the left
lung facilitates visualization of the thoracic aorta.
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• A right radial arterial line (in case of need for left subclavian artery clamping)
and right femoral arterial line (for distal aortic perfusion pressure) should be
placed along with a central venous catheter placement.
• Somatosensory and/or motor evoked potentials (SSEP/MEP) can be considered
for monitoring for spinal cord ischemia (SCI). Evoked potential monitoring has
been shown to be efcacious in detecting SCI and can be used to determine the
need for intercostal artery reimplantation.
– SSEP is conducted via stimulation of the posterior tibial nerves with monitor-
ing at the cervical spinal cord and cortical levels.
– MEPs are conducted via stimulation of the cervical spinal cord with an assess-
ment for lower extremity motor response.
• The patient should then be placed in a right lateral decubitus position (right side
down, left side up), supported by a bean bag, and the left arm should be secured
on an arm board.
• A nal assessment of all catheters, lines, and probes should be conducted after
repositioning and before prepping and draping.
S. K. Lella and A. S. Jassar
Incision andExposure
• A thoracic incision is made, usually in the left fth intercostal space, carefully to
avoid the intercostal neurovascular bundle and is carried down on to the abdomen, several centimeters to the left side of the midline, and carried as far down
as necessary to achieve the exposure necessary for the operation.
• Left pleural cavity is entered by carrying the dissection through the subcutaneous
tissue, chest wall musculature, intercostal muscles, and the pleura. Left lung is
deated to facilitate pleural entry. If needed, the ribs can be incised posteriorly to
improve exposure.
• For the abdominal portion, the dissection is carried down to the rectus sheath,
which is divided to expose the underlying peritoneum.
• The thoracic and abdominal components are then connected with the division of
the anterior costal margin.
• Abdominal aortic exposure can then be proceeded with either a transperitoneal
or retroperitoneal approach
– Transperitoneal approach has a higher risk of splenic injury and increased
uid losses, and it can be performed via a left medial visceral rotation to enter
the retroperitoneal space.
– Retroperitoneal approach makes right iliac system access more difcult and
involves mobilizing the peritoneum and intraabdominal contents away from
the abdominal wall, while keeping the peritoneum intact, to create a plane
toward the aorta.
Cranial
r
Caudal
Left lung
20 Descending Thoracic andThoracoabdominal Aortic Aneurysms
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237
• The diaphragm is incised circumferentially, leaving an adequate margin on the
chest wall for later re-approximation.
• The reno-visceral vessels, distal extent of aneurysm, and planned distal clamp
sites should be identied, exposed, and controlled.
• The ureter crosses over the iliac vessels and should be identied to avoid inadvertent injury.
• Attention is then be turned toward the thoracic aorta with dissection of the pleura
down to the descending aorta (Fig.20.3).
• The proximal clamp site is identied and exposed circumferentially and controlled taking care to avoid injury to the left recurrent laryngeal nerve and pericardiophrenic nerve.
• Finally, the aorta is subsequently exposed at the various anticipated clamp sites
based on reno-visceral bypasses.
Inflow
cannula
Anterior
Heart
Fig. 20.3 Intraoperative image of thoracoabdominal aorta after complete exposure
Aorta
Posterior
Pump sucke
Outflow
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S. K. Lella and A. S. Jassar
Extracorporeal Circulation
• While these operations were historically performed in a clamp and sew manner,
some form of distal perfusion strategy is commonly implemented today
(Figs.20.4, 20.5 and 20.6)
– Passive external bypass (e.g., axillofemoral bypass)
– Gott shunt
– Partial heart bypass (left atrial-aortic/femoral bypass)
– Complete heart bypass (femoral venous, aortic/femoral arterial) with or with-
out deep hypothermic circulatory arrest
Fig. 20.4 External axillofemoral bypass and Gott shunt
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Fig. 20.5 Left and right atrial-femoral bypasses with branch cannulas to reno-visceral vessels
• Method of distal aortic perfusion is selected based on surgeon preference and
patient anatomy.
• Regardless of the method chosen, the goal is to reduce ischemic time of the renovisceral organs, extremities, and the spinal cord, while facilitating various aortic
and branch anastomosis.
Here, we describe the left atrial-femoral artery bypass technique.
• After the aorta and branch vessels have been sufciency dissected out, the inow
and outow for distal aortic perfusion should be exposed.
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Fig. 20.6 Complete heart
bypass with deep
hypothermic circulatory
arrest
S. K. Lella and A. S. Jassar
– Inow: The left inferior pulmonary vein can be exposed via division of the
inferior pulmonary ligament and the pericardium.
– Outow: An oblique groin incision can be used to expose the left common
femoral artery. Alternately, a portion of the aorta distal to the most distal
clamp site can be chosen to provide ow to the lower body. Technique of
femoral cannulation is described below.
• Prolene purse-string sutures are then placed at both the inow and outow sites.
• The patient is heparinized, although full heparinization is not necessary for partial heart bypass.
• A pulmonary venotomy is made through the purse string suture, and a drainage
cannula is inserted and secured via a tourniquet and silk ties.
• The femoral artery is accessed via a micropuncture kit, and serial dilations are
performed over a wire to accommodate the arterial cannula, which is similarly
secured.
• Both cannulas can then be deaired and connected to the bypass circuit.
• Flow rates from the pulmonary vein to the femoral artery can be adjusted
throughout the procedure based on the right femoral arterial line pressure and
SSEP/MEP to maintain adequate distal perfusion pressure while the aorta is
clamped.
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241
Arterial Reconstruction
• Based on the disease pathology, the visceral and renal vessels can either be reattached as individual branches or en-bloc as an inclusion patch.
• Prefabricated grafts are available with additional branches for the visceral and
renal vessels already attached to the aortic graft.
• Alternately, these grafts can be self-constructed by sewing additional limbs onto
the main aortic graft prior to cross-clamping.
– Main aortic graft is generally made of Dacron as are the celiac/superior mes-
enteric/and right renal artery bypasses.
– Ringed (reinforced) polytetrauoroethylene is commonly used as material for
left renal artery bypass to prevent kinking.
• Once ready, the proximal aorta is clamped as the partial heart bypass circuit is
started.
• A second aortic clamp is placed on the distal descending aorta. During this time,
lower body perfusion is maintained with the bypass circuit that diverts the blood
from the left atrium to the femoral artery.
• The isolated portion of the aorta (between the two clamps) is incised, and backbleeding from small intercostal vessels is controlled by ligating these vessels.
Large intercostal vessels are identied and noted for later reimplantation. Backbleeding from these larger intercostal vessels can be controlled by placing small
balloon tipped catheters into their ostia.
• The proximal anastomosis is performed while paying attention to the proper orientation of the branch vessels on the graft to alight with patient’s anatomy.
• After completion of the proximal anastomosis, the proximal clamp is shifted on
to the graft to allow pressurization and inspection of the proximal anastomosis.
• The distal aortic clamp is sequentially moved distally while each bypass or anastomosis to the reno-visceral vessels is performed.
• During periods of renal ischemia, cold Plegisol® (Pzer, New York City,
NewYork, USA) solution (contains potassium chloride, sodium chloride, calcium chloride, and magnesium chloride) or cold blood is infused into the kidneys
to reduce the risk of renal injury with ischemia.
• Care should be taken to ensure appropriate graft length and orientation to prevent
kinking of the branch vessel bypasses in the nal resting position of the viscera.
• Finally, the distal clamp is moved to the normal portion of the distal aorta, and
the distal anastomosis is performed.
• Selected intercostal arteries can be reimplanted on to the aortic graft, either
directly or using a separate 12–14mm diameter graft.
• Based on the clinical situation, the sequence of the various anastomosis can be
altered.
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S. K. Lella and A. S. Jassar
Closure
• Once the reconstruction is complete (Fig.20.7), the bypass circuit is discontinued. The cannulae are removed. The pulmonary vein opening is closed by tying
down the purse string sutures, with additional reinforcement as needed. The
femoral arteriotomy is directly repaired to prevent narrowing.
• Protamine can be administered, if desired, for reversal of heparin to help achieve
hemostasis.
• The native aorta can then be sewn over the prosthetic graft to reduce the risk of
aorto-enteric stulas.
• Diaphragm is reapproximated to the chest wall.
• Abdominal fascia is closed.
Fig. 20.7 Intraoperative image after replacement of aorta with Dacron tube graft with individual
bypasses to the reno-visceral vessels
20 Descending Thoracic andThoracoabdominal Aortic Aneurysms
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• Chest tubes are left in the left chest cavity prior to chest closure, which is performed in several layers with reapproximating of the ribs and chest wall
musculature.
• Subcutaneous tissue and skin incisions are closed.
• Often, exible bronchoscopy is performed at the end of the procedure to clear
respiratory secretions.
• The patient is transferred to the intensive care unit for further care.
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Postoperative Care andComplications
• Patients are initially managed in the ICU postoperatively for close monitoring of
hemodynamic, respiratory, and neurologic status.
• Sedation is weaned as tolerated, and a neurologic exam is obtained and monitored to assess for SCI.
• Patients are extubated in the ICU based on clinical progress.
• Cardiac function may need to be optimized with the use of inotropes or vasopressors to maintain adequate cardiac output and perfusion pressure.
• Supplementation with crystalloid/colloids, blood products, and/or vasopressors
may be necessary.
• Patients are meticulously monitored for signs of reno-visceral and lower extremity ischemia via physical exam for lower extremity sensation and strength, labs
(creatinine, lactate, LFTs, blood glucose levels), development of oliguria/anuria
despite adequate resuscitation, and bloody bowel movements.
Spinal Cord Ischemia
• SCI is one of the most feared complications after DTAA and TAAA repairs and
requires diligent monitoring for symptoms.
• Patients are at risk of spinal cord ischemia with TEVAR and open surgical repair
due to interruption of spinal cord blood supply from the aorta through the segmental intercostal arteries, either due to coverage by the stent graft, or exclusion
and ligation during surgical repair.
• The risk for SCI increases as the length of the excluded aortic segment increases
due to the increasing number of segmental arteries that are effected.
• Several techniques are implemented to reduce the risk of SCI perioperatively:
– Augmentation of spinal perfusion pressure (increased MAP goals of at least
>90mmHg and decreased spinal uid pressure via CSF drainage to maintain
a cerebral perfusion pressure (MAP-ICP) of >70mmHg).
– Increased oxygen carrying capacity goals (higher hemoglobin levels and oxy-
gen saturation).
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– Intraoperative spinal cord cooling.
– Although controversial, intravenous corticosteroids and naloxone use.
• Delayed paraplegia can occur (highest 48–72h postoperatively), so these higher
parameters are maintained for several days after the operation.
S. K. Lella and A. S. Jassar
Bleeding
• Given the complexity of the procedure, with loss of coagulant factors, hemodilution, and possible hypothermia, coagulopathy is not uncommon.
• Chest tube output, hemodynamics and blood hematocrit values should be
assessed closely to monitor for bleeding.
• Coagulation prole should be monitored for targeted blood product
administration.
• If there is a signicant amount of bleeding or continued bleeding despite adequate correction of coagulopathy, return to the OR may be necessary.
Pulmonary
• Pulmonary complications are the most common type of complications after open
DTAA and TAAA repairs given the high incidence of smoking history for these
patients.
• In addition to appropriately weaning patients toward extubation, they should be
optimized with chest physiotherapy, early mobilization, incentive spirometry,
and adequate pain control.
Ongoing Surveillance
• All patients who undergo TEVAR or those with remaining dissection or diseased
segment of the aorta must be followed lifelong with surveillance imaging.
• Ongoing medical management and risk factor modication must continue.
Further Reading
Acher C, Wynn M.Outcomes in open repair of the thoracic and thoracoabdominal aorta. J Vasc
Surg. 2010;52:3S. https://doi.org/10.1016/j.jvs.2010.06.137.
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