Coordination among the surgeon, anesthesiologist, and perfusionist is critical during a DTAA or TAAA repair procedure. Management of hemodynamics during aortic clamping and unclamping, blood volume management, anticoagulation and hemostasis, and proper lung management occur in real time, with anticipation and preparation by the anesthesia team. Swan-Ganz catheters are routinely used for hemodynamic monitoring. The arterial catheter is placed in the right radial artery whenever the left subclavian artery flow may be interrupted during aortic clamping. A large-bore central venous line is necessary for volume return. We re-infuse filtered, unwashed whole blood from the cell-saver through a rapid infusion system during periods of substantial blood loss. With careful scavenging of shed blood and meticulous surgical hemostasis, operations without the use of blood and blood products are frequently possible. However, when coagulopathy does occur after the cross-clamp is released, rapid replacement of blood components with fresh-frozen plasma, platelets, and cryoprecipitate is necessary. Left lung isolation, usually by a double-lumen endobronchial tube, is necessary for exposure, although this may not be critical in extent IV TAAA repairs. The lung is handled minimally during anticoagulation to prevent lung hematoma and contusion. Deflating the left lung reduces retraction trauma to the lung, improves exposure, and alleviates the risk of cardiac compression. When motor evoked potentials are used for spinal cord monitoring, muscle paralytics must be avoided. Sodium bicarbonate solution is routinely infused to prevent acidosis during aortic cross-clamping, and mannitol can be given before cross-clamping to enhance renal perfusion. Proximal blood pressure, afterload, and cardiac performance are closely monitored by Swan-Ganz catheter and transesophageal echocardiography probe when necessary and are aggressively maintained.
Surgical Adjuncts for Organ Protection
Organ ischemia is a major source of the morbidity related to DTAA and TAAA repair. We currently employ a multimodal approach (Table 53-1) in an attempt to maximize organ protection during these operations (Fig. 53-7).57 The rationale for and details of several important strategies are discussed in the following sections.
Table 53-1 Current Strategy for Spinal Cord and Visceral Protection during Descending and Thoracoabdominal Aortic Aneurysm Repair ||Download (.pdf)
Table 53-1 Current Strategy for Spinal Cord and Visceral Protection during Descending and Thoracoabdominal Aortic Aneurysm Repair
- Moderate heparinization (1 mg/kg)
- Permissive mild hypothermia (32–34°C, nasopharyngeal)
- Aggressive reattachment of segmental arteries, especially between T8 and L1
- Perfusion of renal arteries with 4°C crystalloid solution when possible
- Sequential aortic clamping when possible
|Extent I and II thoracoabdominal repairs|
- Cerebrospinal fluid drainage
- Left heart bypass during proximal anastomosis
- Selective perfusion of celiac axis and superior mesenteric artery during intercostal and visceral anastomoses
Drawings illustrating an extent II repair of a thoracoabdominal aortic aneurysm (A) that extends from the left subclavian artery to the aortoiliac bifurcation. (B) During the repair, a left heart bypass circuit provides distal aortic perfusion, and a cold renal delivery system provides selective renal hypothermia. The proximal portion of the aneurysm is isolated between clamps placed on the aortic arch (between the left common carotid and left subclavian arteries), the mid-descending thoracic aorta, and the left subclavian artery. (C) Whenever possible, the phrenic, vagus (indicated by X), and recurrent laryngeal nerves are preserved during the repair. The isolated segment of aorta is opened longitudinally and divided circumferentially a few centimeters beyond the proximal clamp. (D) Patent intercostal arteries in this region are oversewn. (E) The proximal anastomosis is performed with continuous polypropylene suture. (F) Left heart bypass is stopped, the proximal clamp is repositioned onto the graft, flow is restored to the left subclavian artery, and the remainder of the aneurysm is opened longitudinally. (G) Balloon perfusion catheters are inserted into the celiac and superior mesenteric arteries to deliver selective visceral perfusion from the left heart bypass circuit, and into the renal arteries to intermittently deliver cold crystalloid. Patent lower intercostal arteries are reattached to an opening in the graft. (H) The aortic clamp is repositioned to restore intercostal perfusion. The celiac axis, superior mesenteric, and right renal arteries are reattached to an opening in the side of the graft. (I) The aortic clamp is repositioned to restore visceral and right renal perfusion. The mobilized left renal artery is reattached. (J) The aortic clamp is repositioned to restore left renal perfusion. The distal anastomosis at the aortoiliac bifurcation completes the repair.
Potential benefits of heparinization include preserving the microcirculation and preventing embolization. Additionally, by inhibiting the clotting cascade, the use of heparin may help to reduce the incidence of disseminated intravascular coagulation.
Heparin (1 mg/kg) is administered intravenously before aortic clamping or the start of left heart bypass (LHB). After this small heparin dose is administered, the activated clotting time generally ranges from 220 to 270 seconds.
Hypothermia decreases the metabolic demand of tissues and is protective during ischemic states. The protective effects of hypothermia on the spinal cord are well accepted.58,59 Mechanisms of spinal protection may involve membrane stabilization and reduced release of excitatory neurotransmitters.60,61 We routinely use mild passive systemic hypothermia during DTAA and TAAA repairs. The patient's temperature is allowed to drift down to a nasopharyngeal temperature of 32 to 33°C. After the aortic repair, rewarming can be accomplished by irrigating the thoracic and abdominal cavities with warm saline.
Profound systemic hypothermia on full cardiopulmonary bypass is an operative strategy for organ protection. Kouchoukos and colleagues62–64 have published several reports showing that hypothermic cardiopulmonary bypass with circulatory arrest can safely and substantially protect against paralysis and renal, cardiac, and visceral organ system failure during operations on the thoracic and thoracoabdominal aorta. Despite these protective effects, many clinicians avoid using this approach, principally because of the associated risks of coagulopathy, pulmonary dysfunction, and massive fluid shift. We use hypothermic circulatory arrest selectively when the aneurysm anatomy precludes safe proximal clamping.
Disruption of blood flow to the spinal cord and abdominal viscera contributes significantly to the development of ischemic complications. Conversely, maintaining flow through spinal and visceral arteries during all or part of the anatomic repair should reduce the duration of organ ischemia and prevent associated morbidity.65 Borst et al.66 found that using LHB for distal perfusion during DTAA and TAAA repair effectively unloads the proximal circulation during aortic occlusion and maintains adequate perfusion of distal vital organs, thereby reducing early mortality and renal failure. Further, combined distal perfusion and aggressive reattachment of distal intercostal arteries decreased the risk of spinal cord damage.
Typically used during the proximal aortic anastomosis, LHB is achieved by establishing a temporary bypass from the left atrium to either the femoral artery (most commonly the left) or the distal descending thoracic aorta with a closed-circuit in-line centrifugal pump (Fig. 53-7B). The left atrial cannula is placed via an opening in the inferior pulmonary vein (see Fig. 53-7B). When we first began using LHB, cannulation of the distal descending thoracic aorta (usually at the level of the diaphragm) was used solely as an alternative to femoral artery cannulation in patients with femoral or iliac artery occlusive disease. However, because this technique causes few complications and eliminates the need for femoral artery exposure and repair, distal aortic cannulation has become our preferred approach. Careful examination of CT or MR images assists selection of an appropriate site for direct aortic cannulation. Areas with intraluminal thrombus (see Fig. 53-4) are avoided because cannulation could lead to distal embolization. Bypass flows are adjusted to maintain normal proximal arterial and venous filling pressures. Flows between 1500 and 2500 mL/min are generally used. Left heart bypass facilitates rapid adjustment of proximal arterial pressure and cardiac preload, thereby reducing the need for pharmacologic intervention. Because LHB effectively unloads the left ventricle, it is useful in patients with suboptimal cardiac reserve.
Paraplegia remains an index complication specific to distal aortic surgery. Historically, paraplegia rates have been as high as 30% for extensive aortic replacements. With modern operative techniques and spinal adjuncts, paraplegia rates in aortic centers are currently 2 to 5%.67–69 Because multiple adjuncts are used in combination, it is difficult to attribute the improvements in outcome to one technique.
Somatosensory evoked potential (SSEP) and motor evoked potential (MEP) monitoring have been used for intraoperative assessment of spinal cord function. Motor evoked potential monitoring involves electrical excitation of the motor cortex or motor neurons and measuring the amplitude of the resulting motor response in the peripheral muscles of the arms and legs. Monitoring MEPs allows real-time assessment of spinal cord motor function and was approved for this use during surgical TAAA repair by the FDA in 2003. Because the motor function of the anterior horn of the spinal cord is more susceptible than the posterior horn to ischemia and infarction, MEP changes are a sensitive indicator of spinal cord ischemia and are predictive of adverse neurologic events.70–72 In contrast, SSEP monitoring is less sensitive because the sensory pathways on the dorsal horn are more resistant to injury and are sometimes spared when ischemic injury occurs. Irreversible loss of either MEPs or SSEPs is highly predictive of immediate neurologic deficit on recovery.73 Monitoring MEPs precludes the use of neuromuscular paralytic agents.
Significant attenuation or loss of MEPs can occur within 2 minutes of acute spinal cord ischemia, and infarction can occur within 10 minutes at normothermia.74 Several studies have examined the use of MEP monitoring to guide spinal perfusion–enhancing measures (eg, reattaching more segmental arteries, increasing distal and proximal perfusion pressures, and enhancing cerebrospinal fluid [CSF] drainage) to improve the outcomes of TAAA and DTAA repair. For example, Jacobs et al.75 published excellent results in a series of 184 patients who underwent TAAA repair with a protocol that included LHB, CSF drainage, and MEP monitoring. The authors found that MEP was a sensitive technique for assessing spinal cord ischemia and identifying the segmental arteries that critically contribute to spinal cord perfusion. With this protocol, the incidence of neurologic deficit after TAAA repair was 2.7%. Other series of TAAA and DTAA repairs have found similarly low rates of postoperative paraplegia and paraparesis when MEP is used in this fashion.72,76 Our current practice is to monitor MEP in all extent II TAAA repairs and selectively in any other high-risk aortic repairs in which prolonged cross-clamping is anticipated, such as reoperative repairs and those involving difficult anatomy.
Cerebrospinal Fluid Drainage
The drainage of CSF in the context of aortic surgery for spinal cord protection was tested in animal models in the early 1960s.77 The rationale for CSF drainage was that it would enhance spinal perfusion by decreasing the pressure on the cord during aortic cross-clamping. Today, the practice is well accepted in TAAA repair, although the exact mechanisms of this adjunct's benefits remain controversial.78–82 In our study of 145 patients who underwent extent I or II TAAA repair, patients were randomly assigned to receive CSF drainage or no CSF drainage. Postoperatively, paraplegia or paraparesis developed in nine patients (13%) in the control group but in only two patients (2.6%) in the CSF drainage group (p = .03).83 Additionally, a meta-analysis of eight studies (three randomized controlled trials and five cohort studies) of CSF drainage in TAAA repair found that CSF drainage substantially reduced the incidence of postoperative neurologic impairment (p < .0001).84 Although the safety of CSF drainage has been shown clinically,85 known risks include intra-cranial bleeding, perispinal hematoma, meningitis, and spinal headaches.
We routinely use CSF drainage in patients undergoing Crawford extent I or II TAAA repairs because of the higher risks of paraplegia in these extensive TAAA repairs. We selectively use CSF drainage during less extensive repairs, such as DTAA or extent III or IV TAAA repairs, depending on the individual risk factors involved; for example, we would use CSF drainage in a redo aortic operation in which the spinal collateral is compromised and a long cross-clamp time is anticipated because of the complex configuration of the aneurysm. The intrathecal catheter is placed through the second or third lumbar space preoperatively after induction of anesthesia and is maintained 2 to 3 days postoperatively in the intensive care unit. The catheter allows both monitoring of the CSF pressure and therapeutic drainage of the fluid. The CSF is allowed to drain passively from the catheter and can be aspirated with a closed collection system as needed to keep the CSF pressure between 8 and 10 mm Hg during the operation and between 10 and 12 mm Hg during the early postoperative period. Once the patients are awake and neurologic exams confirm that they are able to move their legs, the CSF pressures are allowed to rise to a higher range of 15 to 18 mm Hg. To prevent intracranial hemorrhage, we avoid draining more than 25 mL per hour.
Regional Spinal Hypothermia
Regional spinal cord hypothermia can be accomplished by direct infusion of cold perfusate into the epidural or intrathecal space and intravascular cold perfusion of isolated thoracic aortic segments (with the expectation that the intercostal vessels will deliver the cold perfusate to the spinal cord). Epidural cooling for regional spinal cord hypothermia is effective in preventing paraplegia after aortic cross-clamping in canine and leporine models.86–89 Additionally, a series of 337 TAAA repairs reported by Cambria and colleagues90 showed that, in patients who underwent extent I, II, or III TAAA repairs, the incidence of spinal cord ischemic injury was reduced from 19.8 to 10.6% after the introduction of epidural cooling at their institution in 1993. A similar technique, cold perfusion into isolated aortic segments, has been tested in animal models to show that cord temperature and, consequently, the extent of ischemic spinal cord injury can be effectively reduced by this method.91
Left Heart Bypass for Spinal Protection
Left heart bypass appears to provide the greatest benefit to patients who undergo the more extensive repairs. Our own retrospective review of 1250 consecutive extent I or extent II TAAA repairs found that using LHB (in 666 cases) reduced the incidence of spinal cord deficits only in patients who underwent extent II repairs.92 In patients who underwent extent I repairs, the incidence of paraplegia was similar in the LHB and no-LHB groups, even though the LHB group had significantly longer aortic clamp times. This finding suggests that, by providing spinal cord protection, LHB gives the surgeon more time to create secure anastomoses. A propensity-score analysis of 387 of our patients who underwent DTAA repair with (n = 46) or without (n = 341) LHB during the construction of the proximal anastomosis found no effect of LHB on postoperative paraplegia and paraparesis rates.93 Data from series in which LHB and CSF drainage were used together suggest that combining these adjuncts may further reduce rates of spinal cord injury.94,95 Because patients who undergo extensive TAAA repairs (extents I and II) are at greatest risk of postoperative paraplegia or paraparesis, we routinely use LHB to provide distal aortic perfusion during the proximal portion of the aortic repair.
Segmental Artery Reattachment and Sequential Graft Clamping
Because of the often tenuous nature of the blood supply to the spinal cord, we take an aggressive approach to reattaching patent segmental arteries. Intimal atherosclerosis, particularly in medial degenerative fusiform aneurysms, obliterates many intercostal and lumbar arteries and complicates matters anatomically. Patent segmental arteries from T7 to L2 are selectively reattached as patches to one or more openings made in the graft (Fig. 53-7G). Large arteries with little or no back-bleeding are considered particularly important. When none of these arteries is patent, endarterectomy of the aortic wall and removal of calcified intimal disease can be considered as a means of identifying arteries suitable for reattachment. After intercostal arteries are reattached, the proximal clamp is often moved down the graft to restore intercostal perfusion. Sequential clamping restores perfusion to the proximal branch vessels and will decrease the ischemic time to the spinal cord. However, this benefit must be weighed against the additional time needed to control the potential bleeding from the proximal aortic anastomosis, the intercostal patch, and the collateral intercostal and lumbar branches that often results when the clamp is moved below the intercostal patch.
Postoperative management remains critical to spinal cord protection. Adequate blood pressure, preload, and cardiac inotropic state are carefully maintained to keep spinal perfusion sufficient. In the absence of postoperative bleeding, blood pressure should be kept near its preoperative baseline level. Delayed paraplegia can arise hours to days after aortic surgery.67 In the immediate postoperative period, strategies to reverse paraplegia and paraparesis include inducing systemic hypertension; placing a CSF drain, if one is not already present; decreasing CSF pressure; administering cardiac inotropes, mannitol, or steroids; correcting anemia; and preventing fever. Recovery from paraplegia is possible, but if cord function does not return promptly after these measures are taken, such a recovery is not likely.
Postoperative renal failure after DTAA and TAAA remains an important complication and is predictive of mortality.96 Distal aortic perfusion with LHB provides renal perfusion during proximal anastomosis. Once the renal vessels are exposed during distal repair, the renal arteries can be directly perfused with cold (4°C) crystalloid (Fig. 53-7G). Our current technique is to infuse 400 to 600 mL of cold lactated Ringer's (LR) solution every 6 to 10 minutes. We have previously reported on a group of patients who underwent Crawford extent II TAAA repair with LHB and who were randomly assigned to receive either renal artery perfusion of cold LR solution for renal cooling or to isothermic blood perfusion from the LHB circuit.97 Multivariate analysis confirmed that cold crystalloid perfusion was independently protective against acute renal dysfunction. Other groups continue to selectively perfuse the renal arteries with blood from the LHB circuit.
Similarly, distal aortic perfusion by LHB provides flow to the mesenteric branches during the initial portion of a TAAA repair. Once the visceral origins are exposed, selective visceral perfusion can be delivered through separate balloon perfusion catheters that are placed within the origins of the celiac and superior mesenteric arteries; these catheters are attached to the LHB circuit via a Y-line from the arterial perfusion line (Fig. 53-7B). This system provides oxygenated blood to the abdominal viscera while the intercostal and visceral branches are being reattached to the graft (Figs. 53-7G,H). Reducing hepatic ischemia in this fashion may decrease the risk of postoperative coagulopathy, and reducing bowel ischemia may decrease the risk of bacterial translocation.
Incisions and Aortic Exposure
Aneurysms limited to the descending thoracic aorta are approached through a full posterolateral thoracotomy (Fig. 53-8A). In most cases, the left pleural space is entered through the sixth intercostal space; however, if the aneurysm predominantly involves the upper portion of the descending thoracic aorta, the fifth intercostal space provides better access to the distal aortic arch. Exposure of the distal descending thoracic aorta is enhanced by dividing the costal margin without dividing the diaphragm.
Drawings illustrating techniques for repairing a descending thoracic aortic aneurysm. (A) In the clamp-and-sew technique, the operation is performed through a posterolateral thoracotomy (inset). Clamps are placed on the aortic arch (between the left common carotid and left subclavian arteries) and the left subclavian artery. The aorta is opened longitudinally and divided circumferentially a few centimeters beyond the proximal clamp. (B) After the proximal anastomosis is completed, the aortic clamp is repositioned onto the graft, flow is restored to the left subclavian artery, and the remainder of the aneurysm is opened longitudinally. An open distal anastomosis completes the repair. (C) As an alternative to the clamp-and-sew technique, left heart bypass can be used to provide distal aortic perfusion during the repair.
The full thoracoabdominal incision extends from the left posterior chest (between the scapula and the spine), crosses the costal margin, and traverses obliquely to the umbilicus. The length and level vary according to the anatomy of the aneurysm. The incision is gently curved as it crosses the costal margin to reduce the risk of tissue necrosis at the apex of the lower portion of the musculoskeletal tissue flap (Fig. 53-9A). Stabilized on a bean bag, the patient is placed in a modified right lateral decubitus position with the shoulders placed at 60 to 80 degrees and the hips rotated to 30 to 40 degrees from horizontal. In extent I and II repairs, which require access to the left subclavian artery and distal arch in the upper chest, our standard approach is through the sixth intercostal space. The upper or lower ribs may be divided posteriorly to achieve additional proximal or distal exposure, respectively, as needed. For extent III aneurysm repairs, entering through the seventh or eighth intercostal space will allow adequate access. Extent IV aneurysms are approached via a straight oblique incision through the ninth or tenth interspace (Fig. 53-9B). Ending the incision distally at the level of the umbilicus will allow access to the aortic bifurcation. The incision can be extended toward the pubis if iliac aneurysms also require repair.
Drawings of the typical incisions used in thoracoabdominal aortic aneurysm repairs. (A) A curvilinear incision is used to approach the aorta in extent I, II, and III thoracoabdominal aneurysm repairs. (B) A straighter, oblique incision is used to approach extent IV thoracoabdominal aortic aneurysm repairs.
For thoracoabdominal access, the diaphragm is divided partially or completely in a circular fashion to protect the phrenic nerve and preserve as much diaphragm as possible. The crus of the diaphragm is divided at the hiatus, and a 3- to 4-cm rim of diaphragmatic tissue is left posterolaterally on the chest wall to facilitate closure when the operation is complete. Below the diaphragm, the retroperitoneum is entered lateral to the left colon, and medial visceral rotation is performed to expose the aorta. A dissection plane is developed anterior to the psoas muscle, and the left kidney, left colon, spleen, and left ureter are retracted anteriorly and to the right. The abdominal aortic segment is approached transperitoneally; opening the peritoneum permits direct inspection of the abdominal viscera and its blood supply after aortic reconstruction is completed. An entirely retroperitoneal approach can be used in patients with a “hostile abdomen,” ie, patients with multiple prior abdominal operations or a history of extensive adhesions, peritonitis, or both.
The left renal artery is identified but generally does not require mobilization. The aorta is approached laterally to avoid injury to the mesenteric vessels and the abdominal organs. Commonly, a large lumbar branch of the left renal vein courses posteriorly around the aorta. This branch may be ligated and divided as needed. An anomalous retroaortic left renal vein is occasionally encountered and should be preserved. If the retroaortic renal vein or its tributaries require division for exposure, direct reanastomosis or interposition grafting to the inferior vena cava can be performed if the left kidney appears congested and shows distended collaterals.
For DTAA and extent I and II TAAA repairs, options for establishing proximal control include applying a proximal aortic clamp distal to the left subclavian artery; applying an aortic clamp between the left subclavian and the left carotid artery and applying a separate bulldog clamp to the left subclavian artery; applying an aortic clamp to an existing graft during an elephant trunk operation; or open anastomosis under hypothermic circulatory arrest with full cardiopulmonary bypass when an aortic clamp cannot be safely applied. The decision is based on the anatomy of the aneurysm. We use aortic clamping distal to the left subclavian artery whenever possible, although others have advocated using circulatory arrest routinely.98
In aneurysms suitable for aortic clamping, the distal aortic arch is gently mobilized by dividing the remnant of the ductus arteriosus. The vagus and recurrent laryngeal nerves are identified (see Fig. 53-7C). The vagus nerve may be divided below the recurrent nerve to provide additional mobility, thereby protecting the recurrent nerve from injury. Preserving the recurrent laryngeal nerve is particularly important in patients with chronic obstructive pulmonary disease and reduced pulmonary function. If the aneurysm encroaches on the left subclavian artery, clamping proximal to the left subclavian artery should be anticipated; the left subclavian artery is then circumferentially mobilized to enable placement of a bulldog clamp.
After heparin is administered, the proximal clamp is applied to the proximal descending thoracic aorta or the distal transverse aortic arch between the left common carotid and left subclavian arteries (see Figs. 53-7B and 53-8A). When LHB is used, it is initiated at a flow rate of 500 mL/min just before the proximal aorta is clamped. After the proximal clamp is applied, LHB flow is increased to 2 L/min and a second distal aortic clamp is placed between T4 and T7 (Fig. 53-8C). After the aorta is opened, patent upper intercostal arteries are oversewn (Fig. 53-7D). In cases of chronic dissection, the partition between the true and false lumens is completely removed. The aorta is transected 2 to 3 cm beyond the proximal clamp and is separated from the esophagus to allow the surgeon to place full-thickness sutures in the aortic wall without injuring the esophagus. A 22- or 24-mm, gelatin-impregnated woven Dacron graft is used in most patients. The proximal anastomosis is performed with continuous polypropylene suture (Fig. 53-7E). Most anastomoses are made with 3-0 polypropylene suture; however, in patients with particularly fragile aortic tissues, such as patients with acute aortic dissection or Marfan syndrome, 4-0 polypropylene sutures are commonly used. Felt strips are generally not used; instead, intermittent polypropylene mattress sutures with felt pledgets are used to reinforce selected portions of the anastomoses. The use of surgical adhesives is avoided in these operations.
Open Anastomosis under Hypothermic Circulatory Arrest
In repairs of large aneurysms at the distal arch or aneurysms with contained rupture, or in redo operations in which safe dissection and clamping are not possible, an alternative strategy is total cardiopulmonary bypass with hypothermic circulatory arrest. Arterial inflow is established by placing a cannula in the distal aorta or the femoral artery. Venous drainage is usually established by inserting a long percutaneous cannula into the femoral vein and advancing it into the right atrium with transesophageal echocardiographic guidance. The left atrium or left ventricle can be vented via a right-angled sump cannula placed in the left pulmonary vein to prevent cardiac distension. Total cardiopulmonary bypass is initiated, and the patient is cooled to electrocerebral silence. Circulatory arrest is initiated, and the aneurysm is opened. Direct antegrade cerebral perfusion into the left carotid artery can be accomplished via a separate balloon catheter arising from the arterial limb of the circuit. An open proximal anastomosis is performed. After this anastomosis is completed, a Y-limb from the arterial line is connected to a side-branch of the graft. The graft is deaired and clamped, pump flow to the upper body is resumed, and the remainder of the aortic repair is performed.
A staged operative procedure is preferred in patients who present with extensive aneurysmal disease involving the ascending aorta, aortic arch, and descending thoracic or thoracoabdominal aorta (Fig. 53-10A). When the DTAA or TAAA is not causing symptoms and is not substantially larger than the ascending aorta, the proximal aortic repair is performed first. This allows treatment of valvular and coronary artery occlusive disease during the first operation.
Drawings illustrating the two-stage elephant trunk repair of an extensive aneurysm (A) involving the ascending, transverse arch, and entire thoracoabdominal aorta. (B) The first stage includes graft replacement of the ascending aorta and transverse aortic arch. A segment of the graft (the trunk) is left suspended within the aneurysmal descending thoracic aorta. (C) During the second stage, the graft trunk is retrieved and (D) used for the proximal anastomosis. (E) The completed repair includes reattachment patches for a pair of intercostal arteries and the visceral arteries. (Figures B-D reproduced with permission from Baylor College of Medicine. Figure E reproduced with permission from LeMaire SA, Price MD, Parenti JL, Johnson ML, Lay AD, Preventza O, Huh J, Coselli JS. Early Outcomes after aortic arch replacement by using the Y-graft technique. Ann Thorac Surg 2011;91:700-708. Figure 4A. Copyright Elsevier.)
Our current preference for reconstruction of the innominate, left carotid, and left subclavian artery is separate end-to-end anastomoses with a branched trifurcated graft (Fig. 53-10B). The bypass to the left subclavian artery during the first stage is not critical, and the left subclavian artery origin can remain intact on the native aorta. The aorta itself can be replaced with a skirted elephant trunk graft, which facilitates the distal aortic anastomosis to aneurysmal tissue. The proximal aortic anastomosis is placed to the supravalvar ascending aorta, and the distal skirt anastomosis can be placed fairly anteriorly on the aortic arch at the level of the innominate artery, facilitating hemostasis. The proximal end of the trifurcated graft is then anastomosed to an opening in the mid-ascending aspect of the aortic graft. The distal aortic anastomosis later becomes unimportant when the distal elephant trunk anastomosis to the descending aorta is completed at the second stage (Fig. 53-10C-E). The presence of the graft elephant trunk within the descending aorta allows secure clamping of even very large aneurysms distal to the left subclavian artery. If this artery was not bypassed during the arch vessel reconstruction, a side branch from the descending aorta can be anastomosed to the subclavian artery from the left chest during the second stage.99
Reversed Elephant Trunk Repairs
Conversely, in patients with similarly extensive aneurysmal disease who present with a DTAA or TAAA that has ruptured, causes symptoms (eg, back pain), or is considerably larger than the ascending aorta, the DTAA or TAAA is treated during the initial operation, and the ascending aorta and transverse aortic arch are repaired in a second procedure. During this “reversed” elephant-trunk repair (Fig. 53-11), a portion of the proximal end of the aortic graft is inverted down into the lumen during the first operation and is later used to facilitate second-stage repair of the ascending and transverse aortic arch.100
Drawings illustrating the two-stage reverse elephant trunk repair of an extensive aneurysm (A) involving the ascending, transverse arch, and thoracoabdominal aorta. (B) The first stage involves graft replacement of the thoracoabdominal aorta. The proximal portion of the graft is invaginated, and the folded edge is used to create the proximal anastomosis. (C) After reattachment of intercostal arteries, a beveled distal anastomosis is performed behind the visceral ostia. (D) After the first stage is completed, a segment of graft (the trunk) is left suspended within the descending thoracic aortic graft. (E) During the second stage, the graft trunk is retrieved through the open aortic arch, and (F) used to replace the arch and ascending aorta, (G) which completes the repair.
Intercostal Patch Anastomosis and Completion of the DTAA Repair
After the proximal anastomosis is completed, LHB is discontinued and the distal aortic clamp is removed. The remainder of the aneurysm is opened longitudinally to its distal extent (Fig. 53-7F). The blood in the open aorta is scavenged via cell saver and returned as whole blood by a rapid infuser system. If the aneurysm was clamped proximal to the left subclavian artery, the aortic clamp is moved down onto the graft and the left subclavian artery clamp is removed; this restores blood flow to the left vertebral artery and to spinal collaterals. For repairs that extend to the diaphragm or beyond, patent lower intercostal arteries are selected and reattached to an opening cut in the side of the graft (Fig. 53-7G). If the aortic tissue is particularly friable, a separate, 8-mm graft can be attached in an end-to-end fashion to the selected intercostal vessels. In DTAA repairs, the distal anastomosis is then performed (Fig. 53-8B) to the open distal aorta. For aneurysms arising from chronic dissections, the membrane between the true and false lumen is fenestrated distally to ensure that both lumens are perfused.
Visceral Branch Vessel Anastomoses
In patients with TAAAs, after the descending thoracic aortic repair is completed, the remainder of the aneurysm is opened longitudinally (Fig. 53-7F). This incision runs posterior to the origin of the left renal artery and continues to the distal extent of the aneurysm. When present, the remaining dissecting membrane is excised. The origins of the visceral and renal branches are identified. Cold crystalloid is intermittently delivered to the renal arteries via balloon catheters (Fig. 53-7G). In patients receiving LHB, balloon cannulas are also placed in the celiac and superior mesenteric arteries so that selective visceral perfusion can be delivered from the pump circuit. Subsequently, the celiac, superior mesenteric, and renal arteries are reattached. In extent I repairs, the reattachment of the visceral arteries is often incorporated into a beveled distal anastomosis (Fig. 53-11C), but in extent II and III repairs, the visceral artery origins are reattached to one or more oval openings in the graft (Fig. 53-7H). In 30 to 40% of patients, the origin of the left renal artery is displaced laterally and is best attached to a separate opening in the graft (Fig. 53-7I). Patients with genetic disorders such as Marfan or Loeys-Dietz syndrome are prone to aneurysms involving their visceral reattachment patch; a multibranched graft enables separate bypasses to each of the vessels, thereby minimizing the amount of remaining aortic tissue and reducing the risk of recurrent aneurysms. Multibranched grafts are also useful in patients with large aneurysms that have caused wide displacement of the celiac, superior mesenteric, and renal arterial ostia (Fig. 53-12). Visceral artery stenosis is encountered in at least 25% of patients and necessitates endarterectomy (if anatomically suitable), stenting, or interposition bypass grafting.54,101
Drawings showing (A) a thoracoabdominal aortic aneurysm with wide displacement of the celiac, superior mesenteric, and both renal arterial ostia. (B) The aorta has been replaced with a multibranched graft that facilitates separate reattachment of each of the visceral arteries.
Distal Aortic and Iliac Anastomoses
When the TAAA extends below the renal arteries, a distal anastomosis is performed near the aortic bifurcation (Fig. 53-7J). In patients with iliac artery aneurysms, a bifurcation graft is sewn onto the end of the straight graft; the graft's limbs are then anastomosed to the common iliac, external iliac, or common femoral artery, depending on the extent of disease. The right limb of the bifurcation graft is tunneled retroperitoneally into the pelvis near the right iliac artery. Exposure of the left iliac artery is more straightforward from the left retroperitoneal incision. Care is taken to preserve circulation to at least one of the internal iliac arteries.
After all clamps are removed, heparin is reversed with protamine sulfate. Hemostasis is achieved by surgically reinforcing the anastomoses and administering blood products as necessary. The renal, visceral, and peripheral circulations are assessed. To ensure that renal function is adequate, blue dye is administered intravenously, and transit time to urine output is measured. The bowel, spleen, and liver are all assessed for adequacy of perfusion. The spleen is examined for capsular injury; if a splenic hematoma is present, the spleen is removed to avoid postoperative bleeding and hypotension. The aneurysm wall is then loosely wrapped around the aortic graft. Two posteriorly located thoracic drainage tubes and a closed-suction retroperitoneal drain are placed before closure. The diaphragm is closed with continuous polypropylene suture; postoperative disruption of the diaphragmatic repair is exceedingly rare.