Exposure of the Carotid Bifurcation

The common carotid artery bifurcates approximately 2.5 cm below the angle of the mandible. Normally, the sternocleidomastoid muscle, the posterior belly of the digastric muscle, and the omohyoid muscle bound the carotid bifurcation. Thus, a skin incision placed along the anterior border of the sternocleidomastoid muscle facilitates exposure of the carotid sheath.

The surgeon must be aware of the location of important cranial and somatic nerves during carotid endarterectomy. The mandibular ramus of the facial nerve is vulnerable to injury during this operation. Nerve damage by retraction or surgical dissection can cause temporary or permanent dysfunction. Turning the head toward the opposite side draws the mandibular ramus well below the mandible and increases the possibility of facial nerve injury.

The great auricular nerve (C-2 and C-3 dermatomes) should be protected in its location on the sternocleidomastoid muscle just anterior to and below the ear. Damage to this nerve results in numbness of the posterior aspect of the auricle and may cause distressing ipsilateral occipital headaches.

The common facial vein comes into view as the incision is deepened. This vessel courses superficially to the carotid bifurcation to join the internal jugular vein. It serves as an important landmark during the dissection. Several small vessels coursing toward the sternocleidomastoid muscle are nutrient branches from the superior thyroid artery and vein. These vessels should be ligated and divided to avoid troublesome postoperative bleeding. In the typical carotid dissection, the common carotid artery should be exposed above the level of the omohyoid muscle. Once this vessel is isolated, further distal dissection along its medial aspect facilitates exposure of the superior thyroid and external carotid arteries. Dissection in the V of the carotid bifurcation should be avoided, because this area is extremely vascular. It is wise to encircle the internal carotid artery well above the level of gross atherosclerotic disease. This dissection is usually 1 to 2 cm above the bifurcation and thereby avoids the highly vascular carotid sinus tissue.

The descending branch of the hypoglossal nerve (ansa cervicalis) is located anterior and parallel to the sternocleidomastoid muscle. If this branch is followed upward, the main hypoglossal nerve trunk can be located. Division of the descending branch of the hypoglossal nerve near its origin allows the main nerve trunk to be displaced upward and forward, thus providing higher exposure of the internal carotid artery. A nutrient vein and artery associated with the sternocleidomastoid muscle course in immediate relation to this nerve at this level. Care should be taken to avoid injury to the underlying hypoglossal nerve when these vessels are ligated and divided. This maneuver allows the nerve to retract superomedially and out of harm’s way. Division of this artery-vein “sling” about the hypoglossal nerve facilitates exposure of the internal carotid artery under the posterior belly of the digastric muscle.

The surgeon must also maintain an awareness of the location of the vagus nerve and its branches. It lies within the carotid sheath between the common carotid artery and the internal jugular vein. Normally, it is directly behind the internal carotid artery at its origin. Care must be taken to prevent injury to the nerve at this vulnerable location. Additional care is required to prevent vagus nerve injury during repeated carotid exposure, because the nerve, which may be encased in scar tissue, frequently courses anterior to the carotid bifurcation. The superior laryngeal nerve arises from the vagus nerve above the carotid bifurcation, passes behind the internal carotid artery, and descends medial to the superior thyroid artery. Care must be taken during mobilization of this vessel not to injure the superior laryngeal nerve or its external branch (Figure 4-1). The external branch of the superior laryngeal nerve sometimes passes between the branches of the superior thyroid artery or is adherent to it. Table 4-1 lists the locations and the tests for function of the important nerves encountered during exposure of the carotid bifurcation.

FIGURE 4-1 Note the vulnerable location of the external branch of the superior laryngeal nerve to the superior thyroid artery.

TABLE 4-1 Regional Nerves Encountered during Exposure of the Carotid Bifurcation

A carotid arteriotomy should be created proximal to the carotid bulb and lateral to the carotid flow divider in the typical endarterectomy scenario. This incision is then lengthened distally through the diseased internal carotid artery under direct vision to a point where there is normal-appearing intima. It is critical not to make this arteriotomy on the anterior aspect of the internal carotid artery near the carotid sinus, because this is a relatively fixed area that is difficult to reapproximate without creating a focal narrowing that is at risk for restenosis. It is wise to find the correct endarterectomy plane at the level of the carotid bulb. Endarterectomy then proceeds proximally first, and the specimen is excised sharply with Potts scissors at the level of the common carotid artery. Everting the external carotid artery into the carotid bulb facilitates endarterectomy at this level. Next, the transition point between the atherosclerotic plaque to be removed and the remaining nondiseased internal carotid artery is located. This step is critical in the performance of a technically sound carotid endarterectomy; if it is done correctly, tacking sutures are rarely required. Meticulous care is then taken to ensure that no loose areas of media remain through the endarterectomized surface. In the author’s practice, Bovine patch angioplasty reapproximates the arteriotomy, and intraoperative duplex ultrasound scanning completes the procedure. The reader is referred to Wylie’s Atlas of Vascular Surgery for color illustrations of the steps used to perform a classic carotid endarterectomy.¹

For eversion endarterectomy, the carotid artery is obliquely transected at the transition between the proximal internal carotid artery and the carotid bulb. Plaque control with forceps and gentle eversion of the internal carotid artery enable one to establish an appropriate endarterectomy plane of dissection. This maneuver enables visualization of a distal break point that will allow the plaque to feather away from the mid to distal internal carotid artery without the need for tacking sutures. Proximally, angled Potts scissors can be used to create a longitudinal arteriotomy, which opens the carotid bulb and common carotid artery similar to a standard endarterectomy. This move facilitates endarterectomy at the level of the carotid bulb and external carotid artery. The transected internal carotid artery can be shortened if necessary and then reattached using a continuous Prolene suture. Appropriate alignment of the internal carotid artery to the carotid bulb frequently requires a longitudinal incision of the medial aspect of the artery with Potts scissors.

The value of cranial nerve protection during carotid surgery cannot be overemphasized. Despite this admonition, cranial nerve injury (CNI) remains a significant postoperative complication of carotid endarterectomy.^2–6 Sajid and colleagues³ reviewed the incidence of CNI after carotid endarterectomy over a 25-year period of time. This metaanalysis included 10,847 patients in 31 studies and compared results that were published before 1995 (15 publications) with those published after 1995 (16 publications). The overall incidence of CNI was 9.4% (1020 injured nerves), and the incidence was higher in publications that occurred before 1995 (10.6% versus 8.3%). Not surprisingly, there was a significant range in the incidence of CNI among different vascular centers, which varied from 1.35% to 31%. The hypoglossal nerve, vagus nerve, and its branches and facial nerves were most often injured, whereas glossopharyngeal and spinal accessory nerve injuries occurred less frequently. Fortunately, almost all (99%) CNIs were transient, and nerve function returned within 3 months with conservative therapy only. Permanent and often disabling CNI occurs with an incidence of 0.5% to 1% after carotid endarterectomy.

In a single-center study published in 1999, Ballotta and colleagues⁵ reviewed 200 consecutive carotid endarterectomies in Italy. There were 25 cranial nerve injuries (12.5%) in 24 patients, distributed as follows: hypoglossal (11), recurrent laryngeal (8), superior laryngeal (2), marginal mandibular (2), greater auricular (2). Fortunately, the deficits were transient, with all but four resolving by 6 months. The mean recovery time was 5.8 months, with a range of 1 week to 37 months. Forssell and associates⁶ reviewed 663 consecutive carotid endarterectomy patients in Malmö, Sweden, who were examined preoperatively and postoperatively at the Department of Phoniatrics to determine cranial nerve function. Seventy-five carotid operations (11.4%) resulted in one or more cranial nerve injuries. These injuries included 70 hypoglossal, 8 recurrent laryngeal, 2 glossopharyngeal, and 2 superior laryngeal injuries. Only two nerve injuries (0.30%) were permanent. The frequency of injury increased with a junior surgeon, shunt use, and patch closure.

In summary, cranial nerve injuries are usually caused by direct trauma such as stretch, retraction, clamping, or transection. Nerve transection should be rare in experienced hands. Reapproximating the epineurium primarily with a fine suture at the time of injury is the best way to repair a transected cranial nerve. Most cranial nerve injuries are transient, with full recovery within 3 to 6 months, on average.

Exposure of the Distal Internal Carotid Artery

One of the most difficult surgical exposures is that of the distal internal carotid artery. The surgeon must contend with many vital structures within a confined space. This exposure is frequently made more difficult by the presence of a space-occupying vascular lesion or a vascular injury with hemorrhagic staining and displacement of the tissues. Structures that overlie the distal internal carotid artery in the neck include the facial nerve, parotid gland, ramus of the mandible, and mastoid and styloid processes. The hypoglossal nerve, glossopharyngeal nerve, digastric and stylohyoid muscles, and occipital and posterior auricular arteries cross the distal internal carotid artery. The distal cervical internal carotid artery courses progressively deeper to enter the petrous canal of the temporal bone.

Exposure routinely begins at the level of the common carotid artery proximal to the carotid bifurcation. The omohyoid muscle serves as a landmark for the proximal extent of this exposure. The dissection continues distally, protecting the vagus nerve, which lies immediately behind the internal carotid artery. The hypoglossal nerve is exposed, and the descending branch is divided to displace the hypoglossal nerve forward. The digastric and stylohyoid muscles are divided to facilitate this exposure. In addition, the styloid process and the stylohyoid ligament are excised. The glossopharyngeal and superior laryngeal nerves must be identified and preserved. One is now working in a progressively narrowing triangle, with inadequate space to perform any major vascular reconstructive procedure.

Anatomic dissection in human cadaver specimens demonstrates that division of the posterior belly of the digastric muscle facilitates exposure of the internal carotid artery to the middle of the first cervical vertebra. Anterior subluxation of the mandible improves exposure to the superior border of the first cervical vertebra. The addition of styloidectomy to the maneuvers described previously extends the exposure cephalad, approximately 0.5 cm.⁷

Fisher and associates described a unique technique of wire fixation of the mandible to hold its subluxed position during the operative procedure.⁸ The 12 to 15 mm of space obtained converts the triangle described earlier into a narrow rectangle (Figure 4-2). It is important to avoid dislocation of the mandible, because serious injury can occur to the temporomandibular joint and even to the contralateral internal carotid artery. In the discussion of Fisher and associates’ paper,⁸ Stanley suggested that a towel clip placed on the angle of the mandible through two small stab incisions would allow the subluxation to be fixed by minimal retraction. Dossa and associates⁹ also suggested that temporary mandibular subluxation can be accomplished in a safe and expeditious manner using diagonal, interdental Steinmann pin wiring. Figure 4-3 shows a diagram of the relationship of the mandibular condyle to the auricular eminence and infratemporal fossa.

FIGURE 4-2 The narrow triangle of exposure (A) for the high internal carotid artery is expanded to a narrow rectangle (B) by anterior subluxation of the condyle of the mandible.

(From Fisher DF, Jr, Clagett GP, Parker JI, et al: Mandibular subluxation for high carotid exposure. J Vasc Surg 1:727, 1984.)

FIGURE 4-3 Anterior subluxation moves the condyle of the mandible to the articular eminence but not to the infratemporal fossa, as would occur with dislocation of the mandible.

(From Fisher DF, Jr, Clagett GP, Parker JI, et al: Mandibular subluxation for high carotid exposure. J Vasc Surg 1:727, 1984.)

In situations requiring more room for vascular reconstruction, transection of the mandibular ramus with either translocation or temporary removal of the condyle and ramus fragment affords wider exposure. Wylie and associates¹⁰ described this approach and provided detailed color illustrations of the involved anatomy.

Following induction of anesthesia, arch bars and wires immobilize the mandible. The usual carotid endarterectomy incision is extended posteriorly to a point behind the ear. The carotid bifurcation and internal carotid artery are exposed as described previously. The mandibular ramus of the facial nerve is protected. The angle of the mandible is exposed, and the periosteum is elevated toward the mandibular notch anteriorly and posteriorly. The mandibular ramus is divided vertically using a power saw posterior to the foramen of the inferior alveolar artery and nerve. The posterior bone fragment is gently rotated out and upward as the pterygoid muscles are divided, allowing the fragment’s removal. The bone fragment is preserved in chilled lactated Ringer solution until it is replaced after arterial reconstruction.

Once the mandibular ramus is removed, the digastric and stylohyoid muscles are divided, and the dissection is continued to the skull base. Care should be taken to protect the hypoglossal, glossopharyngeal, and vagus nerves, which are in immediate relation to the distal internal carotid artery. The mandibular fragment is returned to its anatomic location after completion of the internal carotid artery reconstruction, and interrupted nonabsorbable sutures close the temporomandibular joint capsule. A thin titanium plate is used to fix the mandibular fragment in place. The cervical fascia and platysma muscle are closed in layers, followed by routine skin closure.

Exposure of Aortic Arch Branches and Associated Veins

The most widely accepted direct route for the surgical exposure of the innominate and proximal left common carotid arteries, as well as the superior vena cava and its confluent brachiocephalic veins, is through a full median sternotomy. Although this approach is certainly appropriate in the trauma setting, elective aortic arch branch vessel exposure can be performed with a limited approach. Mini sternotomy is a less invasive surgical exposure for the direct treatment of aortic arch branch vessels and associated major veins.¹¹ Similar to a median sternotomy, this surgical approach provides excellent exposure of the aortic arch branch vessels, with the exception of the left subclavian artery. The first portion of the left subclavian artery is not readily accessible from either anterior approach, because the aortic arch passes obliquely posterior and to the left after its origin from the base of the heart.

Mini sternotomy is performed by first making a limited skin incision measuring 7 to 8 cm in the midline. This incision should extend from the sternal notch to just past the angle of Louis. The manubrium and upper sternum are divided in the midline down to the third intercostal space with a narrow blade mounted on a redo sternotomy oscillating saw (Stryker, Kalamazoo, Mich.). The sternum is then transected transversely at the third intercostal space, creating an upside-down T incision (Figure 4-4). Care is taken not to injure the internal mammary arteries, which are adjacent to the sternum. After accurate hemostasis along the periosteal edges, a Rienhoff or similar pediatric sternal retractor is placed to open the upper sternum. The skin incision can be extended upward along the anterior border of either sternocleidomastoid muscle, with division of the strap muscles to expose the proximal right common carotid artery or the more distal left common carotid artery. This extension can also be used to expose the carotid bifurcation.

FIGURE 4-4 Skin incision and mini-sternotomy sternal division.

(From Sakopoulos AG, Ballard JL, Gundry SR: Minimally invasive approach for aortic branch vessel reconstruction. J Vasc Surg 31:200, 2000.)

The two lobes of the thymus gland are separated in the midline, and if the surgeon carefully observes the pleural bulge during positive-pressure inspiration, entry into either pleural space can be avoided. Nutrient vessels to the thymus gland are carefully ligated and divided, keeping a dry field for visibility. These vessels arise from the internal thoracic artery and drain into the internal thoracic or brachiocephalic veins. The upper pericardium is then opened vertically, and the edges are sewn to the skin with silk suture.

The left brachiocephalic vein can be visualized in the upper portion of the wound. A thymic vein may join this vessel inferiorly, and an inferior thyroid vein may require ligation and division as it joins the brachiocephalic vein superiorly. After complete mobilization of the left brachiocephalic vein, the anterior surface of the aortic arch can be visualized, as well as the origin of the innominate artery. The base of the heart and the innominate and left common carotid arteries are thus exposed (Figure 4-5). The recurrent laryngeal nerve must be protected during exposure of the distal innominate artery. It courses from the vagus nerve anteriorly around the origin of the subclavian artery to return in the tracheoesophageal groove to its termination in the larynx.

FIGURE 4-5 The upper sternum is divided and separated, exposing the ascending aorta and arch vessels.

(From Sakopoulos AG, Ballard JL, Gundry SR: Minimally invasive approach for aortic branch vessel reconstruction. J Vasc Surg 31:200, 2000.)

Innominate or left common carotid artery endarterectomy, patch angioplasty, or bypass can then be performed in the usual fashion (Figure 4-6). After the procedure, a 19 French Blake drain (Johnson and Johnson, Cincinnati, Ohio) is placed in the mediastinum and brought out laterally through one of the intercostal spaces. This drain is connected to a Heimlich valve grenade suction device. Chest tubes are not used. Two wires are used to bring the upper and lower sternal edges of the T together, and two more are placed in the manubrium. If necessary, another wire placed as a figure eight at the level of the second intercostal space completely rejoins the divided upper sternum. After approximating the muscular and subcutaneous planes in two layers, the skin is closed in a subcuticular fashion.

FIGURE 4-6 Surgical exposure of an innominate artery with visible atherosclerotic stenosis. A, Repair by proximal exclusion and ascending aorta–to–innominate artery bypass. B, Repair by endarterectomy and patch angioplasty.

(From Sakopoulos AG, Ballard JL, Gundry SR: Minimally invasive approach for aortic branch vessel reconstruction. J Vasc Surg 31:200, 2000.)

Exposure of the Origin of the Right Subclavian Artery and Vein

The origin of the right subclavian artery is exposed through a sternotomy incision with extension above and parallel to the clavicle. The right sternohyoid and sternothyroid muscles are divided, followed by exposure of the scalene fat pad. Branches of the thyrocervical trunk are divided, and the dissection is deepened to expose the anterior scalene muscle. The phrenic nerve should be identified and protected as it courses from lateral to medial across the surface of the anterior scalene muscle to pass into the superior mediastinum. The proximal right subclavian artery comes into view with division of the anterior scalene muscle just above its insertion on the first rib.

Traumatic vascular injury at the confluence of the subclavian artery and internal jugular and subclavian veins is difficult to manage solely through a supraclavicular approach. Ideally, sternotomy for proximal vascular control should be followed by supraclavicular extension of the incision. However, in the event that the injury is exposed without proximal control, the incision should be promptly extended via a sternotomy while an assistant maintains compression of the vessels against the undersurface of the sternum to temporarily control hemorrhage (Figure 4-7). Alternatively, temporary percutaneous balloon occlusion of the distal innominate artery from a femoral or brachial artery approach can be lifesaving and greatly facilitates this exposure.

FIGURE 4-7 Exposure of the anterior aortic arch branches through a median sternotomy incision. Note the location of the phrenic, vagus, and recurrent laryngeal nerves, which must be identified and protected. Ao, Aorta.

(From Ernst C: Exposure of the subclavian arteries. Semin Vasc Surg 2:202, 1989.)

Exposure of the Origin of the Left Subclavian Artery

The left subclavian artery arises from the aortic arch posteriorly and from the left side of the mediastinum; therefore it cannot be adequately exposed for vascular reconstruction through a sternotomy incision. Traumatic injuries and aneurysms of the proximal left subclavian artery should be approached through the left side of the chest. The preferred exposure is an anterolateral thoracotomy through the fourth intercostal space or the bed of the resected fourth rib.

If the vascular injury or aneurysm is extensive, it is wise to prepare the left upper extremity for inclusion in the operative field so that it can be positioned for a second supraclavicular incision. This allows ready access to the second portion of the subclavian artery to gain distal vascular control. Anterolateral exposure of the left side of the chest also facilitates partial occlusion of the aortic arch for lesions involving the origin of the subclavian artery. The phrenic and vagus nerves must be identified and preserved after the pleura is opened and before the dissection of the first portion of the subclavian artery.

In situations in which there is exigent bleeding into the pleural space from a traumatic injury of the proximal left subclavian artery and percutaneous balloon occlusion is not possible, prompt vascular control can be obtained an anterior thoracotomy in the third or fourth intercostal space. This exposure facilitates placement of a vascular clamp across the origin of the bleeding subclavian artery (Figure 4-8). An inframammary incision is preferred in women, with the breast mobilized superiorly for the exposure just described.

FIGURE 4-8 Anterior thoracotomy with placement of an occluding vascular clamp for control of exigent bleeding from the proximal left subclavian artery.

(From Trunkey D: Great vessel injury. In Blaisdell F, Trunkey D, editors: Trauma management, vol 3, Cervicothoracic trauma, New York, 1986, Thieme, p 255.)

Exposure of the Subclavian and Vertebral Arteries

Exposure of the second portion of the subclavian artery is accomplished through a supraclavicular incision beginning over the tendon of the sternocleidomastoid muscle and extending laterally for 8 to 10 cm. The platysma muscle is divided, and the scalene fat pad is mobilized superolaterally. Thyrocervical vessels are ligated and divided as encountered, with exposure of the anterior surface of the anterior scalene muscle. The phrenic nerve can be seen coursing in a lateral to medial direction over this muscle and should be gently mobilized and preserved. The thoracic duct must also be protected at its termination with the confluence of the internal jugular, brachiocephalic, and subclavian veins. Unrecognized injury can result in a lymphocele or lymphocutaneous fistula.

The anterior scalene muscle is divided just above its point of insertion on the first rib to facilitate exposure of the subclavian artery. Division of this muscle should be done under direct vision and without cautery, because the brachial plexus is immediately adjacent to the lateral aspect of the anterior scalene muscle. The origin of the left vertebral artery arises from the medial surface of the subclavian artery medial to the anterior scalene muscle and behind the sternoclavicular joint. The internal thoracic artery, which originates from the inferior surface of the subclavian artery opposite the thyrocervical trunk, should be protected as the subclavian artery is dissected free of surrounding tissue. Figure 4-9 depicts the essential anatomy of this exposure.

FIGURE 4-9 Exposure of the second portion of the left subclavian artery via a supraclavicular incision. Note that both the lateral head of the sternocleidomastoid muscle and the anterior scalene muscle are divided for this exposure.

Resection of subclavian artery aneurysms and emergency exposure for vascular injury involving the second and third portions of this vessel require wide exposure. This can be accomplished by resecting the clavicle, including the periosteum. The latter structure, when preserved, results in reossification of a deformed clavicle.

The surgical exposure of the distal vertebral artery is described in detail in Chapter 19 of this text and in the surgical literature.¹² Injury to the intraosseous portion of the vertebral artery with associated hemorrhage is best managed by embolic occlusion proximal and, if possible, distal to the area of injury.

Exposure of the Axillary Artery

The proximal axillary artery is exposed by a short incision made between the clavicular and sternal portions of the pectoralis major muscle. Branches of the thoracoacromial vessels are divided to expose the axillary vein first and then the axillary artery above and posterior to the vein. Dissection medial to the pectoralis minor muscle provides appropriate exposure of the axillary artery for axillofemoral bypass graft origin. If additional exposure is required laterally, a portion of the pectoralis minor muscle can be divided near its insertion into the coracoid process of the scapula.

The second portion of the axillary artery is more difficult to expose because it lies directly behind the pectoralis major muscle. Extension of the previously mentioned incision continues across the distal portion of the pectoralis major muscle at the anterior axillary fold and out onto the midline of the proximal medial surface of the arm (Figure 4-10). The tendinous portion of the muscle is divided near its insertion to expose the axillary contents. The pectoralis minor muscle can also be divided if more medial exposure is desired.

FIGURE 4-10 Incision used for exposure of the axillary artery.

Exposure of the Thoracic Outlet

Either a supraclavicular or a transaxillary approach facilitates surgical exposure of the thoracic outlet. Roos described the transaxillary approach for first rib resection in the management of thoracic outlet syndrome.¹³ However, current treatment approaches for thoracic outlet syndrome favor supraclavicular exposure of the neurovascular structures within the superior thoracic aperture. Essential anatomic elements of this approach have been detailed in Wylie’s Atlas of Vascular Surgery.¹⁴

A transverse supraclavicular incision based 1.5 cm above the medial half of the clavicle is deepened to develop subplatysmal flaps and to expose the scalene fat pad. Reflection of the fat pad superolaterally facilitates exposure of the anterior scalene muscle. This exposure also requires ligation and division of the transverse cervical artery and vein and resection of the omohyoid muscle.

Identification and careful manipulation of the phrenic nerve are essential to avoid excessive traction or injury. Complete removal of the anterior scalene muscle begins at the level of the first rib and ends at the transverse processes of the cervical vertebrae. Subtotal removal of the middle scalene muscle in a plane parallel to and just inferior to the long thoracic nerve exposes all five roots and three trunks of the brachial plexus.

This unencumbered exposure of the brachial plexus facilitates neurolysis and complete mobilization of the nerve roots. Additional myofibrous bands or bony anomalies are removed at this time. If the course of the lower trunk and C8 to T1 nerve roots are deviated by the first rib, the rib should be partially or totally removed to free the path.

Incision of the Sibson fascia and displacement of the dome of the pleura inferiorly help to fully expose the inner aspect of the first rib. Gentle anteromedial retraction of the plexus ensures adequate posterior division of the first rib near the T1 nerve root. Anteriorly, the rib is transected distal to the scalene tubercle. This approach is useful for rib resection in association with axillosubclavian vein thrombosis. A counterincision just below the clavicle can be used to facilitate anterior transection of the first rib, but this counterincision is rarely needed in the usual dissection. Final removal of the first rib requires division of intercostal muscle attachments to the second rib and division of any other soft tissue.

The scalene fat pad can be wrapped around the plexus if split in a sagittal plane. Repositioning of the fat pad decreases dead space and may help to prevent incorporation of the brachial plexus into the healing scar tissue. The wound is closed in layers after secure hemostasis and reapproximation of the lateral head of the sternocleidomastoid muscle.

Exposure of the Descending Thoracic and Proximal Abdominal Aorta

No single approach is better for extensive exposure of the thoracic and abdominal aorta than a properly positioned thoracoabdominal incision. After pulmonary artery and radial artery line placement and dual-lumen tracheal intubation, the patient is placed in a modified right lateral decubitus position, with the hips rotated 45 degrees from horizontal. This position allows exposure of both groins if needed. A beanbag device is helpful to support the patient’s position on the operating table. The free left upper extremity should be passed across the upper chest and supported on a cushioned Mayo stand. In this way, thoracoabdominal aortic exposure is gained by unwinding the torso, as described by Stoney and Wylie.¹⁵

The extent of thoracic aorta to be exposed will determine which rib interspace to enter. The fourth or fifth intercostal space is used when the entire thoracoabdominal aorta from the subclavian artery origin through the abdominal aorta is to be exposed, whereas the seventh or eighth intercostal space allows mid to terminal thoracic aortic exposure plus wide abdominal aortic visualization. Dividing the respective lower rib posteriorly facilitates this exposure. The thoracic incision is continued across the costal margin in a paramedian plane to the level of the umbilicus (Figure 4-11). If the terminal aorta and iliac vessels are to be exposed, the incision is extended to the left lower quadrant.

FIGURE 4-11 Incision options for thoracoabdominal aortic procedures are based on the extent of thoracic aorta to be exposed and the desire to stay in an extraperitoneal plane.

(From Rutherford RB: Thoracoabdominal aortic exposures. In Rutherford RB, editor: Atlas of vascular surgery: basic techniques and exposures, Philadelphia, 1993, WB Saunders, p 223.)

With the left lung deflated, the origin of the left subclavian artery and proximal descending thoracic aorta can be dissected free of surrounding tissue to facilitate aortic cross-clamping. The vagus and recurrent laryngeal nerves are densely adherent to the aorta just proximal to the subclavian artery, and meticulous care should be taken not to injure these structures. Division of the inferior pulmonary ligament exposes the middle and distal descending thoracic aorta. The diaphragm is radially incised toward the aortic hiatus, and the left diaphragmatic crus is divided to expose the terminal descending thoracic aorta. Alternatively, just the central tendinous portion of the diaphragm can be divided, or it can be incised circumferentially at a distance of approximately 2.5 cm from the chest wall.

The left retroperitoneal space is developed in a retronephric extraperitoneal plane, because surgical exposure of the thoracoabdominal aorta is greatly facilitated by forward mobilization of the left kidney. Division of the median arcuate ligament and lumbar tributary to the left renal vein allows further medial rotation of the abdominal viscera and left kidney. Clearing the posterolateral surface of the thoracoabdominal aorta facilitates aortotomy. With this exposure, the origins of the left renal artery, celiac axis, and the superior mesenteric artery can then be visualized and dissected free of surrounding tissue, as indicated by the disease process present (Figure 4-12). Dissection over the anterior aorta just distal to the left renal artery and underneath the medially rotated left renal vein will bring the right renal artery into view. Alternatively, the origin of this vessel can be readily identified from within the aorta if it is too scarred across the anterior portion of the abdominal aorta or if the aneurysm is too large to safely perform the maneuver described previously.

FIGURE 4-12 Thoracoabdominal aortic exposure from the origin of the left subclavian artery to the common iliac arteries.

(From Rutherford RB: Thoracoabdominal aortic exposures. In Rutherford RB, editor: Atlas of vascular surgery: basic techniques and exposures, Philadelphia, 1993, WB Saunders, p 233.)