08 Mediastinal Vessels
08 Mediastinal Vessels
In this video, we will discuss the proper technique for exposure and repair of the mediastinal vessels.
We will begin by reviewing the anatomy, the necessary instruments, proper patient positioning, then demonstrate exposure of the mediastinal vessels through a median sternotomy. Finally, we will discuss tips and pitfalls of this procedure.
In the upper mediastinum, just above the reflection of the pericardium on the ascending aorta, lies the aortic arch, with its three major branches the innominate artery-- which gives rise to the right subclavian and right common carotid artery-- the left common carotid artery, and the left subclavian artery, which is most posterior.
The left innominate vein crosses laterally, just superior to the aortic arch, and joins the right innominate vein at a right angle to form the superior vena cava. Note the location of the right recurrent laryngeal nerve, as it loops around the right subclavian artery.
Segment:3 Instruments and Positioning.
The patient should be positioned supine with the arms abducted out at 90 degrees. The patient should be prepped and draped from the neck to the knees to allow for extension of the incision, as well as for possible saphenous vein harvest if needed.
Instruments should include a sternotomy tray, sternal saw, or lebsche knife, a Finochietto or Canadian sternal retractor, vascular instruments, and assorted vascular conduits. Median sternotomy provides excellent exposure to the mediastinal vessels. This incision may be extended to the neck if needed, and also across the left clavicle if exposure of the left subclavian artery is needed.
Despite the excellent exposure of asternotomy, patients presenting without vital signs should be managed instead with a resuscitative thoracotomy, and exposure to the mediastinal vessels can be improved by extending to a clamshell thoracotomy.
Segment:4 Exposure and Technique .
The skin incision is made from the sternal notch to below the xiphoid process. The incision is carried down through the fascia to the sternum, and the sternum is scored with electrocautery. The inner clavicular ligament at the sternal notch is divided with electrocautery so as to allow purchase for the sternal saw.
Pass the finger under the sternum from above and below to allow for safe passage of the sternal saw. Ventilations are temporarily suspended, the hook of the saw is engaged at the suprasternal notch, and upward traction is maintained as the sternum is divided in the midline. The sternum is then gently spread manually, and the Finochietto chest wall retractor is spread in the upper part of sternum with the opening facing superorly.
The pericardium is divided to expose the heart and the root of the aorta so that they may be inspected for any injuries. Just superior to the investment of the pericardium on the aorta, the left innominate vein is encountered. A vessel loop is placed around it in order to aid with retraction and exposure to the aortic branches. Once the innominate vein is isolated with a vessel loop, it is retracted and the innominate artery, which is located anteriorly on the right side of the aortic arch, can be carefully dissected.
A vessel loop is then used to isolate the innominate artery at its origin. Distal to the innominate artery, on the aortic arch, is the origin of the left common carotid artery. The left common carotid artery is similarly dissected and isolated using a vessel loop. Note the relatively posterior and lateral position of the left subclavian artery.
Because of its location, exposure through a median sternotomy is challenging and may require extension of the sternotomy over the left clavicle. The origins of the major branches of the aortic arch are now completely exposed and isolated, yielding proximal control if necessary secondary to an injury located more distal on the vessels. If exposure of the superior vena cava is required, the left innominate vein is dissected to its convergence with the right innominate vein becoming the superior vena cava.
Note the near perpendicular relationship between the left innominate vein and the superior vena cava. Superior vena cava injuries should always be repaired as ligation is associated with unacceptable morbidity and mortality. Distal exposure of the innominate artery through a median sternotomy is challenging and may require extension of the sternotomy over the right clavicle to expose the takeoff of the right subclavian artery, or over the right neck to expose the takeoff of the right common carotid artery.
Demonstrated here is the distal most extent of exposure of these vessels through a sternotomy. The right common carotid artery is first dissected and isolated using a vessel loop. Note the location of the right recurrent laryngeal nerve as it loops around the right subclavian artery during exposure. Care should be taken to preserve this nerve during the exposure.
Next, a vessel loop is used to isolate the proximal right subclavian artery. Although routine ligation of the left innominate vein is not necessary during exposure of the mediastinal vessels, if it is injured or preventing adequate exposure for repair of the vessels, ligation is generally well-tolerated with arm edema being the most common sequelae. Repair of injuries should only be attempted if able to be performed without stricture greater than 50%, as this will lead to increased risk for DVT and PE.
Segment:5 Tips and Pitfalls.
A median sternotomy provides excellent exposure to the aortic arch and its branches. In patients presenting without vital signs, a left anterolateral thoracotomy, or resuscitative thoracotomy incision, should be used for exposure and extension to a clamshell thoracotomy can facilitate exposure of the mediastinal vessels. With a clamshell thoracotomy incision, remember to ligate the internal mammary arteries. Intraoperative air embolism is a common and potentially lethal complication because of negative venous pressure in the severely hypovolemic patient.
Early control of venous injuries is recommended to decrease the risk of air embolus. Primary repair of the aortic arch branches is preferred if possible without stenosis greater than 50%. If not, a synthetic graft should be utilized. Injuries of the descending thoracic aorta are best approached with a left posterolateral incision. Thank you.