Sternotomy - pediagenosis
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Saturday, June 1, 2019

Sternotomy


Sternotomy

Step 1. Operative Steps
Full Sternotomy
  The most essential consideration in performing a sternotomy is that it is done through the midline. The suprasternal notch and xyphoid process are used as landmarks. The latter sometimes has an asymmetric configuration and therefore it is helpful to control the edge of the ribs on both sides to find the middle. A paramedian sternotomy may be harmful to the sternum and is a significant risk factor for sternum instability, which could lead to disturbances in wound healing.

    The patient is placed supine on the operating table. A linear incision is made from just above the sternal angle to the level of the xiphoid process. Subcutaneous fat and presternal fascia are divided, and the linea alba is divided inferiorly about 2 to 3 cm to obtain adequate exposure of the pericardium (Fig. 1.1). It is essential to divide the interclavicular ligament at the top of the suprasternal notch using electrocautery. Special attention should be taken to identify the veins crossing this area—the jugular venous arch. Injury of the veins in this area could injure other important structures, such as the trachea or brachiocephalic artery, if the bleeding is not controlled, especially if the view is limited due to small incisions. There are also veins crossing the upper part of the xyphoid cartilage, which should be identified and cauterized. The midline of the sternum is marked by electrocautery. Scissors could be used to divide the xyphoid process separately. The sternum is divided with a saw in a caudocranial fashion, with close attention paid to staying on the midline. The sternum could be also be divided in a craniocaudal fashion, changing the direction of the saw blade.
 It is prudent to ask the anesthesiologist to stop the mechanical ventilation to avoid unnecessary opening of the pleura with the saw. The saw should be lifted slightly against the posterior plate of the sternum, and care should be taken to avoid injury to the pericardium, thymus, and innominate vein. If the peritoneum is opened accidentally, it is important to close the peritoneum expeditiously to avoid fluid incorporation and subsequent adhesion in the peritoneum. Extension of the incision cranially facilitates exposure of the arch and supraaortic vessels. On the other hand, the gastroepiploic artery could be harvested, extending the incision into the peritoneal space.
   In patients with previous cardiac procedures, extra attention must be paid not to injure the cardiac structures, which could lead to hemorrhagic shock or an air embolism, with lethal consequences. Careful blunt dissection may be performed below the xyphoid process to free the pericardial and pleural adhesions. Gentle elevation of the sternum with sharp hooks or unloading and establishing a cardiopulmonary bypass (CPB) over the femoral vessels may be advisable in select cases as a safeguard. In case of redo, computed tomography (CT) and magnetic resonance imaging (MRI) are helpful imaging modalities to evaluate the risk of reentry.
  After sternum division, hemostasis is obtained by cauterizing the periosteal surface of the sternum. Bone wax may be used to seal the bone marrow and control bleeding, although some surgeons prefer to simply apply a towel.
 In redo cases, it is crucial to dissect the attachment to the edge of the sternum before retracting because the retraction could injure structures, such as the lung or innominate vein through tension.

Figure 1.1 Standard median sternotomy. Identification and division at the middle of the sternum is the A and O. The skin incision could be reduced to ca. 10 cm and still divide the sternum completely.


Step 2. Partial Sternotomy
  An upper or lower partial sternotomy may be used for certain procedures, such as isolated aortic or mitral valve repair or replacement or bypass surgery with certain target vessels. The sternum could be divided into different patterns through the third or fourth intercostal space—J shape, L shape, or inverted T shape (Fig. 1.2). The fourth intercostal space usually enables a good exposure of the aorta and root to be obtained. Access to the right atrium could be limited, which makes direct insertion of the venous cannula into the appendage of the right atrium laborious. It is important to have the option to cannulate the femoral vein if exposure of the right atrium is not sufficient, especially in the case of a smaller incision through the third intercostal space. Venting through the pulmonary artery may be useful in select cases with limited access to the upper right pulmonary vein.
 A small incision has the advantage of reducing the wound area and preventing wound infections due to sternum instability, reducing the requirement for a blood transfusion, and shortening the stay in the intensive care unit. Small incisions are also preferred by the patients for cosmetic reasons.
A partial sternotomy gives good exposure of the aortic root and could be selected to reduce the incidence of sternum instability and wound infection.
Figure 1.2 A partial sternotomy gives good exposure of the aortic root and could be selected to reduce the incidence of sternum instability and wound infection.


Step 3. Sternotomy Closure
    At the end of the procedure, chest drains are placed through separate stab incisions at the epigastrium. Care must be taken so that the drain passes through the fascia of the rectus muscle, avoiding the epigastric pedicle. If necessary, chest drains for the pleura should be placed through the fifth or sixth intercostal space or through a subcostal tunnel from a stab incision below the costal arch.
    After thorough hemostasis and placement of chest drains, the sternum is closed using six to eight stainless steel wires. Consideration for ensuring the stability of the manubrium is essential. The risk of cutting by wires could be reduced through placement of the wires through the intercostal space. Care should be taken to stay close to the edge to minimize the risk of injury to the internal thoracic artery. Bands or plates could be used as an alternative to the wires to stabilize a fragile sternum with osteoporosis, or a paramedian sternotomy could be carried out in select cases.
    The insertion sites of the wires are controlled for bleeding. The wires are tied individually or by putting two together in a figure-of-eight fashion. Reinforcement of the sternum edge is advisable in case of asymmetric division of the sternum by placing an extralongitudinal wire at both sides of the sternum to avoid cutting through the wire, as proposed by Robicsek et al.3 (Fig. 1.3). Wire tips are then buried in the presternal fascia. The linea alba is closed using running or interrupted fascia closure sutures, and the subcutaneous tissue is closed using absorbable sutures. Skin closure is performed using subcuticular sutures or skin staples.

Figure 1.3 Closure of the sternum with additional bilateral longitudinal wires for reinforcement introduced from Robiscek.


Keywords : Cardiac Surgical Techniques, Surgical Incisions, Basic Techniques, sternotomy, partial sternotomy, lateral anterolateral thoracotomy, posterolateral thoracotomy, Thoracotomy, Approaches in Thoracotomy, Thoracotomy Closure, Further Considerations


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