TSRA Content:
Authors: Sasha Kraev, MD, and Charles Shieh, MD
This is a revision and update from the previous edition of the TSRA Primer in Cardiothoracic Surgery written by Lina Elfaki, MD, Candidate MSc, and Najah Adreak, MD, MSc.
For most open cardiac surgical procedures, the patient is positioned supine on the operating table. Minimally invasive and open thoracoabdominal aortic surgeries may deviate from this. Placing intra-operative monitors is a key part of cardiac surgical preparation.
These are as follows:
1. EKG leads placed outside of the field
2. Intra-aortic balloon pump leads
3. Oximetry monitoring peripherally with near infrared spectrometry and end tidal CO2 measured off the endotracheal tube
4. Sedation and EEG-derivative monitors
5. Radial arterial line is preferred and left, and right preference depends on the operation. For some aortic cases, multiple arterial lines might be necessary, including a femoral line
6. Blood pressure cuff placed on the arm opposite to the arterial line
7. Central venous access and/or pulmonary artery catheter (a SWAN-GANZ catheter) closely monitor cardiac function. Newer generation continuous cardiac output and hemodynamics monitors can be used as well.
To provide the best access to the surgical field for the surgeons and assistants, the right and possibly the left arm are to be tucked at the side with padding. Care must be taken to pad all the joints and to protect all the monitoring equipment. A shoulder roll or donut-shaped head pad should be positioned behind the scapulae to open the angle between the chin and the sternum. Pads should be placed behind the patient’s knees to keep them in a neutral position. Warming pads can be placed under the patient. Defibrillator pads are needed for emergency defibrillation when internal defibrillation is not possible. This is especially true for re-do and minimally invasive operations. Regardless of the operation planned, the patient should be prepped with antiseptic from chin down to the knees to allow quick access to the groin vessels for emergency peripheral cannulation and to the proximal saphenous veins for urgent conduits. For coronary artery bypass grafting, both legs should be prepped circumferentially for vein harvesting. The patient is then draped by the surgical team.
Once the patient is draped, other monitoring lines are brought on the field.
These include:
● Retrograde cardioplegia pressure line and other pressure monitors as necessary
● Pacemaker and internal defibrillator cables passed off to anesthesia
● CO2 infusion line, when used, is connected to the tank
● Cell-saver suction, waste suction, and bovie cauteries are passed to the circulating nurse
● Cardiopulmonary bypass lines are passed to the perfusionist and secured to the drapes
Types of Surgical Incisions
Median Sternotomy:
This is the most common approach for cardiac and aortic arch procedures, usually extending from the jugular notch to the xiphoid process. It is also utilized for management of traumatic chest injuries. Given its wide utility, the remainder of the chapter will focus on this incision.
Clamshell Incision (Bilateral Transverse Thoracosternotomy):
This is an alternative approach to expose the heart and pleural space. This incision is used for double lung and heart-lung transplants as well as ascending aorta, aortic arch and descending thoracic aorta procedures when made through the fourth intercostal space. It involves a bilateral submammory incision through the fourth or fifth intercostal space and extends through the pectoralis major muscles to enter the hemithoraces. A drawback is that it requires ligation of the internal thoracic arteries for sternal division.
Anterolateral Thoracotomy:
This incision exposes the right side of the heart. On the right side, it is utilized for Blalock-Hanlon atrial septectomy or valvular replacement following a median sternotomy. On the left side, it is useful for isolated bypass grafting of the circumflex artery or mitral valve replacement. The patient lies supine, and the right chest is elevated using a roll beneath the shoulders. The incision can be extended across the midline through the sternum if needed. Aortic arterial and bicaval venous cannulation is done, while cardioplegia.
How to Perform a Sternotomy
Median sternotomy is a basic skill not only for cardiac surgery, but also for other thoracic operations . There are many steps that are dependent on surgeon preference. The most important part to performing a sternotomy is to stay midline. This starts with marking of the incision. Palpate the sternal notch and the xiphoid. Draw a line connecting the two. Palpate the edges of the sternum to make sure that the line is in fact midline over the sternum. Hold the #10 blade like a violin bow and make the incision in a stroke motion. The length of the incision depends on the exposure desired, but most often it will go from just below the sternal notch to the xiphoid process. Extending the superior extent of the incision along the anterior border of the sternocleidomastoid muscle exposes the aortic arch for arch procedures while a perpendicular extension of the incision through the third intercostal space exposes the proximal descending thoracic aorta.
Once the skin incision is made, the incision is deepened to the periosteal fascia using a bovie cautery. Use your index and middle finger to pull apart the lateral edges of the incision and provide counter traction as you deepen your incision layer by layer. The midline will be identified by the decussation of fibers. If you note that you are cutting through muscle, stop and reassess your midline as you are likely off of midline. Dissect the xiphoid process then move upwards to dissect the sternal notch from the connective tissue band at its top. The saw easily cuts the bone, but it will get caught up in the soft tissues, soone should be able to pass their finger under the sternal notch and xiphoid process with no soft tissues in the way. There are no major blood vessels, but one can find multiple vein perforators that can be clipped, or addressed with an aggressive bovie cautery. Beware of a high-riding innominate artery in elderly females and do not cauterize too deep. Free the xiphoid in the same fashion.
Once the sternal notch and the xiphoid are free, the midline should be re-established. Palpate the edges of the sternum again. If there are still layers in the way, a tonsil or other sharp instrument can be used to feel the insertion of the ribs and passed in the interspace on both sides. This will orient you to the midline. Use the bovie cautery to mark the midline in multiple spots. Use the bovie cautery to connect the dots down to the periosteum. This will mark the line the saw will pass.
Make sure the sternal saw works. Ask the anesthesiologist to hold respirations to drop the lungs back and prevent their injury. The sternal saw usually has a hook that can be placed around the sternal notch. The blade of the saw should be at a slight upward angle to pull up the sternum and avoid injuring the innominate vein. Once positioned, start the saw and guide it down the midline established previously with the bovie cautery. It is ok to go slow. You want to avoid jerking movements or a wavy incision. Good preparation with the cautery line will help guide you. Don't forget to tell the anesthesiologist to resume respirations once the sternotomy is complete. Push the sides of the sternum apart with your fingers. With a little tug, there should be enough mobility and space established. This is usually the most hemorrhagic part, so use the cell-saver and place a lap pad under the sternum to tamponade any bleeders. Spread the sternum; use the bovie to stop bleeding from the periosteal edges. Use bone wax, rolled up gelfoam, or vancomycin paste to control bleeding from the sternal bone marrow. Once bleeding is controlled, the sternal retractor can be placed.
With the sternotomy retractor in place, control the bleeding from the underside of the sternum. There is usually a lot of bleeding from the strap/infrahyoid muscles above the sternum. Liberal use of electrocautery is necessary. Vascular clips might be required. Bleeding should be controlled in the sub-xiphoid layers of the wound as well. Missing a pumping vessel in those locations is an opportunity to avoid bringing the patient back to the OR for bleeding.
Repeat Sternotomies
Repeat sternotomies are challenging because of the adhesions that form following the first procedure between the heart and the chest wall. Therefore, caution is needed when opening the chest to avoid injuring the heart. Initial peripheral cannulation – axillary or femoral artery and femoral vein for adults - provides a safety measure in case a major vessel is injured upon sternal re-entry.
Complications of a Sternotomy
Median sternotomy complications are rare given how commonly this approach is used in cardiac surgery. However, peri-operatively, caution must be taken to avoid opening the pericardium and injuring the innominate vein with the saw. It is also important to ensure a midline incision. Insufficient closure of the sternum thereafter puts the patient at risk of sternal complications. Post-operatively, these include sternal wound infection, bleeding, dehiscence, brachial plexus injury, and keloid scarring. If the edges are not aligned properly, the bone is ischemic, or the sternotomy incision is not midline, the sternal wound may not heal appropriately. This is associated with sternal dehiscence and wound infections, which may require debridement and reclosure. Patients at highest risk of poor wound healing include those with diabetes, obesity, continued smoking, osteopenia, immunosuppression, and chronic pulmonary disease. Technical factors associated with poor healing include internal thoracic artery harvest and excessive electrocautery use. To prevent dehiscence and infection peri-operatively, ensure the sternotomy incision is midline and sternal wires are appropriately placed transsternal. In higher risk patients or non-midline incisions, sternal plating can be utilized with screws across the sternum. Post-operatively, smoking cessation and optimized glycemic control improve sternal perfusion and promote healing.