Chapter 15 – Cardiac Injuries




Abstract






  • The pericardium envelops the heart and attaches to the roots of the great vessels. This includes the ascending aorta, pulmonary artery, pulmonary veins, the last 2–4 cm of superior vena cava, and inferior vena cava.
  • The phrenic nerves descend on the lateral surfaces of the pericardium.
  • Acute accumulation of as little as 200 mL of fluid in the pericardial sac may result in fatal cardiac tamponade.
  • The right atrium is paper thin, approximately 2 mm. The left atrium is slightly thicker at approximately 3 mm.
  • The right ventricle is approximately 4 mm thick and the left ventricular wall thickness is approximately 12 mm.
  • The two main coronary arteries, left main and right coronary arteries, originate at the root of the aorta, as it exits the left ventricle. The left main coronary artery divides into the left anterior descending artery (LAD) and the circumflex artery, and provides blood supply to the left heart. The right coronary artery divides into the right posterior descending and acute marginal arteries, supplying blood to the right heart, as well as the sinoatrial and atrioventricular nodes responsible for regulating cardiac rhythm.





Chapter 15 Cardiac Injuries


Demetrios Demetriades , Zachary D. Warriner , and Scott Zakaluzny



Surgical Anatomy




  • The pericardium envelops the heart and attaches to the roots of the great vessels. This includes the ascending aorta, pulmonary artery, pulmonary veins, the last 2–4 cm of superior vena cava, and inferior vena cava.



  • The phrenic nerves descend on the lateral surfaces of the pericardium.



  • Acute accumulation of as little as 200 mL of fluid in the pericardial sac may result in fatal cardiac tamponade.



  • The right atrium is paper thin, approximately 2 mm. The left atrium is slightly thicker at approximately 3 mm.



  • The right ventricle is approximately 4 mm thick and the left ventricular wall thickness is approximately 12 mm.



  • The two main coronary arteries, left main and right coronary arteries, originate at the root of the aorta, as it exits the left ventricle. The left main coronary artery divides into the left anterior descending artery (LAD) and the circumflex artery, and provides blood supply to the left heart. The right coronary artery divides into the right posterior descending and acute marginal arteries, supplying blood to the right heart, as well as the sinoatrial and atrioventricular nodes responsible for regulating cardiac rhythm.





Figure 15.1 Surface anatomy of the heart and great vessels. Note the attachment of the pericardium to the roots of the major vessels. IVC, inferior vena cava; LADA, left anterior descending artery; RCA, right coronary artery; SVC, superior vena cava.



General Principles




  • Cardiac injuries are highly lethal and most victims die at the scene. In those who survive to the emergency department, immediate diagnosis and surgical intervention remain the cornerstones of survival. The diagnosis is based on clinical examination and the FAST (Focused Assessment Sonography for Trauma) exam. There is no role for diagnostic pericardiocentesis in a hospital environment, and those with questionable injuries should undergo formal echocardiogram.








    Figure 15.2 (a, b) Subxiphoid cardiac view obtained via FAST (Focused Assessment with Sonography for Trauma) exam demonstrating cardiac tamponade. Hypoechoic hemopericardium is visualized between the myocardium and pericardium.




  • Most patients with cardiac injuries have no signs of life or present with severe hypotension on arrival. If there is a short prehospital time or small cardiac injury, the patient may arrive with normal initial vital signs.



  • The majority of cardiac injuries are due to penetrating trauma from stab wounds or gunshot wounds. Stab wounds usually involve the right ventricle and gunshot wounds often damage multiple chambers or internal cardiac structures. Cardiac rupture due to blunt trauma is usually fatal and the victims die before reaching medical care. Blunt injuries are predominantly right-sided.



  • Patients with no vital signs or imminent cardiac arrest on arrival should be managed with a resuscitative emergency room thoracotomy (see Chapter 4 Emergency Room Resuscitative Thoracotomy).



  • Cardiac bypass is almost never required during the initial operation for cardiac repair. The use of temporary intra-aortic balloon pump augmentation or ECMO may be considered in ongoing cardiogenic shock.



  • Injuries to the low-pressure cardiac chambers may be complicated by air embolism. Look for air bubbles in the coronary veins. If seen, place the patient in Trendelenburg position and aspirate the right ventricle.



Special Surgical Instruments




  • The emergency room thoracotomy tray should be kept simple, with only the absolutely necessary instruments (scalpel, Finochietto retractor, two Duval lung forceps, two vascular clamps, one long Russian forceps, four hemostats, one bone cutter, one pair of long scissors, one pair of suture scissors). In addition, good lighting, working suction, and an internal defibrillator should be immediately available.



  • In the operating room, the thoracotomy trauma tray should include a power sternal saw, Lebsche knife with hammer, and bone cutter. The surgeon and skilled assistant should wear a headlamp for optimal lighting in anatomically difficult areas.





Figure 15.3 Instruments required for median sternotomy: sternal power saw, Lebsche knife, hammer, Finochietto retractor.



Patient Positioning




  • For an emergency room left thoracotomy, the patient remains supine on the gurney, with the left arm abducted or elevated above the head. Antiseptic solution is applied on the skin over the anterior chest and bilateral hemithoraces. There is no time for draping or meticulous antiseptic precautions.



  • In the operating room, the patient is placed in the supine position with both arms abducted at 90° to allow anesthesia access to the extremities. The left arm may be elevated further above the head if a left anterolateral thoracotomy is to be performed. The skin preparation and draping should include the anterior chest and both hemithoraces. The abdomen should be included if there are suspected associated intra-abdominal injuries.



Incisions




  • The choice of incision depends on the clinical condition of the patient, the location of the operation (emergency room or operating room), the need for thoracic aortic cross-clamping, and the suspected anatomical site of cardiac injury.



  • Patients transported to the emergency room with no vital signs or in imminent cardiac arrest should undergo an immediate left anterolateral thoracotomy on the gurney. This incision is fast, does not need power instruments, and allows cross-clamping of the thoracic aorta for resuscitation purposes (see Chapter 4).



  • In most patients undergoing operation in the operating room, a median sternotomy is the incision of choice. It provides good exposure to the heart and both lungs, it is relatively bloodless, and is associated with less postoperative pain and fewer complications. However, the exposure of the posterior heart or cross-clamping of the aorta may be difficult.



  • A left thoracotomy in the operating room is preferable to sternotomy in patients who might need cross-clamping of the aorta or in suspected cases of injury to the posterior wall of the heart.



  • Extension of the left thoracotomy into the right chest to create a clamshell incision may be required in patients with bilateral chest trauma (see Chapter 14), or if exposure of the mediastinal vessels from the left chest alone is inadequate.


Figure 15.4



(a) Median sternotomy incision extends from the suprasternal notch superiorly to the xiphoid process inferiorly, and is carried down to the sternum.





(b) The sternum is scored in the midline to guide the sternal saw.



Median Sternotomy Incision


Sep 4, 2020 | Posted by in EMERGENCY MEDICINE | Comments Off on Chapter 15 – Cardiac Injuries
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