Chapter 35

Temporary thoracic aortic occlusion should be performed during an Emergency Department thoracotomy for hypovolemic shock. It preserves cerebral and coronary artery perfusion pressure.1 The blood flow to the viscera below the cross clamp, however, falls to less than 10 percent of baseline flow.2 This can be advantageous since it stops distal hemorrhage, but it can later result in the undesired metabolic consequences of acidosis, hyperkalemia, and multiple organ system failure.3,4

The aorta begins at the left ventricle and gives rise to the arteries of the body, directly or indirectly (Figure 35-1). It leaves the ventricle and is directed upward as the ascending aorta. It arches to the left and backwards at the level of the sternal angle to become the aortic arch. The arch gives rise to the brachiocephalic trunk, left common carotid artery, and left subclavian artery. The aortic arch is directed inferiorly after giving rise to the left subclavian artery and is known as the descending aorta. The descending aorta is subdivided into the thoracic portion above the diaphragm and the abdominal portion below the diaphragm. It descends through the posterior mediastinum, lying first against the left side of the fifth thoracic vertebral body. As it descends, it gradually approaches the midline of the 12th thoracic vertebral body, at which point it passes through the diaphragm.

###### FIGURE 35-1

Anatomy of the aorta and surrounding structures of the mediastinum and left hemithorax. The mediastinal pleura has been removed to visualize the underlying structures.

The esophagus is a thin, muscular tube measuring approximately 2.0 to 2.5 cm in diameter. It descends along the vertebral bodies. It travels forward, away from the vertebral bodies, and to the right at the level of the ninth thoracic vertebral body. It traverses the diaphragm at the level of the 10th thoracic vertebral body. It lies posterior and medial to the descending thoracic aorta throughout most of its course. It migrates as it travels distally, so that its lower part lies in front of the aorta just above the diaphragm (Figure 35-1).

The primary reason to occlude the descending thoracic aorta is to temporarily direct blood flow from below the diaphragm to preserve flow to the brain and heart. The descending thoracic aorta may be occluded in patients with penetrating thoracic or abdominal trauma in which hypovolemic shock and clinical deterioration are not responsive to aggressive fluid resuscitation and blood transfusion. These patients should have the appropriate indications to perform an anterolateral thoracotomy (Chapter 31). The thoracic aorta may also be occluded immediately prior to laparotomy if the patient has a tense abdomen filled with blood. The abdominal incision will decompress the abdomen and result in hypotension, decreased coronary and cerebral perfusion pressure, exsanguination, and death. Uncontrollable hemorrhage below the diaphragm can be controlled by temporarily ...

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