Nagelhout Ch. 28 Thoracic Aortic Aneurysms Flashcards

Vessel Wall Layers

• The vessel wall consists of three layers: tunica adventitia, tunica media, and tunica intima.

Aneurysm Types

• False aneurysms involve only the adventitia layer.
• Fusiform aneurysms have a spindle-shaped bulge.
• Saccular aneurysms feature a sac-like bulge on one side.

Aortic Dissection

• Aortic dissection is characterized by a tear in the intima, allowing blood to flow through a false passage.

Dissection Classifications

• Debakey Classification:
  • Type I: Originates in the ascending aorta, may extend to the aortic arch and descending aorta.
  • Type II: Starts and is confined to the ascending aorta.
  • Type III: Originates in the descending aorta and extends distally.
• Stanford Classification:
  • Type A: Involves the ascending aorta.
  • Type B: Does not involve the ascending aorta.

Thoracoabdominal Aneurysms

• Crawford classification identifies five types based on the anatomical location of the aneurysm relative to the renal arteries and intercostal spaces.

Causes of Aneurysms

• Atherosclerosis is the most common cause of aneurysms.
• Descending and distal thoracic aorta aneurysms are the most prevalent types, commonly fusiform.

Diagnosis and Symptoms

• Symptoms include pain, stridor, hoarseness, and cough due to compression of thoracic structures.
• Aortic insufficiency may occur with ascending aneurysms.
• Diagnosis is made using CT or MRI imaging.

Surgical Interventions

• Resection of the ascending aorta requires cardiopulmonary bypass (CPB) and administration of heparin.
• Aortic valve replacement may be necessary when the aneurysm is near the aortic arch.
• Circulatory arrest is indicated to protect cerebral perfusion in cases of transverse arch aneurysms.

Anesthesia and Monitoring

• Anesthesia for descending thoracic aneurysm repair involves a double lumen tube and a left lateral decubitus position.
• A-line and pulse oximetry should be monitored on the right side to avoid complications from left subclavian impingement.

Dissection and Surgical Risks

• Hypertension is a significant factor contributing to aortic dissection and vessel wall integrity loss.
• Surgical treatment for type A dissections is necessary due to high rupture risk.
• Repair of descending thoracoabdominal aneurysms is recommended at sizes of 6 cm or greater.

Postoperative Considerations

• Poor surgical outcomes correlate with renal, cardiac, and neurological dysfunctions.
• Preoperative renal function is crucial for predicting post-operative renal failure.
• Paraplegia is one of the most severe consequences following thoracic aortic surgery.

Neurological Considerations

• Hoarseness may occur due to left recurrent laryngeal nerve involvement, which is closely related to the aortic arch.
• Establishing CSF access through lumbar drains can help monitor intracranial pressure.
• Monitoring spinal cord perfusion pressure is essential; it is calculated as arterial BP minus CSF pressure.

Preventing Spinal Cord Injury

• Efforts to mitigate spinal cord injury risk include SSEP and MEP monitoring, CSF drainage, mild hypothermia, and reattachment of intercostal arteries.
• Immediate and delayed spinal cord injuries can occur, influenced by dissection type, cross-clamp time, and surgical techniques.

Complications

• Early complications post-thoracoabdominal aortic aneurysm repair include respiratory failure, myocardial infarction, and early paraplegia.
• Late complications can include delayed paraplegia, graft thrombosis, and infection.

Postoperative Management

• After surgery, replace the double lumen tube with a single lumen unless airway edema is observed.
• Monitor for recurrent laryngeal nerve damage which could lead to respiratory issues during extubation.