Anesthesia for Thoracic and Abdominal Aneurysms
Thoracic aortic lesions occur in two major types; saccular and fusiform aneurysms and aortic dissections. The most common sites for fusiform and saccular aneurysms are just distal to the left subclavian artery, but they may occur in the ascending, arch, or descending thoracic aorta. Among the causes of saccular and fusiform aneurysms are syphilis, atherosclerosis, trauma, aortic valve disease, coarctation, infection, aortitis, or cystic medial degeneration. The elastica of the aorta is weakened so that the pressure of blood causes dilatation of the wall. Stagnant and turbulent blood flow next to the wall may line the aneurysm with clot. Thoracic aortic dissections result from cystic medial necrosis, with mucoid and cystic degeneration of the elastic fibers in the media of the aorta. Diseases such as hypertension, Marian’s syndrome, Takayasu’s disease, coarctation, or aortic hypoplasia are often associated with thoracic aortic dissection. Trauma, pregnancy, or atherosclerosis are less common etiologies. The dissection begins with a large tear in the aortic intima through which dissecting blood disrupts the media and peels the intima from the adventitia over a varying length of aorta. Aortic dissections are classified according to location: type I begins in the ascending aorta, but the dissection may extend throughout the aorta; type II is limited to the ascending aorta; type III begins in the descending aorta (Figure 18.1) (27).
KeywordsAortic Arch Aortic Dissection Thoracic Aorta Abdominal Aortic Aneurysm Left Subclavian Artery
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