Hume Memorial LecturePrevention of spinal cord complications in aortic surgery
Section snippets
Anatomy
Knowledge of the arterial blood supply of the spinal cord is essential to an understanding of the pathophysiology of paraplegia occurring after operations on the aorta. The spinal cord, like the entire central nervous system, has a maximum ischemic time of 8 minutes, as estimated from the animal model.4 Three spinal arteries, one anterior and two posterior, arise cephalad from branches of the vertebral arteries and run lengthwise, ending in a conus plexus of lumbosacral branches (Figure 1). 5
Coarctation
This congenital aortic lesion is generally recognized and repaired in infancy or childhood by excision of the coarcted area with end-to-end anastomosis or patch aortoplasty. Enlarged intercostals around the lesion usually provide adequate collateral flow during aortic cross-clamping. However, if the coarcted area is not very stenotic, the collaterals may not have enlarged enough to be adequate during cross-clamping to supply the distal cord with the resulting complication of paraplegia.
Traumatic rupture of the descending thoracic aorta
Thoracic isthmic aortic rupture after blunt trauma results in a posterior tear or complete aortic separation, which may be held in place by adventitial tissue just distal to the ductus arteriosus. Early recognition and timely operation may allow direct repair of a tear, but often an interposition graft is necessary.12, 13 Some surgeons use the “clamp and go” technique without an adjunct bypass.14, 15, 16 Although the incidence of paraplegia with cross-clamp times of over 30 minutes exceeds 10%,
Localized descending thoracic aneurysm
The first successful resection of a thoracic aneurysm of the descending aorta was performed by Lam and Aram24 in 1951 (Figure 3). An internal Lucite tube was used to conduct blood through an aortic homograft as it was inserted in place of the aneurysm (Figure 4). The procedure required 24 minutes of cross-clamping to insert the temporary Lucite bypass with resulting partial paraplegia. This operation was not only the first reported thoracic aortic resection with grafting, but also the first
Thoracoabdominal aneurysmectomy
The first thoracoabdominal aneurysmectomy (type 4) was performed by Etheredge et al25(Figure 5) in 1954 by use of a homograft, using a temporary aorto-aorta shunt and inserting the celiac and superior mesentery arteries (SMAs) separately into the graft (Figure 6). An aortogram 11 years later showed wide patency of all anastomoses. Subsequently, many surgeons have made numerous contributions to the successful expansion of the field to include aneurysmectomy of the entire descending and
Infrarenal aortic surgery
In 1957, Adams and von Geertruyden55 presented a review of paraplegia after aortic surgery, in which they stated that it does not occur in infrarenal surgery. However, in the discussion of the paper, McCune mentioned two such cases. Both patients had ruptured abdominal aortic aneurysms he observed that extended into the external iliac arteries, so that it was impossible to reestablish either hypogastric artery. He also speculated that the hypogastric vessels may supply some circulation to the
Comments
Although advances in the surgical management of diseases of the aorta over the past decade have lowered the incidence of postoperative paraplegia, its incidence remains unacceptably high. Although use of both the inclusion and segmental clamping techniques has been widely accepted, additional ancillary modalities continue to be debated. Further experience with the use of evoked potentials, selective spinal cord cooling, deep hypothermia with circulatory arrest, and selective angiography to
Conclusions to minimize paraplegia
- 1.
Coarctation
In an infant or child, measure clamped distal aortic pressure. If it is below 50 mm Hg, use simple aorto-aorta bypass. In an adult, use left heart bypass with centrifugal pump, without heparin.
- 2.
Localized Descending Aorta Aneurysm or Traumatic Tear
Employ left heart bypass with centrifugal pump, without heparin.
- 3.
Extensive Thoracic or Thoracoabdominal Aneurysm
- 3.1.
Obtain preoperative selective angiogram of artery of Adamkiewicz, if available.
- 3.2.
Employ inclusion and sequential clamping.
- 3.3.
Employ
- 3.1.
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2013, Journal of Cardiothoracic and Vascular AnesthesiaCitation Excerpt :As depicted in Figure 1, the time to spinal cord injury with ischemia varies with the residual blood flow. A complete loss of blood flow may result in spinal cord neuronal death in about 8 minutes,59 with incomplete ischemia resulting in paralysis usually after 15 minutes. As cross-clamp time increases, a gradual increase in the risk and severity of paralysis occurs until approximately 60 minutes when the incidence of paralysis is nearly 100%.60,61