Critical Care Medicine-Neurologic Disorders>>>>>Vascular Disorders
Question 3#

A 78-year-old female with a previous history of a thoracic endovascular aortic repair (TEVAR) complicated by endoleak presents to the ICU after undergoing additional endovascular graft placement for extension of the original repair.

Which of the following IS NOT a risk factor for postoperative spinal cord ischemia (SCI)?

a. History of prior aneurysm repair
b. Extension of the repair to include coverage of the left subclavian artery
c. Mild intraoperative hypothermia
d. Pre-existing chronic renal insufficiency

Correct Answer is C

Comment:

Correct Answer: C

The risk of SCI following thoracic endovascular aortic repair (TEVAR) is ∼10%. Early identification and treatment of this devastating complication is critical in preventing permanent neurologic deficit. Prior aneurysm repair (A), magnitude of the repair, coverage of the left subclavian artery (B), and pre-existing chronic renal insufficiency (D) have all been shown to have higher incidences of SCI post TEVAR. Spinal cord perfusion is dependent on one anterior and two posterior spinal arteries as well as a cervical vascular network proximally and pelvic vascular network distally. Proximal supply to the cervical vascular network is via the subclavian arteries that give rise to the vertebral arteries and then the anterior spinal artery. Thus, left carotid subclavian artery bypass should be considered before TEVAR when the proximal stent graft is expected to cover the origin of the left subclavian artery. The distal spinal cord is supplied by a pelvic vascular network, which arises from the lumbar and sacral arteries and forms a collateral network with branches of the inferior mesenteric and hypogastric arteries. Disruptions of either the proximal or distal collateral networks can place watershed areas of the spinal cord at risk of ischemia.

Strategies that increase spinal cord perfusion pressure (mean arterial pressure minus cerebrospinal fluid [CSF] pressure) as well as decrease metabolism and oxygen demand can reduce SCI post repair. Mild hypothermia (C) decreases metabolism and oxygen demand and would therefore be protective rather than a risk factor for developing postoperative ischemia.

CSF drainage is one intervention that can increase spinal cord perfusion pressure and potentially decrease the incidence of SCI after TEVAR. A recent Cochrane review in 2012 based on three randomized controlled trials of 287 patients examined the role perioperative drainage of cerebrospinal fluid in patients undergoing thoracoabdominal and thoracic aortic aneurysm repair. It is the mainstay of neuroprotection along with additional strategies that increase spinal cord perfusion pressure and oxygen delivery, such as augmentation of the mean arterial pressure and correction of severe anemia.

Postoperative SCI is a potentially devastating complication following TEVAR. Maintaining or augmenting spinal perfusion pressure and reducing metabolic demands are the mainstays of therapy for both prevention and treatment.

References:

  1. Ullery BW, Cheung AT, Fairman RM, et al. Risk factors, outcomes, and clinical manifestations of spinal cord ischemia following thoracic endovascular aortic repair. J Vasc Surg. 2011;54(3):677-684.
  2. Feezor R, Martin T, Hess P, et al. Extent of aortic coverage and incidence of spinal cord ischemia after thoracic endovascular aneurysm repair. Ann Thorac Surg. 2008;86:1809-1814.