J Cardiovasc Surg
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Review
Spinal cord ischemia in open and endovascular thoracoabdominal aortic aneurysm repair: new concepts.
For more than half a century ischemic spinal cord injury (SCI) and consecutively permanent paraplegia remained the most devastating complication after open and endovascular thoracoabdominal aortic aneurysm (TAAA) repair. Various neuroprotective strategies (e.g., motor-/somatosensory evoked potential monitoring and cerebrospinal fluid drainage) used as adjuncts have lowered the SCI; maybe most importantly, the modern collateral network (CN) has begun to replace the classic understanding of spinal cord blood supply implying several consequences. ⋯ Currently, two promising new concepts--potentially advancing spinal protection in open and endovascular TAAA repair--address these issues: 1) non-invasive real-time monitoring of the paraspinous CN-oxygenation via near-infrared spectroscopy (NIRS) as an alternative to the demanding direct neuromonitoring; and 2) preconditioning of the CN as minimally invasive, endovascular "first stage" to increase the resilience of spinal cord perfusion prior to definite aortic repair. This article illustrates both concepts discussing: 1) the clinical application of thoracic and lumbar collateral NIRS monitoring to indirectly detect spinal cord hypoperfusion; and 2) minimally invasive selective segmental artery coil-embolization (MISACE) for (arteriogenic) preconditioning of the CN prior to extensive open or endovascular staged TAAA repair.
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The aim of this review was to explore current literature pertaining to the use of permissive hypotension in the treatment of abdominal aortic aneurysms. A literature search using Metalib, a database search engine, provided at the Royal Free and University College of London (UCL) yielded articles using the keywords "permissive hypotension" and "hypotensive resuscitation" when linked to "abdominal aortic aneurysm" and "rupture". The articles studying permissive hypotension in animals and humans in trauma, and in patients with abdominal aortic aneurysm were reviewed. ⋯ The safety of permissive hypotension in patients with ruptured aortic aneurysms was documented and found to be widespread, but there were no randomized trials directly comparing this practice. Evidence from a prospective randomized study on the modality of treatment of ruptured aortic aneurysms suggest that the level of blood pressure is associated with the mortality and a prospective cohort study suggests that, using the complementary concept of "delayed volume resuscitation", the total volume of preoperative fluid resuscitation independent of the blood pressure is predictive of the risk of perioperative death in ruptured aortic aneurysms. To this end, recent clinical publications are now supportive of control of both the volume of preoperative fluid given and blood pressure in this group of patients but clinical studies are few.
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There is a large variability observed in the literature regarding radiation exposure and contrast volume injection during endovascular aortic repair (EVAR). Reducing both in order to decrease their respective toxicities must be a priority for the endovascular therapist. Radiation dose reduction requires a strict application of the "as low as reasonably achievable" principles. ⋯ Additionally, alternative contrast agents, like carbon dioxide (CO2) and gadolinium, have also been evaluated and can be used in specific cases. Contrast-enhanced ultrasound and intravascular ultrasonography are currently developed as potential alternatives to both iodinated contrast use and X-ray during EVAR. Lastly, specific education and training of operators in radiation protection are essential.