Spinal cord protection: lessons learned from open repair.

Abstract

Thoracoabdominal aortic aneurysm repair techniques and perioperative management have undergone many iterations and attempts to reduce complication rates. While respiratory and renal failure are some of the most common complications following aneurysm repair (1), lower extremity paresis/paraplegia is most feared. In an early, large series, the rate of spinal cord injury was as high as 16% (1). Multivariate analysis in this series demonstrated that extent of aneurysm resection and cross-clamp time were significant predictors of paraplegia or paraparesis, among these patients (1). Multiple adjuncts have been attempted in order to reduce or eliminate spinal cord ischemia, with early attempts focused on cardiopulmonary or atriofemoral bypass with systemic cooling, resulting in modest reductions in paraplegia/paraparesis rates (2). The addition of cerebrospinal fluid drainage via intrathecal drain placement either alone, or in combination with intrathecal papaverine administration have shown significant promise in reducing paraplegia/paraparesis in this population and is a surgical adjunct we use at the Cleveland Clinic. Early studies on aortic cross-clamping in baboons demonstrated the combination of cerebrospinal fluid drainage and intrathecal papaverine administration eliminated paraplegia through a combination of dilation and increased blood flow to the lower anterior spinal artery (3). This technique was subsequently tested in a small randomized control trial in thirty-three patients with extent I and II thoracoabdominal aortic aneurysms (4). Only two of 17 patients who received cerebrospinal fluid drainage plus intrathecal papaverine developed spinal cord injury, while seven of 16 developed neurologic injury in the control group (4). Multivariate analysis revealed longer aortic crossclamp time, failure to actively cool with bypass, and postoperative hypotension were associated with neurologic injury, while cerebrospinal fluid drainage plus intrathecal papaverine administration was protective (4). Significant discussion and research has focused on the preservation of segmental blood supply to the spinal cord via re-implantation of intercostal and lumbar arteries at the time of thoracoabdominal aortic repair (2). Contemporary management of intercostal and lumbar arteries during aneurysm repair focuses on re-implantation of patent vessels, when technically feasible, below the sixth thoracic vertebra. Early analysis focusing on this problem found that rates of paraparesis/paraplegia increase if patent intercostals are oversewn, particularly between the levels of T7-L1 (2). However, which arteries to reimplant is debatable and has led some to perform pre-operative selective angiography to determine the key intercostals/lumbars supplying the spinal cord. While re-implantation of these vessels seems important, it comes at the cost of longer aortic cross-clamp times. Thus, surgeons must keep in mind a balance between maintaining blood supply to the spinal cord and ischemic time. More recently there has been a novel approach to spinal cord protection for patients undergoing thoracoabdominal aortic aneurysm repair. The approach, spear-headed by Dr. Christian Etz of University Heart Center in Leipzig, Germany, focuses on the concept of minimally invasive segmental artery coil embolization to pre-condition the spinal cord prior to thoracoabdominal aortic aneurysm repair (5). The investigators are utilizing a technique termed minimally invasive staged segmental artery coil Spinal cord protection: lessons learned from open repair