Excessively high systemic blood pressure in the early phase of reperfusion exacerbates early-onset paraplegia in rabbit aortic surgery

OBJECTIVE

We have demonstrated that therapeutic augmentation of systemic blood pressure during spinal cord ischemia plays an important role in minimizing spinal cord injury in both experimental and clinical aortic surgery. However, there remain concerns that excessively high blood pressure during spinal cord reperfusion may aggravate the reperfusion injury. The purpose of this study is to investigate the effect of high blood pressure during spinal cord reperfusion on postoperative neurologic outcomes after aortic surgery in rabbits.

METHODS

Experiments were performed using a rabbit spinal cord ischemia-reperfusion model in 2 randomly divided groups: (1) In the HR group, the mean blood pressure was maintained at a high level (121 +/- 1.3 mm Hg) during reperfusion with intravenously administered phenylephrine; and (2) in the CR group, the mean blood pressure was not medically controlled (75 +/- 9.1 mm Hg) during reperfusion. Neurologic and histologic assessments and evaluation of early reperfusion injury were performed.

RESULTS

In the HR group, slow and incomplete recovery of transcranial motor-evoked potentials (P = .02) and low neurologic scores (P < .005) were observed during spinal cord reperfusion compared with the CR group. At 48 hours of reperfusion, there were significantly fewer viable neuron cells, more apoptosis, and more perivascular edema with gray matter vacuolation in the HR group (P < .001 for each). At 3 hours, myeloperoxidase activity (P = .0021), vascular permeability (P = .0012), and superoxide generation (P < .0001) were significantly increased in the HR group.

CONCLUSION

Excessively high blood pressure in the early phase of spinal cord reperfusion increased reperfusion injury in the spinal cord, leading to exacerbation of early-onset paraplegia. Avoidance of spinal cord reperfusion with high blood pressure may be one management strategy in thoracoabdominal aortic surgery.

Perioperative spinal cord infarction in nonaortic surgery: report of three cases and review of the literature

Paraplegia caused by a spinal cord infarction (SCI) is a devastating perioperative complication, most often associated with aortic and spine surgery. We present two other clinical scenarios in which perioperative SCI may occur. They happened during surgical procedures performed with epidural anesthesia, in the presence of several specific risk factors such as spinal stenosis, vascular disease, intraoperative hypotension, or the use of epinephrine in the local anesthetic solution. Second, SCI may occur during episodes of postoperative hypotension in patients with a history of aortic aneurysms.

Chronic descending aortic dissections

Aortic dissection involving the descending aorta has a predictable and often debilitating course of progressive dilatation that occurs once patients survive the acute phase of the disease. Important factors that impact the rate and degree of dilatation include the persistence of a false lumen channel (and the amount of thrombus), the control of hypertension, and the presence of an underlying connective tissue disorder. The mainstay of management of chronic descending aortic dissections is antihypertensive therapy including beta-blockade until the dissected aorta becomes significantly aneurysmal. Surgical management is recommended at that point. Multiple advances have been made that have improved the results of operative repair of aneurysmal descending aortic dissections including circulation management methodologies, CSF drainage, neurocerebral monitoring, and more recently, endovascular therapies. The presentation, diagnosis and management of chronic descending aortic dissections are discussed.

Strategies to Manage Paraplegia Risk After Endovascular Stent Repair of Descending Thoracic Aortic Aneurysms

BACKGROUND

Paraplegia is a recognized complication after endovascular stent repair of descending thoracic aortic aneurysms. A management algorithm employing neurologic assessment, somatosensory evoked potential monitoring, arterial pressure augmentation, and cerebrospinal fluid drainage evolved to decrease the risk of postoperative paraplegia.

METHODS

Patients in thoracic aortic aneurysm stent trials from 1999 to 2004 were analyzed for paraplegic complications. Lower extremity strength was assessed after anesthesia and in the intensive care unit. A loss of lower extremity somatosensory evoked potential or lower extremity strength was treated emergently to maintain a mean arterial pressure 90 mmHg or greater and a cerebrospinal fluid pressure 10 mm Hg or less.

RESULTS

Seventy-five patients (male = 49, female = 26, age = 75 +/- 7.4 years) had descending thoracic aortic aneurysms repaired with endovascular stenting. Lumbar cerebrospinal fluid drainage (n = 23) and somatosensory evoked potential monitoring (n = 15) were performed selectively in patients with significant aneurysm extent or with prior abdominal aortic aneurysm repair (n = 17). Spinal cord ischemia occurred in 5 patients (6.6%); two had lower extremity somatosensory evoked potential loss after stent deployment and 4 developed delayed-onset paraplegia. Two had full recovery in response to arterial pressure augmentation alone. Two had full recovery and one had near-complete recovery in response to arterial pressure augmentation and cerebrospinal fluid drainage. Spinal cord ischemia was associated with retroperitoneal bleed (n = 1), prior abdominal aortic aneurysm repair (n = 2), iliac artery injury (n = 1), and atheroembolism (n = 1).

CONCLUSIONS

Early detection and intervention to augment spinal cord perfusion pressure was effective for decreasing the magnitude of injury or preventing permanent paraplegia from spinal cord ischemia after endovascular stent repair of descending thoracic aortic aneurysm. Routine somatosensory evoked potential monitoring, serial neurologic assessment, arterial pressure augmentation, and cerebrospinal fluid drainage may benefit patients at risk for paraplegia.

Acute Descending Aortic Dissections: Management of Visceral, Spinal Cord, and Extremity Malperfusion

Acute descending aortic dissection is considered the most catastrophic event affecting the aorta and occurs two to three times more often than rupture of abdominal aortic aneurysms. The therapeutic aim in treating acute dissection is not only directed at the prevention of aneurysmal development and rupture but also to prevent and treat complications such as malperfusion syndrome. According to Lauterbach and coworkers patients with symptomatic malperfusion syndromes have a 51% mortality rate compared with a 29% mortality rate in patients who do not. The surgical in-hospital mortality rate in patients with mesenteric or peripheral vascular ischemic complications may be as high as 89%. Despite an improvement in diagnosing dissections and malperfusion syndromes, and despite improved operative techniques and a better understanding of the significance of perioperative care, the surgical mortality rate can be as high as 50%. Endovascular techniques are constantly evolving that provide an alternative to open procedures. The goal of this article was to review the pathogenesis of malperfusion syndromes in aortic dissection, discuss the current modalities to treat malperfusion of the spinal cord, viscera, and extremities, and examine the results of the treatments used today.