Circulation of the spinal cord: an important consideration for thoracic surgeons

Extensive deployment of the stented elephant trunk is associated with an increased risk of spinal cord injury

OBJECTIVE

Thoracic aortic aneurysm repair with the stented elephant trunk technique seems to be associated with an increased risk of spinal cord injury. We investigated whether severe atherosclerosis of the distal landing zone or extensive deployment of the stented elephant trunk is associated with increased risk of spinal cord injury.

METHODS

Twenty-five patients underwent thoracic aortic aneurysm repair with the stented elephant trunk technique. The study population included 19 men and had a mean age of 73 +/- 7 years. All patients underwent a median sternotomy with cardiopulmonary bypass and selective cerebral perfusion. The elephant trunk was fixed with a Z-stent distal to the aneurysm during hypothermic circulatory arrest. Thirteen patients underwent concomitant total aortic arch replacement.

RESULTS

Six (24%) patients had spinal cord injury. The presence of severe atherosclerosis at the distal landing zone demonstrated a tendency to increase the incidence of spinal cord injury (36% vs 9%, P = .1218). More distal deployment of the stented elephant trunk was significantly associated with increased risk of spinal cord injury (T8.0 +/- 0.6 vs T6.5 +/- 1.1, P = .0043). Univariate logistic regression analysis identified a history of abdominal aortic aneurysm repair (P = .0296) and the vertebral level of the distal landing zone (P = .0249) as significant independent risk factors for spinal cord injury, and only the latter was significant in multivariate analysis (P = .0396). The combination of a distal landing zone of T7 or greater and a history of abdominal aortic aneurysm repair was the strongest predictor for spinal cord injury (71% vs 6%, P = .0047).

CONCLUSIONS

Spinal cord injury after stented elephant trunk deployment might be related to occlusion of the excessive intercostal arteries or thromboembolism. Patients with a history of abdominal aortic aneurysm repair who require extensive deployment of the stented elephant trunk seem to be at a higher risk for spinal cord injury.

Experimental spinal cord ischemia: Model characterization and improved outcome with arterial hypertension*

OBJECTIVE

Paraplegia from spinal cord ischemia is a devastating complication of thoracoabdominal aortic aneurysm repair. Perioperative hypoperfusion of the spinal cord is a critical determinant of residual neurologic deficits. We determined if functional and histologic outcome is dependent on systemic blood pressure in a rat model of spinal cord ischemia.

DESIGN

Randomized, controlled, prospective study.

SETTING

Research laboratory at a university teaching hospital.

SUBJECTS

Adult male Wistar rats.

INTERVENTIONS

Endotracheally intubated adult male Wistar rats (300-450 g) anesthetized with halothane underwent a thoracotomy and placement of a clip across the descending aorta for 27 mins. Mean proximal arterial blood pressure (MPABP) was monitored with a cannula placed in the left common carotid artery. Halothane was adjusted (1.25-1.5%) to maintain MPABP between 70 and 90 mm Hg (n = 20) or 140 and 150 mm Hg (n = 20). Shamoperated rats (n = 10) had a thoracotomy without aortic clamping at an MPABP of 70-90 mm Hg. Following 1, 24, 48, and 72 hrs of recovery from anesthesia, motor function of the hind paws was scored as follows: 0, no evidence of deficit; 1, toes flat under body when walking but with ataxia; 2, knuckle walks; 3, movements in hind limbs but unable to knuckle walk; 4, no movement, drags hind limbs. Body temperature was maintained between 37 and 38 degrees C throughout the experiment.

MEASUREMENTS AND MAIN RESULTS

All sham operated rats with MPABP 70-90 mm Hg recovered without neurologic deficits, whereas those that underwent aortic occlusion with MPABP between 70 and 90 mm Hg emerged from anesthesia with grade 3 and 4 deficits and remained in this condition without improvement at 72 hrs. Histopathology at 72 hrs demonstrated moderate to severe neuronal loss with involvement of dorsal, intermediate, and ventral horns. Only eight of 20 rats that underwent aortic occlusion with MPABP between 140 and 150 mm Hg had grade 1 and 2 deficits on emergence but had no neurologic deficit after 1 hr. Most of the surviving neurons in these animals appeared normal histologically, particularly motor neurons around the periphery of the ventral horn.

CONCLUSIONS

Systemic blood pressure is a critical determinant of outcome following spinal cord ischemia, and controlled peri-operative blood pressure augmentation may ameliorate neurologic deficits in patients who undergo thoracoabdominal vascular procedures and are at risk for spinal cord hypoperfusion.