title: Experimental spinal cord ischemia: model characterization and improved outcome with arterial hypertension.
abstract: 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.
  
  
  METHODS
  Randomized, controlled, prospective study.
  
  
  METHODS
  Research laboratory at a university teaching hospital.
  
  
  METHODS
  Adult male Wistar rats.
  
  
  METHODS
  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.
  
  
  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.
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
authors.forename: Thomas J K
authors.initials: TJ
authors.lastname: Toung
authors.forename: Yi
authors.initials: Y
authors.lastname: Chang
authors.forename: Mel
authors.initials: M
authors.lastname: Williams
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Crain
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Traystman
authors.forename: Anish
authors.initials: A
authors.lastname: Bhardwaj
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic; D001794:Blood Pressure / Q000502:physiology*; D004195:Disease Models, Animal; D006973:Hypertension / Q000503:physiopathology; D008297:Male; D009046:Motor Neurons / Q000473:pathology; D010264:Paraplegia / Q000209:etiology; D011446:Prospective Studies; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D020760:Spinal Cord Ischemia / Q000473:pathology / Q000503:physiopathology