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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To make the ischemic effect on spinal cord clear, different vessels of the cord of 38 dogs, in 5 groups, were electrically cauterized individually or in combination. The animals in each group were sacrificed in due time periods, and the pathology of corresponding segment of each cord was observed grossly and under electron as well as light microscopes. The findings were described in this paper. As a consequence, the dogs in each group manifested paraplegia varying in degrees. However, dogs with the anterior cord artery and unilateral radicular artery, or both the anterior and posterior cord arteries cauterized developed irreversible, complete paraplegia. Cauterization of the anterior cord artery, or the posterior cord artery and unilateral radicular artery, or the radicular artery on both sides, gave rise to reversible, incomplete paraplegia. Anatomy of vessels of the spinal cord of other 9 dogs were dissected and studied. Their presence and distribution were cited and referred to the discussion about the effect of ischemia induced by electrifying them individually or in combination.
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PMID:[Experimental observations on spinal cord injury produced by electrifying the vessels of the cord in dogs]. 277 30

Four patients with expanding chronic dissecting thoracoabdominal aneurysm underwent total replacement of the thoracoabdominal aorta with reconstruction of all visceral branches, intercostal and lumbar arteries with the aid of femoro-femoral bypass. During aortic cross-clamping, selective celiac and both renal arteries perfusion was performed to prevent the organ ischemia. Somatosensory evoked potentials monitoring or spinal cord evoked potentials monitoring was also performed to detect the spinal cord ischemia. Surgical technique employed in this series was direct anastomosis of onlay patch graft to the normal true lumen from which visceral branches and intercostal and lumbar arteries arise. The celiac artery and left renal artery arise from the false lumen in some cases were reconstructed with graft interposition or direct anastomosis to an opening made in the onlay patch graft. All patients survived the operation, and are leading normal life late in the postoperative period except one who developed partial paraplegia. Total graft replacement of the thoracoabdominal aorta may be a valid technique for the treatment of expanding aneurysms of the dissecting thoracoabdominal aorta.
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PMID:[Total graft replacement of the thoracoabdominal aorta with reconstruction of visceral branches, intercostal and lumbar arteries in expanding chronic dissecting aneurysms of the thoracoabdominal aorta]. 279 7

The contribution of free radical-mediated reperfusion injury to the ischemic damage caused by total arterial occlusion has been investigated in a model of transient spinal cord ischemia in the rabbit. Spinal cord ischemia was produced in 20 anaesthetized rabbits by temporary luminal occlusion (20 min) of the abdominal aorta below the renal arteries. Superoxide dismutase (5 mg/kg) (10 animals) was infused before and during reperfusion below aortic occlusion using an infusion pump that infused the enzyme through the contralateral femoral artery. Control (10 animals) received sterile saline with the same procedure. In this later group, 4 animals developed paraplegia, 4 were paretic and only 2 were normal. However, in the treated group, 6 animals were normal while 3 were paretic and only one appeared paralyzed. We conclude that: a) oxygen free radicals generated during reperfusion are involved in producing the ischemic injury, and b) the ischemic spinal cord injury is prevented by superoxide dismutase.
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PMID:Administration of bovine superoxide dismutase prevents sequelae of spinal cord ischemia in the rabbit. 291 49

Paraplegia secondary to spinal cord ischemia is a too frequent devastating complication of thoracic aneurysm surgery. We examined the ability of veno-arterial bypass (VAB) to ensure adequate spinal cord blood flow during aortic cross-clamping by monitoring spinal cord function via somatosensory evoked potentials (SEP's) and postoperative motor function. Dogs were placed on VAB using a heparin-bonded roller pump circuit without systemic heparinization. SEP latency and amplitude were monitored continuously. The respirator FIO2 was set at 100% while the aorta was cross-clamped for one hour with the bypass adjusted to keep distal arterial pressure at greater than 60 mmHg. After one hour the aorta was unclamped, bypass discontinued, and the animals recovered. SEP's were always present during VAB as long as the distal pressure was kept at greater than 60 mmHg. There were several transient hypotensive episodes (less than 5 min) which were accompanied by reversible loss of SEP's. None of the animals displayed any gait abnormalities post-op. These findings using this simple bypass technique suggest the following conclusions: (1) SEP's degenerate (increased latency and decreased amplitude) in response to hypoxia; (2) spinal cord function can be maintained for up to one hour during hypoxic conditions; (3) SEP's can be used to monitor sensory spinal cord function under these conditions; and (4) heparinless VAB can provide spinal cord protection while also allowing monitoring of SEP's to ensure adequate spinal cord perfusion.
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PMID:Preservation of spinal cord function and prevention of paralysis during aortic occlusion via veno-arterial bypass. 292 82

Nineteen mongrel dogs had 30 minutes of thoracic aortic occlusion to determine the effects that blockade of the renin-angiotensin system may have on preserving spinal cord blood flow and function during a period of temporary spinal cord ischemia. Cross-clamping of the thoracic aorta causes renal ischemia and activates the renin-angiotensin system with resulting increased production of angiotensin II. Angiotensin II is a potent peripheral constrictor and elevated levels may constrict collateral spinal cord circulation. At the time of aortic cross-clamping, 10 dogs received 100 mg/kg of MK422 (intravenous enalapril maleate), a converting enzyme inhibitor, and nine animals served as controls. The blockade of the renin-angiotensin system had no preserving effects on spinal cord flow as measured by microspheres and on spinal cord function as graded with the Tarlov scale. However, the paraplegic animals all had significantly increased lower thoracic and lumbar spinal cord flows 30 minutes after clamp release when compared with those animals that remained neurologically intact. In conclusion, marked hyperemia occurring after a period of hypoperfusion may lead to spinal cord edema and compartment syndrome with resulting paraplegia.
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PMID:The effect of hyperemia on spinal cord function after temporary thoracic aortic occlusion. 317 89

The effect of insulin-induced reduction in blood glucose to 65 +/- 20 mg/dl (mean +/- standard deviation) on recovery of electrophysiological function and extracellular lactate concentration was studied in a rabbit model of spinal cord ischemia. These results were compared to findings in animals with spinal cord ischemia that either were fasted overnight (fasted group: blood glucose 97 +/- 26 mg/dl) or had no pretreatment (control group: blood glucose 172 +/- 65 mg/dl). The aorta was occluded until the postsynaptic waves of the spinal somatosensory evoked potentials (SSEP's) had been absent for 20 minutes, a period of ischemia that produces paraplegia in 100% of untreated rabbits. The total aortic occlusion time was not significantly different in the three groups. Recovery of the SSEP's was significantly better in the insulin-treated animals than in the fasted or control animals. The N3 wave of the SSEP's, which has been found to correlate best with neurological recovery, returned to 65% +/- 48% of the preischemia amplitude in the insulin-treated animals, compared to 40% +/- 34% in the fasted group and 26% +/- 24% in the control animals. Extracellular lactate concentration in the spinal cord increased immediately after occlusion of the aorta, reached a plateau as the postsynaptic waves disappeared from the SSEP's, and then increased a second time during the first 15 minutes of reperfusion. The peak lactate concentration during ischemia and during reperfusion correlated with the preischemia glucose concentration (r = 0.60336 and r = 0.76930, respectively). Lactate concentration in the spinal cord was higher during ischemia and throughout the first 2 hours of reperfusion in the control and fasted animals than in the insulin-treated animals. During the 2nd hour of reperfusion, lactate concentration was significantly higher in the control animals than in the fasted animals. Reduction in blood glucose with insulin improves recovery of electrophysiological function after spinal cord ischemia, probably because of reduced lactic acid production, especially during the early reperfusion period.
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PMID:Protection against spinal cord ischemia with insulin-induced hypoglycemia. 331 14

Paraplegia after thoracoabdominal aneurysm repair can occur in 3% to 40% of patients. This study investigated the efficacy of cerebrospinal fluid (CSF) drainage to protect the spinal cord during aortic cross-clamping (AXC) and the interrelationship between drainage, spinal cord perfusion pressure (SCPP), and changes in somatosensory evoked potentials (SEP) in a canine model of spinal cord ischemia. SCPP was defined as the mean distal aortic pressure minus the CSF pressure. In the experimental group, CSF was drained before AXC. SEP changes were quantitated as time to latency increase of 10% (L-10) and time to complete SEP loss. Drainage of CSF had no significant effect on the distal aortic pressure but significantly increased SCPP from 9.4 to 21.8 mm Hg and decreased the incidence of postoperative neurologic injury. Ischemic SEP changes were highly significant predictors of postoperative neurologic injury, occurring more than two times earlier in the paralyzed and paraparetic animals. Dogs without neurologic injury had significantly higher SCPP, delayed L-10 time, and delayed SEP loss.
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PMID:Somatosensory evoked potentials and spinal cord perfusion pressure are significant predictors of postoperative neurologic dysfunction. 340 57

Spinal cord ischemia presenting as acute paraplegia is an uncommon occurrence not previously reported in the emergency medicine literature. Paraplegia due to spinal ischemia is seen most commonly after intraoperative aortic manipulation; however, acute hypotension and prolonged cardiopulmonary resuscitation are also reported settings. The differential diagnosis of acute, non-traumatic paraplegia includes mechanical spinal cord compression, acute transverse myelitis, and polyneuritis.
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PMID:Ischemic injury to the spinal cord as a cause of transient paraplegia. 358 53

Ischemic spinal cord injury with resulting postoperative paraplegia is an inherent risk for operations on the thoracic aorta. The mechanism of injury is not clearly understood, and numerous adjuncts to avoid this complication have been suggested, with conflicting clinical results. A new technique of hypothermic regional perfusion of the spinal cord is described. Fifteen female pigs weighing 21 to 39 kg were used for the experiment. The control group consisted of 5 animals in which the thoracic aorta was clamped at the distal arch for 30 minutes. All of these animals sustained postoperative neurological damage. Eighty percent sustained postoperative paraplegia, and 20% had severe spasticity of the hind legs that precluded normal ambulation. The experimental group consisted of 10 animals in which hypothermic regional perfusion was performed for 30 minutes after cross-clamping of the distal arch. Perfusion cooling was followed by 30 minutes of ischemia in 5 animals and 45 minutes of ischemia in the remaining 5. All animals that underwent hypothermic regional perfusion were able to walk postoperatively, and no evidence of ischemic injury was found at postmortem examination of the spinal cords. This technique proved to be simple and effective in protecting the spinal cord for up to 45 minutes of ischemia in the experimental group. The clinical implications of this concept are promising for patients undergoing operations on the thoracic aorta.
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PMID:Hypothermic regional perfusion for protection of the spinal cord during periods of ischemia. 359 34

To determine if intraoperative monitoring of somatosensory evoked potentials detects spinal cord ischemia, we subjected 21 dogs to aortic cross-clamping distal to the left subclavian artery. Group I animals (short-term studies, n = 6) demonstrated decay and loss of somatosensory evoked potentials at 8.5 +/- 1.1 minutes after aortic cross-clamping. During loss of somatosensory evoked potentials, significant decreases in spinal cord blood flow occurred in cord segments below T6. Significant reactive hyperemia occurred without normalization of somatosensory evoked potentials after reperfusion. Fifteen Group II animals (long-term studies) were studied to determine the relationship between duration of spinal cord ischemia (evoked potential loss) and subsequent incidence of paraplegia. Extension of aortic cross-clamping for 5 minutes after loss of somatosensory evoked potentials in six dogs resulted in no paraplegia (mean cross-clamp time 12.7 +/- 0.6 minutes). Prolongation of aortic cross-clamping for 10 minutes after evoked potential loss in nine dogs (mean cross-clamp time 17.6 +/- 0.6 minutes) resulted in a 67% (6/9) incidence of paraplegia 7 days postoperatively (p = 0.02 versus 10 minutes of aortic cross-clamping). These findings demonstrate that simple aortic cross-clamping uniformly results in spinal cord ischemia and that such ischemia is detectable by monitoring of somatosensory evoked potentials. Duration of ischemia, as measured by the time of evoked potential loss during the cross-clamp interval, is related to the incidence of postoperative neurologic injury.
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PMID:Monitoring of somatosensory evoked potentials during surgical procedures on the thoracoabdominal aorta. I. Relationship of aortic cross-clamp duration, changes in somatosensory evoked potentials, and incidence of neurologic dysfunction. 361 25


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