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

Thirty-three patients undergoing operations on the descending thoracic or thoracoabdominal aorta were monitored to evaluate causes and effects of spinal cord ischemia as manifested by changes in somatosensory evoked potentials. Maintenance of distal aortic perfusion pressure (greater than 60 mm Hg) by either shunt or bypass techniques in 17 patients resulted in preservation of somatosensory evoked potentials and a normal postoperative neurologic status, irrespective of the interval of thoracic cross-clamping (range 23 to 105 minutes). In 16 other patients in whom cross-clamp time ranged from 16 to 124 minutes, evoked potential loss was observed because of failure to provide distal perfusion (n = 8), inadequate maintenance of distal perfusion pressure (less than 60 mm Hg) despite shunt/bypass (n = 6), or interruption of critical intercostal arteries (n = 2). Incidence of paraplegia in the entire group was 15.1% (5/33) and was limited to only those patients in whom evoked potential loss occurred (5/16, 31.2%) (p = 0.02). Loss of somatosensory evoked potentials for more than 30 minutes resulted in a 71.2% (5/7) incidence of paraplegia, whereas no neurologic deficit was noted in patients (0/26) in whom evoked potential loss was either prevented or limited in duration to 30 minutes (p less than 0.001 versus loss for more than 30 minutes). Intraoperative monitoring of somatosensory evoked potentials is a sensitive indicator of spinal cord ischemia. Simple aortic cross-clamping, failure to maintain distal perfusion pressure above 60 mm Hg, and inability to reimplant critical intercostals in a timely fashion result in a high rate of paraplegia if duration of spinal cord ischemia as measured by somatosensory evoked potentials exceeds 30 minutes. Routine evoked potential monitoring during thoracoabdominal procedures appears useful in assessing the adequacy of spinal cord perfusion. Furthermore, it can alert the surgeon to the necessity for critical intercostal artery reimplantation as well as the need for adjustment or regulation of distal aortic perfusion.
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PMID:Monitoring of somatosensory evoked potentials during surgical procedures on the thoracoabdominal aorta. IV. Clinical observations and results. 361 28

The infrequency of spinal cord infarction and paraplegia after occlusion of the descending thoracic aorta has effectively precluded statistical identification of risk factors. Reversible spinal cord ischemia (SCI), however, is more common, can be detected by intraoperative neurophysiologic monitoring, and can lead to irreversible spinal cord damage. Spinal somatosensory evoked potentials (SEPs) were monitored intraoperatively in 38 patients (18 days to 18 years) undergoing coarctation repair (1982-1986). Although no patients sustained perioperative neurologic dysfunction, 10 of 38 (26%) patients developed reversible SCI, as reflected by greater than 75% loss of SEP N1-P1 interpeak amplitude during aortic occlusion (mean clamp time, 29.1 +/- 1.1 min). During occlusion, seven of 38 (18%) sustained complete loss of the SEP; uniform and prompt (1 to 6 min after clamp release) recovery of the signal occurred in these patients with reperfusion following completion of the repair (n = 6), or temporary institution of partial occlusion (n = 1). By multiple regression analysis the degree of SCI was negatively related to the distal aortic pressure (mean 32.4 +/- 2.4 mm Hg, p = .03), and the occlusion PCO2 (mean 33.1 +/- 1.1 mm Hg; p = .013), and positively related to the change in proximal systolic pressure with aortic occlusion (mean 19.8 +/- 3 mm Hg, p = .003). We conclude that: (1) distal hypotension and SCI commonly occur during aortic occlusion for coarctation repair, and (2) intraoperative interventions that can potentially influence distal aortic perfusion and/or PCO2 should be used judiciously.
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PMID:Identification of risk factors for spinal cord ischemia by the use of monitoring of somatosensory evoked potentials during coarctation repair. 362 38

Spinal cord damage caused by ischemia is a serious, underappreciated, and relatively refractory problem in clinical practice. Research is hampered by a lack of experimental models that appropriately mimic clinical situations. A new model of paraplegia in the rat is presented and evaluated by standard neurologic deficit scoring (1, 4, 18, and 24 hours after occlusion) and by computerized activity monitoring (1 and 18 hours after occlusion). Rats underwent temporary occlusion of the thoracic aorta for 10, 15, or 20 minutes. Experimental groups received glucose (2 gm/kg) and demonstrated a significant elevation in blood glucose (p = 0.001) and were significantly more neurologically impaired at all four time periods (p less than or equal to 0.005) than the ischemic control group, which received equivalent volumes of normal saline solution. Significant differences in neurologic deficit were noted with direct clinical examination and computerized activity monitoring. With the use of the latter system, statistical differences were detected in total distance traveled and number of vertical movements. We conclude the following: (1) Paraplegia is reliably and reproducibly achieved in this rat model; (2) because of the rat's more extensive behavioral repertoire when compared with other models of spinal ischemia (e.g., rabbit), more end points can be monitored and more subtle behavioral deficits discerned; (3) computerized activity monitoring can distinguish varying degrees of neurologic deficit and correlates with clinical neurologic deficit scoring; and (4) glucose exacerbates paraplegia in this model.
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PMID:Paraplegia in the rat induced by aortic cross-clamping: model characterization and glucose exacerbation of neurologic deficit. 365 86

There is a high incidence of paraplegia associated with thoracic aortic cross-clamping, even when cardiopulmonary bypass or shunts are used. In 56 adult baboons, spinal cord blood flow (SCBF), vascular anatomy, and paraplegia rates were evaluated. Tissue blood flow was measured by radioactive microspheres. Various procedures were used to increase SCBF and to prevent ischemia-reperfusion injury. It was found that the rate of paraplegia was inversely correlated with neural tissue ischemia (SCBF) and directly correlated with reperfusion hyperemia. Two methods completely prevented paraplegia. These two methods were a thoracic shunt with occlusion of the infrarenal aorta or cerebrospinal fluid drainage plus intrathecal papaverine injection, both of which were associated with an increased SCBF. Furthermore, papaverine dilated the anterior spinal artery (ASA) (p = 0.007) and increased the blood flow through the lower ASA. Whereas procedures utilizing a calcium channel blocker (flunarizine), allopurinol, superoxide dismutase (SOD), laminectomy alone, and a thoracoabdominal shunt not perfusing the arteria radicularis magna (ARM) all failed to prevent paraplegia, allopurinol (p = 0.026) and SOD (p = 0.004) did prevent gastric stress lesions, indicating that their failure to prevent paraplegia was not due to a lack of activity. Of great clinical interest is that, if a shunt is used and the ARM is perfused, infrarenal aortic cross-clamping increases SCBF, thus preventing paraplegia. Intrathecal application of papaverine proved to be even more effective in increasing SCBF and also completely prevented paraplegia. As this is a safer procedure than the insertion of shunts, this is the method of choice for the prevention of paraplegia associated with thoracic aortic cross-clamping. The preliminary trial using intrathecal papaverine in human beings has thus far shown no adverse side effects from the drug, and no paraplegia has occurred.
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PMID:Cross-clamping of the thoracic aorta. Influence of aortic shunts, laminectomy, papaverine, calcium channel blocker, allopurinol, and superoxide dismutase on spinal cord blood flow and paraplegia in baboons. 372 82

We describe three patients who had painless dissections of the aorta which resulted in neurologic syndromes at the time of presentation. Two patients had acute hemimotor and sensory findings. In one of these cases progression to paraplegia occurred. In a third patient, acute weakness and ischemia of a leg occurred at presentation. We review previously described painless aortic dissections. Such aortic dissections may be suspected in the setting of an acute neurologic event by abnormalities in the examination of the peripheral pulses and the heart and by attention to characteristic chest x-ray changes.
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PMID:Painless dissections of the aorta presenting as acute neurologic syndromes. 373 46

The danger of irreversible ischemic damage to the spinal cord following repair of traumatic aortic rupture has prompted many techniques designed to decrease this risk. Surgical repair was performed on 41 consecutive patients, using four different methods. These included: group 1 (15 patients), left-heart pump bypass with systemic administration of heparin; group 2 (7 patients), heparinized shunt from the ascending aorta to the descending aorta or to the femoral artery; group 3 (14 patients), heparinized shunt from the left ventricle to the aorta or femoral artery; group 4 (5 patients), aortic cross-clamp only. Spinal cord ischemia was not seen in groups 1 or 2, but paraparesis or paraplegia developed in 4 patients in group 3. Severe shock accompanied rupture in all patients in group 4, and no time was taken for a shunt or bypass. Four of the 7 deaths occurred in the operating room in patients who had arrived moribund and in severe shock. In our experience, shunts from the left ventricle to the aorta have failed to protect the spinal cord against ischemia. Left-heart bypass or aorta-to-aorta shunts are now our procedure of choice.
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PMID:Spinal cord ischemia following operation for traumatic aortic transection. 376 13

The evoked spinal cord potential was used for the moniter of the spinal cord ischemia during the operation on the thoracic aorta. At first, experiments were performed on 23 dogs. Following laminectomy and 1t. thoracotomy, evoked spinal cord potential to the stimulation from bipoler electrodes in the midline dorsal subdural space at the level of near L1 were recorded from needle electrode in the intervertebral disk at the level of Th4-5. After baseline measurements, the thoracic aorta was occluded in all dogs by aortic cross-clamping (AXC) distral to the origin of the left subclavian artery. Then 3 types of changes were detected. TYPE-I (n = 8) showed loss of the ESPs during AXC and return after reperfusion. TYPE-II (n = 10) showed no changes during and after AXC. TYPE-III (n = 5) showed return of ESPs after transient loss of them even during AXC. Five of 7 dogs (71%) in TYPE-I and 1 of 5 dogs (20%) in TYPE-III developed paraplegia, but all of them in TYPE-II avoided paraplegia. Secondly, ESP was used for the moniter of spinal cord ischemia during operation on 13 patients. Ten patients showed no changes of ESPs, but 3 showed loss of ESPs during AXC and return after reperfusion of them. No paraplegia appeared. We have concluded that intraoperative ESP monitering is a more reliable indicator of the spinal cord ischemia than other methods previously reported.
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PMID:[The prevention of spinal cord ischemia during the operation on the thoracic aorta utilizing the evoked spinal cord potential (ESP)]. 379 79

Subsequent to traumatic injury of the spinal cord, a series of pathophysiological events occurs in the injured tissue that leads to tissue destruction and paraplegia. These include hemorrhagic necrosis, ischemia, edema, inflammation, neuronophagia, loss of Ca2+ from the extracellular space, and loss of K+ from the intracellular space. In addition, there is trauma-initiated lipid peroxidation and hydrolysis in cellular membranes. Both lipid peroxidation and hydrolysis can damage cells directly; hydrolysis also results in the formation of the biologically active prostaglandins and leukotrienes (eicosanoids). The time course of membrane lipid alterations seen in studies of antioxidant interventions suggests that posttraumatic ischemia, edema, inflammation, and ionic fluxes are the result of extensive membrane peroxidative reactions and lipolysis that produce vasoactive and chemotactic eicosanoids. A diverse group of compounds has been shown to be effective in ameliorating spinal cord injury in experimental animals. These include the synthetic glucocorticoid methylprednisolone sodium succinate (MPSS); the antioxidants vitamin E, selenium, and dimethyl sulfoxide (DMSO); the opiate antagonist naloxone; and thyrotropin-releasing hormone (TRH). With the exception of TRH, all of these agents have demonstrable antioxidant and/or anti-lipid-hydrolysis properties. Thus the effectiveness of these substances may lie in their ability to quench membrane peroxidative reactions or to inhibit the release of fatty acids from membrane phospholipids, or both. Whatever the mode of action, early administration appears to be a requirement for maximum effectiveness.
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PMID:Spinal cord injury and protection. 392 95

Management of dissections of the descending thoracic aorta remains controversial, especially with regard to timing and method of repair. To clarify these and other issues we have reviewed our total experience with repair of descending aortic dissections between 1962 and 1983. The 44 men and 20 women had a mean (+/- SEM) age of 59 +/- 2 years (range, 19 to 83 years), and in all patients the dissection originated in and was limited to the aorta distal to the left carotid artery (Stanford type B, DeBakey types IIIa and IIIb). Twenty-nine patients underwent operation within 2 weeks of the onset of symptoms (acute), and the remainder had later repair (chronic). During repair, circulation distal to the aortic cross-clamp was supported with cardiopulmonary bypass or shunt in two thirds of patients. Overall, 18 deaths occurred less than or equal to 30 days postoperatively (operative risk 28%), and risk was higher in acute (45%) than in chronic (14%) dissections. Operative risk was not significantly related to protection of the distal circulation. The most serious postoperative complication was spinal cord ischemia manifested by paraplegia in five patients (8%) and transient or permanent paraparesis in six patients (9%). Risk of spinal cord ischemia was significantly lower in patients who had protection of the distal circulation during operative repair (8% vs. 44%, p = 0.003). Late survival, including hospital deaths, was 49% +/- 7% at 5 years after operation; 22 of the 46 patients who survived repair were found to have aneurysms involving the thoracic and/or abdominal segments of the aorta. Our results indicate that repair of chronic dissection of the thoracic aorta has a lower operative risk than repair of acute dissections, and initial medical management of acute dissection may be indicated if no early complications occur. Risk of spinal cord ischemia is significantly reduced by cardiopulmonary bypass or shunt and is preferred over aortic cross-clamping alone. Finally, these patients require careful long-term follow-up because of the high incidence of residual or recurrent aortic aneurysms.
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PMID:Early and late results following repair of dissections of the descending thoracic aorta. 394 28

From 1973 through 1983, 19 cases of chronic traumatic aneurysms (CTA) were observed. Initial trauma was well documented in every case. Patients mean age at time of trauma was 22; mean age at time of surgery was 34. Sixty per cent of patients had no apparent thoracic injury at time of trauma. Ninety-five per cent had associated injuries. Ten/nineteen were asymptomatic. Eighteen were operated on. Rupture was complete in 11, partial in 7. One of the partial ruptures was a simple scar on the aorta. Eighteen were located at the site of the aortic isthmus, one was at level T8-T9. Seventeen had a prosthetic dacron graft sutured from inside the aneurysm. The case where a simple scar was found had a dacron wrapping. Spinal cord protection was used in all cases except in one who was already paraplegic preoperatively. Various shunts were used in 12 cases; 1 patient in the by-pass group had paraplegia. CTA is not a benign disease and all cases, even asymptomatic, should be operated on with a very low risk of mortality (0/18). Occurrence of paraplegia still remains a possible complication although the risk of spinal cord ischemia seems lower than in arteriosclerotic dissecting aneurysms. We favour the "old" technique of temporary dacron shunt graft in CTA for simplicity and easy assessment of function ot the shunt.
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PMID:Chronic traumatic aneurysms of the descending thoracic aorta (19 cases). 395 28


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