Risk Of Spinal Cord Ischemia Research Articles

Measurements of Cerebrospinal Fluid Concentrations of S100β Protein During and After Thoracic Endovascular Stent Grafting

Thoracic endovascular aortic repair is associated with postoperative spinal cord ischemia in approximately 1 to 12.5% of all cases. S100beta is a protein that is released during acute damage of the central nervous system. This study was performed to determine the concentration of S100beta in cerebrospinal fluid during and after stenting of the thoracic aorta in patients at high risk for spinal cord ischemia. Prospective clinical study. Eight patients who underwent elective thoracic aortic stent grafting underwent lumbar spinal fluid drainage. These patients were at high risk to develop spinal cord ischemia. CSF samples for analysis of S100beta protein were drawn after induction of anesthesia, during stenting, once every hour the following six hours and 20 hours after repair. No significant increase in S100beta protein could be detected in CSF and no neurological deficits were detected postoperatively. The results of this study show us that there is no significant release of S100beta protein in CSF during stenting of the thoracic aorta in this subgroup of patients at high risk for spinal cord ischemia, consistent with clinical exam that there was no significant damage to the central nervous system.

Assessment of Spinal Cord Circulation and Function in Endovascular Treatment of Thoracic Aortic Aneurysms

In thoracic stent graft repair, the importance of segmental artery (SA) occlusion and the role of blood pressure management during the intraoperative and directly postoperative period are not clear. To study these aspects in relation to spinal cord ischemia, our protocol in the endovascular treatment of descending thoracic aneurysms covering segmental arteries T8 and lower includes preoperative assessment of the spinal cord circulation using magnetic resonance angiography, intraoperative cerebrospinal fluid drainage, and spinal cord function monitoring using motor evoked potentials (MEPs). Thirteen patients with thoracic aortic aneurysms and dissections needing stent graft coverage of T8 and lower were included. In 9 patients, spinal cord circulation was evaluated preoperatively by magnetic resonance angiography. In 12 patients, MEPs were recorded during the endovascular procedure. A combination of both techniques was used in 8 patients. The distal stent graft landing zone covered the intercostal arteries up to T10 in 4 patients, up to T11 in 7 patients, up to T12 in 1 patient, and all SAs to the aortic bifurcation in 1 patient. In 6 patients, the SA feeding the Adamkiewicz artery was covered by the stent graft. In three patients, intersegmental collaterals were present to the SA feeding the Adamkiewicz artery. The MEPs decreased to 50% and 30% in 2 patients, recovering to levels above 50% by elevation of the mean arterial pressure. Postoperatively, no signs of paraplegia were present. We believe that the presence of intersegmental collaterals decreases the risk of spinal cord ischemia during endovascular thoracic aortic aneurysm repair. Monitoring of MEPs during endovascular thoracic procedures shows no decrease in most cases. However, if a decrease of MEPs occurs, this can be reversed by elevation of the mean arterial pressure.

Ascending Aorta-to-Descending Aorta Bypass via Right Thoracotomy for the Re-Coarctation of the Aorta: An Alternative Surgical Approach for Re-Coarctation

Surgical treatment of aortic coarctation is performed with low postoperative complication rates. However, some patients may require additional surgical interventions due to stenosis or re-coarctation of the aorta, and ascending-to-descending aortic bypass via right thoracotomy is a valid alternative approach in the adult population group. Risk of massive intraoperative bleeding due to adhesions at the previous left thoracotomy site and the risk of spinal cord ischemia due to aortic cross-clamping or injury to the recurrent laryngeal nerve may be avoided with right thoracotomy in such cases. In this report, we present an adult patient with re-coarctation of the aorta who was successfully treated by extra-anatomic ascending-to-descending aortic bypass via right thoracotomy without cardiopulmonary bypass.

Anomalous right subclavian artery proximal to juxtaductal coarctation

Two patients with anomalous right subclavian artery proximal to aortic coarctation are reported for their rarity. The embryological basis and surgical implications are briefly discussed. The major surgical implication of this anomaly relates to the risk of spinal cord ischemia and in these cases, the repair was performed safely.

Efficacy and Frequency of Cerebrospinal Fluid Drainage in Operative Management of Thoracoabdominal Aortic Aneurysms

Paraplegia remains the most dreaded complication following thoracoabdominal aortic repair. We investigated the efficacy of cerebrospinal fluid drainage as a spinal cord-protecting modality. We also evaluated the correlation between the frequency of cerebrospinal fluid drainage and the Crawford classification. Spinal cord function was monitored during 20 open surgical procedures (group I) and 27 stent-graft implantations (group II). Evoked potentials and intracranial pressure were monitored in each operation. If intracranial pressure exceeded 15 mmHg, cerebrospinal fluid was drained. Cerebrospinal fluid drainage was necessary in 75 % of patients in group I (Crawford type I: 33 %, type II: 40 %, type III: 20 %, type IV: 7 %) and in 22 % of patients in group II (Crawford type I: 33 %, type II: 66 %). Evoked potential alterations correlated with an increase in intracranial pressure. Timely cerebrospinal fluid drainage reversed these changes in 72 %. Three patients remained paraplegic. Cerebrospinal fluid drainage is a valuable neuroprotective interventional tool to lower the risk of spinal cord ischemia. The combination of neurophysiological monitoring and cerebrospinal fluid drainage optimizes the prevention of paraplegia during aortic repair.

Albert Wojciech Adamkiewicz: The Discoverer of the Variable Vascularity of the Spinal Cord

The present article contains a brief biography as well as a discussion of the more significant contributions of Albert Wojciech Adamkiewicz, Head of General and Experimental Pathology at the Jagiellonian University in Cracow in the years 1879 to 1892, and who is now primarily remembered as the discoverer of the major radicular artery eponymically named "Adamkiewicz's artery." His work as an investigator of the variability of the vasculature of the spinal cord led to his major contributions to present clinical practice in such areas as vascular surgery, neurosurgery, pediatric surgery, and the surgery of the aorta, providing a permanent Polish eponymic accent in major textbooks in these specialties. This article also deals with Adamkiewicz's contributions in other fields, mostly involving the nervous system, such as the development of a new and original method for staining neuronal tissue (double staining of the spinal cord) and his extensive studies of spinal cord degeneration. The authors also present aspects of his career that brought ill fame to Adamkiewicz. These were his claims to have discovered the so-called nervous bodies and anticancer antitoxin, which were both severely criticized by his faculty peers at the Jagiellonian University. The biography is supplemented with an attempt at evaluating Adamkiewicz's entire scientific output, wherein unquestionable achievements and pointed discoveries prevail in comparison with failures.

Emergency endovascular treatment for ruptured abdominal aortic aneurysm and the risk of spinal cord ischemia

Spinal cord ischemia is a rare complication after open surgical repair for ruptured abdominal aortic aneurysms (rAAA). The use of emergency endovascular aortic aneurysm repair (eEVAR) is increasing, and paraplegia has been observed in a few patients. The objective of this study was to assess the incidence and pathogenesis of spinal cord ischemia after eEVAR in greater detail. This was a retrospective analysis of patients who had eEVAR for rAAA in three hospitals in The Netherlands and Belgium during a 3-year study period that ended in February 2004. The use of aortouniiliac devices combined with a femorofemoral crossover bypass was the preferred technique. Patients with postoperative symptoms of spinal cord ischemia were identified and the influence of potential risk factors was assessed. These factors included the presence of common iliac artery aneurysms necessitating device limb extension to the external iliac artery with associated overlapping the hypogastric artery, the prolonged interruption of bilateral hypogastric artery arterial inflow during the procedure (defined "functional aortic occlusion time" >30 minutes), and the occurrence of preoperative hemodynamic shock. Thirty-five patients were treated by EVAR and they constituted the study group. The first-month mortality in the study group with EVAR was 23%. Four patients (11.5%) with EVAR developed paraplegia postoperatively; the unilateral or bilateral hypogastric artery in all four patients became occluded during the procedure. In the other 31 patients who did not have paraplegia, the unilateral or bilateral hypogastric arteries became occluded in 14 patients (45%). This constituted a significant difference in the prevalence of hypogastric artery occlusion in patients with or without paraplegia (P = .04). The functional aortic occlusion time was prolonged in all four patients with paraplegia and in five without spinal cord ischemia (P = .0003). All four patients with spinal cord ischemia presented with hemodynamic shock. This factor did not reach a significant difference from nonparaplegic patients. Emergency EVAR continues to be a promising approach to reduce the high mortality of rAAA, but the incidence of spinal cord ischemia after endovascular treatment of rAAA was worrisome. Although the pathogenesis is most likely multifactorial, interruption of the hypogastric artery inflow appeared to have significant influence. In patients with aneurysmatic common iliac arteries, any effort should be made to minimize hypogastric occlusion time during the procedure and to maintain hypogastric artery inflow afterwards, either by the use of a bell-bottom iliac extension or by electing open repair.

Extracorporeal membrane oxygenation support during repair of traumatic aortic transection.

Acute traumatic aortic transection is a critical condition in victims of major trauma. How to avoid the complications of surgical repair is still a challenge to trauma and cardiovascular surgeons. A 74-year-old woman was referred to our hospital with multiple fractures and hypotension after a motor vehicle accident. Computed tomography revealed acute traumatic aortic transection at the upper thoracic aorta with periaortic hematoma. She underwent repair of the aortic injury after primary survey. The patient received urgent aortic grafting under heparin-free extracorporeal membrane oxygenation support for lower body perfusion. The postoperative course was smooth. No neurologic or hemorrhagic complication was noted. The results of this case indicate that extracorporeal membrane oxygenation could be used as a heparin-free partial bypass system during surgery for traumatic aortic transection. The risk of spinal cord ischemia during aortic clamp or bleeding due to heparinization during conventional cardiopulmonary bypass could be minimized.

Postoperative Paraplegia after Nonvascular Thoracic Surgery

We describe two cases of paraplegia secondary to spinal cord ischemia after thoracic surgery. After reviewing the literature, we report potential risk factors and the clinical scenarios that put patients at higher risk of spinal cord ischemia. Based on these two cases, nursing practice was revised for this susceptible group (>58 years of age, male sex, atherosclerotic disease, diabetes, hypertension and obesity) at our institution, and we were able to rapidly diagnose and successfully treat paraparesis in another patient, without any neurologic sequel. This report emphasizes the importance of vigilant neurologic and hemodynamic monitoring in patients whose intravascular volume is depleted.

Type III Thoracoabdominal Aortic Aneurysm Repair: A Combined Surgical and Endovascular Approach

Thoracoabdominal aortic aneurysm (TAAA) repair is a high-risk procedure and thoracic endovascular stenting has encouraging morbidity and mortality. We report a case of Type III TAAA repair in a patient with previous abdominal and thoracic aortic surgery, using a combined surgical and endovascular approach. This innovative method is a particularly attractive option in ‘redo’ operations such as this since it significantly reduces the extent of dissection and avoids thoracotomy.

Selective Deep Spinal Hypothermia with Vacuum-Assisted Cerebral Spinal Fluid Drainage for Thoracoabdominal Aortic Surgery

Recent experiences from several centers indicate that the overall risk of spinal cord ischemia during thoracoabdominal aortic aneurysm repair has decreased to 5–8%. The results from these centers are rather consistent, despite the use of a variety of spinal protection strategies. An alternative to the various distal aortic perfusion techniques is selective spinal cooling by cold saline lavage. The principle advantage of selective hypothermia is the avoidance systemic heparinization and extracorporeal bypasses, while affording comparable spinal protection. The primary method of spinal cooling was pioneered by Cambria et al. at Massachusetts General Hospital. In their experience, paraplegia or paresis occurred in 6.9% of patients (5-year period, 170 cases). An alternative to the Cambria method utilizes readily available perfusion supplies and offers the potential advantages of lower cerebral spinal fluid-systemic blood pressure differences, more expedient cooling, and deeper spinal hypothermia. This report describes this method and the clinical course of a patient treated with it.

The role of transcranial motor evoked potentials in predicting neurologic and histopathologic outcome after experimental spinal cord ischemia.

Monitoring of myogenic motor evoked potentials to transcranial stimulation (tcMEPs) is clinically used to assess motor pathway function during aortic and spinal procedures that carry a risk of spinal cord ischemia (SCI). Although tcMEPs presumably detect SCI before irreversible neuronal deficit occurs, and prolonged reduction of tcMEP signals is thought to be associated with impending spinal cord damage, experimental evidence to support this concept has not been provided. In this study, histopathologic and neurologic outcome was examined in a porcine model of SCI after different durations of intraoperative loss of tcMEP signals. In 15 ketamine-sufentanil-anesthetized pigs (weight, 35-45 kg) the spinal cord feeding lumbar arteries were exposed. tcMEP were recorded from the upper and lower limbs. Under normothermic conditions, animals were randomly allocated to undergo short-term tcMEP reduction (group A, < 10 min, n = 5) or prolonged tcMEP reduction (group B, 60 min, n = 10), resulting from temporary or permanent clamping of lumbar segmental arteries. Neurologic function was evaluated every 24 h, and infarction volume and the number of eosinophilic neurons and viable motoneurons in the lumbosacral spinal cord was evaluated 72 h after induction of SCI. In all animals except one, segmental artery clamping reduced tcMEP to below 25% of baseline. All but one animal in group A had reduced tcMEP for less than 10 min and had normal motor function and no infarction at 72 h after the initial tcMEP reduction. Seven animals in group B (70%) had reduced tcMEP signals for more than 60 min and were paraplegic with massive spinal cord infarction at 72 h. Two animals (one in both groups) had tcMEP loss for 40 min, with moderate infarction and normal function. In general, histopathologic damage and neurologic dysfunction did not occur when tcMEP amplitude recovered within 10 and 40 min after the initial decline, respectively. Prolonged reduction of intraoperative tcMEP amplitude is predictive for postoperative neurologic dysfunction, while recovery of the tcMEP signal within 10 min after the initial decline corresponds with normal histopathology and motor function in this experimental model. This finding confirms that intraoperative tcMEPs have a good prognostic value for neurologic outcome during procedures in which the spinal cord is at risk for ischemia.

Risk of spinal cord ischemia after endograft repair of thoracic aortic aneurysms

Background: Surgical repair of thoracoabdominal aneurysms may be associated with a significant risk of perioperative morbidity including spinal cord ischemia, which occurs at a rate of between 5% and 21%. Spinal cord ischemia after endovascular repair of thoracic aortic aneurysms (TAAs) has also been reported. This investigation reviews the occurrence of spinal cord ischemia after endovascular repair of descending TAAs at the Mount Sinai Medical Center. Patients and Methods: Between May 1997 and April 2001, 53 patients underwent endovascular exclusion of their TAA. Preprocedure computed tomography scanning and angiography were performed on all patients. All were performed in the operating room using C-arm fluoroscopy. Physical examinations and computed tomography scans were performed at discharge and at 1, 3, 6, and 12 months postoperatively and then annually thereafter. Spinal cord ischemia developed in three of the 53 patients (5.7%) postoperatively. In one patient, cord ischemia developed that manifested as early postoperative left leg weakness occurring after concomitant open infrarenal abdominal and endovascular TAA repair. The neurologic deficit resolved 12 hours after spinal drainage, steroid bolus, and the maintenance of hemodynamic stability. The remaining two patients developed delayed onset paralysis, one patient on the second postoperative day and the other patient 1 month postrepair. Both of these patients had previous abdominal aortic aneurysm repair, and both required long grafts to exclude an extensive area of their thoracic aortas. Irreversible cord ischemia and paralysis occurred in both of these patients. Conclusions: Endovascular repair of TAA has shown a promising reduction in operative morbidity; however, the risk of spinal cord ischemia remains. Concomitant or previous abdominal aortic aneurysm repair and long segment thoracic aortic exclusion appear to be important risk factors. Spinal cord protective measures (ie, cerebrospinal fluid drainage, steroids, prevention of hypotension) should be used for patients with the aforementioned risk factors undergoing endovascular TAA repair. (J Vasc Surg 2001;34:997-1003.)

Surgical repair of aneurysms involving the suprarenal, visceral, and lower thoracic aortic segments: early results and late outcome.

The purpose of this study is to review our experience with surgical repair of lower thoracoabdominal and suprarenal aortic aneurysms to determine early and late survival rates and identify factors influencing morbidity and survival among these patients. From 1989 through 1998, 165 consecutive patients underwent repair of 108 thoracoabdominal (55 group III and 53 group IV) and 57 suprarenal aneurysms. The study group consisted of 109 men and 56 women with a mean age of 70 years (median, 70 years; range, 29-89 years). Mean aneurysm diameter was 6.9 cm (median, 6.5 cm; range, 4-12 cm). There were 125 aneurysms (76%) repaired electively; 40 repairs (24%) were nonelective. The cause of 12 aneurysms (7%) was chronic aortic dissection; the remaining 153 (93%) were degenerative aneurysms. The early postoperative (30-day) mortality rates were 7% (9/125) for elective and 23% (9/40) for nonelective operations (P =.016). For both elective and urgent procedures, early mortality was 1.8% (1/57) for suprarenal aneurysm repair, 11% (6/53) for group IV thoracoabdominal aneurysms, and 20% (11/55) for group III thoracoabdominal aneurysms (P =.013, suprarenal vs group III). Spinal cord ischemia occurred after 6% (10/165) of aneurysm repairs (4% paraplegia, 2% paraparesis). None of the 57 suprarenal aneurysm repairs were complicated by spinal cord ischemia, whereas it occurred in 2% (1/53) of group IV thoracoabdominal aneurysms and 16% (9/55) of group III thoracoabdominal aneurysms (P =.001, suprarenal vs group III; P =. 016, group IV vs group III). Three (25%) of the 12 patients with dissection developed spinal cord ischemia; this compared with seven (5%) of 153 patients with degenerative aneurysms (P =.027). The cumulative 3-year survival rate for the entire series was 71% (95% CI, 64%-79%), and 5-year survival was 50% (95% CI, 40%-60%). Aneurysms involving the suprarenal, visceral, and lower thoracic aorta may be repaired with acceptable perioperative mortality and late survival rates. The risk of spinal cord ischemia is increased for patients with aortic dissection and may be stratified according to the proximal extent of the aneurysm.

ADVANCES IN SELF-LIMITED GENE EXPRESSION OF PROTECTIVE INTRACELLULAR PROTEINS IN-VIVO IN RAT BRAIN USING mRNA / CATIONIC LIPID COMPLEXES

S346 Introduction. mRNA transfection and expression of reporter gene proteins in vivo in rat central nervous system (CNS) and in neuronal and non-neuronal cells using non-viral delivery have been described [1]. Cationic lipid/mRNA complexes stabilize the nucleic acid in the extracellular environment [2]. Stabilizing sequences in the optimized DNA construct, from which the mRNA is transcribed, serve the same function in the intracellular milieu [3]. These data support the feasibility of mRNA therapy for pre-operative expression of protective intracellular proteins. Heat shock proteins (HSP) are members of a highly conserved family of molecular chaperones, some of which are rapidly induced by heat stress. Pretreatment with heat shock leads to increased survival after ischemic and hypoxic stress in cells, perfused organs, and in whole animals [4]. Transient expression of the inducible, protective isoform of the HSP70, HSP70-1, also known as HSP72 [5], by delivery of mRNA is therefore hypothesized to be a means of improving cellular survival, and would be anovel application of gene transfer technology. Surgical patients present a unique situation, for whom a risk of surgical, ischemic, or hypoxic stress can be predicted. Despite the best anesthetic management, surgical manipulation during neurosurgical resection can create regional ischemia and hypoxic regions of brain. If hypotension and hyperventilation contribute to a decreased cerebral perfusion pressure, hypoperfusion can be even more significant, leading to areas of "watershed" neural tissue that is at risk for cell death [6]. The same can occur during cardiac bypass, due to an embolic shower of both gases and particulate from atherosclerotic vessel walls. Surgical procedures which require hypothermic circulatory arrest are also associated with neurological or neuropsychological deficits in the human. Risks of spinal cord ischemia leading to paraplegia after thoracic aneurysm surgery can be as high as 15%. Transient expression of protective intracellular proteins before a potentially severe stress could allow recovery of a greater fraction of the cells at risk. Methods. A variety of stabilized reporter mRNA transcripts encoded by HSP70-1, beta-galactosidase (beta-gal) and P. pyralis luciferase cDNA have been used to transfect neuronal and non-neuronal cells in culture. Transfections were optimized using novel cationic lipids [7] and formulation conditions [8]. Uptake and translation was demonstrated by chemiluminescent reaction assay of either beta-gal or luciferase and by Elisa and Western blot analysis of HSP70-1. Nucleic acid/cationic lipid complexes were then injected or infused into rat CNS parenchyma and ventricle and tissues were assayed for chemiluminescence. Results. Expression using mRNA in 30 to 45 minutes is seen, with a peak in expression at 6 hours. Levels of expression with mRNA transcripts compare well with DNA transfections, however DNA transfections take longer to reach similar levels of expression. Delivery, uptake and expression of HSP70-1 is demonstrated in vitro in neuronal cells and in vivo in rat brain. Formulation methods for in vivo transfection have been optimized [8] (see Table 1). Experiments which quantify protective effects of exogenous HSP70-1 expression are underway.Table 1: Results of in vivo rat brain transfections. Rats #1 and 2 were transfected with 2[micro sign]g DNA, all others received 2[micro sign]g mRNA. Injections were unilateral (#1-3) or bilateral (#4-6). Left ventricles were used as negative controls in #1-3. Luciferase in controls was not significantly above zero.Conclusions. Transfection with mRNA/cationic lipid complexes, which are self-limited, rapidly achieves significant expression of intracellular proteins. Results support the further development of mRNA-based HSP therapy for pre-operative protection from ischemic CNS damage.

A computer-controlled, closed-loop infusion system for infusing muscle relaxants: Its use during motor-evoked potential monitoring

A microcomputer-controlled closed-loop infusion system (MCCLIS) has been developed that provides stable intraoperative levels of partial neuromuscular blockade. Complete neuromuscular blockade interferes with intraoperative motorevoked potential (MEP) monitoring used for patients undergoing surgical procedures that place them at risk for spinal cord ischemia. Nine patients were studied during which the MCCLIS maintained stable levels of partial neuromuscular blockade and allowed transcranial magnetic motor-evoked potential (TcM-MEP) monitoring during thoracoabdominal aortic aneurysmectomy. The use of TcM-MEP for monitoring intraoperative spinal cord function was balanced against surgical considerations for muscle relaxation with 80% to 90% neuromuscular blockade fulfilling each requirement. Intraoperative adjustment of partial neuromuscular blockade to facilitate TcM-MEP monitoring was also possible with the MCCLIS. The MCCLIS should allow for further investigation into the sensitivity, specificity, and predictability of TcM-MEP monitoring for any patient at risk for intraoperative spinal cord ischemia including those undergoing thoracoobdominal aortic aneurysmectomy.

One-stage segmental resection of extensive thoracoabdominal aneurysms with left-sided heart bypass

Purpose: The purpose of this study is to describe a technique for resection of extensive thoracoabdominal aneurysms, which the authors believe will lower morbidity and mortality rates.Methods: In an effort to minimize the risk of spinal cord ischemia, we have used a combination of sided heart bypass (left atrium to left femoral artery) with local cooling of the intercostal and visceral arteries and segmental resection of the aneurysm. Segmental resection of the aneurysm allows perfusion of the spinal cord and abdominal viscera as the proximal anastomosis is completed and as each pair of intercostal arteries is reimplanted. An attempt is made to reimplant all pairs of intercostal arteries from T8 to L2. Before the intercostal or visceral arteries are reimplanted, that segment of aorta is cooled with cold crystaloid solution. Thus no segment of the aorta is exposed to warm ischemia for more than 30 minutes. Left-sided heart bypass allows the patient's temperature to be maintained between 35° and 37° C.Results: We have used this technique in 23 patients with types I and II (Crawford's classification) thoracoabdominal aneurysms. Seven patients (30%) had dissections or rupture associated with their aneurysms and underwent emergency operation. One of these seven patients became paraplegic after operation, for a 4.3% incidence of paraplegia. One patient died of multiple organ failure after operation. No patient had kidney failure requiring dialysis.Conclusions: We believe that our technique allows the operation to be performed in a deliberate manner with a low incidence of paraplegia and kidney failure.

Acute traumatic isthmic aortic rupture. Long-term results in 49 patients.

Forty-nine patients who sustained acute traumatic rupture of the aorta at the level of the isthmus were treated in our hospital between 1976 and 1990. Four patients died before surgery and 45 patients were operated upon using a pump oxygenator partial bypass in all but 2 cases (1 clamp and sew and 1 shunt). The tear was circumferential in 33 and partial in 12 cases. Direct suture was used in the 12 partial and in 21 of the circumferential tears. A dacron tube was used in 12 patients. Hospital mortality was 3 resulting from brain damage, prolonged shock before surgery and necrosis of the colon 4 weeks after operation. No paraplegia was observed. There were 2 cases of neurological disturbance (2 spinal cord dysfunction 5 and 8 days, respectively, after surgery). These complications were transient. Among the 42 survivors, 1 was lost to follow-up. The clinical aortic status of the remaining 41 was excellent. Aortic reconstitution as assessed by digital aortic angiography was excellent in the 33 cases examined with 2 exceptions (graft stenosis, false aneurysm). Our experience and review of a large series indicate: the use of a partial bypass with pump oxygenator decreases the probability of medullary ischemia, but the risk of spinal cord ischemia is not eliminated. When intra-abdominal lesions are life-threatening, laparotomy must preceed thoracotomy. Clinical results assessed in long-term survivors are excellent, especially after direct repair.

Sodium nitroprusside decreases spinal cord perfusion pressure during descending thoracic aortic cross-clamping in the dog

Paraplegia is a devastating complication of surgery on the descending thoracic aorta. During surgical repair, the aorta is cross-clamped, and nitroprusside is often used to treat arterial hypertension that can occur above the cross-clamp. Twenty-one dogs were studied to determine the effects of nitroprusside on intraspinal pressures, mean aortic pressures below the cross-clamp, and spinal cord perfusion pressure. Perfusion pressure in spinal radicular arteries originating below the aortic cross-clamp was estimated as the distal aortic pressure minus intraspinal pressure. Nitroprusside was used to return the mean arterial pressure above the cross-clamp to values similar to the pre-cross-clamp levels in 7 dogs. Fourteen animals did not receive sodium nitroprusside. Aortic cross-clamping resulted in small but significant increases in intraspinal pressure (4.3 ± 0.8 to 7.5 ± 0.9 mm Hg in non-nitroprusside-treated dogs, and 3.4 ± 1.0 to 5.6 ± 1.5 mm Hg in the nitroprusside group before nitroprusside). Nitroprusside caused a further increase in intraspinal pressure (5.6 ± 1.5 to 8.3 ± 2.2 mm Hg) and a decrease in aortic pressure below the cross-clamp (26 ± 5 to 18 ± 4 mm Hg). The increase in intraspinal pressure and the decrease in aortic pressure below the crossclamp after nitroprusside resulted in a decrease in spinal cord perfusion pressure from 19 ± 5 mm Hg to 11 ± 4 mm Hg. Because nitroprusside decreases spinal cord perfusion pressure and may increase the risk of spinal cord ischemia, the avoidance of large doses of nitroprusside to arbitrarily return mean arterial pressure above the cross-clamp to pre-cross-clamp levels is recommended.

Early and late results following repair of dissections of the descending thoracic aorta.

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.