Combined use of cerebral spinal fluid drainage and naloxone reduces the risk of paraplegia in thoracoabdominal aneurysm repair

Does high-dose opioid anesthesia exacerbate ischemic spinal cord injury in rabbits?

PURPOSE

Intrathecal morphine given during a post-ischemic period has been reported to have the potential to exacerbate ischemic spinal cord injury. However, it remains unknown whether synthetic opioids administered systemically exacerbate ischemic injury. We sought to compare the damage of the spinal cord after transient spinal cord ischemia in rabbits anesthetized with three different regimens; isoflurane, fentanyl with isoflurane, and remifentanil with isoflurane.

METHODS

We assigned rabbits to three groups (n = 9 in each); an isoflurane group (isoflurane 1 minimum alveolar concentration [MAC]), a fentanyl group (isoflurane 0.5 MAC + 100 microg x kg(-1) i.v. fentanyl given over 30 min before aortic occlusion), and a remifentanil group (isoflurane 0.5 MAC + 1 microg x kg(-1) x min(-1) i.v. remifentanil started 30 min before aortic occlusion and maintained until 1 h after reperfusion). Spinal cord ischemia was produced by occluding the abdominal aorta for 13 min. Hindlimb motor function (score range: 4, normal to 0, paraplegia) was assessed daily for 7 days, and then the number of normal neurons in the anterior spinal cord was counted.

RESULTS

Severe motor dysfunction (score < or = 1) was observed in seven, four, and five animals in the isoflurane, fentanyl, and remifentanil groups, respectively. There were no significant intergroup differences in neurological scores. There were no differences in the numbers of normal neurons among the three groups (22 +/- 22, 42 +/- 30, 33 +/- 28, respectively).

CONCLUSION

Our results suggest that neither i.v. fentanyl nor i.v. remifentanil added to 0.5 MAC isoflurane exacerbated ischemic spinal cord injury in rabbits when compared to 1 MAC isoflurane.

Albert Wojciech Adamkiewicz (1850-1921): unsung hero behind the eponymic artery

The artery of Adamkiewicz is an important radiculomedullary artery supplying the spinal cord, especially the lumbar enlargement. Anatomical knowledge of this artery is important for avoiding serious neurological complications during surgery performed in this region--for neurosurgeons and interventional radiologists treating intramedullary tumors and spinal arteriovenous malformations, traumatologists performing spinal fusions, thoracic surgeons treating aortic aneurysms, and urologists and pediatric surgeons conducting retroperitoneal dissections. However, the biography of the talented Polish pathologist Albert Adamkiewicz, after whom the landmark artery is named, has not been described adequately in the existing neurosurgical literature. The authors bring to light the historical perspective of the eponymic artery and provide a recapitulation of other significant contributions made by Adamkiewicz, mostly involving the nervous system. His research papers on the histology of neuronal tissues and neurodegenerative diseases had high scientific merit, but the discovery of the anticancer antitoxin "cancroin" and his postulation of a cancer-causing parasite he named "Coccidium sarcolytus" met with harsh criticism and eventually led to his ill fame. The biography is supplemented with a brief overview of the important surgical implications of the artery of Adamkiewicz.

A quantitative assessment of the impact of intercostal artery reimplantation on paralysis risk in thoracoabdominal aortic aneurysm repair

OBJECTIVES

We previously demonstrated an 80% reduction in paraplegia risk using hypothermia, naloxone, steroids, spinal fluid drainage, intercostal ligation, and optimizing hemodynamic parameters. This report demonstrates that intercostal revascularization for the last 3 years further reduced our paraplegia risk index by 75%.

METHODS

We evaluated 655 patients who had thoracic or thoracoabdominal aneurysm repair for factors that affected paraplegia risk including aneurysm extent, acuity, cardiac function, blood pressure mean arterial pressure, and spinal fluid drainage with naloxone (SFDN). Eighteen patients died during or shortly after surgery leaving 637 patients for analysis of paralysis. We evaluated the effect of intercostal reimplantation (IRP) using a highly accurate (r(2) > 0.88) paraplegia risk index we developed and published previously.

RESULTS

Fifty-eight percent of patients were male with a mean age of 67. Thirty-three percent were acute with rupture, acute dissection, mycotic aortitis, and trauma. Eighty (12%) had dissections. Thirty-five patients had paraplegia or paraparesis (5.4%). Significant factors by univariate analysis (P < 0.05) were Crawford type 2, acuity, SFDN, cardiac index after unclamping, mean arterial pressure during crossclamping, and IRP. In multivariate modeling, aneurysm extent, SFDN, acuity, and IRP remained significant (P < 0.02). The paraplegia risk index declined from 0.20 to 0.05 (P < 0.03).

CONCLUSIONS

The incidence of paralysis after TAAA repair decreased from 4.83% to 0.88% and paralysis risk index decreased from 0.26 to 0.05 when intercostal artery reimplantation was added to neuroprotective strategies that had already substantially reduced paralysis risk. These findings suggest that factors that affect collateral blood flow and metabolism account for approximately 80% of paraplegia risk and intercostal blood flow accounts for 20% of risk. This suggests a limit to paraplegia risk reduction in thoracoabdominal endograft patients. Early results in this emerging field support this prediction of high paraplegia risk with thoracoabdominal branched endografts with extensive aortic coverage.

Hypothermia for spinal cord injury

BACKGROUND CONTEXT

Interest in systemic and local hypothermia extends back over many decades, and both have been investigated as potential neuroprotective interventions in a number of clinical settings, including traumatic brain injury, stroke, cardiac arrest, and both intracranial and thoracoabdominal aortic aneurysm surgery. The recent use of systemic hypothermia in an injured National Football League football player has focused a great deal of attention on the potential use of hypothermia in acute spinal cord injury.

PURPOSE

To provide spinal clinicians with an overview of the biological rationale for using hypothermia, the past studies and current clinical applications of hypothermia, and the basic science studies and clinical reports of the use of hypothermia in acute traumatic spinal cord injury.

STUDY DESIGN/SETTING

A review of the English literature on hypothermia was performed, starting with the original clinical description of the use of systemic hypothermia in 1940. Pertinent basic science and clinical articles were identified using PubMed and the bibliographies of the articles.

METHODS

Each article was reviewed to provide a concise description of hypothermia's biological rationale, current clinical applications, complications, and experience as a neuroprotective intervention in spinal cord injury.

RESULTS

Hypothermia has a multitude of physiologic effects. From a neuroprotective standpoint, hypothermia slows basic enzymatic activity, reduces the cell's energy requirements, and thus maintains Adenosine Triphosphate (ATP) concentrations. As such, systemic hypothermia has been shown to be neuroprotective in patients after cardiac arrest, although its benefit in other clinical settings such as traumatic brain injury, stroke, and intracranial aneurysm surgery has not been demonstrated. Animal studies of local and systemic hypothermia in traumatic spinal cord injury models have produced mixed results. Local hypothermia was actively studied in the 1970s in human acute traumatic spinal cord injury, but no case series of this intervention has been published since 1984. No peer-reviewed clinical literature could be found, which describes the application of systemic hypothermia in acute traumatic spinal cord injury.

CONCLUSIONS

Animal studies of acute traumatic spinal cord injury have not revealed a consistent neuroprotective benefit to either systemic or local hypothermia. Human studies of local hypothermia after acute traumatic spinal cord injury have not been published for over two decades. No peer-reviewed studies describing the use of systemic hypothermia in this setting could be found. Although a cogent biological rationale may exist for the use of local or systemic hypothermia in acute traumatic spinal cord injury, there is little scientific literature currently available to substantiate the clinical use of either in human patients.

Surgical strategy for advanced gastric cancer with a concomitant thoracoabdominal aortic aneurysm requiring arterial reconstruction of the visceral branches

A 70-year-old man who presented with hematemesis was found to have advanced gastric cancer concomitant with a thoracoabdominal aortic aneurysm (TAAA), which involved all branches of the visceral arteries. The patient underwent the following staged operations: first, radical resection of the advanced gastric cancer with simultaneous reconstruction of the visceral branches, followed 1 month later by endovascular aortic replacement of the TAAA. He recovered uneventfully and was discharged without any paralytic complications or sign of graft infection.

Contemporary results of open repair of ruptured descending thoracic and thoracoabdominal aortic aneurysms

OBJECTIVE

The purpose of this study was to evaluate the results of open repair for ruptured descending thoracic and thoracoabdominal aortic aneurysm (RDTAA).

METHODS

A retrospective review identified 41 consecutive cases of open surgical repair in 40 patients presenting with nontraumatic, atherosclerotic RDTAA from 1996 to 2006. Patients with traumatic injuries or complicated dissections were excluded. Patient characteristics and preoperative, intraoperative, and postoperative variables were collected from the medical record. Univariate and logistic regression were used to identify factors contributing to mortality and morbidity in these patients.

RESULTS

The operative mortality rate was 26.8% (11/41). All but two deaths occurred within 24 hours of operation; seven were intraoperative. Overall actuarial survival rates at 1 and 2 years were 53.7% and 47.1%, respectively. For those who survived to hospital discharge, the respective numbers were 73.3% and 64.4%. Intraoperative hypotension and blood transfusion requirements were independent predictors of perioperative death. Octogenarians had a mortality rate equivalent to that of the younger population (25% vs 27.6%; not significant). There was a strong trend toward an improved outcome in the latter part (2003-2006) compared with the first part (1995-2002; 13.6% vs 42.1%, respectively; P = .075).

CONCLUSIONS

Direct open repair for RDTAA can be achieved with acceptable mortality and morbidity rates even in elderly patients. Improved outcome can be expected with increased volume and experience. This series should help establish a reference against which the results of endovascular endeavors and hybrid procedures could be compared.

Treatment methods for spinal cord injury caused by acute type B aortic dissection

Acute distal aortic dissection rarely causes spinal cord ischemia presenting with paraplegia or paraparesis. Spinal cord involvement has poor outcomes, and there is no established effective treatment for this disorder. In this report we describe the acute conservative treatment of two cases of paraplegia/paraparesis due to acute type B aortic dissection. Early reversal of lower-limb dysmobility was achieved.

Thoracic and Thoracoabdominal Aneurysm Repair: Is Reimplantation of Spinal Cord Arteries a Waste of Time?

BACKGROUND

The impact of different strategies for management of intercostal and lumbar arteries during repair of thoracic and thoracoabdominal aortic aneurysms (TAA/A) on the prevention of paraplegia remains poorly understood.

METHODS

One hundred consecutive patients with intraoperative monitoring of motor evoked potentials (MEP) and somatosensory evoked potentials (SSEP) during TAA/A repair involving serial segmental artery sacrifice (October 2002 to December 2004) were reviewed.

RESULTS

Operative mortality was 6%. The median intensive care unit stay was 2.5 days (IQ range: 1-4 days), and the median hospital stay 10.0 days (IQ range: 8-17 days). Potentials remained unchanged during the course of serial segmental artery sacrifice, or could be returned to baseline levels by anesthetic and blood pressure manipulation, in 99 of 100 cases. An average of 8.0 +/- 2.6 segmental artery pairs were sacrificed overall, with an average of 4.5 +/- 2.1 segmental pairs sacrificed between T7 and L1, where the artery of Adamkiewicz is presumed to arise. Postoperative paraplegia occurred in 2 patients. In 1, immediate paraplegia was precipitated by an intraoperative dissection, resulting in 6 hours of lower body ischemia. A second ambulatory patient had severe paraparesis albeit normal cerebral function after resuscitation from a respiratory arrest.

CONCLUSIONS

With monitoring of MEP and SSEP, sacrifice--without reimplantation--of as many as 15 intercostal and lumbar arteries during TAA/A repair is safe, resulting in acceptably low rates of immediate and delayed paraplegia. This experience suggests that routine surgical implantation of segmental vessels is not indicated, and that, with evolving understanding of spinal cord perfusion, endovascular repair of the entire thoracic aorta should ultimately be possible without spinal cord injury.

Contemporary results of open surgical repair of descending thoracic aortic aneurysms

Considerable progress has been made in the refinement of operative strategies to repair descending thoracic aortic aneurysms (TAA). While no single strategy has totally eliminated the postoperative morbidities of renovisceral and spinal cord ischemic complications, contemporary reports from centers of excellence detail admirable rates of overall risk in the 5-10% range. Balancing these risks represents a clinical dilemma for the aortic surgeon and a thoughtful, logical risk analysis of the individual patient presentation is clearly warranted before TAA repair. In this article, we review surgical approaches to TAA and adjunctive methods, examine the reports from centers of excellence, and elucidate the challenges yet to be overcome in the management of patients with aneurysms of the descending thoracic aorta.

The mitochondrial K-ATP channel opener, diazoxide, prevents ischemia-reperfusion injury in the rabbit spinal cord

Paraplegia resulting from ischemia is a catastrophic complication of thoracoabdominal aortic surgery. The current study was designed to investigate the effects of diazoxide (DZ) on mitochondrial structure, neurological function, DNA damage-repair, and apoptosis in spinal cord ischemia-reperfusion injury. Rabbits were subjected to 30 minutes of spinal cord ischemia and reperfusion (1 hour) with or without diazoxide (n = 6 in each group) by clamping and releasing the infrarenal aorta. The neurological functional score was significantly improved in the DZ-treated ischemia-reperfusion injury group. Electron microscopic studies demonstrated that mitochondrial damage in the spinal cord after injury was significantly reduced by DZ. Mitochondrial superoxide and hydrogen peroxide levels were also markedly decreased in the DZ-treated injury group compared with the untreated group. DZ decreased levels of the oxidative DNA damage product 8-oxoG and increased levels of the DNA repair enzyme OGG-1. Furthermore, DZ inhibited apoptosis via caspase-dependent and -independent pathways. These studies indicate for the first time that the mitochondrial K-ATP channel opener diazoxide improves neurological function after spinal cord ischemia and reperfusion by diminishing levels of reactive oxygen species, decreasing DNA oxidative damage, and inhibiting caspase-dependent and -independent apoptotic pathways while preserving mitochondrial structure.

Experimental study on the protective effects of edaravone against ischemic spinal cord injury

OBJECTIVE

Reactive free radical species are thought to be involved in ischemic spinal cord injury. We investigated the effects of edaravone (Mitsubishi Pharma Co, Tokyo, Japan), a free radical scavenger, on spinal ischemia-reperfusion injury in a rabbit model. We also sought to estimate free radicals in the spinal cord using the microdialysis method.

METHODS

Spinal cord ischemia was induced in New Zealand White rabbits. The animals were then divided into 4 groups. In the first experiment, which was carried out in group A (non-edaravone treated) and group B (edaravone treated), we assessed neurologic function and evaluated spinal cord histopathology. In the second experiment, which was performed in group C (non-edaravone treated) and group D (edaravone treated), we sequentially estimated the level of free radical species in the spinal cord with the microdialysis method.

RESULTS

In the first experiment group B showed better neurologic function than group A. The number of viable neurons in the spinal cord gray matter was also higher in group B than in group A. The second experiment revealed that the level of free radical species was lower in group D at 75, 90, and 150 minutes after the beginning of reperfusion compared with levels seen in group C. The appearance of free radical species in the latter group was found to have a biphasic pattern, with peaks at 75 and 150 minutes after the beginning of reperfusion.

CONCLUSION

Edaravone exerted a significant protective effect on the spinal cord against ischemia-reperfusion injury by suppressing the level of free radical species, which was demonstrated with the microdialysis method.

Combined stent-graft and surgical treatment for a thoracoabdominal aortic aneurysm in a high risk patient

We report a case of thoracoabdominal aortic aneurysm (TAAA) Crawford type I with high-risk factors. A 74-year-old woman, who had a history of myocardial infarction with severe left ventricular dysfunction, asthma, and hypothyroidism, underwent endovascular stent-graft replacement for TAAA and simultaneous surgical reconstruction of the visceral arteries to avoid thoracotomy and extracorporeal circulation. Postoperatively she suffered from weakness of the left leg, with suspected paraparesis, but recovered muscular strength to some extent and was discharged in a wheelchair on postoperative day 74.

Naloxone lowers cerebrospinal fluid levels of excitatory amino acids after thoracoabdominal aortic surgery

OBJECTIVE

Although naloxone has been used to prevent ischemic spinal cord injury (SCI), its effect on excitatory amino acids (EAAs) has not been understood. We investigated the clinical significance of naloxone by measuring EAAs in the cerebrospinal fluid (CSF) in patients undergoing thoracoabdominal aortic surgery.

METHODS AND SUBJECTS

Twenty-seven patients (15 men and 12 women; mean age, 66 +/- 12 years) undergoing prosthetic replacement of the thoracoabdominal aorta (n = 19) or the descending thoracic aorta (n = 8) from April 1997 to June 2003 under distal perfusion and mild hypothermia were enrolled in this cohort study with historical controls. Their etiology was 7 dissections and 20 nondissections. In 16 patients (naloxone group), intravenous infusion of naloxone (1 microg/kg/h) was continued until the patients became alert. In the remaining 11 patients (control group) naloxone was not given. CSF drainage was used in all patients. CSF levels of EAAs, glutamate, aspartate, and glycine were measured at 6 points in time until 72 hours postoperatively, using a high-performance liquid chromatography method.

RESULTS

In 5 patients with SCI (2 patients in control group, 3 in naloxone group), CSF levels of glutamate and glycine continued to increase even at 72 hours postoperatively, and were significantly more elevated than those in patients without SCI ( P < .0001, glutamate; P = .0006, glycine). Postoperative maximum levels of CSF glutamate and glycine were also significantly higher in patients with postoperative SCI than in patients without SCI (glutamate: 215.3% +/- 158.6% vs 32.9% +/- 37.3% increase from baseline, P < .0001; glycine: 309.1% +/- 218.2% vs 89.2% +/- 103.1% increase from baseline, P = .0036). CSF levels of glutamate and aspartate in naloxone group were significantly lower than those in control group ( P = .0161, glutamate; P < .0001, aspartate). Postoperative maximum level of CSF aspartate was also significantly lower in the naloxone group than in the control group (8.3% +/- 75.5% vs 119.7% +/- 120.6% increase from baseline, P = .0077). In multivariate logistic regression analysis, postoperative maximum CSF glutamate >100% from baseline ( P < .001) and postoperative maximum level of CSF glycine ( P = .005)were identified as the independent risk factors for SCI. Both SCI ( P < .001) and postoperative maximum level of CSF glycine ( P = .005) were the independent predictors for postoperative maximum level of CSF glutamate >100% from baseline.

CONCLUSIONS

CSF levels of EAAs are elevated in patients with SCI. CSF glutamate is the strongest independent predictor of SCI. Naloxone is effective in lowering CSF levels of EAAs.

Two-Stage Combined Endovascular and Surgical Approach for Recurrent Thoracoabdominal Aortic Aneurysm

PURPOSE

To present a 2-stage combined endovascular and surgical approach for recurrent thoracoabdominal aortic aneurysm (TAAA).

CASE REPORT

A 78-year-old man with previous surgical repairs of infrarenal abdominal and descending thoracic aortic aneurysms was referred for dysphagia due to an enlarging 9-cm aneurysm extending from the mid thoracic to the suprarenal aorta. Because no suitable endograft was available, an open repair was attempted, but the presence of a "frozen" chest made the redo procedure extremely difficult. A 2-stage treatment was thus decided upon. First, a retrograde bifurcated bypass graft was implanted from the abdominal aortic graft to the superior mesenteric and celiac arteries. Twenty days later, the TAAA was successfully excluded with a stent-graft, during which spinal fluid drainage was performed to prevent paraplegia. At 6 months, computed tomography showed patency of the endoprosthesis and visceral grafts. At 1 year, the patient remains asymptomatic.

CONCLUSIONS

This case illustrates that a 2-stage combined endovascular and surgical approach may be a safe and effective alternative to reoperation for recurrent TAAA.

Preoperative selective intercostal angiography in patients undergoing thoracoabdominal aneurysm repair

OBJECTIVE

This study was designed to test the hypothesis that detection of the location of the major artery supplying the spinal cord, that is, the artery of Adamkiewicz or the great radicular artery (GRA), with angiography would help prevent paraplegia. Knowing which intercostal artery provides this important branch would enable prompt, focused revascularization.

METHOD

The surgical outcome in 131 patients with Crawford extent 1 and 2 degenerative aneurysms and 69 patients with descending thoracic aortic dissection was correlated with findings on selective intercostal arteriograms. Angiographic maneuvers were done with care, and the procedures were aborted if there was loose or "shaggy" mural thrombus, significant tortuosity, or difficulty entering each dissection channel. No attempts were made to find major contributions proximal to T6. Subarachnoid drains were placed in all patients, and all but five patients underwent distal aortic perfusion with controlled cooling to 32 degrees F. Five patients underwent cold circulatory arrest, enabling replacement of the distal aortic arch. We defined paraplegia simply as the inability to walk at hospital discharge, paraparesis as impaired ambulation, and both as having spinal cord dysfunction (SCD).

RESULTS

A GRA was found in 65 (43%)of the 151 patients studied. Of the 65 patients with the GRA identified, SCD developed in 3 (4.6%) patients. Thirteen of 135 (9.6%) patients in whom the GRA was not identified, either because they were not studied or were studied and the GRA was not found, developed SCD (P =.35) However, when the GRA was identified, SCD occurred only in the group with aortic dissection. None of the 45 patients with degenerative aneurysms with the GRA identified had SCD, compared with 9 of 55 (16%) patients studied but without a GRA found (P =.01).

CONCLUSION

The approach with selective intercostal angiography did not improve overall results. One third of our patients were not studied, and they fared as well as patients who were studied and the GRA was localized (not studied, 4 of 49, 8% with SCD; GRA localized, 3 of 65, 5% with SCD; P =.8). However, when the GRA was found, SCD occurred only in patients with aortic dissection. The studies confirmed the concept that the existence of mural thrombus in degenerative aneurysms results in the occlusion of many intercostal arteries, leaving those remaining patent to supply rich vascular watersheds through acquired collateral channels. As a result, in the group of patients with degenerative aneurysms, the identification of the critical intercostal artery allows focused reimplantation with uniform success. This is not the case in patients with aortic dissection. In those patients, most intercostal vessels remain patent, such that the insertion of one pair is insufficient to supply the paravertebral plexus and the spinal cord. Finally, failure to identify the GRA angiographically with our methods does not provide assurance that the GRA does not exist. Therefore negative findings did not provide license to ligate all intercostal arteries.

Cerebrospinal fluid drainage for thoracic and thoracoabdominal aortic aneurysm surgery

BACKGROUND

During aortic aneurysm surgery, cross-clamping can lead to inadequate blood supply to the spinal cord resulting in neurological deficit. Cerebrospinal fluid drainage (CSFD) may increase the perfusion pressure to the spinal cord and hence reduce the risk of ischaemic spinal cord injury.

OBJECTIVES

To determine the effect of CSFD during thoracic and thoracoabdominal aortic aneurysm (TAAA) surgery on the risk of developing spinal cord injury.

SEARCH STRATEGY

The reviewers searched the Cochrane Peripheral Vascular Diseases Group Specialised Trials Register (last searched October 2003), the Cochrane Central Register of Controlled Trials (CENTRAL) database (last searched Issue 4, 2003), MEDLINE and EMBASE, and reference lists of relevant articles. Recent conference proceedings were scanned.

SELECTION CRITERIA

Randomised trials involving CSFD during thoracic and TAAA surgery.

DATA COLLECTION AND ANALYSIS

Both reviewers assessed the quality of trials independently. One reviewer (SNK) extracted data and the other reviewer (GS) verified the data.

MAIN RESULTS

Three trials, with a total of 287 participants operated on for type I or II TAAA, were included. In the first trial of 98 patients, neurological deficits in the lower extremities occurred in 14 (30%) CSFD and 17 (33%) controls. The deficit was observed within 24 hours of the operation in 21 (68%), and from 3 to 22 days in 10 (32%). CSFD did not have a significant benefit in preventing ischaemic injury to the spinal cord. The second trial of 33 patients used a combination of CSFD and intrathecal papaverine. It showed a statistically significant reduction in the rate of postoperative neurological deficit (p = 0.039), compared to controls. Analysis was undertaken after only one third of the estimated sample size had entered the trial. In the third trial TAAA repair was performed on 145 patients. CSFD was initiated during the operation and continued for 48 hours after surgery. Paraplegia or paraparesis occurred in 9 of 74 patients (12.2%) in the control group versus 2 of 82 patients (2.7%) with CSFD (p = 0.03). Overall, CSFD resulted in an 80% reduction in the relative risk of postoperative deficits. Meta-analysis showed an odds ratio (OR) of 0.48 (0.25 to 0.92; confidence interval (CI) 95%). For CSFD trials only OR was 0.57 (0.28 to 1.17) and for intention-to-treat in CSFD only studies OR remained unchanged.

REVIEWER'S CONCLUSIONS

There are limited data supporting the role of CSFD in thoracic and thoracoabdominal aneurysm surgery for prevention of neurological injury. Further clinical and experimental studies are indicated.

Distal aortic perfusion and cerebrospinal fluid drainage for thoracoabdominal and descending thoracic aortic repair: ten years of organ protection

OBJECTIVE

To report the long-term results of our experience using cerebrospinal fluid drainage and distal aortic perfusion in descending thoracic and thoracoabdominal aortic repair.

SUMMARY BACKGROUND DATA

Repair of thoracoabdominal and thoracic aortic aneurysm by the traditional clamp-and-go technique results in a massive ischemic insult to several major organ systems. Ten years ago, we began to use distal aortic perfusion and cerebrospinal fluid drainage (adjunct) to reduce end-organ ischemia.

METHODS

Between January 1991 and February 2003, we performed 1004 thoracoabdominal or descending thoracic repairs. Adjunct was used in 741 (74%) of 1004. Multivariable data were analyzed by Cox regression. Number needed to treat was calculated as the reciprocal of the risk difference.

RESULTS

Immediate neurologic deficit was 18 (2.4%) of 741 with adjunct and 18 (6.8%) of 263 without (P < 0.0009). In high-risk extent II aneurysms, the numbers were 11 (6.6%) of 167 with adjunct, and 11 (29%) of 38 without. Long-term survival was improved with adjunct (P < 0.002). The long-term survival results persisted after adjustment for age, extent II aneurysm, and preoperative renal function.

CONCLUSION

Use of adjunct over a long period of time has produced favorable results; approximately 1 neurologic deficit saved for every 20 uses of adjunct overall. In extent II aneurysms, where the effect is greatest, this increases to 1 saved per 5 uses. Adjunct is also associated with long-term survival, which is consistent with mitigation of ischemic end-organ injury. These long-term results indicate that cerebrospinal fluid drainage and distal aortic perfusion are safe and effective adjunct for reducing morbidity and mortality following thoracic and thoracoabdominal aortic repair.

Regional hypothermia with epidural cooling for prevention of spinal cord ischemic complications after thoracoabdominal aortic surgery

Multiple operative adjuncts have been developed and clinically applied to reduce the incidence of spinal cord ischemic complications (SCI) after thoracoabdominal aneurysm (TAA) repair. Hypothermia is known to reduce oxygen requirements in central nervous tissue and has been successfully applied in the arena of central cardioaortic surgery. Based on our experimental and clinical results, we have employed regional hypothermia by epidural cooling to ameliorate SCI during TAA repair in over 300 patients. This review describes the results obtained in our experience using an approach to TAA repair whereupon the spinal cord is protected during surgery by regional hypothermia via epidural cooling.

The use of left heart bypass in the repair of thoracoabdominal aortic aneurysms: current techniques and results

The surgical repair of thoracoabdominal aortic aneurysms (TAAA) remains challenging. The prevention of spinal cord ischemic complications requires a multidisciplinary approach. The protective effect of left heart bypass (LHB), particularly regarding spinal cord ischemia, during the repair of extensive TAAA is evaluated here. Data from 1,250 consecutive patients who underwent the repair of extent I or extent II TAAA over a 16-year period was prospectively entered into a database. LHB was used in 666 (53.3%) patients. This group was retrospectively compared with 584 (46.7%) patients who had undergone surgery without the use of LHB. A total of 1,173 (93.8%) patients were 30-day survivors. Paraplegia or paraparesis developed postoperatively in 68 (5.5%) patients. In patients with extent I TAAA, paraplegia and paraparesis rates in the LHB cohort (9 of 290, 3.1%) and those without LHB (13 of 313, 4.2%) were statistically similar (P=0.866). The latter was observed despite the fact that longer clamp times were used in the LHB group. In patients with extent II TAAA, the LHB group had a statistically significant lower incidence of paraplegia or paraparesis (17 of 375, 4.5%) compared with the non-LHB group (29 of 259, 11.2%; P=0.019). In our experience, we identified LHB as protective for reducing the risk of postoperative paraplegia and paraparesis in patients who underwent the repair of extent I and extent II TAAA, the latter statistically significant.

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

The spinal cord has significant thoracic arterial watershed areas rendering it vulnerable to intraoperative ischemic damage, clearly mandating a need for postoperative neurologic monitoring. Mechanisms of hypoperfusion include aortic cross-clamping, rib retraction, intercostal artery interruption, and costovertebral junction bleeding. We report cases of primary lung cancer resection, resection of pulmonary metastasis adherent to the thoracic aorta, resection of cartilaginous tumor with chest wall invasion, and esophagomyotomy for achalasia-all complicated by postoperative paraplegia. We review spinal cord circulation, describe mechanisms and patterns of neurologic dysfunction of susceptible watershed areas, and outline roles of preoperative spinal angiography and intraoperative evoked potentials.

Early ischemic preconditioning without hypotension prevents spinal cord injury caused by descending thoracic aortic occlusion

OBJECTIVE

Postoperative neurologic deficits after thoracic aortic reconstruction vary widely. Our previous study showed that delayed ischemic preconditioning could prevent spinal cord injury caused by occlusion of the descending thoracic aorta in pigs. We investigated early ischemic preconditioning in the same model.

METHODS

Twenty-eight pigs were divided into 4 groups: group 1 (n = 6) underwent a sham operation, group 2 (n = 6) underwent aortic occlusion for 20 minutes, group 3 (n = 8) underwent aortic occlusion for 35 minutes, and group 4 (n = 8) underwent aortic occlusion for 20 minutes and underwent aortic occlusion 80 minutes later without hypotension for 35 minutes. Aortic occlusion was accomplished by using 2 balloon occlusion catheters placed fluoroscopically at T6 to T8 above the diaphragm and at the aortic bifurcation. Neurologic evaluation was performed by an independent observer according to the Tarlov scale (0-4). The lower thoracic and lumbar spinal cords were harvested at 120 hours and examined histologically with hematoxylin-and-eosin stain. Histologic results (number of neurons and grade of inflammation) were scored (0-4) and were similarly analyzed. Statistical analysis was by means of the Kruskal-Wallis test.

RESULTS

Group 4 had a better neurologic outcome at 24, 48, and 120 hours in comparison with group 3 (P <.001). The histologic changes were proportional to the neurologic test scores, with the more severe and extensive gray matter damage in animals of group 3 (number of neurons, P <.001; grade of inflammation, P <.001).

CONCLUSION

Early ischemic preconditioning without hypotension protects against spinal cord injury after aortic occlusion, as confirmed by using the Tarlov score and histopathology.

Estimating group mortality and paraplegia rates after thoracoabdominal aortic aneurysm repair

BACKGROUND

Most clinical studies regarding thoracoabdominal aortic aneurysm (TAAA) surgery are retrospective comparisons involving heterogeneous groups of patients. Risk models that evaluate susceptibility bias enhance interpretation of these intergroup comparisons. The purpose of this analysis was to derive group risk models for mortality and paraplegia after TAAA repair.

METHODS

Data regarding 1,220 consecutive patients undergoing TAAA repair were analyzed via multiple logistic regression with stepwise model selection. Categorical preoperative risk factors that predicted 30-day mortality and paraplegia were used to develop risk models.

RESULTS

Fifty-eight patients (4.8%) died within 30 days and 56 patients (4.6%) developed paraplegia or paraparesis. Predictors of mortality were rupture, renal insufficiency, symptomatic aneurysms, and Crawford extent II repairs. Extent of repair and acute presentation were predictors of paraplegia. The derived risk models estimated mortality and paraplegia rates that correlated well with actual frequencies reported in other contemporary series (regression slopes = 0.87 and 1.06, respectively).

CONCLUSIONS

The derived risk models accurately estimate paraplegia and mortality rates in groups of patients. Prospective model validation will be required to confirm their accuracy.

Ruptured descending and thoracoabdominal aortic aneurysms

BACKGROUND

Advances in end-organ protection have dramatically reduced the incidence of the life-threatening complications associated with the elective repair of thoracoabdominal and descending thoracic aortic aneurysms. However, in the setting of a ruptured thoracic aneurysm, one may not have the luxury of complex end-organ support. We analyzed our experience with ruptured thoracic aneurysms to define morbidity and mortality in the present era.

METHODS

One hundred seventy-two patients with thoracoabdominal or descending thoracic aneurysms were operated on between July 1997 and October 2001. Forty presented with either a contained or free rupture. Three techniques were used for aortic reconstruction: clamp and sew, left heart bypass, and hypothermic circulatory arrest. Adjuncts for neurologic and renal support were used when circumstances and anatomy permitted.

RESULTS

Seven of 40 patients died in the hospital (17.5%). Four patients died intraoperatively, all of acute myocardial infarction. Five of the seven deaths were in patients who presented in shock. Two patients (5%) experienced paraplegia, 3 (7.5%) had renal failure requiring hemodialysis, 8 (20%) required a tracheostomy, and 6 (15%) had recurrent nerve palsies. There was one stroke (2.6%). Mean diameter of ruptured aneurysms was 8.5 cm.

CONCLUSIONS

Ruptured thoracic aneurysms can be repaired with a gratifying rate of salvage. Rapid diagnosis and triage for repair is necessary to avoid progressive deterioration into shock. The incidence of myocardial infarction, and the mortality associated with this event, underscores the need for aggressive cardiac evaluation in the elective thoracic aneurysm patient. The size at rupture also emphasizes the need for earlier referral for elective aneurysm repair.

Mild hypothermia does not increase bacterial proliferation on implanted vascular grafts

BACKGROUND

Mild hypothermia may offer protection against spinal cord ischemia during aortic surgery. However, hypothermia also promotes postoperative infection via two mechanisms: peripheral vasoconstriction and impairment of various immune functions. If mild hypothermia aggravates graft infections, immune function impairment would presumably be the most important factor because thermoregulatory vasoconstriction does not appreciably reduce aortic blood flow. We therefore tested the hypothesis that resistance to vascular graft infection is not reduced by mild perioperative hypothermia in dogs.

METHODS

After colonization with a solution of Staphylococcus epidermidis, prostheses were used to replace the infrarenal aorta in 20 dogs. During surgery, the dogs were randomly assigned to maintain of normothermia or passive cooling. Seven days later, grafts were recovered for bacteriologic study.

RESULTS

Colony counts for the grafts removed from the normothermic and hypothermic dogs did not differ significantly.

CONCLUSIONS

Mild perioperative hypothermia does not increase proliferation of S epidermidis on aortic vascular grafts.