Changes in cerebrospinal fluid pressure and lactate concentrations during thoracoabdominal aortic aneurysm surgery

The utility of therapeutic hypothermia on cerebral autoregulation

Cerebral autoregulation (CA) dysfunction is a strong predictor of clinical outcome in patients with acute brain injury (ABI). CA dysfunction is a potential pathologic defect that may lead to secondary injury and worse functional outcomes. Early therapeutic hypothermia (TH) in patients with ABI is controversial. Many factors, including patient selection, timing, treatment depth, duration, and rewarming strategy, impact its clinical efficacy. Therefore, optimizing the benefit of TH is an important issue. This paper reviews the state of current research on the impact of TH on CA function, which may provide the basis and direction for CA-oriented target temperature management.

Safety of perioperative cerebrospinal fluid drain as a protective strategy during descending and thoracoabdominal open aortic repair

Objective

We present our experience with routine application of the cerebrospinal fluid (CSF) drain (CSFD) during open aortic repair.

Methods

We retrospectively reviewed 100 patients with descending thoracic aortic aneurysm (DTAA) or thoracoabdominal aortic aneurysm (TAAA) or who underwent CSFD insertion before open repair between 2006 and 2017. All CSFDs were inserted by the cardiovascular anesthesia team. The goal was to keep intracranial pressure <10 mm Hg during the surgical procedure by draining CSF at a rate of 20 to 30 mL/h. Postoperatively, CSFD was set to maintain the lumbar pressure <10 mm Hg to reduce the risk of postoperative paraplegia. CSFD was part of our standard cord protection regimen.

Results

The mean patient age was 65.4 ± 11.7 years, and 60 (60%) were male. A CSFD was successfully inserted in all patients. The mean hospital length of stay was 11.9 ± 11.8 days, and hospital mortality was 6%. Postoperative transient paresis was observed in 4 patients (4%), and permanent paraplegia was seen in 2 (2%). CSFD-related complications were reported in 14 patients (14%). Complications included persistent CSF leakage and blood-tinged CSF with and without intracranial hemorrhage and spinal cutaneous fistula in 7 (7%), 9 (9%), and 1 (1%), respectively. Long-term survival was excellent (68.4% at 10 years).

Conclusions

CSFD is a safe practice when applied routinely as an adjunct strategy to prevent paraplegia in surgical management of DTAA and TAAA. We feel that this contributed to good early and late clinical results.

Ischemic spinal cord injury - experimental evidence and evolution of protective measures

BACKGROUND

Paraplegia remains one of the most devastating complications of descending and thoracoabdominal aortic repair. The aim of this review is to outline the current state of art in the rapidly developing field of spinal cord injury (SCI) research.

METHODS

A review of PubMed and Web of Science databases was performed using the following terms and their combinations: spinal cord, injury, ischemia, ischemia-reperfusion, ischemic spinal cord injury, paraplegia, paraparesis. Articles published before July 2019 were screened and included if considered relevant.

RESULTS

The review focuses on the topic of SCI and the developments concerning methods of monitoring, diagnostics and prevention of SCI.

CONCLUSIONS

Translation of novel technologies from bench to bedside and into everyday clinical practice is challenging, however each of the developing areas hold great promise in SCI prevention.

Could Cerebrospinal Fluid Biomarkers Offer Better Predictive Value for Spinal Cord Ischaemia Than Current Neuromonitoring Techniques During Thoracoabdominal Aortic Aneurysm Repair - A Systematic Review

Objective

Cerebrospinal fluid (CSF) drainage is a technique that has significantly reduced the incidence of spinal cord ischaemia (SCI). We present results of a systematic review to assess the literature on this topic in relation to thoracoabdominal aortic aneurysm repair (TAAR).

Methods

Major medical databases were searched to identify papers related to CSF biomarkers measured during TAAAR.

Results

Fifteen papers reported measurements of CSF biomarkers with 265 patients in total. CSF biomarkers measured included S-100ß, neuron-specific endolase (NSE), lactate, glial fibrillary acidic protein A (GFPa), Tau, heat shock protein 70 and 27 (HSP70, HSP27), and proinflammatory cytokines. Lactate and S-100ß were reported the most, but did not correlate with SCI, which was also the case with NSE and TAU. GFPa showed significant CSF level rises, both intra and postoperative in patients who suffered SCI and warrants further investigation, similar results were seen with HSP70, HSP27 and IL-8.

Conclusions

Although there is significant interest in this topic, there still remains a significant lack of high-quality studies investigating CSF biomarkers during TAAR to detect SCI. A large and multicentre study is required to identify the significant role of each biomarker.

Neuroprotection by Therapeutic Hypothermia

Hypothermia therapy is an old and important method of neuroprotection. Until now, many neurological diseases such as stroke, traumatic brain injury, intracranial pressure elevation, subarachnoid hemorrhage, spinal cord injury, hepatic encephalopathy, and neonatal peripartum encephalopathy have proven to be suppressed by therapeutic hypothermia. Beneficial effects of therapeutic hypothermia have also been discovered, and progress has been made toward improving the benefits of therapeutic hypothermia further through combination with other neuroprotective treatments and by probing the mechanism of hypothermia neuroprotection. In this review, we compare different hypothermia induction methods and provide a summarized account of the synergistic effect of hypothermia therapy with other neuroprotective treatments, along with an overview of hypothermia neuroprotection mechanisms and cold/hypothermia-induced proteins.

Thoracoabdominal Aortic Aneurysm Repair: What Should the Anaesthetist Know?

The surgical repair of descending thoracic aortic (DTA) and thoracoabdominal aortic aneurysms (TAAAs) presents one of the greatest challenges for anaesthesiologists. The challenge comes from the fine balance of complex medical issues in the setting of altered physiology that occurs during the perioperative period. Patients presenting for TAAA repair usually have multiple pre-existing comorbid conditions involving their cardiac, pulmonary and renal systems; and aneurysm repair poses a direct and immediate threat to these systems in addition to that to the gastrointestinal and neurologic systems. Operative mortality in thoracoabdominal aortic surgery is quite high to the extent of 5%-12% with a 5-year survival rate of 70%-79% for DTA aneurysm and 59% for thoracoabdominal aortic aneurysm surgeries. Complex haemodynamic changes associated with the clamping and declamping of aorta requires thorough knowledge and expertise for the management of TAAA. We present a brief review on the anaesthetic management and possible complications that anaesthetists should be aware of during TAAA repair.

A Systematic Review of the Use of Biochemical Markers in the Assessment of Spinal Cord Ischemia in Thoracoabdominal Aortic Aneurysm Repair

Introduction:

Despite advances in perioperative critical care and surgical technique, spinal cord ischemia remains a devastating complication of thoracic and thoracoabdominal aortic aneurysm repair. Biochemical markers present in peripheral blood and cerebrospinal fluid (CSF) may be useful in assessing spinal cord injury. We systematically analyze and report the role of all reported biochemical markers that have been used in assessing and diagnosing spinal cord ischemia in thoracic and thoracoabdominal aortic aneurysm repair.

Methods:

Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines were used for this review. Published literature was searched to identify all studies reporting on the use of biochemical markers in thoracoabdominal aortic aneurysm repair in the assessment of spinal cord ischemia. Marker-specific and patient-specific data were extracted from all studies and where possible, subgroup analysis was performed on marker-specific data sets.

Results:

Fourteen studies of 321 patients undergoing thoracic and thoracoabdominal aortic aneurysm repair were eligible for further analysis. Seven distinct biochemical markers were used in both CSF and blood samples: S100B proteins (S100B), neurone-specific enolase, lactate dehydrogenase, glial fibrillary acidic protein (GFAp), neurofilament triplet protein (NFL) and Tau protein, and glucose. There was substantial evidence demonstrating the heightened levels of S100, NFL, and GFAp in CSF in patients with spinal cord ischemia. There is however, wide variability in the correlation of the same 6 biochemical markers in peripheral blood and spinal cord ischemia.

Conclusions:

In patients with spinal cord injury, dramatic rises occur with S100B, NFL, and GFAp in CSF. However, further work is needed if biochemical markers are to impact on the future of thoracoabdominal aortic aneurysm repair.

Minocycline Before Aortic Occlusion Reduces Hindlimb Motor Impairment, Attenuates Spinal Cord Damage and Spinal Astrocytosis, and Preserve Neuronal Cytoarchitecture in the Rat

OBJECTIVES

Spinal cord ischemia secondary to trauma or a vascular occlusive event is a threatening phenomenon. The neuroprotective properties of minocycline have been shown in several models of central nervous system diseases and after spinal cord ischemia; however, the benefit of using the drug requires additional confirmation in different animal models. Astrocytes are essential as regulators of neuronal functions and for providing nutrients. The authors hypothesized that astrocytes in the spinal cord may be an important target for minocycline action after ischemia and thus in the prevention of secondary spreading damage.

DESIGN

A prospective, randomized animal study.

SETTING

University research laboratory, single institution.

PARTICIPANTS

Adult male Sprague Dawley rats, weighing between 400 and 450 g.

INTERVENTIONS

A model of spinal cord ischemia in the rat was used for this study to determine whether a single, high-dose (10 mg/kg) of minocycline protects against damage to the neuronal cytoskeleton, both in the white and gray matter, and whether it reduces glial fibrillary acidic protein levels, which is an index for prevention of astrocyte activation during ischemia. Thirty minutes before thoracic aorta occlusion, minocycline was administered for 18 minutes using a 2 F Fogarty catheter.

MEASUREMENTS AND MAIN RESULTS

Minocycline given prophylactically significantly mitigated severe hindlimb motor impairment and reduced glial fibrillary acidic protein plus astrocytosis in both the white and gray matter of the spinal cord, caudal to the occlusion. Neuronal histologic cytoarchitecture, which was severely and significantly compromised in control animals, was preserved in the minocycline-treated animals.

CONCLUSIONS

This study's data imply that minocycline may attenuate reactive astrocytosis in response to injury with better neurologic outcome in a model of spinal cord ischemia in rats. The data suggest that future use of minocycline, clinically, might be advantageous in surgeries with a potential risk for paraplegia due to spinal cord ischemia.

Spinal Cord is the Primary Site of Action for Skeletal Muscle Relaxation by Sevoflurane

MINI: A modified selective anesthetics delivery rabbit model was used validated to a better preferential anesthesia than previous models. Furthermore, we found evidence that primarily the spinal cord mediated the skeletal muscle relaxation action of sevoflurane.

STUDY DESIGN

A randomized, in vivo study was performed to explore the skeletal muscle relaxation action site of sevoflurane.

OBJECTIVE

The aim of this study was to investigate the skeletal muscle relaxation action of sevoflurane by a modified selective anesthetics delivery rabbit model.

SUMMARY OF BACKGROUND DATA

The action site and mechanisms of skeletal muscle relaxation caused by sevoflurane were unclear, so a modified selective anesthetics delivery model was used.

METHODS

Sixteen male New Zealand White rabbits were randomly assigned to the sevoflurane or sham group. In situ measurement of train of four, maximum single twitch, and tetanic muscle force of left tibialis anterior muscle was repeatedly measured at three time points: at the beginning of lower torso bypass (baseline value), during preferential sevoflurane delivery to the brain (brain value), during preferential sevoflurane delivery to the spinal cord (spinal cord value).

RESULTS

When 1.5MAC sevoflurane was administrated via the lungs, the arterial concentration and partial pressure of sevoflurane in the upper torso were 205.27 ± 16.23 μg/mL and 29.16 ± 1.05 mmHg, whereas in the lower torso bypass circulation were 10.39 ± 4.50 μg/mL and 1.79 ± 0.97 mmHg. Conversely, the arterial concentration and partial pressure of sevoflurane in the upper torso were 14.04 ± 5.33 μg/mL and 2.25 ± 0.84 mmHg, whereas those values were 199.38 ± 11.61 μg/mLl and 29.20 ± 1.08 mmHg in the lower torso, when 1.5MAC sevoflurane was delivered via an oxygenator. In sevoflurane group, maximum single twitch and tetanic muscle force were significantly reduced compared with baseline (single: P = 0.046; tetanic: P = 0.001) or brain values (single: P = 0.005; tetanic: P = 0.001), when spinal cord was selectively anesthetized. In the sham group, there were no significant differences among the three conditions compared.

CONCLUSION

A modified selective anesthetics delivery rabbit model has been validated, which provided evidence that the spinal cord, not the brain, was the primary site mediating the skeletal muscle relaxation action of sevoflurane.

LEVEL OF EVIDENCE

5.

Bypass Techniques for Descending Thoracic Aortic Surgery

The conduct of partial left heart bypass or partial car diopulmonary bypass (CPB) during surgery involving the descending thoracic aorta or thoracoabdominal aorta is one of the most unappreciated and misunder stood extracorporeal circulation procedures in cardio vascular surgery. It is different from conventional CPB, and although some uninitiated practitioners consider it simpler, it is in fact more complicated than conven tional CPB and involves different concepts. It requires expertise and skill in regulating the flow, pressure, and oxygenation of blood going to both the proximal and distal parts of the body and management of the special bypass or shunt procedures used, specialized monitor ing, and knowledge about the protection and preserva tion of organs both proximal and distal to the aortic clamping. It demands exquisite communication and un derstanding of the unique problems faced by the sur geon, anesthesiologist, and perfusionist.

Minocycline Effectively Protects the Rabbit's Spinal Cord From Aortic Occlusion-Related Ischemia

OBJECTIVES

To identify the minocycline anti-inflammatory and antiapoptotic mechanisms through which it is believed to exert spinal cord protection during aortic occlusion in the rabbit model.

DESIGN

An animal model of aortic occlusion-related spinal cord ischemia. Randomized study with a control group and pre-ischemia and post-ischemia escalating doses of minocycline to high-dose minocycline in the presence of either hyperglycemia, a pro-apoptotic maneuver, or wortmannin, a specific phosphatidylinositol 3-kinase antagonist.

SETTING

Tertiary medical center and school of medicine laboratory.

PARTICIPANTS

Laboratory animals-rabbits.

INTERVENTIONS

Balloon obstruction of infrarenal aorta introduced via femoral artery incision.

RESULTS

Severe hindlimb paralysis (mean Tarlov score 0.36±0.81 out of 3) was observed in all the control group animals (9 of 11 with paraplegia and 2 of 11 with paraparesis) compared with 11 of 12 neurologically intact animals (mean Tarlov score 2.58±0.90 [p = 0.001 compared with control]) in the high-dose minocycline group. This protective effect was observed partially during a state of hyperglycemia and was completely abrogated by wortmannin. Minocycline administration resulted in higher neurologic scores (p = 0.003) and a shift to viable neurons and more apoptotic-stained nuclei resulting from reduced necrosis (p = 0.001).

CONCLUSIONS

In a rabbit model of infrarenal aortic occlusion, minocycline effectively reduced paraplegia by increasing the number of viable neurons in a dose-dependent manner. Its action was completely abrogated by inhibiting the phosphatidylinositol 3-kinase pathway and was inhibited partially by the pro-apoptotic hyperglycemia maneuver, indicating that the activation of cell salvage pathways and mitochondrial sites are possible targets of minocycline action in an ischemic spinal cord.

Therapeutic Hypothermia in Spinal Cord Injury: The Status of Its Use and Open Questions

Spinal cord injury (SCI) is a major health problem and is associated with a diversity of neurological symptoms. Pathophysiologically, dysfunction after SCI results from the culmination of tissue damage produced both by the primary insult and a range of secondary injury mechanisms. The application of hypothermia has been demonstrated to be neuroprotective after SCI in both experimental and human studies. The myriad of protective mechanisms of hypothermia include the slowing down of metabolism, decreasing free radical generation, inhibiting excitotoxicity and apoptosis, ameliorating inflammation, preserving the blood spinal cord barrier, inhibiting astrogliosis, promoting angiogenesis, as well as decreasing axonal damage and encouraging neurogenesis. Hypothermia has also been combined with other interventions, such as antioxidants, anesthetics, alkalinization and cell transplantation for additional benefit. Although a large body of work has reported on the effectiveness of hypothermia as a neuroprotective approach after SCI and its application has been translated to the clinic, a number of questions still remain regarding its use, including the identification of hypothermia's therapeutic window, optimal duration and the most appropriate rewarming rate. In addition, it is necessary to investigate the neuroprotective effect of combining therapeutic hypothermia with other treatment strategies for putative synergies, particularly those involving neurorepair.

A novel microwave sensor to detect specific biomarkers in human cerebrospinal fluid and their relationship to cellular ischemia during thoracoabdominal aortic aneurysm repair

Thoraco-abdominal aneurysms (TAAA) represents a particularly lethal vascular disease that without surgical repair carries a dismal prognosis. However, there is an inherent risk from surgical repair of spinal cord ischaemia that can result in paraplegia. One method of reducing this risk is cerebrospinal fluid (CSF) drainage. We believe that the CSF contains clinically significant biomarkers that can indicate impending spinal cord ischaemia. This work therefore presents a novel measurement method for proteins, namely albumin, as a precursor to further work in this area. The work uses an interdigitated electrode (IDE) sensor and shows that it is capable of detecting various concentrations of albumin (from 0 to 100 g/L) with a high degree of repeatability at 200 MHz (R(2) = 0.991) and 4 GHz (R(2) = 0.975).

Spinal cord injury following thoracic and thoracoabdominal aortic repairs

Objective

To discuss the currently available approaches to prevent spinal cord injury during thoracic and thoracoabdominal aortic repairs.

Methods

We carried out a PubMed search up to 2013 using the Medical Subject Headings: “aortic aneurysm/surgery” and “spinal cord ischemia”; “aortic aneurysm, thoracic/surgery” and “spinal cord ischemia”; “aneurysm/surgery” and “spinal cord ischemia/cerebrospinal fluid”; “aortic aneurysm/surgery” and “paraplegia”. All 190 original articles satisfying our inclusion criteria were analyzed for incidence, predictors, and other pertinent variables related to spinal cord injury, and we compared the results in recent publications with those in earlier reports.

Results

The mean age of the 38,491 patients was 65.3 ± 4.9 years. The overall incidence of paraplegia and/or paraparesis was 7.1% ± 6.1% (range 0%–32%). The incidence of spinal cord injury before 2000, from 2001 to 2007, and 2008–2013 was 9.0% ± 6.7%, 7.0% ± 6.1%, and 5.9% ± 5.2%, respectively ( p = 0.019). Various predictors of spinal cord injury were identified, extent of disease being the most common. Modification of surgical techniques, use of adjuncts, and better understanding of spinal cord perfusion physiology were attributed to the decrease in postoperative spinal cord injury in recent years.

Conclusions

Spinal cord injury after thoracic and thoracoabdominal aortic repair poses a real challenge to cardiovascular surgeons. However, with evolving surgical strategies, identification of predictors, and use of various adjuncts over the years, the incidence of spinal cord injury after thoracic/thoracoabdominal aortic repair has declined. Embracing a multimodality approach offers a good insight into combating this grave complication.

Intrathecal lactate as a predictor of early- but not late-onset spinal cord injury in thoracoabdominal aneurysmectomy

OBJECTIVE

To evaluate the role of intrathecal lactate as an early predictor of spinal cord injury during thoracoabdominal aortic aneurysmectomy.

DESIGN

Observational study.

SETTING

University hospital.

PARTICIPANTS

Forty-four consecutive patients scheduled to undergo thoracoabdominal aortic aneurysmectomy. Two patients had a type-B dissecting aneurysm while the other 42 patients suffered from degenerative aneurysm.

INTERVENTIONS

None.

METHODS

During surgery, samples of cerebrospinal fluid and arterial blood were withdrawn simultaneously to evaluate lactate concentration. Samples were collected at 4 fixed times during and after surgery: T1 (beginning of the intervention), T2 (15 minutes after aortic cross-clamping), T3 (just before unclamping), T4 (end of surgery).

MEASUREMENTS AND MAIN RESULTS

Mean lactate levels in cerebrospinal fluid rose consistently and steadily from the beginning of the intervention until after surgery (T1 = 1.83 mmol/L), T2 = 2.10 mmol/L, T3 = 2.72 mmol/L, T4 = 3.70 mmol/L). Seven patients developed spinal cord injury; two of them had delayed injury occurring 24 hours after the end of surgery; the remaining 5 had early onset. In this group of 5 patients, preoperative cerebrospinal fluid lactate levels were significantly (p = 0.04) higher than those of the other 37 patients preoperatively (2.12 ± 0.35 v 1.79 ± 0.29 mmol/L).

CONCLUSIONS

Preoperative cerebrospinal lactate concentration is elevated in patients who will develop early-onset spinal cord injury after thoracoabdominal aortic aneurysmectomy. This may allow a better stratification of these patients, suggesting a more aggressive strategy of spinal cord function preservation, such as systematic reimplanting of intercostal arteries, and possibly obtaining a better outcome.

Subarachnoid fluid lactate and paraplegia after descending aorta aneurysmectomy: two compared case reports

We report a comparison of two cases regarding subjects who underwent thoracoabdominal aorta aneurysmectomy. During the procedure we monitored cerebrospinal fluid lactate concentration. One patient experienced postoperative paraplegia and his cerebrospinal fluid lactate concentration was much higher than that in the other case, whose postoperative outcome was uneventful. Consequently we consider that monitoring the lactate concentration in cerebrospinal fluid during thoracic aorta surgical procedures may be a helpful tool to predict the ischemic spine-cord injury allowing for trying to recover it precociously.

[Spinal cord protection during open and endovascular surgery in thoracic and thoracoabdominal aorta diseases]

In recent decades great advances have been made in surgical procedures for treating thoracic and thoracoabdominal aorta defects. Associated mortality and morbidity rates have dropped considerably, mainly in major reference centers, but nonetheless continue to be significant. The need for new strategies to reduce mortality and morbidity has made endovascular approaches an attractive alternative for high-risk surgical patients. The most feared complications of these procedures include paraparesis and paraplegia, which have devastating consequences on patients' quality of life. We provide an updated review of the pathophysiology of spinal cord ischemia in open and endovascular surgery, as well as perioperative measures designed to protect the spinal cord in both types of procedure.

Intrathecal lactate concentration and spinal cord injury in thoracoabdominal aortic surgery

OBJECTIVE

The aim of this study was to evaluate the role of lactate as an early predictor of spinal cord injury during thoracoabdominal aortic aneurysm repair.

DESIGN

Observational study.

SETTING

University hospital.

PARTICIPANTS

Sixteen consecutive patients (10 men and 6 women) scheduled to undergo thoracoabdominal aortic aneurysm repair were enrolled in the study. All patients were affected by atherosclerotic aneurysmal pathology.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

During surgery, the authors simultaneously withdrew samples of cerebrospinal fluid and arterial blood to evaluate pO(2), pCO(2), pH, and lactate concentration. Samples were collected at 5 fixed times during and after surgery: T1 (before aortic cross-clamping), T2 (15 minutes after clamping), T3 (just before unclamping), T4 (end of surgery), and T5 (4 hours after the end of surgery). Lactate levels in cerebrospinal fluid rose consistently during aortic cross-clamping (T1 = 1.89 mmol/L, T2 = 2.21 mmol/L, T3 = 2.88 mmol/L, T4 = 3.655 mmol/L, and T5 = 3.16 mmol/L). Lactate concentrations in the cerebrospinal fluid were significantly higher in the 4 patients who developed neurologic injury, even at T1 (before surgery), than in those who did not end in spinal cord injury with the 4 highest values belonging to the 4 patients who later developed spinal cord injury.

CONCLUSIONS

This study has the potential to elucidate the time course of early lactate level elevation during thoracoabdominal aortic aneurysm repair and its clinical use in predicting the development of postoperative spinal cord injury.

Ischemia as a possible effect of increased intra-abdominal pressure on central nervous system cytokines, lactate and perfusion pressures

INTRODUCTION

The aims of our study were to evaluate the impact of increased intra-abdominal pressure (IAP) on central nervous system (CNS) cytokines (Interleukin 6 and tumor necrosis factor), lactate and perfusion pressures, testing the hypothesis that intra-abdominal hypertension (IAH) may possibly lead to CNS ischemia.

METHODS

Fifteen pigs were studied. Helium pneumoperitoneum was established and IAP was increased initially at 20 mmHg and subsequently at 45 mmHg, which was finally followed by abdominal desufflation. Interleukin 6 (IL-6), tumor necrosis factor alpha (TNFa) and lactate were measured in the cerebrospinal fluid (CSF) and intracranial (ICP), intraspinal (ISP), cerebral perfusion (CPP) and spinal perfusion (SPP) pressures recorded.

RESULTS

Increased IAP (20 mmHg) was followed by a statistically significant increase in IL-6 (p = 0.028), lactate (p = 0.017), ICP (p < 0.001) and ISP (p = 0.001) and a significant decrease in CPP (p = 0.013) and SPP (p = 0.002). However, further increase of IAP (45 mmHg) was accompanied by an increase in mean arterial pressure due to compensatory tachycardia, followed by an increase in CPP and SPP and a decrease of cytokines and lactate.

CONCLUSIONS

IAH resulted in a decrease of CPP and SPP lower than 60 mmHg and an increase of all ischemic mediators, indicating CNS ischemia; on the other hand, restoration of perfusion pressures above this threshold decreased all ischemic indicators, irrespective of the level of IAH.

Effect of Central Venous Pressure on Spinal Cord Oxygenation

To analyze the effect of central venous pressure on cerebrospinal fluid oxygen tension and intrathecal pressure, multiparameter sensors were introduced into the intrathecal space for continuous monitoring of cerebrospinal fluid PO2, PCO2, and intrathecal pressure in 15 pigs. After 20 min of aortic clamping, hypervolemia was established for 20 min, followed by normovolemia. The animals were divided into 3 groups: in group 1, cerebrospinal fluid PO2 = 0% at some time during crossclamping; in group 2, cerebrospinal fluid PO2 was <50%; and in group 3, cerebrospinal fluid PO2 remained ≥50%. Mean decreases in cerebrospinal fluid PO2 during the initial 20 min of crossclamping were 82%, 57%, and 15% in groups 1, 2, and 3, respectively. Following induction of hypervolemia, central venous and cerebrospinal fluid pressures increased simultaneously; this caused a significant decrease in cerebrospinal fluid PO2 in group 2 only. In this model, aortic clamping did not increase cerebrospinal fluid pressure if central venous pressure was not elevated. The detrimental effect of elevated intrathecal pressure on cerebrospinal fluid oxygenation was seen only in animals with an intermediate degree of spinal cord ischemia. This might have important implications for the prevention of paraplegia during thoracoabdominal aortic replacement.

The effect of cerebrospinal fluid on the biomechanics of spinal cord: an ex vivo bovine model using bovine and physical surrogate spinal cord

STUDY DESIGN

A biomechanical study using ex vivo bovine spinal cord and dura, and a synthetic surrogate spinal cord with bovine dura.

OBJECTIVE

To investigate the effect of cerebrospinal fluid (CSF) on spinal cord deformation characteristics and to evaluate the biofidelity of a new surrogate spinal cord using an ex vivo bovine model of the burst fracture process.

SUMMARY OF BACKGROUND DATA

Spinal cord injury is associated with significant personal, economic and social costs. The role of CSF during the injury event and its effect on the spinal cord deformation and neurologic injury is not well understood. Such knowledge could inform preventative strategies and clinical interventions and aid the development and validation of experimental and computational models.

METHODS

The transverse impact of a propelled bone fragment analogue with bovine and surrogate cord models was recorded with high speed video and the images analyzed to determine deformation trajectories. Each cord specimen was tested in 3 states: with dura and CSF, with dura only, and without dura. The effect of these states on deformation magnitude, duration, and energy loss parameters was assessed. RESULTS.: The estimated spinal cord deformation was significantly reduced, although not eliminated, in the presence of CSF when compared to the bare state. The duration of deformation was generally increased in the presence of CSF, though this difference was not statistically significant. This may indicate a reduction in the cord-fragment interaction force for a given impulse. The dura was found to have no significant effect on deformation parameters for the bovine spinal cord. The deformation of the surrogate cord gave similar trends for the different states in comparison to the bovine cord, but was significantly less than the bovine spinal cord for all conditions.

CONCLUSION

The results indicate that the protective mechanism of CSF may not eliminate cord deformationunder the high energy transverse impact characteristic of a burst fracture. However, CSF may contribute to a lessening of cord deformation and applied force.

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

OBJECTIVES

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.

DESIGN

Prospective clinical study.

MATERIALS AND METHODS

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.

METHODS

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.

RESULTS

No significant increase in S100beta protein could be detected in CSF and no neurological deficits were detected postoperatively.

CONCLUSIONS

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.

Clinical prospective study of biochemical markers and evoked potentials for identifying adverse neurological outcome after thoracic and thoracoabdominal aortic aneurysm surgery

BACKGROUND

Neurological deficit after repair of a thoracic or thoracoabdominal aortic aneurysm (TAA/TAAA) remains a devastating complication. The aim of our study was to investigate the clinical value of biochemical markers [S-100B, neurone-specific enolase (NSE) and lactate dehydrogenase (LD)], evoked potentials and their combinations for identifying adverse neurological outcome after TAA/TAAA surgery.

METHODS

From 69 patients, cerebrospinal fluid and blood samples for biochemical analysis were drawn after the induction of anaesthesia, during the cross-clamp period, 5 min, 2, 4, 6, 8, and 19 h, respectively, after reperfusion. In addition, continuous perioperative recording of motor-evoked potentials after transcranial electrical stimulation (tcMEP) and somatosensory-evoked potentials was carried out. Furthermore, neurological examinations were performed.

RESULTS

In patients with a defined decrease in lower extremity tcMEP during the cross-clamp period, we found that combinations of the serum concentrations of S-100B and tcMEP ratios at 4, 6, and 8 h after reperfusion had a positive and negative predictive value of 100% in predicting adverse neurological outcome after TAA/TAAA surgery. Furthermore, combinations of the serum concentrations of S-100B and NSE or LD at 19 h after reperfusion had both a positive and negative predictive value of 100% in identifying patients with adverse outcome after TAA/TAAA repair.

CONCLUSIONS

TcMEP monitoring during TAA/TAAA surgery seems to be an effective but not completely sufficient guide in our protective multi-modality strategy. Combinations of the serum concentrations of S-100B and tcMEP ratios during the early reperfusion period might be associated with adverse neurological complications. Furthermore, biochemical markers could detect central nervous system injury on the first postoperative day and may have prognostic value.

Correlations of Cerebrospinal Fluid Pressure with Hemodynamic Parameters During Thoracoabdominal Aortic Aneurysm Repair

Central venous pressure (CVP) has long been thought to correlate with cerebrospinal fluid (CSF) pressure during thoracoabdominal aortic aneurysm repair. We examined hemodynamic factors during thoracoabdominal aortic aneurysm surgery to determine their relationship with CSF pressure and aortic cross-clamping. Hemodynamic parameters and CSF pressure were measured in 124 patients at six different stages during repair of descending thoracic or thoracoabdominal aortic aneurysms: skin incision, left lung collapse, pump on, aortic clamp on, aortic clamp off, and pump off. Stepwise multiple regression analysis was used for statistical analysis. CVP was a weak predictor for CSF pressure at the beginning of surgery and when the pump was initiated. At the onset of left lung collapse, cardiac output correlated with CSF pressure. There were no predictors during aortic cross-clamping. Model r2 values were low, ranging 0.03-0.15. We found no hemodynamic predictors of CSF pressure throughout the period of aortic cross-clamping during descending thoracic or thoracoabdominal aortic aneurysm surgery. Model r2 values were low, indicating generally poor prediction of CSF pressure.

Biochemical alterations in cerebrospinal fluid during thoracoabdominal aortic cross-clamping in dogs

Spinal cord damage during and after thoracoabdominal aortic cross-clamping continues to be a major problem. Somatosensory and motor evoked potentials have been used to monitor spinal cord function but their value for predicting paraplegia has been controversial. The aim of this study was to measure biochemical markers in the cerebrospinal fluid (CSF) and correlate changes with spinal cord ischemia. Since neural tissue utilizes only glucose as substrate for its metabolism and energy supply, we measured changes of metabolites of anaerobe glycolysis. In a canine model in which general anesthesia was used, the thoracoabdominal aorta was cross-clamped proximally and distally for 60 min. Hemodynamic parameters, blood gases, and glucose level were monitored continuously. Blood and CSF sampling were performed at baseline, at 15, 30, and 55 min during cross-clamping, and at 5 and 15 min after aortic declamping. Levels of lactate (1.7 +/- 0.1 to 3.2 +/- 0.3 mmol/L), pCO2 (43 +/- 2 to 35 +/- 1.6 mmHg), and neuron-specific enolase (NSE) (5.17 +/- 0.5 to 13.0 +/- 3.5 mg/L) in CSF showed significant changes (p < 0.05) during clamping and reperfusion. Changes in CSF lactate and NSE levels correlate with the duration of spinal cord ischemia. These markers of ischemic metabolism appear suitable to monitor the degree of spinal cord ischemia during thoracoabdominal cross-clamping and may be useful to predict the efficacy of preventive methods.

Complications of lumbar drainage after thoracoabdominal aortic aneurysm repair

OBJECTIVES

Paraplegia remains a frequent complication of thoracoabdominal aortic aneurysm (TAAA) repair. Many adjunct therapies have been developed to address this complication. Lumbar drainage is frequently used in an attempt to decrease intrathecal pressure and improve intramedullary perfusion pressure. The effectiveness of this therapy is unclear, and the complications of lumbar drainage used for this indication are unknown. We present a case of intraspinal hematoma with significant neurologic deficit after TAAA repair and review the associated complications of lumbar drains placed for TAAA.

METHODS

The charts of all patients undergoing operations for TAAA repair were reviewed. Patients who underwent perioperative placement of a lumbar drain were included regardless of aneurysm type or etiology. Demographics, Crawford grade, and perioperative parameters and complications were reviewed.

RESULTS

Sixty-five patients underwent TAAA repair with 62 (95%) receiving a preoperative lumbar drain. There were two (3.2%) intraspinal hemorrhagic complications, including one patient with a poor neurologic outcome. No infections or other complications directly related to drainage were identified. Multivariate logistic regression analysis failed to demonstrate a significant association between lumbar drain complications and perioperative and intraoperative parameters such as blood loss or hypotension, level of drain placement, and Crawford grade.

CONCLUSIONS

Lumbar drainage is a frequent adjunct to TAAA repair. However, placement of the drain itself can be associated with significant complications whose aggravating factors may be unidentifiable. Complications resulting from lumbar drainage should be considered in any patient who has postoperative lower extremity neurologic deficits.

Outcome of thoracoabdominal aortic operations using deep hypothermia and distal exsanguination

BACKGROUND

Operation of the descending and thoracoabdominal aorta may be affected by a significant perioperative morbidity, mainly because of ischemic damage of the spinal cord and malperfusion of the abdominal organs.

METHODS

A comparative analysis was performed on two consecutive series of patients operated between 1982 and 1998. Group 1 consisted of 90 patients operated with moderate hypothermic left heart bypass. Group 2 included 38 patients operated using deep hypothermic cardiopulmonary bypass and a period of circulatory arrest while performing the proximal anastomosis and distal exsanguination during confection of the distal anastomosis.

RESULTS

Main demographic factors and causes of the aortic disease were similar in both groups. Early mortality was significantly higher in the group of patients with aortic cross-clamping (15 of 90, 16%) than in those operated with circulatory arrest (2 of 38, 5.2%), p < 0.001. Paraplegia occurred in 8 patients in the group operated with mild hypothermia (8.8%) but in only 1 patient (2.6%) when deep hypothermia had been used.

CONCLUSIONS

In our experience, deep hypothermia combined with distal exsanguination significantly improved the early postoperative outcome after operation of the descending and thoracoabdominal aorta. This technique allowed easy confection of proximal and distal anastomoses, and the duration of the operation was not prolonged significantly through this approach.

Use of lumbar cerebrospinal fluid drainage in thoracoabdominal aortic aneurysm repairs

Thoracoabdominal aortic aneurysm repairs present many challenges, and the complication of paraplegia remains a concern for both the surgeon and the nurse caring for the patient in the postoperative period. Paraplegia can occur secondary to spinal cord ischemia from prolonged aortic clamping during the repair of the descending thoracic aorta. Paraplegia is a devastating complication for the patient and family. Multiple adjunct techniques have been instituted to prevent reduced spinal cord perfusion during and after the operation, including the use of shunts and cardiopulmonary bypass, femoral artery-femoral vein bypass, left atrial-femoral artery bypass, and selective revascularization of the dominant intercostal artery. Other methods, such as somatosensory evoked potential monitoring during the operation and regional spinal hypothermia techniques, have not reduced the incidence of paraplegia. Improved outcomes have been seen with the use of methods to reduce cerebrospinal fluid (CSF) pressure. One such method is the use of external CSF drainage during the operation, followed by use of a lumbar drain system for as long as 72 hours after the operation. This system setup uses a transducer to monitor CSF pressure and a drip chamber to drain CSF to maintain a normal pressure. This article describes thoracoabdominal aneurysms, surgical techniques to repair the aneurysm, and the use of external CSF drainage and related nursing care measures.

The relationship between evoked potentials and measurements of S-100 protein in cerebrospinal fluid during and after thoracoabdominal aortic aneurysm surgery

OBJECTIVE

This study was performed to correlate the changes in concentration of S-100 protein in the cerebrospinal fluid (CSF) during and after thoracoabdominal aortic aneurysm (TAAA) surgery with the results of somatosensory and motor evoked potential monitoring.

METHODS

The study was designed as a prospective study at St Antonius Hospital in Nieuwegein, The Netherlands. The participants were 19 patients who were undergoing elective TAAA surgery. CSF samples for analysis of S-100 protein were drawn after the induction of anesthesia, during the cross-clamp period of the critical aortic segment, after 5 minutes of reperfusion of this segment, during the closure of the skin, and 24 hours after the closure of the skin. In all the patients, continuous intraoperative recording of myogenic motor potentials evoked by transcranial electrical stimulation (tcMEP) and somatosensory potentials evoked by stimulation of the posterior tibial nerve took place to monitor the integrity of the spinal cord. The operative technique consisted of staged or sequential clamping to maximize the beneficial effect of the distal perfusion by the left heart bypass, continuous CSF drainage to keep the CSF pressure below 10 mm Hg, and moderate hypothermia (32 degrees C rectal temperature). We correlated the measured concentrations of S-100 protein in CSF with the results of evoked potential monitoring during surgery and the number of intercostals reimplanted and oversewn.

RESULTS

In all the patients, the concentration of S-100 protein was increased in CSF. The highest concentration of S-100 protein was found in the CSF sample taken 5 minutes after reperfusion of the critical aortic segment. There was a good (negative) correlation between the changes in S-100 protein in CSF and the changes in motor evoked potential monitoring during the cross-clamp period. The best (negative) correlation was detected between the S-100 protein elevation in the CSF sample drawn 5 minutes after reperfusion and the tcMEP amplitude reduction during clamping (r = -0.73; P =.007). No relation was found between the S-100 protein dynamics in CSF and somatosensory evoked potential monitoring. A positive (r = 0.58; P =.05) correlation was found between the change in tcMEP amplitude during clamping and the number of reattached intercostals. A moderate to good (r = -0.5 to -0.7; P <.05) correlation between the number of reattached intercostals and the changes in S-100 protein concentration in CSF during TAAA surgery was found. Our data show that transient elevations in S-100 protein after cross clamping are larger in those patients with marked decrease in tcMEP from baseline during the cross-clamp period.

CONCLUSION

A correlation is shown between an increasing concentration of S-100 protein in CSF and a reduction in tcMEP amplitude during cross clamping of the aorta. The S-100 protein in CSF seems to be a marker of potential clinical value in the evaluation of the effects of procedures to detect and reduce spinal cord ischemia.

Normal serum concentrations of S-100 protein and changes in cerebrospinal fluid concentrations of S-100 protein during and after thoracoabdominal aortic aneurysm surgery: Is S-100 protein a biochemical marker of clinical value in detecting spinal cord ischemia?

PURPOSE

This study was performed to determine the concentration of S-100 protein in serum and in the cerebrospinal fluid (CSF) during and 24 hours after thoracoabdominal aortic aneurysm repair.

METHODS

This prospective study was performed at St. Antonius Hospital in Nieuwegein, The Netherlands. Eight patients who underwent elective thoracoabdominal aortic surgery participated in the study. Arterial blood and CSF samples for analysis of S-100 protein were drawn after induction of anesthesia, during the cross-clamp period of the critical segment, after 5 minutes of reperfusion, during the closure of the skin, and 24 hours after closure of the skin.

RESULTS

No increase in S-100 protein concentration could be detected in serum (< 0.2 microg/L). The S-100 protein concentration in CSF increased during the procedure in all patients (4.2 +/- 3.1 microg/L). However, in one patient, who became paraplegic, the S-100 protein concentration in CSF increased even further after 24 hours (10 microg/L).

CONCLUSIONS

The preliminary results suggest that S-100 protein in CSF may be a marker of clinical value in evaluating the effects of measures to detect and reduce spinal cord ischemia.