Protection from postischemic spinal cord injury by perfusion cooling of the epidural space

Anti-paralytic medicinal plants - Review

Paralysis is the loss of the ability of one or more muscles to move, due to disruption of signaling between the nervous system and muscles. The most common causes of paralysis are stroke, head injury, spinal cord injury (SCI) and multiple sclerosis. The search for cure of paralysis is yet to be found. Many ethnobotanical surveys have reported the use of medicinal plants by various ethnic communities in treating and curing paralysis. The present review discusses the use of medicinal plants in India for ameliorating and curing paralytic conditions, as well as discuses some of the important developments in future possible applications of medicinal plants in treatment of paralysis. This review reports the use of 37 medicinal plants for their application and cure of ailments related to paralysis. Out of the 37 plants documented, 11 plants have been reported for their ability to cure paralysis. However, the information on the documented plants were mostly found to be inadequate, requiring proper authentication with respect to their specificity, dosage, contradictions etc. It is found that despite the claims presented in many ethnobotanical surveys, the laboratory analysis of these plants remain untouched. It is believed that with deeper intervention on analysis of bioactive compounds present in these plants used by ethic traditional healers for paralysis, many potential therapeutic compounds can be isolated for this particular ailment in the near future.

Management of Thoracic Aneurysm

A review of the literature on the management of thoracic aneurysm is presented. These patients have various comorbid conditions and need thorough work-ups. Aneurysms can be classified according to shapes and locations. Various methods to maintain hemodynamic stability with adequate endorgan perfusion are presented. The success of the operation depends upon preoperative anticipation and preparation for adequate organ perfusion and hemodynamic stability along with good communication between the anesthesiologist and the surgical team.

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.

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.

Mild hypothermia as a treatment for central nervous system injuries: Positive or negative effects

Besides local neuronal damage caused by the primary insult, central nervous system injuries may secondarily cause a progressive cascade of related events including brain edema, ischemia, oxida-tive stress, excitotoxicity, and dysregulation of calcium homeostasis. Hypothermia is a beneficial strategy in a variety of acute central nervous system injuries. Mild hypothermia can treat high intra-cranial pressure following traumatic brain injuries in adults. It is a new treatment that increases sur-vival and quality of life for patients suffering from ischemic insults such as cardiac arrest, stroke, and neurogenic fever following brain trauma. Therapeutic hypothermia decreases free radical produc-tion, inflammation, excitotoxicity and intracranial pressure, and improves cerebral metabolism after traumatic brain injury and cerebral ischemia, thus protecting against central nervous system dam-age. Although a series of pathological and physiological changes as well as potential side effects are observed during hypothermia treatment, it remains a potential therapeutic strategy for central nervous system injuries and deserves further study.

The effect of hypothermia on sensory-motor function and tissue sparing after spinal cord injury

BACKGROUND CONTEXT

In recent years, hypothermia has been described as a therapeutic approach that leads to potential protective effects via minimization of secondary damage consequences, reduction of neurologic deficit, and increase of motor performance after spinal cord injury (SCI) in animal models and humans.

PURPOSE

The objective of this study was to determine the therapeutic efficacy of hypothermia treatment on sensory-motor function and bladder activity outcome correlated with the white and gray matter sparing and neuronal survival after SCI in adult rats.

STUDY DESIGN

A standardized animal model of compression SCI was used to test the hypothesis that hypothermia could have a neuroprotective effect on neural cell death and loss of white and/or gray matter.

METHODS

Animals underwent spinal cord compression injury at the Th8-Th9 level followed by systemic hypothermia of 32.0°C with gradual re-warming to 37.0°C. Motor function of hind limbs (BBB score) and mechanical allodynia (von Frey hair filaments) together with function of urinary bladder was monitored in all experimental animals throughout the whole survival period.

RESULTS

Present results showed that hypothermia had beneficial effects on urinary bladder activity and on locomotor function recovery at Days 7 and 14 post-injury. Furthermore, significant increase of NeuN-positive neuron survival within dorsal and ventral horns at Days 7, 14, and 21 were documented.

CONCLUSIONS

Our conclusions suggest that hypothermia treatment may not only promote survival of neurons, which can have a significant impact on the improvement of motor and vegetative functions, but also induce mechanical allodynia.

"White cord syndrome" of acute tetraplegia after anterior cervical decompression and fusion for chronic spinal cord compression: a case report

Paralysis is the most feared postoperative complication of ACDF and occurs most often due to an epidural hematoma. In the absence of a clear etiology, inadequate decompression or vascular insult such as ischemia/reperfusion injury are the usual suspects. Herewith we report a case of complete loss of somatosensory evoked potentials (SSEPs) during elective ACDF at C4-5 and C5-6 followed by postoperative C6 incomplete tetraplegia without any discernible technical cause. A postoperative MRI demonstrated a large area of high signal changes on T2-weighted MRI intrinsic to the cord "white cord syndrome" but no residual compression. This was considered consistent with spinal cord gliosis with possible acute edema. The acute decompression of the herniated disc resulted in cord expansion and rush-in reperfusion. We postulate that this may have led to disruption in the blood brain barrier (BBB) and triggered a cascade of reperfusion injuries resulting in acute neurologic dysfunction. At 16 months postoperatively our patient is recovering slowly and is now a Nurick Grade 4.

Combined use of an epidural cooling catheter and systemic moderate hypothermia enhances spinal cord protection against ischemic injury in rabbits

BACKGROUND

Epidural placement of a cooling catheter can protect against ischemic spinal cord injury. With the use of rabbits, we investigated whether this epidural cooling technique, when combined with systemic moderate hypothermia, can protect the spinal cord against ischemic metabolic stress.

METHODS

New Zealand white rabbits (n = 28) were assigned to 1 of 4 different groups. Animals underwent abdominal aortic occlusion for 30 minutes using a 3F balloon catheter. Group 1 (n = 7) underwent epidural cooling by the catheter and systemic moderate hypothermia (35 °C) induced with a cooling blanket. Group 2 (n = 7) underwent epidural cooling under systemic normothermia (38.5 °C). Group 3 (n = 7) underwent systemic moderate hypothermia (35 °C) without epidural cooling. Group 4 (n = 7) underwent neither epidural nor blanket cooling as a negative control. Neurologic status of their hind limbs was graded according to the modified Tarlov scale at 1, 2, and 7 days after surgery.

RESULTS

During infrarenal aortic ischemia, epidural temperature was significantly lower in group 1 (18.5 °C ± 0.8 °C) than in group 2 (28.6 °C ± 1.0 °C; P = .0001), group 3 (34.2 °C ± 0.06 °C; P = .0001), or group 4 (38.5 °C ± 0.2 °C; P = .0001). Hind limb function recovery was greater in group 1 (mean Tarlov score, 4.9 ± 0.057) than in group 2 (2.6 ± 0.3; P = .0028), group 3 (2.1 ± 0.34; P = .0088), or group 4 (0.0 ± 0.0; P = .0003).

CONCLUSIONS

Epidural cooling catheter combined with systemic moderate hypothermia produced additive cooling ability and protected the spinal cord against ischemia in rabbits more effectively than either intervention alone.

Role of induced hypothermia in thoracoabdominal aortic aneurysm surgery

For more than 50 years, hypothermia has been used in aortic surgery as a tool for neuroprotection. Hypothermia has been introduced into thoracoabdominal aortic aneurysm (TAAA) surgery by many cardiovascular centers to protect the body's organs, including the spinal cord. Numerous publications have shown that hypothermia can prevent immediate and delayed motor dysfunction after aortic cross-clamping. Here, we reviewed the historical application of hypothermia in aortic surgery, role of hypothermia in preclinical studies, cellular and molecular mechanisms by which hypothermia confers neuroprotection, and the role of systemic and regional hypothermia in clinical protocols to reduce and/or eliminate the devastating consequences of ischemic spinal cord injury after TAAA repair.

Spinal cord hypothermia without systemic hypothermia

BACKGROUND AND PURPOSE

Hypothermia has been shown to be beneficial in the setting of acute SCI. However, widespread use has been hindered by the need for systemic hypothermia as the vehicle for achieving spinal cord hypothermia. This study demonstrates that localized spinal cord hypothermia can be achieved via a percutaneous approach while maintaining systemic normothermia.

MATERIALS AND METHODS

Five Yucatan swine underwent catheterization of the subarachnoid space and infusion of room temperature, chilled, and iced PL solutions into the cervical spinal canal, with drainage from the lumbar canal. Thermocouples were placed within the spinal cord and in the subarachnoid space and recorded during infusions and recovery from hypothermia.

RESULTS

Results demonstrated that hypothermia as low as 16.8°C is feasible in the spinal cord with retention of systemic normothermia, with strong (r = 0.95) correlation between the spinal cord temperature and the CSF temperature. Degrees of cooling varied with flow rates and with infusate temperature.

CONCLUSIONS

While the data are preliminary in a small group of animals, the ability to rapidly create a wide range of controlled spinal cord hypothermia while preserving normal body temperature warrants wider exploration. The study also indicates that further investigation of the hypothesis that CSF temperature monitoring may be an acceptable surrogate for direct spinal cord temperature monitoring should be pursued.

Panax notoginsenoside produces neuroprotective effects in rat model of acute spinal cord ischemia-reperfusion injury

ETHNOPHARMACOLOGICAL RELEVANCE

Acute spinal cord ischemia-reperfusion injury (SCII) is associated with pathological changes, including inflammation, edema, and neuronal apoptosis. Panax notoginsenoside (PNS), an important traditional Chinese medicine, has shown a variety of beneficial effects, including homeostasis maintenance, anti-myocardial ischemia activities, and neuroprotective functions. However, whether it can produce neuroprotective effects in SCII and the underlying mechanisms remain largely elusive.

AIM OF THE STUDY

In the present study, we investigated the effects of PNS on neurological and histopathological changes after SCII as well as the underlying mechanisms.

MATERIALS AND METHODS

Sixty-four adult rats were randomly assigned into one of the four groups: the sham group, the ischemic group, the PNS group, and the Methylprednisolone group. A rat model of SCII was adopted from a commonly used protocol that was initially proposed by Zivin. Neurological function was evaluated with the Basso, Beattie and Bresnahan (BBB) locomotor rating scale. Histopathological changes were examined with hematoxylin and eosin staining as well as Nissl staining. Immunohistochemistry and Western blot were conducted to compare the changes in tumor necrosis factor-α, interleukin-1β, interleukin-10, aquaporin-4 (AQP-4), member 6 of the TNF receptor superfamily (Fas), and Fas ligand (FasL) in the spinal cord. Finally, neuronal apoptosis was measured by electron microscopy.

RESULTS

The BBB scores of the PNS-treated injured animals were significantly increased. The gross histopathological examination showed restored neuronal morphology and increased number of neurons after the PNS treatment. The PNS treatment decreased SCII-induced up-regulation of cytokine levels. In addition, PNS suppressed the increased expression of AQP-4 after SCII, suggesting an anti-edema effect. Finally, PNS treatment inhibited injury-induced apoptosis and reduced the expression levels of apoptosis-related proteins, Fas and FasL, confirming its anti-apoptosis effects against SCII.

CONCLUSION

The current findings suggest that PNS produces robust neuroprotective effects in spinal cord ischemia-reperfusion injury, and this role may be mediated by its anti-inflammation, anti-edema, and anti-apoptosis actions.

Hypothermic treatment for acute spinal cord injury

Spinal cord injury (SCI) is a devastating condition that affects approximately 11,000 patients each year in the United States. Although a significant amount of research has been conducted to clarify the pathophysiology of SCI, there are limited therapeutic interventions that are currently available in the clinic. Moderate hypothermia has been used in a variety of experimental and clinical situations to target several neurological disorders, including traumatic brain and SCI. Recent studies using clinically relevant animal models of SCI have reported the efficacy of therapeutic hypothermia (TH) in terms of promoting long-term behavioral improvement and reducing histopathological damage. In addition, several clinical studies have demonstrated encouraging evidence for the use of TH in patients with a severe cervical spinal cord injury. Moderate hypothermia (33°C) introduced systemically by intravascular cooling strategies appears to be safe and provides some improvement of long-term recovery of function. TH remains an experimental clinical approach and randomized multicenter trials are needed to critically evaluate this potentially exciting therapeutic intervention targeting this patient population.

Hydroxysafflor Yellow A protects spinal cords from ischemia/reperfusion injury in rabbits

Background

Hydroxysafflor Yellow A (HSYA), which is one of the most important active ingredients of the Chinese herb Carthamus tinctorius L, is widely used in the treatment of cerebrovascular and cardiovascular diseases. However, the potential protective effect of HSYA in spinal cord ischemia/reperfusion (I/R) injury is still unknown.

Methods

Thirty-nine rabbits were randomly divided into three groups: sham group, I/R group and HSYA group. All animals were sacrificed after neurological evaluation with modified Tarlov criteria at the 48th hour after reperfusion, and the spinal cord segments (L4-6) were harvested for histopathological examination, biochemical analysis and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining.

Results

Neurological outcomes in HSYA group were slightly improved compared with those in I/R group. Histopathological analysis revealed that HSYA treatment attenuated I/R induced necrosis in spinal cords. Similarly, alleviated oxidative stress was indicated by decreased malondialdehyde (MDA) level and increased superoxide dismutase (SOD) activity after HSYA treatment. Moreover, as seen from TUNEL results, HSYA also protected neurons from I/R-induced apoptosis in rabbits.

Conclusions

These findings suggest that HSYA may protect spinal cords from I/R injury by alleviating oxidative stress and reducing neuronal apoptosis in rabbits.

Effects of iloprost and piracetam in spinal cord ischemia-reperfusion injury in the rabbit

STUDY DESIGN

Experimental Study.

OBJECTIVES

The aim of this study was to investigate the neuroprotective effects of iloprost and piracetam on spinal cord ischemia/reperfusion (I/R) injury in the rabbit.

SETTINGS

The Experimental Research Center of Selcuk University, Konya, Turkey.

METHODS

A total of 24 rabbits were divided into four groups of six rabbits each, as follows: group 1 (n = 6) sham, laparotomy only; group 2 (n = 6) I/R; group 3 (n = 6) I/R+iloprost; and group 4 (n = 6) I/R+piracetam. I/R was established in groups 2, 3 and 4. Subsequently, they were followed up neurologically for 24 h until the rabbits were killed; biochemical and histopathological examinations of samples from the spinal cord were carried out.

RESULTS

Neurological examination results were significantly better in the iloprost and piracetam groups compared with the I/R group (P < 0.05). Neuroprotection was achieved with iloprost and piracetam by suppressing malondialdehyde (P < 0.05), increasing glutathione peroxidase activity (P < 0.05) and decreasing the xanthine oxidase level. In histopathological assessment, iloprost and piracetam groups were statistically different from the I/R group in terms of the number of apoptotic neurons in gray matter and white matter, as well as in terms of degenerated neurons and glial cells (P < 0.05). No statistical difference was determined between the four groups in the number of degenerated glial cells (P > 0.05).

CONCLUSION

This study has shown that iloprost and piracetam have neuroprotective effects in I/R injury both neurologically and histopathologically because of inhibition of lipid peroxidation.

Protection in animal models of brain and spinal cord injury with mild to moderate hypothermia

For the past 20 years, various laboratories throughout the world have shown that mild to moderate levels of hypothermia lead to neuroprotection and improved functional outcome in various models of brain and spinal cord injury (SCI). Although the potential neuroprotective effects of profound hypothermia during and following central nervous system (CNS) injury have long been recognized, more recent studies have described clinically feasible strategies for protecting the brain and spinal cord using hypothermia following a variety of CNS insults. In some cases, only a one or two degree decrease in brain or core temperature can be effective in protecting the CNS from injury. Alternatively, raising brain temperature only a couple of degrees above normothermia levels worsens outcome in a variety of injury models. Based on these data, resurgence has occurred in the potential use of therapeutic hypothermia in experimental and clinical settings. The study of therapeutic hypothermia is now an international area of investigation with scientists and clinicians from every part of the world contributing to this important, promising therapeutic intervention. This paper reviews the experimental data obtained in animal models of brain and SCI demonstrating the benefits of mild to moderate hypothermia. These studies have provided critical data for the translation of this therapy to the clinical arena. The mechanisms underlying the beneficial effects of mild hypothermia are also summarized.

Paraplegia after aortic aneurysm repair versus traumatic spinal cord injury: functional outcome, complications, and therapy intensity of inpatient rehabilitation

OBJECTIVE

To compare outcomes, complications, and therapy intensity of inpatient rehabilitation in patients with paraplegia caused by spinal cord injury associated with aortic aneurysm repair (SCI-AA) versus patients with traumatic spinal cord injury (SCI).

DESIGN

Case-controlled study.

SETTING

SCI unit in a rehabilitation center.

PARTICIPANTS

Seventeen patients with SCI-AA and 17 patients with traumatic SCI.

INTERVENTION

Standard rehabilitation therapy for SCI.

MAIN OUTCOME MEASURES

Length of stay (LOS) in acute and rehabilitation hospitals; FIM instrument scores; FIM change; FIM efficiency; complications; therapy intensity; and ambulatory state and return to community at discharge.

RESULTS

No significant differences were noted in acute and rehabilitation LOS and admission FIM scores. Discharge FIM scores, FIM change, and FIM efficiencies were significantly lower in the SCI-AA group, which had many complications related to AA and SCI. Intensity of rehabilitation sports therapy in the SCI-AA group was significantly lower than that of the traumatic SCI group, but total therapy intensity did not differ significantly. Both had similar rates of return to ambulatory state and discharge to the community.

CONCLUSIONS

SCI-AA patients had many complications that interfered with rehabilitation therapy, and could not achieve functional gains comparable to those with traumatic SCI. However, both groups achieved comparable success with return to ambulatory state and discharge to the community.

Anti-apoptotic and neuroprotective effects of Tetramethylpyrazine following spinal cord ischemia in rabbits

Background

Tetramethylpyrazine (TMP) is one of the most important active ingredients of a Chinese herb Ligusticum wallichii Franchat, which is widely used in many ischemia disorders treatments. However, the exact mechanism by which TMP protects the spinal cord ischemia/reperfusion (I/R) injury is still unknown. For this purpose, rabbits were randomly divided into sham group, control group and TMP group. After the evaluation of neurologic function, the spinal cords were immediately removed for biochemical and histopathological analysis. Apoptosis was measured quantitatively by the terminal transferase UTP nick end-labeling (TUNEL) method and confirmed by electron microscopic examination, the expression of Bax and Bcl-2 was immunohistochemically evaluated and quantified by Western blot analysis.

Results

Neurologic outcomes in the TMP-group were significantly better than those in the control group (P < 0.05). TMP decreased spinal cord malondialdehyde (MDA) levels and ameliorated the down regulation of spinal cord superoxide dismutase (SOD) activity. TMP significantly reduced the loss of motoneurons and TUNEL-positive rate. Greater Bcl-2 and attenuated Bax expression was found in the TMP treating rabbits.

Conclusion

These findings suggest that TMP has protective effects against spinal cord I/R injury by reducing apoptosis through regulating Bcl-2 and Bax expression.

An Epidural Cooling Catheter Protects the Spinal Cord Against Ischemic Injury in Pigs

BACKGROUND

Using swine, we investigated whether epidural placement of a cooling catheter rather than infusing iced saline solution could protect the spinal cord from ischemia during aortic surgery.

METHODS

We divided 14 domestic pigs into two groups of 7 each. Each underwent epidural catheter placement preceding 30 minutes of aortic cross-clamping distal to the origin of the left subclavian artery. In group 1, cold water was circulated continuously through the lumen of the catheter connected to an external unit. In group 2, animals received catheter placement without cooling. Spinal cord somatosensory evoked potentials were recorded. Neurologic status involving hind limbs was graded sequentially after surgery.

RESULTS

At aortic cross-clamping, spinal temperature in group 1 (31.7 degrees +/- 0.6 degrees C) was significantly lower than in group 2 (37.8 degrees +/- 0.4 degrees C; p < 0.0001). No significant elevation of intrathecal pressure accompanied cooling with the catheter (group 1, 8.1 +/- 1.7 mm Hg; group 2, 8.0 +/- 1.5 mm Hg). Mean duration of total loss of potentials was significantly shorter in group 1 (7.4 +/- 3.8 minutes) than group 2 (19.7 +/- 7.3 minutes; p = 0.0002). Pigs in group 1 exhibited better hind limb function recovery (mean Tarlov score, 4.7 +/- 0.5) than group 2 (0.6 +/- 0.8; p = 0.0017). Group 1 showed normal histologic characteristics, whereas group 2 showed loss of motor neurons in the ventral horns.

CONCLUSIONS

Epidural cooling catheter without iced saline infusion can cool the spinal cord without elevating intrathecal pressure, protecting the cord against ischemia.

Effects of epidural hypothermic saline infusion on locomotor outcome and tissue preservation after moderate thoracic spinal cord contusion in rats

Object. Regionally delivered hypothermia has advantages over systemic hypothermia for clinical application following spinal cord injury (SCI). The effects of local hypothermia on tissue sparing, neuronal preservation, and locomotor outcome were studied in a moderate thoracic spinal cord contusion model.

Methods. Rats were randomized to four treatment groups and data were collected and analyzed in a blinded fashion. Chilled saline was perfused into the epidural space 30 minutes postcontusion to achieve the following epidural temperatures: 24 ± 2.3°C (16 rats), 30 ± 2.4°C (13 rats), and 35 ± 0.9°C (13 rats). Hypothermia was continued for 3 hours when a 45-minute period of rewarming was instituted. In a fourth group a moderate contusion only was induced in 14 animals. Rectal (core) and T9–10 (epidural) temperatures were measured continuously. Locomotor testing, using the Basso-Beattie-Bresnahan (Ba-Be-Br) scale, was performed for 6 weeks, and rats were videotaped for subsequent analysis. The lesion/preserved tissue ratio was calculated throughout the entire lesion cavity and the total lesion, spinal cord, and spared tissue volumes were determined. The rostral and caudal extent of gray matter loss was also measured. At 6 weeks locomotor recovery was similar in all groups (mean Ba-Be-Br Scale scores 14.88 ± 3.71, 14.83 ± 2.81, 14.50 ± 2.24, and 14.07 ± 2.39 [p = 0.77] for all four groups, respectively). No significant differences in spared tissue volumes were found when control and treatment groups were compared, but gray matter preservation was reduced in the infusion-treated groups.

Conclusions. Regional cooling applied 30 minutes after a moderate contusive SCI was not beneficial in terms of tissue sparing, neuronal preservation, or locomotor outcome. This method of cooling may reduce blood flow in the injured spinal cord and exacerbate secondary injury.

Erdosteine ameliorates neurological outcome and oxidative stress due to ischemia/reperfusion injury in rabbit spinal cord

OBJECTIVE

Oxygen-derived free radicals have been suggested as important in degeneration after spinal cord ischemia. The aim of this study was to investigate whether erdosteine has a protective effect against spinal cord ischemia during aortic cross clamping.

MATERIALS AND METHODS

New Zealand White rabbits (n=21) were divided into three groups. In the ischemia/reperfusion group (I/R) (n=8), the infrarenal aorta of rabbits was cross clamped for 21 min and then reperfused. In erdosteine group, the administration of erdosteine solution (50 mg/kg) was started two days before aortic cross-clamping and rabbits (n=8) were subjected to ischemia and reperfusion. Animals in control group (n=5) underwent a surgical procedure similar to the other groups but the aorta was not clamped. The animals were sacrificed at 72 h and histopathological, and biochemical analyses were carried out on the lumbar spinal cords.

RESULTS

Erdosteine treatment was associated with improved neurological function in the postoperative period. Histopathological examination of spinal cord tissues in erdosteine group revealed changes consistent with mild ischemic injury, but rabbits in I/R group with paraplegia had total destruction of the motor neurons. Biochemical analyses of spinal cord tissues, in the I/R group, revealed a significant increase in the superoxide dismutase, xanthine oxidase, adenosine deaminase and myeloperoxidase activities, and a significant depletion in glutathione peroxidase activity when compared to that of control rabbits. Erdosteine treatment prevented the increase of all these enzymes except adenosine deaminase. Ischemia/reperfusion produced a significant increase in the tissue malondialdehyde levels. Ischemia/reperfusion-induced increments in malondialdehyde content of the spinal cord were significantly prevented by erdosteine treatment.

CONCLUSIONS

The present study demonstrated that erdosteine treatment before aortic cross clamping ameliorates neurological outcome, neuronal injury and oxidative stress in the rabbit spinal cord.

The protective effect of nebivolol on ischemia/reperfusion injury in rabbit spinal cord

The aim of this experimental study was to investigate whether nebivolol has protective effects against neuronal damage induced by spinal cord ischemia/reperfusion (I/R). Twenty-one rabbits were divided into three groups: group I (control, no I/R), group II (only I/R) and group III (I/R+nebivolol). Spinal cord ischemia was induced by clamping the aorta both below the left renal artery and above the aortic bifurcation. Seventy-two hours postoperatively, the motor function of the lower limbs was evaluated in each animal. The animals were sacrificed at 72 h, and histopathological and biochemical analyses were carried out in the lumbar spinal cords. The motor deficit scores in nebivolol group were different from I/R group at 72 h (3.25+/-0.70 vs. 1.75+/-1.28, p=0.01). I/R produced a significant increase in the superoxide dismutase (SOD), xanthine oxidase (XO), adenosine deaminase (ADA) and myeloperoxidase (MPO) activities in spinal cord tissue when compared with control group. Nebivolol treatment prevented the increase of all those enzymes activities produced by I/R. A significant decrease in spinal cord glutathione peroxidase (GSH-Px) level was seen in I/R group and nebivolol treatment prevented the decrement in the spinal cord tissue GSH-Px contents. On the other hand, I/R produced a significant increase in the spinal cord tissue malondialdehyde (MDA) and nitric oxide (NO) contents, this was prevented by nebivolol treatment. In conclusion, this study demonstrates a considerable neuroprotective effect of nebivolol on neurological, biochemical and histopathological status during periods of spinal cord I/R in rabbits.

MCI-186 reduces oxidative cellular damage and increases DNA repair function in the rabbit spinal cord after transient ischemia

BACKGROUND

Paraplegia is a serious complication of operations on the thoracic and thoracoabdominal aorta. To investigate the mechanism by which motor neurons are damaged during these operations, we have reported a rabbit model of spinal cord ischemia. We also tested whether a free radical scavenger MCI-186 that is useful for treating ischemic damage in the brain can protect against ischemic spinal cord damage.

METHODS

Fifteen minutes of ischemia was induced, then MCI-186 or vehicle was injected intravenously. Cell damage was analyzed by observing the function of the lower limbs and by counting the number of motor neurons. To investigate the mechanism by which MCI-186 prevents ischemic spinal cord damage, we observed the immunoreactivity of 8-hydroxy-2'-deoxyguanosine as an oxidative DNA damage marker and redox effector as a DNA repair marker.

RESULTS

In sham control, 8-hydroxy-2'-deoxyguanosine was not observed, and the nuclear expression of redox effector was observed. In vehicle injection group (group I), the nuclear expression of 8-hydroxy-2'-deoxyguanosine was observed at 1 and 2 days after reperfusion. The nuclear expression of redox effector was observed at 8 hours and 1 day, and disappeared at 2 days after transient ischemia. In MCI-186 injection group (group M), the nuclear expression of 8-hydroxy-2'-deoxyguanosine was not observed, and redox effector was observed at 8 hours and 1 and 2 days.

CONCLUSIONS

These results suggest that redox effector decreased in motor neurons after transient ischemia and this reduction preceded oxidative DNA damage. MCI-186 works as a radical scavenger and reduced oxidative DNA damage, so redox effector did not disappear. MCI-186 could be a strong candidate for a use as a therapeutic agent in the treatment of ischemic spinal cord injury.

Left atrial-inferior vena cava bypass achieves retroperfusion of the porcine spinal cord: morphologic and preliminary physiologic studies

BACKGROUND

Spinal cord injury remains a devastating complication after procedures on the descending thoracic aorta. A new model for retrograde perfusion of the spinal cord during aortic cross-clamping was evaluated for its potential role in preventing spinal cord injury after thoraco-abdominal aortic surgery.

METHODS

Retrograde perfusion of the spinal cord was established in juvenile pigs using partial bypass from the left atrium to the isolated inferior vena cava. Flow was maintained for a 60-min period of aortic occlusion. Morphologic studies of spinal cord blood flow were obtained using injection of a dilute barium-gelatin-chromatin dye solution. Physiologic cooling of the spinal cord was achieved using varying degrees of hypothermic retroperfusion.

RESULTS

Five animals underwent a 30-min period of retroperfusion followed by dye injection. Dye was identified in spinal cord venules and capillaries, most heavily concentrated in the lumbar and lower thoracic cord. Thirteen animals underwent a 60-min period of normothermic (37 degrees C), mild hypothermic (27 degrees C), moderate hypothermic (17 degrees C), or deep hypothermic (7 degrees C) retroperfusion; mean spinal cord temperatures were 35.2, 32.2, 28.0, and 24.4 degrees C, respectively.

CONCLUSIONS

Retrograde perfusion of the porcine spinal cord using a left atrial to inferior vena cava partial bypass circuit can be accomplished and can be used with hypothermic perfusate to produce cooling of the spinal cord. This new technique warrants further investigation into spinal cord protection and potential application for operations on the descending thoracic aorta.

Epidural cooling for the prevention of ischemic injury to the spinal cord during aortic occlusion in a rabbit model: determination of the optimal temperature

PURPOSE

This experiment was designed for the determination of the optimal epidural cooling temperature for the allowance of spinal cord protection with minimal side effects during an aortic occlusion-induced spinal cord ischemia model in rabbits.

METHODS

Spinal cord ischemia was induced in rabbits with infrarenal aortic occlusion for 40 minutes. Spinal cord cooling was effected with epidural infusion of normal saline solution at the following different temperatures: group 1, 17 degrees C (n = 6); group 2, 24 degrees C (n = 6); group 3, 32 degrees C (n = 6); and group 4, 39 degrees C (n = 3). Sham-operated rabbits without aortic occlusion were used as controls with epidural infusion at healthy body temperature (39 degrees C; n = 3). Motor function was assessed at 48 hours with Tarlov's criteria, and the animals were killed. The spinal cord was sectioned into multiple segments, and semiquantitative histologic scoring (0 to 5) was used to grade ischemic injury.

RESULTS

Cooling solution and spinal cord temperatures showed linear correlation (r = 0.95). All the rabbits in groups 1 (except one with mild weakness), 2, and 3 were neurologically intact, and all in group 4 had paraplegia develop (P < .001). One rabbit in group 1 died from increased intracranial pressure (ICP). Mean blood pressure, ICP, and body temperature were similar among the groups. Histology correlated with the clinical findings. In groups 1 and 2, minimal histologic changes were noted. Low-grade ischemic changes were present in group 3 in the low-lumbar and mid-lumbar segments. Severe ischemic injury occurred at the same segments in group 4 (P < .05).

CONCLUSION

These study results suggest that in rabbits satisfactory spinal cord protection during aortic occlusion can be achieved at moderate regional hypothermia (24 degrees C). Large volume infusion for the achievement of profound hypothermia may cause deleterious effects of increased ICP and is not warranted.

Establishment of a local cooling model against spinal cord ischemia representing prolonged induction of heat shock protein

OBJECTIVES

Paraplegia is one of the serious complications of thoracoabdominal aortic operations. Regional hypothermia protects against spinal cord ischemia although the protective mechanism remains unknown. We attempted to create a simple model of local cooling under transient spinal cord ischemia and evaluated the effect using functional and histologic findings.

METHODS

Male domesticated rabbits were divided into 3 groups: control, normothermic group (group N), and local hypothermic group (group H). A balloon catheter was used for spinal cord ischemia by abdominal aortic clamping. A cold pack attached to the lumbar region could lower the regional cord temperature initially. Neurologic function was evaluated by the Johnson score. Cell damage was analyzed by observing motor neurons with the use of hematoxylin and eosin staining, terminal deoxynucleotidyl transferase-mediated deoxy-uracil triphosphate biotin in situ nick end labeling (TUNEL), and immunoreactivity of heat shock protein.

RESULTS

Physiologic estimation showed that local hypothermia improved the functional deficits (group N, 1.3 +/- 0.9; group H, 4.9 +/- 0.3; P =.0020). Seven days after reperfusion, there was a significant difference in the motor neuron numbers between groups N and H (group N, 7.2 +/- 1.9; group H, 20.4 +/- 3.2; P =.0090). The number of TUNEL-positive motor neurons was reduced significantly (group N, 7.2 +/- 2.4; group H, 1.0 +/- 0.7; P =.0082). Heat shock protein immunoreactivity was prolonged up to 2 days after reperfusion in the hypothermic group.

CONCLUSIONS

These results suggest that local hypothermia extended the production of heat shock protein in spinal cord motor neurons after reperfusion and inhibited their apoptotic change.

Posttraumatic hypothermia reduces polymorphonuclear leukocyte accumulation following spinal cord injury in rats

The present study addresses the effects of moderate posttraumatic hypothermia (32 degrees C) on the temporal and regional profile of polymorphonuclear leukocyte (PMNL) accumulation after traumatic spinal cord injury (SCI). We hypothesized that posttraumatic hypothermia would reduce the degree of inflammation by reducing PMNL infiltration. Rats underwent moderate spinal cord injury at T10 using the NYU impactor device. In the first study, the temporal profile of myeloperoxidase (MPO) activity (a marker of neutrophil accumulation) under normothermic (37 degrees C) conditions was determined. The animals were allowed to survive for 3 or 24 h, or 3 or 7 days after SCI. Spinal cords were dissected into five segments rostral and caudal to the injury site. Additional animals were studied for the immunocytochemical visualization of MPO. In the second study, rats were sacrificed at 24 h after a monitoring period of normothermia (36.5 degrees C/3 h) or hypothermia (32.4 degrees C/3 h) with their controls. In the time course studies, MPO enzymatic activity was significantly increased at 3 and 24 h within the traumatized T10 segment compared to controls. MPO activity was also increased at 3 h within the rostral T8 and T9 segments and caudal T11 and T12 segments compared to controls. At 24 h after trauma, MPO activity remained elevated within both the rostral and caudal segments compared to control. By 3 days, the levels of MPO activity were reduced compared to the 24-h values but remained significantly different from control. Neutrophils that exhibited MPO immunoreactivity were seen at 6 and 24 h, with a higher number at 3 days. PMNLs were located within the white and gray matter of the lesion and both rostral and caudal to the injury site. Posttraumatic hypothermia reduced MPO activity at 24 h in the injured spinal cord segment, compared to normothermic values. The results of this study indicate that a potential mechanism by which hypothermia improves outcome following SCI is by attenuating posttraumatic inflammation.

Spinal cord complications of thoracoabdominal aneurysm surgery

BACKGROUND

Although rare, paralysis secondary to spinal cord ischaemia after aortic aneurysm surgery is a devastating complication. Many papers have been published on this topic but without a clear consensus on the best way of minimizing the problem. Recent articles have included advanced pharmacological approaches and the literature has been reviewed in light of these.

METHODS

Relevant papers were identified by an extensive text word search of the Medline database and a review of quoted articles.

RESULTS

Spinal cord complications are commoner after the repair of Crawford type II aneurysms than less extensive aneurysms. The presence of dissection, rupture and prolonged clamp times are associated with an increased incidence. About a quarter of all cord problems develop over 24 h after surgery and this may be due to a reperfusion type injury, although the exact mechanisms are by no means clear.

CONCLUSION

A combination of rapid surgery, left heart bypass for the repair of more extensive aneurysms, free spinal drainage and the avoidance of postoperative hypoxia and hypotension help to minimize spinal cord ischaemia. No pharmacological agent has yet been shown conclusively to improve outcome in the clinical setting.

Technique of selective spinal cord cooling in rat: methodology and application

In a number of interventions, it is desirable to be able to produce a rapid but readily reversible change in spinal cord temperature (SCT) without altering general body temperature and to maintain this selective spinal cord hypothermia stable for an extended interval. To accomplish this, we developed a technique of subcutaneous perfusion cooling in rat. This was accomplished by constructing a copper heat exchanger which was readily implanted into subcutaneous space overlying the upper thoracic to upper sacral spinal segments. The heat exchanger was then perfused with fluid from an external temperature bath maintained at (8 degrees C) at a perfusion rate of 100 ml/min. The temperature of the heat exchanger was controlled by regulating the pump with a feed back controller driven by a thermocouple placed percutaneously into the paraspinal musculature. A series of studies were performed to demonstrate the characteristics and utility of this cooling technique. Lowering the pump set point to 24 degrees C resulted in a fall in the intrathecal temperature (ITT) to 27 +/- 0.3 degrees C within 15 min with no significant changes observed in rectal temperature (37.5- > 37.2 degrees C). Change in intrathecal temperature showed a highly significant correlation with changes in paravertebral muscle temperature (r = 0.977). The hypothermic state could be readily maintained for extended intervals up to 5 h and an underbody heating pad was used to maintain rectal temperature between 35-36.5 degrees C. Lowering the ITT from 37 degrees C-27 degrees C evoked a temperature-dependent increase in the latency of precooling spinal somatosensory evoked potentials (SSEPs) with the highest sensitivity observed in postsynaptic components. Returning the set point temperature back to 37 degrees C produced a rapid recovery of the SSEPs latencies. Consistent with previously published data, selective spinal cord hypothermia (27 degrees C) provided complete protection against otherwise injurious interval of normothermic ischemia produced by balloon occlusion of the descending aorta. This technique provides a simple, relatively non-invasive and reliable experimental tool for studying the effect of selective, acute and/or prolonged spinal cord hypothermia.

Epidural regional hypothermia for prevention of paraplegia after aortic occlusion: experimental evaluation in a rabbit model

PURPOSE

The efficacy of epidural regional hypothermia in the prevention of acute and delayed-onset paraplegia, as well as possible complications and limitations of this technique to a clinically acceptable form, were evaluated in 49 New Zealand white rabbits.

METHODS

A modified rabbit spinal cord ischemia model of infrarenal aortic occlusion for 30 minutes was employed. The study was performed in two phases. In phase I (n=20), regional hypothermia induced by epidural perfusion of iced normal saline solution (4 degrees C) was tested versus control in 10 rabbits each (groups A and B). In phase II (n=29) the animals were subdivided into three groups to study the kinetics of absorbtion and distribution of methylene blue (group C; n=10), radiographic contrast material (group D; n=9), and measurement of cerebrospinal pressure while an epidural iced solution was or was not infused (group E; n=10).

RESULTS

At 24 and 48 hours, all of the normothermic animals showed irreversible paraplegia (Tarlov score 0). In contrast, at 24 hours none of the rabbits undergoing epidural cold infusion were paraplegic, although at 48 hours one animal had weakness of a hindlimb (Tarlov score 3). Plasma concentration-time profiles of a continuous epidural perfusion with methylene blue showed that the spinal canal is a highly compliant space. Epidurographs showed that epidural perfusion tends to spread more in a cephalic than caudal direction and the main uptake is by the vascular compartment. Despite the large volumes infused (78.75 ml/hr; range, 50 to 100 ml), we observed only a modest transient increase in cerebrospinal fluid pressure (from 2.5 +/- 0.3 mm Hg to 5.4 +/- 0.1 mm Hg), although some animals had intracranial hypertension.

CONCLUSIONS

Regional hypothermia induced by epidural cold perfusion has a highly protective effect against the ischemic spinal cord damage. However, this method probably does not avoid the risk of delayed-onset paraplegia. An important limitation of this technique is the difficulty of controlling the intrathecal pressures.

One-stage intrathoracic repair of extended aortic aneurysms

Aneurysms of the entire thoracic aorta are usually approached in two to three stages. From 1990 to 1994, we performed one-stage aortic replacement from the root to the diaphragm in 16 patients (8 men and 8 women with a mean age of 55.7 years, range 49 to 73). There were 11 type A dissections, 7 of which were acute. Six patients underwent aortic valve reconstruction; seven had aortic root replacement by Bentall or Cabrol techniques. In two cases, the innominate artery had to be replaced by a vascular graft separately in addition to reimplantation of the supraaortic branches as an island flap into the arch prosthesis. In eight cases, a median sternotomy was used; eight had a bilateral transverse thoracotomy. The procedure was performed under deep hypothermic circulatory arrest in all cases (mean duration 50.5 min, range 38 to 62 min). Two patients, both operated upon for an acute dissection, expired perioperatively: one due to a bronchopneumonia, and one because of a thrombosed Cabrol graft to the right coronary artery. No patient developed bleeding or neurological complications. At a mean follow-up of 26.9 months (1 to 50 months), all patients discharged from the hospital were still alive. Four patients underwent subsequent thoracoabdominal aortic replacement. This experience suggests that complete thoracic aortic replacement can be performed in a single session with an operative risk comparable to that of the conventional two-stage approach. The bilateral transverse thoracotomy affords excellent exposure. The lack of spinal cord ischemia may be the result of spinal cord protection with hypothermic circulatory arrest and use of the open-clamp technique.