Spinal cord protection: development of a paraplegia-preventive solution

Protective effect of lutein on spinal cord ischemia-reperfusion injury in rats

OBJECTIVES

Paraplegia is deterioration in motor or sensory function of the lower limbs that can occur after modification of a thoracoabdominal aortic aneurysm. The purpose of this survey was to determine the protective action of lutein on spinal cord ischemia-reperfusion (I-R) damage.

MATERIALS AND METHODS

Thirty-five male rats were distributed into five groups: intact, sham, dimethyl sulfoxide (I-R+DMSO), low dose lutein (I-R+0.2 mg/kg lutein), and high dose lutein (I-R + 0.4 mg/kg lutein). Thirty minutes before surgery, a single dose lutein or DMSO was administered to rats of experimental groups. Next, the abdominal aorta was clamped exactly under the left renal artery and proximal to the abdominal aortic bifurcation for 60 min. All animals were evaluated by neurological function and histological and biochemical examinations at 72 hr after I-R.

RESULTS

The mean motor deficit index (MDI) scores in lutein groups were lower compared with the DMSO group (P<0.001). Plasma level of malondialdehyde in lutein groups decreased compared with the DMSO group (P<0.05). Plasma level of total antioxidative capacity was increased in the high lutein group compared with low dose lutein and sham groups (P<0.05). Mean number of normal motor neurons in lutein groups was greater compared with the DMSO group (P<0.001). There was a significant negative correlation between MDI scores and the number of normal neurons (r= -0.764, P<0.001).

CONCLUSION

Findings of the present study demonstrate that lutein may support spinal cord neurons from I-R damage.

Comparative effects of methylprednisolone and tetracosactide (ACTH1-24) on ischemia/reperfusion injury of the rabbit spinal cord

INTRODUCTION

Tetracosactide is an engineered peptide that applies the same biological impacts as the endogenous adrenocorticotropic hormone. Previous studies indicated that tetracosactide has anti-inflammatory, antioxidant and neurotrophic activity. In this study, we hypothesized that tetracosactide may have protective effects in spinal cord ischemia-reperfusion injury.

MATERIAL AND METHODS

Rabbits were randomized into the accompanying four groups of eight animals each: group 1 (control), group 2 (ischemia), group 3 (methylprednisolone) and group 4 (tetracosactide). In the control group, just a laparotomy was performed. In the various groups, the spinal cord ischemia model was made by the impediment of the aorta only caudal to the renal vein. Neurological assessment was conducted with the Tarlov scoring system. Levels of myeloperoxidase, malondialdehyde and catalase were analyzed, similar to the activities of xanthine oxidase and caspase-3. Histopathological and ultrastructural assessments were additionally performed.

RESULTS

After ischemia-reperfusion injury, increments were found in the tissue myeloperoxidase levels (p < 0.001), malondialdehyde levels (p < 0.001), xanthine oxidase action (p < 0.001) and caspase-3 movement (p < 0.001). Conversely, both serum and tissue catalase levels were diminished (p < 0.001 for both). After the administration of tetracosactide, declines were seen in the tissue myeloperoxidase levels (p < 0.001), malondialdehyde levels (p = 0.003), xanthine oxidase action (p < 0.001) and caspase-3 movement (p < 0.001). Conversely, both the serum and tissue catalase levels were expanded (p < 0.001). Besides, tetracosactide treatment indicated enhanced results related to the histopathological scores (p < 0.001), the ultra-structural score (p = 0.008) and the Tarlov scores (p < 0.001).

CONCLUSIONS

The findings showed for the first time that tetracosactide shows significant neuroprotective activity against ischemia-reperfusion injury of the spinal cord.

Cu, Zn-Superoxide Dismutase Increases the Therapeutic Potential of Adipose-derived Mesenchymal Stem Cells by Maintaining Antioxidant Enzyme Levels

In the present study, we investigated the ability of Cu, Zn-superoxide dismutase (SOD1) to improve the therapeutic potential of adipose tissue-derived mesenchymal stem cells (Ad-MSCs) against ischemic damage in the spinal cord. Animals were divided into four groups: the control group, vehicle (PEP-1 peptide and artificial cerebrospinal fluid)-treated group, Ad-MSC alone group, and Ad-MSC-treated group with PEP-1-SOD1. The abdominal aorta of the rabbit was occluded for 30 min in the subrenal region to induce ischemic damage, and immediately after reperfusion, artificial cerebrospinal fluid or Ad-MSCs (2 × 10⁵) were administered intrathecally. In addition, PEP-1 or 0.5 mg/kg PEP-1-SOD1 was administered intraperitoneally to the Ad-MSC-treated rabbits. Motor behaviors and NeuN-immunoreactive neurons were significantly decreased in the vehicle-treated group after ischemia/reperfusion. Administration of Ad-MSCs significantly ameliorated the changes in motor behavior and NeuN-immunoreactive neuronal survival. In addition, the combination of PEP-1-SOD1 and Ad-MSCs further increased the ameliorative effects of Ad-MSCs in the spinal cord after ischemia. Furthermore, the administration of Ad-MSCs with PEP-1-SOD1 decreased lipid peroxidation and maintained levels of antioxidants such as SOD1 and glutathione peroxidase compared to the Ad-MSC alone group. These results suggest that combination therapy using Ad-MSCs and PEP-1-SOD1 strongly protects neurons from ischemic damage by modulating the balance of lipid peroxidation and antioxidants.

Taurine Potentiates the Efficacy of Hypothermia

To assess the protective effect of exogenous taurine on the central nervous system, spinal cord ischemia was induced for 60 minutes in 16 rabbits randomized into 3 groups. Group 1 (n = 5) had hypothermia targeted to 30.5°C and 10 mmol·kg−1 taurine, group 2 (n = 5) had hypothermia targeted to 29.5°C, and group 3 (n = 6) had hypothermia targeted to 30°C. Group 1 was cooled to 30.6 ± 0.07°C and group 2 was cooled to 29.4 ± 0.07°C; both had total functional recovery (rabbits able to keep normal posture, to walk, and to hop) within 6 hours of reperfusion. None of the group 3 animals that were cooled to 29.9 ± 0.05°C recovered function. It was concluded that taurine combined with hypothermia protected the spinal cord from 60 minutes of ischemia at a temperature that could not otherwise ensure protection. The protective effect contributed by taurine was equivalent to 1.2°C.

Effects of Aloe Vera on Spinal Cord Ischemia-Reperfusion Injury of Rats

AIM

The purpose of this study was to evaluate the possible protective/therapeutic effects of aloe vera (AV) on ischemia-reperfusion injury (I/R) of spinal cord in rats.

MATERIALS AND METHODS

A total of 28 Wistar Albino rats were divided into four random groups of equal number (n = 7). Group I (control) had no medication or surgery; Group II underwent spinal cord ischemia and was given no medication; Group III was administered AV by gastric gavage for 30 days as pre-treatment; Group IV was administered single dose intraperitoneal methylprednisolone (MP) after the ischemia. Nuclear respiratory factor-1 (NRF1), malondialdehyde (MDA) and superoxide dismutase (SOD) levels were evaluated. Tissue samples were examined histopathologically and neuronal nitric oxide synthase (nNOS) and nuclear factor-kappa B (NF-κB) protein expressions were assessed by immunohistochemical staining.

RESULTS

NRF1 and SOD levels of ischemia group were found to be lower compared to the other groups. MDA levels significantly increased after I/R. Treatment with AV and MP resulted in reduced MDA levels and also alleviated hemorrhage, edema, inflammatory cell migration and neurons were partially protected from ischemic injury. When AV treatment was compared with MP, there was no statistical difference between them in terms of reduction of neuronal damage. I/R injury increased NF-κB and nNOS expressions. AV and MP treatments decreased NF-κB and nNOS expressions.

CONCLUSIONS

It was observed that aloe vera attenuated neuronal damage histopathologically and biochemically as pretreatment. Further studies may provide more evidence to determine the additional role of aloe vera in spinal cord ischemia reperfusion injury.

Neuroprotective effects of testosterone on ischemia/reperfusion injury of the rabbit spinal cord

AIM

Previous studies demonstrated the neuroprotective effects of testosterone, but no previous study has examined the neuroprotective effects of testosterone on spinal cord ischemia/reperfusion injury. The purpose of this study was to evaluate whether testosterone could protect the spinal cord from ischemia/reperfusion injury.

METHODS

Rabbits were randomised into four groups of eight animals as follows: group 1 (control), group 2 (ischemia), group 3 (methylprednisolone) and group 4 (testosterone). In the control group only a laparotomy was performed. In all other groups, the spinal cord ischemia model was created by the occlusion of the aorta just caudal to the renal artery. Levels of malondialdehyde and catalase were analysed, as were the activities of caspase-3, myeloperoxidase, and xanthine oxidase. Histopathological and ultrastructural evaluations were performed. Neurological evaluation was performed with the Tarlov scoring system.

RESULTS

After ischemia-reperfusion injury, increases were found in caspase-3 activity, myeloperoxidase activity, malondialdehyde levels, and xanthine oxidase activity. In contrast, decreases in catalase levels were observed. After the administration of testosterone, decreases were observed in caspase-3 activity, myeloperoxidase activity, malondialdehyde levels, and xanthine oxidase activity, whereas catalase levels increased. Furthermore, testosterone treatment showed improved results concerning histopathological scores, ultrastructural score and Tarlov scores.

CONCLUSIONS

Our results revealed for the first time that testosterone exhibits meaningful neuroprotective activity following ischemia-reperfusion injury of the spinal cord.

Impact of aortic cross-clamping time on peripheral nerves: experimental model

PURPOSE

The present study investigated the correlation between extend aortic cross-clamping time and peripheral nerve injury on rats.

METHODS

24 male, Sprague Dawley rats were divided into 3 groups; (a) control group: abdomen was directly closed after reached aorta, and followed by 72 hours, (b) short-term ischaemia-reperfusion group: peripheral nerve ischemia was induced in rats by supraceliac aortic occlusion for 20 min followed by 72 h of reperfusion, (c) long-term ischaemia-reperfusion group: peripheral nerve ischemia was induced for 30 min followed by 72 h of reperfusion. Preoperative and postoperative, electromyography (EMG) recordings were done. End of 72 h, the sciatic nerves were harvested from each animal for histopathological and biochemical analysis.

RESULTS

The mean compound muscle action potential (CMAP) amplitude of long-term ischaemia-reperfusion group was statically significant reduced when compared to the control group (p <0.01). However, the mean distal latency value of long-term ischaemia-reperfusion group was statically significant increased (p <0.01). On the other hand, there were statically significant differences between the results of malondialdehyde, edema and ischemia fiber degeneration grades on control and long-term ischaemia-reperfusion group (p <0.001).

CONCLUSION

This study demonstrated that the extending cross clamping time directly harms the peripheral nerve of rats.

Cilostazol, a type III phosphodiesterase inhibitor, reduces ischemia/reperfusion-induced spinal cord injury

BACKGROUND

Spinal cord injury is still a devastating complication after surgical repair of thoracoabdominal aortic pathologies. In this study, we investigated the protective effect of cilostazol, a type III phosphodiesterase inhibitor, against ischemia/reperfusion (I/R)-induced spinal cord injury in rats.

METHODS

Twenty-four rats were assigned to 3 experimental study groups: the control group (sham operation, n = 8); the ischemia group (nontreated, n = 8), which underwent aortic occlusion without pharmacologic intervention; and the cilostazol-treated group (n = 8), which received 20 mg/kg cilostazol per day orally for 3 days before spinal ischemia. All animals underwent a 45-minute period of spinal cord ischemia via clamping of the abdominal aorta between the left renal artery and the aortic bifurcation; removal of the aortic clamp was followed by reperfusion. Neurologic status was assessed before spinal ischemia and at 48 hours after the operation. All animals were sacrificed at 48 hours after the operation. Spinal cords were harvested for histopathologic examination and biochemical analyses for the malondialdehyde (MDA) level and superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities.

RESULTS

Tarlov scores at postoperative hour 48 tended to be higher in the cilostazol-treated group than in the nontreated ischemia group (mean ± SD, 3.66 ± 0.40 versus 2.32 ± 0.80; P = .08). Spinal cord tissue MDA levels (per gram protein) were lower in the cilostazol-treated group than in the nontreated ischemia group (0.27 ± 0.01 mmol/g versus 0.33 ± 0.04 mmol/g, P = .026), and the cilostazol-treated group had higher activities of tissue SOD (519.6 ± 56.3 U/g versus 438.9 ± 67.4 U/g, P = .016) and GSH-Px (4.07 ± 1.37 U/g versus 3.21 ± 1.02 U/g, P = .47) than the nontreated ischemia group. Histopathologic analyses demonstrated that cilostazol treatment attenuated I/R-induced cellular damage.

CONCLUSION

Administration of cilostazol before spinal cord ischemia reduced neurologic injury and produced clinical improvement by attenuating oxidative stress in this rat spinal cord I/R model.

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.

Rosuvastatin, a new generation 3-hydroxy-3-methylglutaryl coenzyme a reductase inhibitor, reduces ischemia/reperfusion-induced spinal cord tissue injury in rats

BACKGROUND

Severe neurological injury still represents one of the most devastating complications occurring after surgical repair of thoracoabdominal aneurysms. We aimed to investigate the role of rosuvastatin (RSV) against ischemia/reperfusion injury in an experimental model of spinal cord ischemia in rats.

METHODS

Experimental groups included control group (n = 8), ischemia/reperfusion group (n = 8) undergoing aortic occlusion without pharmacologic treatment, and RSV-treated group (n = 8) receiving 10 mg/kg/day of RSV orally for 3 days before spinal cord ischemia. Spinal cord ischemia was induced by occlusion of the abdominal aorta between the left renal artery and aortic bifurcation for 45 minutes, followed by reperfusion. Neurological status was assessed before spinal ischemia and at 48 hours postoperatively. Spinal cords were harvested for histopathologic examination with hematoxylin-eosin staining and biochemical analysis for tissue malondialdehyde, superoxide dismutase, and glutathione peroxidase levels.

RESULTS

Decreased spinal cord tissue malondialdehyde levels (p = .01) and increased tissue superoxide dismutase (p = .01) and glutathione peroxidase (p = .09) levels were observed in the RSV-treated group, as compared with the ischemia group. Histopathologic analyses demonstrated typical changes of ischemic necrosis in the ischemia group; however, RSV attenuated tissue necrosis. Total injury score in the RSV-treated group was significantly decreased, as compared with the ischemia group (p < .05). The Tarlov scores at 48 hours postoperatively were higher in the RSV group as compared with the ischemia group.

CONCLUSION

RSV administration before spinal cord ischemia reduces spinal cord tissue injury by increasing antioxidant enzyme levels and may reduce the incidence of associated neurological dysfunction.

The change of the spinal cord ischemia-reperfusion injury in mitochondrial passway and the effect of the Ginkgo biloba extract's preconditioning intervention

In order to explore whether the apoptosis in ischemia-reperfusion injury could be affected by Ginkgo biloba extract (GBE) and the free radical scavenger GBE could suppress this affection. Rabbits were randomly divided into sham group, ischemia group, ischemia-reperfusion group (1, 6, 24, 48 h), the drug group (1, 6, 24, 48 h). Measure the rate of apoptosis by flow cytometry, the caspase 9 and apoptosis-inducing factor (AIF) in the cytoplasm and serum by ELISA. Compared with the sham group and ischemia group, the reperfusion group increased the rate of apoptosis, the caspase 9 and AIF in serum have a peak at 24 h after reperfusion, in the cytoplasm the peak at 6 h.GBE inhibit performance has the systemic and local aspects. The apoptosis of nerve cells after spinal cord ischemia-reperfusion has the relationship with the mitochondrial caspase-dependent and caspase-independent pathways and both the local and systemic role. GBE inhibits nerve cell apoptosis by these ways.

Methylene blue decreases ischemia-reperfusion (I/R)-induced spinal cord injury: an in vivo study in an I/R rabbit model

OBJECTIVES

To evaluate the effects of intravenous methylene blue (MB) administration on ischemia-reperfusion (I/R) injury of the spinal cord (SC).

METHODS

16 rabbits were randomly assigned either to group M (n = 8; receiving MB, intervention group) or group C (n = 8; control group) and underwent a 30-min period of SC ischemia by clamping the abdominal aorta between the left renal artery and the aortic bifurcation. 15 min before clamping, rabbits received either intravenous MB (10 mg/kg; group M) or normal saline (group C). The two groups were compared 24 h postoperatively both histologically and for neurological function, using a Tarlov score. Measurements to determine levels of malondialdehyde (MDA) and glutathione (GSH) in the SC tissue were also performed.

RESULTS

Neurological impairment and spinal tissue MDA levels were significantly lower in animals treated with MB (p < 0.001). In contrast, spinal GSH levels were significantly higher in group M (p < 0.001). Histological examination revealed that the integrity of the SC was better preserved in the MB group, whereas cords from the control group exhibited evidence of acute neuronal injury.

CONCLUSIONS

The prophylactic use of MB reduces neurological injury and improves clinical outcomes in the rabbit SC I/R model. These effects are probably mediated by the drug's antioxidant properties.

Resveratrol, a natural red wine polyphenol, reduces ischemia-reperfusion-induced spinal cord injury

BACKGROUND

Severe neurologic injury still represents one of the most devastating complications after surgical repair of thoracoabdominal aneurysms. We therefore aimed to investigate the protective effect of resveratrol, a natural polyphenol antioxidant present in grapes and wine, in an experimental model of spinal cord ischemia-reperfusion injury.

METHODS

Sixteen rabbits were assigned either to group A (n = 8; receiving resveratrol, treated group) or group B (n = 8; control group, nontreated group) and underwent a 30-minutes period of spinal cord ischemia by clamping the abdominal aorta between the left renal artery and the aortic bifurcation. Fifteen minutes before clamping, rabbits received either intravenous resveratrol (100 microg/kg; group A) or normal saline (group B). Functional assessment with Tarlov score at 8, 16, and 24 hours postoperatively, histopathologic assessment of the spinal cord, measurements of malondialdehyde levels, and myeloperoxidase activity in the spinal cord were performed.

RESULTS

Neurologic impairment (Tavlov score for group A = 4.38 +/- 1.19 and for group B = 0.38 +/- 0.74, p < 0.001), malondialdehyde levels (47.71 +/- 7.81 nmol/g versus 86.56 +/- 11.39 nmol/g, p < 0.001), and myeloperoxidase activity (2.13 +/- 0.72 nm/min versus 3.75 +/- 0.78 nm/min, p = 0.002) were significantly lower in the resveratrol-treated animals. Additionally, pathologically assessed outcomes were better in the resveratrol-treated group. The total number of motor neurons in the gray matter was significantly lower in the nontreated group than in the resveratrol-treated group (14.26 +/- 2.94 versus 29.12 +/- 3.64, p = 0.003).

CONCLUSIONS

Prophylactic use of resveratrol reduced neurologic injury and provided clinical improvement by attenuating the inflammatory milieu in the rabbit spinal cord ischemia/reperfusion model.

Ischemia and reperfusion in skin flaps: effects of mannitol and vitamin C in reducing necrosis area in a rat experimental model

PURPOSE: The aim of the present study was to develop an experimental model of ischemia-reperfusion injury in rat skin flap and to verify the effect of mannitol and vitamin C on reducing necrosis area. METHODS: A 6-x 3-cm groin skin flap was raised and submitted to 8 hours of ischemia by clamping the vascular pedicle and to 7 days of reperfusion. The animals were divided in four groups: S1 and S2 (10 animals each) and C and T (14 animals each). In groups S1 and S2 skin flaps were not submitted to ischemia and animals received lactated Ringer's solution (S1) and antioxidant solution (S2 ). In groups C and T, flaps were subjected to 8 hours of warm ischemia and animals received Lactated Ringer's solution (Group C) and antioxidant solution immediately before reperfusion, (Group T). Flap survival was evaluated on the seventh day using a paper template technique and computer-assistant imaging analysis of necrotic and normal areas. RESULTS: Statistical analysis showed no area differences between groups C and T. CONCLUSION: The experimental model provided consistent necrotic area in control groups and drugs used were not effective in improving skin flap survival.

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

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

Clinical implications of ischaemia-reperfusion injury

Ischaemia-reperfusion injury (IRI) is a complex interplay between biochemical, cellular, and vascular endothelial factors. The clinical sequelae are organ specific, and may also involve systemic inflammatory responses. In this article, we outline an overview of the pathophysiology of IRI, with direct reference to histological and physiological changes seen in individual organs, and present the data on experimental methods of prevention.

Dietary intakes and serum concentrations of vitamin E and total carotenoids of healthy adults with severe physical disabilities are lower than matched controls

Millions of people worldwide have severe chronic physical disabilities (e.g., polio, spinal cord injury). We hypothesized that these people are at risk for poor antioxidant nutrient intakes and status, because of their typically low energy expenditures and low socioeconomic status. We surveyed antioxidant nutrient intakes and concentrations in subjects with physical disabilities and age matched non-disabled controls. Only one subject with physical disabilities ate five or more servings of vegetables per day. The group had low intakes of vegetables (minus potatoes) and citrus fruits, and trends for low intakes of all antioxidant nutrients. Serum a-tocopherol and total carotenoid concentrations were lower in subjects with physical disabilities, while retinol and individual carotenoids showed non-significant lower trends. Since adequate antioxidant nutrients are associated with decreased chronic disease risk, nutrition professionals might improve the health of patients with physical disabilities by periodically monitoring their intakes and status of antioxidant nutrients.

An intraaortic solution trial to prevent spinal cord injury in a rabbit model

OBJECTIVES

to evaluate the effectiveness of an intraaortic delivered solution on preventing spinal cord injury.

DESIGN

forty rabbits were allocated into five equal groups.

MATERIALS AND METHODS

one clamp was placed just distal to the left renal artery, and another was placed just above the iliac bifurcation for 40 min. Group 1 was not infused (control group). Through a 24G vascular catheter inserted into the isolated aortic segment, 20 ml of LR solution at room temperature (Group 2) 20 ml of LR solution at 3 degrees C (Group 3), and 20 ml of LR solution at 3 degrees C containing 30 mg/kg of methylprednisolone (Group 4) were infused over 3 min. In Group 5, 10 mg/kg of vitamins E and C were delivered two days before the experiment, and 20 ml of LR solution at 3 degrees C containing 30 mg/kg of methylprednisolone, and 10 mg/kg of vitamins E and C was infused at the operation. Postoperative spinal cord function was assessed using Tarlov's criteria.

RESULTS

the neurologic status of Groups 3, 4, and 5 was significantly superior to that of Groups 1 and 2. No paraplegia was observed in Groups 4 and 5. Spastic paraplegia occurred in all rabbits of Groups 1 and 2, and in 20% of Group 3. In the electron microscopic evaluation of spinal cord specimens, normal histologic structure was observed in Groups 4 and 5, whereas, some derangements were observed in all others.

CONCLUSIONS

intraaortic infusion of a hypothermic blended solution containing methylprednisolone, vitamins C and E provided best protection against postischaemic spinal cord dysfunction.

Protection of the spinal cord with pentobarbital and hypothermia

BACKGROUND

Ischemic spinal cord damage during thoracic aortic operations has not been eliminated despite application of various adjuncts. We experimentally investigated the protective effects of pentobarbital and hypothermia on the spinal cord subjected to ischemia.

METHODS

Among nine groups of 6 rabbits each, groups AI to AIII underwent 20-minute infrarenal aortic occlusion, and groups BI to BVI underwent 40-minute occlusion. Five milligrams per kilogram of pentobarbital was administered to groups AII and BII; 10 mg/kg in groups AIII, BIII, and BVI; 20 mg/kg in group BIV; and none in groups AI, BI, and BV. In groups BV and BVI, hypothermia was induced. Forty-eight hours postoperatively, the motor function of the lower limbs was evaluated.

RESULTS

Statistically significant recovery of motor function was observed in animals in groups AII, AIII, BIII, BIV, BV, and BVI.

CONCLUSIONS

Pentobarbital showed dose-dependent protective effects of the spinal cord. Moderate hypothermia alone also showed protective effects. Combined use of pentobarbital and hypothermia resulted in highly significant recovery of spinal cord function.

Pharmacologic neuroprotection in experimental spinal cord ischemia: a systematic review

Various surgical procedures may cause temporary interruption of spinal cord blood supply and may result in irreversible ischemic injury and neurological deficits. The cascade of events that leads to neuronal death following ischemia may be amenable to pharmacological manipulations that aim to increase the tolerable duration of ischemia. Many agents have been evaluated in experimental spinal cord ischemia (SCI). In order to investigate whether an agent is available that justifies clinical evaluation, the literature on pharmacological neuroprotection in experimental SCI was systematically reviewed to assess the neuroprotective efficacy of the various agents. In addition, the strength of the evidence for neuroprotection was investigated by analyzing the methodology. The authors used a systematic review to conduct this evaluation. The included studies were analyzed for neuroprotection and methodology. In order to be able to compare the various agents for neuroprotective efficacy, relative risks and confidence intervals were calculated from the data in the results sections. A total of 103 studies were included. Seventy-nine different agents were tested. Only 14 of the agents tested did not afford protection at all. A large variation was observed in the experimental models to produce SCI. This variation limited comparison of the individual agents. In 48 studies involving 31 single agents, the relative risks and confidence intervals could be calculated. An analysis of the methodology revealed poor temperature management and lack of statistical power in the majority of the 103 studies. The results suggest that numerous agents may protect the spinal cord from transient ischemia. However, poor temperature management and lack of statistical power severely weakened the evidence. Consequently, clinical evaluation of pharmacological neuroprotection in surgical procedures that carry a risk of ischemic spinal cord damage is not justified on the basis of this study.

The role of directly applied hypothermia in spinal cord injury

STUDY DESIGN

The effect of intense local hypothermia was evaluated in a precision model of spinal canal narrowing and spinal cord injury in rats. The spinal cord injury was cooled with a custom cooling well used over the epidural surface. Basso, Beattie, and Bresnahan (BBB) motor scores and transcranial magnetic motor-evoked potential (tcMMEP) responses were used after injury to accurately evaluate neurologic recovery.

OBJECTIVE

This study was undertaken to determine whether the prognosis for neurologic recovery in a standardized rat spinal cord injury model is altered by the direct application of precisely controlled hypothermia to the area of injury.

SUMMARY OF BACKGROUND DATA

The role of hypothermia in the treatment of spinal cord injuries with neurologic deficits remains undefined. Hypothermia may decrease an area of spinal cord injury and limit secondary damage, therefore improving neurologic recovery. However, it has been difficult to consistently apply localized cooling to an area of spinal cord injury, and the use of systemic hypothermia is fraught with complications. This fact, along with the unavailability of a precise spinal cord injury model, has resulted in inconsistent results, both clinically and in the laboratory. In a rat model of spinal cord injury, 37 C and 19 C temperatures were used to study the role of hypothermia on neurologic recovery.

METHODS

Male Spraque-Dawley rats (n = 52; weight, 277.7 g) were anesthetized with pentobarbital and subjected to laminectomy at T10. The rats were divided into three groups: 1) placement of a 50% spacer in the epidural space (16 rats), 2) severe (25 g/cm) spinal cord injury (16 rats), 3) 50% spacer in combination with spinal cord injury (16 rats). Eight rats in each group were tested at two temperatures: normothermic (37 C) and hypothermic (19 C). With the use of a specially designed hypothermic pool placed directly over the spinal cord for 2 hours, epidural heating to 37 C, and epidural cooling to 19 C was accomplished. Simultaneous measurements of spinal cord and body temperatures were performed. The rats underwent behavior testing using the BBB motor scores and serial tcMMEPs for 5 weeks. Statistical methods consisted of Student's t tests, one-way analysis of variance, Tukey post hoc t tests and chi2 tests.

RESULTS

There was a significant improvement in motor scores in rats subjected to hypothermia compared with those that were normothermic after insertion of a 50% spacer. This improvement was observed during the 5-week duration of follow-up. In the severe spinal cord injury group and the spinal cord injury-spacer groups, no significant improvement in motor scores were obtained when the spinal cord was exposed to hypothermia.

CONCLUSION

The results demonstrate that there is a statistically significant (P < 0.05) improvement in neurologic function in rats subjected to hypothermia (19 C) after insertion of a spacer that induced an ischemic spinal cord injury. This indicates that directly applied hypothermia may be beneficial in preventing injury secondary to ischemic cellular damage. The data demonstrated minimal therapeutic benefit of hypothermia (19 C) after a severe spinal cord injury.

The neuroprotective effects of intrathecal administration of the selective N-type calcium channel blocker ziconotide in a rat model of spinal ischemia

PURPOSE

Spinal cord ischemia and resulting paraplegia represent a major complication associated with surgical repair of the thoracoabdominal aorta. Although the mechanism of spinal neuronal degeneration during ischemia is unclear, it may involve excessive calcium influx via N-type voltage-sensitive calcium channels (VSCCs). The neuroprotective capacity of intrathecal (IT) administration of the selective N-type VSCC blocker ziconotide, previously shown to be potently analgesic, was studied.

METHODS

In a rat aortic occlusion model, spinal cord ischemia was induced for 8, 9, or 10 minutes by occluding the descending thoracic aorta. Ziconotide was administered IT as (1) a continuous infusion of 300 or 600 ng/kg/h initiated 24 hours before ischemia and continuing an additional 24 hours or (2) a 0.3 microgram bolus injected 45 minutes before the induction of ischemia. Animals were allowed to live for 24 hours, and recovery of motor function was evaluated during this period. Spinal cords were processed using a silver impregnation technique and microtubule-associated protein type II (MAP2) immunohistochemistry.

RESULTS

Continuous IT infusion of ziconotide provided significant protection against 8- and 9-minute occlusions, but not 10-minute occlusions, as indicated by recovery of motor function, degree of spinal neuronal degeneration, and loss of MAP2 immunoreactivity. Acute IT pretreatment with ziconotide provided transient protection during the initial 4 hours of reperfusion; however, this protective effect was no longer present at 24 hours.

CONCLUSION

These data implicate N-type VSCC activation in spinal neuronal degeneration caused by transient spinal ischemia, because selective blockade of this channel by continuous IT infusion of ziconotide was protective against injurious intervals of spinal ischemia. Based on these findings, ziconotide may provide both neuroprotection and preemptive analgesia for aortic aneurysm surgery.

Prevention of spinal cord ischaemic complications after thoracoabdominal aortic surgery

Since the publication of prior reviews on this topic, substantial clinical experience with a variety of operative strategies to prevent ischaemic cord complications has been reported. The available data on angiographic localisation of critical intercostal vessels, and, in particular, the evoked potential response to cross-clamping in patients indicates that risk of paraplegia varies considerably even among patients with equivalent TAA extent. Factors such as individual development of the ASA, patent critical intercostals, and the particulars of collateral circulation when intercostal aortic ostia are already occluded likely account for this variability. Information available from SSEP monitoring relative to the dynamic course of cord ischaemia with cross-clamping, and the parallel, if not, frustrating experience with angiographic localisation and intercostal vessel reconstruction indicates that a narrow temporal threshold of cord ischaemia with clamping is present in many patients. This reinforces the importance of both expeditious clamp intervals, critical intercostal re-anastomoses, and the desirability of neuroprotective manoeuvres during cross-clamp induced cord ischemia. As suggested in compelling experimental work our contemporary clinical experience, and predicted by prior reviewers, regional cord hypothermia provides significant promise for limiting or eliminating, in particular, immediate perioperative deficits. Avoidance of postoperative hypotension, spinal cord oedema, and preservation of critical intercostal vessels are additional strategies necessary to impact the development of delayed deficits favourably.

Spinal cord protection during surgical procedures on the descending thoracic and thoracoabdominal aorta: a critical overview

During the past three decades, significant advances have been made in the surgical treatment of the diseases affecting the aorta. Despite these important advances, paraplegia remains a devastating complication of the surgical procedures on the thoracic and thoracoabdominal aorta. Paraparesis and paraplegia occur as a direct result of the interruption of blood flow to the spinal cord during the surgical procedures. A number of techniques have been advocated for the prevention of spinal cord ischemic injury. This article critically reviews our current understanding of the extent of this problem, the mechanism of injury, and the methods that have been devised to reduce the frequency of paraplegia following surgical procedures on the descending aorta.

Clinical experience with epidural cooling for spinal cord protection during thoracic and thoracoabdominal aneurysm repair

PURPOSE

This report summarizes our experience with epidural cooling (EC) to achieve regional spinal cord hypothermia and thereby decrease the risk of spinal cord ischemic injury during the course of descending thoracic aneurysm (TA) and thoracoabdominal aneurysm (TAA) repair.

METHODS

During the interval July 1993 to Dec. 1995, 70 patients underwent TA (n = 9, 13%) or TAA (n = 61) (type I, 24 [34%], type II, 11 [15%], type III, 26 [37%]) repair using the EC technique. The latter was accomplished by continuous infusion of normal saline (4 degrees C) into a T11-12 epidural catheter; an intrathecal catheter was placed at the L3-4 level for monitoring of cerebrospinal fluid temperature (CSFT) and pressure (CSFP). All operations (one exception, atriofemoral bypass) were performed with the clamp-and-sew technique, and 50% of patients had preservation of intercostal vessels at proximal or distal anastomoses (30%) or by separate inclusion button (20%). Neurologic outcome was compared with a published predictive model for the incidence of neurologic deficits after TAA repair and with a matched (Type IV excluded) consecutive, control group (n = 55) who underwent TAA repair in the period 1990 to 1993 before use of EC.

RESULTS

EC was successful in all patients, with a 1442 +/- 718 ml mean (range, 200 to 3500 ml) volume of infusate; CSFT was reduced to a mean of 24 degrees +/- 3 degrees C during aortic cross-clamping with maintenance of core temperature of 34 degrees +/- 0.8 +/- C. Mean CSFP increased from baseline values of 13 +/- 8 mm Hg to 31 +/- 6 mm Hg during cross-clamp. Seven patients (10%) died within 60 days of surgery, but all survived long enough for evaluation of neurologic deficits. The EC group and control group were well-matched with respect to mean age, incidence of acute presentations/aortic dissection/aneurysm rupture, TAA type distribution, and aortic cross-clamp times. Two lower extremity neurologic deficits (2.9%) were observed in the EC patients and 13 (23%) in the control group (p < 0.0001). Observed and predicted deficits in the EC patients were 2.9% and 20.0% (p = 0.001), and for the control group 23% and 17.8% (p = 0.48). In considering EC and control patients (n = 115), variables associated with postoperative neurologic deficit were prolonged (> 60 min) visceral aortic cross-clamp time (relative risk, 4.4; 95% CI, 1.2 to 16.5; p = 0.02) and lack of epidural cooling (relative risk, 9.8; 95% CI, 2 to 48; p = 0.005).

CONCLUSION

EC is a safe and effective technique to increase the ischemic tolerance of the spinal cord during TA or TAA repair. When used in conjunction with a clamp-and-sew technique and a strategy of selective intercostal reanastomosis, EC has significantly reduced the incidence of neurologic deficits after TAA repair.