Infrarenal aortic occlusion in the rabbit to assess the effect of flunarizine in the prevention of ischemic spinal cord injury

The Neuroprotective and Anti-inflammatory Effects of Diltiazem in Spinal Cord Ischaemia–Reperfusion Injury

The protective effects of diltiazem were examined in a rabbit model of spinal cord ischaemia–reperfusion induced by infrarenal aortic occlusion for 30 min. In the diltiazem group ( n = 6), an intravenous infusion (2 μg/kg per min) was started 10 min before ischaemia induction; normal saline solution was infused in the control group ( n = 6). Neurological function was assessed using modified Tarlov criteria 24 h after surgery. Plasma samples were analysed for interleukin (IL)-6 and IL-10. Spinal tissue was analysed for malondialdehyde, nitric oxide and reduced glutathione activities. Tarlov scores of the diltiazem-treated rabbits indicated significantly improved hind-limb motor function compared with the control group. The diltiazem group also had better quantitative and qualitative histopathological findings. Diltiazem infusion significantly reduced IL-6 levels 3 and 24 h after reperfusion compared with the control group. The mean IL-10 level in the diltiazem group was significantly higher than in the control group 24 h after reperfusion. It is concluded that diltiazem has cytoprotective and anti-inflammatory properties, leading to reduced spinal cord injury.

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.

Memantine for prevention of spinal cord injury in a rabbit model

BACKGROUND

This study was conducted to investigate the effect of memantine, a noncompetitive N-methyl-d-aspartate receptor antagonist, on the neurologic outcome of spinal cord ischemia after aortic occlusion.

MATERIALS AND METHODS

New Zealand White rabbits were anesthetized and spinal cord ischemia was induced for 40 minutes by infrarenal aortic occlusion. Animals were randomly allocated to 3 groups. Group 1 (n = 8, control) received no pharmacologic intervention, group 2 (n = 8) received intra-aortic memantine infusion (20 mg/kg) after aortic crossclamping, and group 3 (n = 8) was treated with systemic memantine infusion (20 mg/kg) 45 minutes before aortic occlusion. Neurologic status was scored by the Tarlov system (in which 4 is normal and 0 is paraplegia) at 12, 24, 36, and 48 hours after the operation. Lumbar spinal root stimulation potentials and motor evoked potentials from lower limb muscles were monitored before, during, and after the operation. After the animals were killed, the spinal cords were studied histopathologically.

RESULTS

All potentials disappeared shortly after aortic crossclamping. They returned earlier in both memantine-treated groups than in the placebo group. Histologic examination of spinal cords revealed a few abnormal motor neurons in memantine-treated rabbits but found extensive injury in the control group. At 12 hours the median Tarlov scores were 0 in the control group (group 1), 2 in the intra-aortic memantine group (group 2, P =.001 versus control), and 3 in the systemic group (group 3, P =.0002 versus control). At 24 hours median Tarlov scores were 0, 2.5 (P =.0002), and 4 (P =. 0002), respectively. Finally, at both 36 and 48 hours median Tarlov scores were 0, 3 (P =.0006), and 4 (P =.0002), respectively.

CONCLUSION

Memantine significantly reduced neurologic injury related to spinal cord ischemia and reperfusion after aortic occlusion.

Effect of spinal cord preconditioning on paraplegia during cross-clamping of the thoracic aorta

BACKGROUND

Paraplegia is a devastating complication of operations for thoracic or thoracoabdominal aneurysms. Preconditioning the brain with sublethal ischemia induces resistance to subsequent ordinarily lethal ischemia (ischemic tolerance). We investigated whether ischemic tolerance could be induced by preconditioning canine spinal cord. The role of heat-shock proteins (HSP) in this process was investigated.

METHODS

In experiment 1, the preconditioning group (n = 6) had aortic cross-clamping for 20 minutes, whereas controls (n = 6) had no cross-clamping. After 48 hours the aorta was cross-clamped for 60 minutes in both groups. Neurologic examination was performed 24 hours later and the spinal cord was studied for immunohistochemically. In experiment 2, either 48 hours after 20 minutes of clamping or after sham operation (n = 4), HSP were investigated immunohistochemically.

RESULTS

In experiment 1, 3 of 6 controls became paraplegic but none of the 6 preconditioning group dogs became paraplegic. The HSP appeared on sections from all 6 PC dogs and 3 control dogs that did not exhibit paraplegia. In experiment 2, HSP were present in clamped animals but could not be detected after sham operation.

CONCLUSIONS

Ischemic tolerance was induced by preconditioning the canine spinal cord, in which HSP are believed to be involved.