Anesthetic Preconditioning with Sevoflurane Does Not Protect the Spinal Cord After an Ischemic-Reperfusion Injury in the Rat

The effect of sevoflurane versus propofol anesthesia on troponin I after congenital heart surgery, a randomized clinical trial

Background:

The ischemic preconditioning phenomenon can save myocardium against move severe ischemic damages and reduce infarction size and furthermore a heart rhythm disturbance. In this study we examine relationship between troponin I (as a structural myocardial protein) level and anesthetic agents in the children.

Materials and Methods:

In this study 84 children under 12 years age before cardiac surgery were divided randomly into two groups of 42 each. For anesthetic maintenance sevoflurane with dose of 0.5-1 MAC was used in Group 1 and 100-150 mg/kg/min of intravenous propofol in Group 2 for maintenance of anesthesia. Troponin I level was assessed 2 before and 1 hour after anesthetic induction. Outcome measures included the serum cardiac troponin I level in children before and after surgery in two study groups.

Results:

There was no significant difference between two groups in indices and both groups were homogenous in this point of view. The troponin I level after surgery was significantly increased in two groups. In the sevoflurane group it was 0.04 ± 0.12 to 0.05 ± 0.09 ng/ml (P value = 0.003) and the propofol group was 0.12 ± 0.26 to 0.19 ± 0.38 ng/ml (P value = 0.001).

Conclusions:

In this study two Anesthetic regimens were compared to assess the mean troponin I level before and after pediatric closed heart surgery, and it was shown that mean troponin level before and after surgery in the sevoflurane group was less than the propofol group. But this result was not statistically significant. These results indicate that although more protective effects of sevoflurane on myocardial injuries during pediatric cardiac surgery is predominant but this effect has no significant difference in the propofol group.

Sevoflurane preconditioning ameliorates neuronal deficits by inhibiting microglial MMP-9 expression after spinal cord ischemia/reperfusion in rats

Background

Microglia are the primary immune cells of the spinal cord that are activated in response to ischemia/reperfusion (IR) injury and release various neurotrophic and/or neurotoxic factors to determine neuronal survival. Among them, matrix metalloproteinase-9 (MMP-9), which cleaves various components of the extracellular matrix in the basal lamina and functions as part of the blood spinal cord barrier (BSCB), is considered important for regulating inflammatory responses and microenvironmental homeostasis of the BSCB in the pathology of ischemia. Sevoflurane has been reported to protect against neuronal apoptosis during cerebral IR. However, the effects of sevoflurane preconditioning on spinal cord IR injury remain unclear. In this study, we investigated the role of sevoflurane on potential genetic roles of microglial MMP-9 in tight junction protein breakdown, opening of the BSCB, and subsequent recruitment of microglia to apoptotic spinal cord neurons.

Results

The results showed significant upregulation of MMP-9 in rats with IR-induced inflammation of the BSCB compared to that of the sham group, manifested as dysfunctional BSCB with increased Evans blue extravasation and reduced expression of occludin protein. Increased MMP-9 expression was also observed to facilitate invasion and migration of activated microglia, imaging as high Iba-1 expression, clustered to neurons in the injured spinal cord, as shown by double immunofluorescence, and increased proinflammatory chemokine production (CXCL10, CCL2). Further, sevoflurane preconditioning markedly improved motor function by ameliorating neuronal apoptosis, as shown by reduced TUNEL-positive cell counts and expression of cleaved caspase-3. These protective effects were probably responsible for downregulation of MMP-9 and maintenance of normal expression of occludin protein indicating BSCB integrity from inflammatory damage, which was confirmed by decreased protein levels of Iba-1 and MMP-9, as well as reduced production of proinflammatory chemokines (CXCL10, CCL2) and proinflammatory cytokines (IL-1β). Intrathecal injection of specific siRNAs targeting MMP-9 had similar protective effects to those of sevoflurane preconditioning.

Conclusions

Preconditioning with 2.4% sevoflurane attenuated spinal cord IR injury by inhibiting recruitment of microglia and secretion of MMP-9; thus inhibiting downstream effects on inflammatory damage to BSCB integrity and neuronal apoptosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13041-014-0069-7) contains supplementary material, which is available to authorized users.

A potential protective effect of alpha-tocopherol on vascular complication in spinal cord reperfusion injury in rats

Background

Paraplegia remains a potential complication of spinal cord ischemic reperfusion injury (IRI) in which oxidative stress induced cyclooxygenase activities may contribute to ischemic neuronal damage. Prolonged administration of vitamin E (α-TOL), as a potent biological antioxidant, may have a protective role in this oxidative inflammatory ischemic cascade to reduce the incidence of paraplegia. The present study was designed to evaluate the preventive value of α-TOL in IRI of spinal cord.

Methods

For this study, 50 male Sprague-Dawley rats were used and divided into five experimental groups (n = 10): Control group (C); α-TOL control group (CE) which received intramuscular (i.m.) α-TOL injections (600 mg/kg); Sham operated group (S), IRI rats were subjected to laparotomy and clamping of the aorta just above the bifurcation for 45 min, then the clamp was released for 48 hrs for reperfusion; and IRIE rats group, received 600 mg/kg of α-TOL i.m. twice weekly for 6 weeks, followed by induction of IRI similar to the IRI group. At the end of the experimental protocol; motor, sensory and placing/stepping reflex evaluation was done. Plasma nitrite/nitrate (NOx) was measured. Then animals' spinal cord lumbar segments were harvested and homogenized for measurement of the levels of prostaglandin E₂ (PGE₂), malondialdehyde (MDA) and advanced oxidation products (AOPP), while superoxide dismutase (SOD) and catalase (CAT) activity were evaluated.

Results

Induction of IRI in rats resulted in significant increases in plasma levels of nitrite/nitrate (p < 0.001) and spinal cord homogenate levels of PGE₂, MDA, advanced oxidation protein products AOPP and SOD with significant reduction (p < 0.001) in CAT homogenate levels. Significant impairment of motor, sensory functions and placing/stepping reflex was observed with IRI induction in the spinal cord (p < 0.001). α-TOL administration in IRIE group significantly improved all the previously measured parameters compared with IRI group.

Conclusions

α-TOL administration significantly prevents the damage caused by spinal cord IRI in rats with subsequent recovery of both motor and sensory functions. Alpha-tocopherol improves the oxidative stress level with subsequent reduction of the incidence of neurological deficits due to spinal cord IRI conditions.

Sevoflurane preconditioning induces rapid ischemic tolerance against spinal cord ischemia/reperfusion through activation of extracellular signal-regulated kinase in rabbits

BACKGROUND

The protective effect of sevoflurane preconditioning against spinal cord ischemia/reperfusion (I/R) is unclear. We designed this study to investigate whether sevoflurane preconditioning could induce rapid ischemic tolerance to the spinal cord in a rabbit model of transient spinal cord ischemia and how the role of extracellular signal-regulated kinase (ERK) is involved.

METHODS

To test whether preconditioning with sevoflurane induces rapid ischemic tolerance, New Zealand White male rabbits were randomly assigned to three groups. Animals in the Sev group received preconditioning with 3.7% sevoflurane (1.0 minimum alveolar anesthetic concentration) in 96% oxygen for 30 min, whereas animals in the O(2) group serving as controls inhaled only 96% oxygen for 30 min. The Sham group received the same anesthesia and surgical preparation but no preconditioning or spinal cord I/R. To evaluate the role of ERK activation in sevoflurane preconditioning, rabbits were randomly assigned to four groups. U0126, an ERK inhibitor, was administered IV 20 min before the beginning of preconditioning in the U0126 + O(2) and U0126 + Sev groups. Dimethylsulfoxide was administered IV at the same time in the vehicle + O(2) and vehicle + Sev groups. At 1 h after preconditioning, the animals were subjected to spinal cord I/R induced by infrarenal aorta occlusion. All animals were assessed at 48 h after reperfusion with modified Tarlov criteria, and the spinal cord segments (L5) were harvested for histopathological examination, TUNEL staining, and Western blot of phosphor-ERK1/2.

RESULTS

The animals in the Sev group had higher neurological scores and more normal motor neurons than those in the O(2) group (P < 0.01 for each comparison). Compared with vehicle + Sev group, the U0126 + Sev group had worse neurological outcomes, fewer viable neurons, more apoptotic neurons, and significantly decreased ERK1/2 phosphorylation (P <or= 0.01 for each comparison). There were no significant differences in the outcomes among vehicle + O(2), U0126 + O(2), and U0126 + Sev groups.

CONCLUSIONS

This study demonstrates that sevoflurane preconditioning induces rapid tolerance to spinal cord I/R in rabbits, and the tolerance is possibly mediated through the activation of ERK. These data suggest that sevoflurane preconditioning might provide a new practical method for protecting perioperative spinal cord I/R.

Effect of ischemic post-conditioning on spinal cord ischemic-reperfusion injury in rabbits

OBJECTIVES

To investigate the potential protective effect of ischemic post-conditioning (Post-con) on ischemia-reperfusion injury of the rabbit spinal cord, and to determine if there is an additive neuroprotective effect when ischemic preconditioning (IPC) and Post-con are combined.

METHODS

Forty New Zealand white rabbits were randomly divided into four groups: group Control (C; n=10), aortic occlusion (AOC; for 30 min; group IPC (n=10) three cycles of three-minute AOC plus three-minute reperfusion before the 30-min AOC; group Post-con (n=10), three cycles of three-minute reperfusion plus three-minute AOC immediately upon reperfusion after 30-min AOC; group IPC+Post-con (n=10), where animals were subjected to both IPC and Post-con. At six hours, 24 hr and 48 hr following reperfusion, neurological function was assessed according to Tarlov scores, and at 48 hr, the spinal cords were procured for the histopathologic evaluation, by comparing the number of intact alpha-motor neurons in the anterior horn.

RESULTS

The median count (and quartiles) of intact alpha-motor neurons was greatest in group Post-con 73 (69-76) and group IPC+Post-con 29 (22-42) compared to the numbers of viable alpha-motor neurons in groups C 6 (4-9) and IPC 15 (11-18) (P < 0.001). The numbers of animals who developed paraplegia according to Tarlov criteria were 7/10 in groups Post-con and IPC+Post-con, compared to 9/10 animals in each of groups C and IPC.

CONCLUSIONS

This laboratory investigation provides histological evidence that Post-con may protect the spinal cord from moderate to severe ischemia reperfusion injury. Ischemic preconditioning conferred no additional benefits in this rabbit model. The results have potential clinical implications for patients undergoing thoracoabdominal aortic reconstructive surgery.