Perioperative neuroprotection

Effect of remote ischemic preconditioning on cerebral vasospasm, biomarkers of cerebral ischemia, and functional outcomes in aneurysmal subarachnoid hemorrhage (ERVAS): A randomized controlled pilot trial

BACKGROUND:

Cerebral vasospasm can complicate aneurysmal subarachnoid hemorrhage (aSAH), contributing to cerebral ischemia. We explored the role of remote ischemic preconditioning (RIPC) in reducing cerebral vasospasm and ischemia and improving outcomes after aSAH.

MATERIALS AND METHODS:

Patients with ruptured cerebral aneurysm undergoing surgical clipping and meeting the trial criteria were randomized to true RIPC (n = 13) (inflating upper extremity blood pressure cuff thrice to 30 mmHg above systolic pressure for 5 min) or sham RIPC (n = 12) (inflating blood pressure cuff thrice to 30 mmHg for 5 min) after ethical approval. A blinded observer assessed outcome measures-cerebral vasospasm and biomarkers of cerebral ischemia. We also evaluated the feasibility and safety of RIPC in aSAH and Glasgow Outcome Scale-Extended (GOSE).

RESULTS:

Angiographic vasospasm was seen in 9/13 (69%) patients; 1/4 patients (25%) in true RIPC group, and 8/9 patients (89%) in sham RIPC group (P = 0.05). Vasospasm on transcranial Doppler study was diagnosed in 5/25 (20%) patients and 1/13 patients (7.7%) in true RIPC and 4/12 patients (33.3%) in sham RIPC group, (P = 0.16). There was no difference in S100B and neuron-specific enolase (NSE) levels over various time-points within groups (P = 0.32 and 0.49 for S100B, P = 0.66 and 0.17 for NSE in true and sham groups, respectively) and between groups (P = 0.56 for S100B and P = 0.31 for NSE). Higher GOSE scores were observed with true RIPC (P = 0.009) unlike sham RIPC (P = 0.847) over 6-month follow-up with significant between group difference (P = 0.003). No side effects were seen with RIPC.

CONCLUSIONS:

RIPC is feasible and safe in patients with aSAH and results in a lower incidence of vasospasm and better functional outcome.

Effect of remote ischemic preconditioning on cerebral vasospasm and biomarkers of cerebral ischemia in aneurysmal subarachnoid hemorrhage (ERVAS): A protocol for a randomized, controlled pilot trial

INTRODUCTION:

Cerebral vasospasm is a dreaded complication of aneurysmal subarachnoid hemorrhage (aSAH) predisposing to delayed cerebral ischemia. We intend to study the cerebroprotective effects of remote ischemic preconditioning (RIPC) in patients with aSAH.

MATERIALS AND METHODS:

This is a single-center, prospective, parallel group, randomized, pilot trial, approved by the Institutional Ethics Committee. Patients with aSAH admitted to our hospital for surgical clipping; fulfilling the trial inclusion criteria will be randomized to true RIPC (n = 12) (inflating upper extremity blood pressure cuff thrice for 5 min to 30 mmHg above systolic blood pressure) or sham RIPC (n = 12) (inflating blood pressure cuff thrice for 5 min to 30 mmHg) in 1:1 allocation ratio using a computerized random allocation sequence and block randomization.

RESULTS:

Our primary outcome measure is vasospasm on cerebral angiography and transcranial Doppler study, and concentration of serum S100B and neuron-specific enolase at 24 h after RIPC and on day 7 of ictus. Our secondary outcomes are safety of RIPC, cerebral oxygen saturation, and Glasgow coma score, and extended Glasgow outcome scale scores at discharge and at 1, 3, and 6 months following discharge. Outcome measures will be assessed by an observer blinded to the study intervention.

CONCLUSION:

If our preliminary results demonstrate a beneficial effect of RIPC, this would serve as a clinically applicable and safe preemptive method of protection against cerebral ischemia.

Successful Management of Massive Air Embolism During Cardiopulmonary Bypass Using Multimodal Neuroprotection Strategies

Complications and critical events during cardiopulmonary bypass (CPB) are very challenging, difficult to manage, and in some instances have the potential to lead to fatal outcomes. Massive cerebral air embolism is undoubtedly a feared complication during CPB. If not diagnosed and managed early, its effects are devastating and even fatal. It is a catastrophic complication and its early diagnosis and intraoperative management are still controversial. This is why the decision-making process during a massive cerebral air embolism represents a challenge for the entire surgical, anesthetic, and perfusion team. All caregivers involved in this event must synchronize their responses quickly, harmoniously, and in such a way that all interventions lead to minimizing the impact of this complication. Its occurrence leaves important lessons to the surgical team that faces it. The best management strategy for a complication of this type is prevention. Nevertheless, a surgical team may ultimately be confronted with such an occurrence at some point despite all the prevention strategies, as was the case with our patient. That is why, in each institution, no effort should be spared to establish cost-effective strategies for early detection and a clear and concise management protocol to guide actions once this complication is detected. It is the duty of each surgical team to determine and clearly organize which strategies will be followed. The purpose of this case study was to demonstrate that a massive air embolism can be rapidly detected using near-infrared spectroscopy monitoring and can be successfully corrected with a multimodal neuroprotection strategy.

Specific ion channels contribute to key elements of pathology during secondary degeneration following neurotrauma

BACKGROUND

Following partial injury to the central nervous system, cells beyond the initial injury site undergo secondary degeneration, exacerbating loss of neurons, compact myelin and function. Changes in Ca²⁺ flux are associated with metabolic and structural changes, but it is not yet clear how flux through specific ion channels contributes to the various pathologies. Here, partial optic nerve transection in adult female rats was used to model secondary degeneration. Treatment with combinations of three ion channel inhibitors was used as a tool to investigate which elements of oxidative and structural damage related to long term functional outcomes. The inhibitors employed were the voltage gated Ca²⁺ channel inhibitor Lomerizine (Lom), the Ca²⁺ permeable AMPA receptor inhibitor YM872 and the P2X₇ receptor inhibitor oxATP.

RESULTS

Following partial optic nerve transection, hyper-phosphorylation of Tau and acetylated tubulin immunoreactivity were increased, and Nogo-A immunoreactivity was decreased, indicating that axonal changes occurred acutely. All combinations of ion channel inhibitors reduced hyper-phosphorylation of Tau and increased Nogo-A immunoreactivity at day 3 after injury. However, only Lom/oxATP or all three inhibitors in combination significantly reduced acetylated tubulin immunoreactivity. Most combinations of ion channel inhibitors were effective in restoring the lengths of the paranode and the paranodal gap, indicative of the length of the node of Ranvier, following injury. However, only all three inhibitors in combination restored to normal Ankyrin G length at the node of Ranvier. Similarly, HNE immunoreactivity and loss of oligodendrocyte precursor cells were only limited by treatment with all three ion channel inhibitors in combination.

CONCLUSIONS

Data indicate that inhibiting any of a range of ion channels preserves certain elements of axon and node structure and limits some oxidative damage following injury, whereas ionic flux through all three channels must be inhibited to prevent lipid peroxidation and preserve Ankyrin G distribution and OPCs.

Risk factors for development of postoperative cerebellar mutism syndrome in children after medulloblastoma surgery

OBJECTIVE Postoperative cerebellar mutism syndrome (pCMS) occurs in 7%-50% of children after cerebellar tumor surgery. Typical features include a latent onset of 1-2 days after surgery, transient mutism, emotional lability, and a wide variety of motor and neurobehavioral abnormalities. Sequelae of this syndrome usually persist long term. The principal causal factor is bilateral surgical damage (regardless of tumor location) to any component of the proximal efferent cerebellar pathway, which leads to temporary dysfunction of cerebral cortical regions as a result of diaschisis. Tumor type, cerebellar midline location, and brainstem involvement are risk factors for pCMS that have been identified repeatedly, but they do not explain its latent onset. Ambiguous or negative results for other factors, such as hydrocephalus, postoperative meningitis, length of vermian incision, and tumor size, have been reached. The aim of this study was to identify perioperative clinical, radiological, and laboratory factors that also increase risk for the development of pCMS. The focus was on factors that might explain the delayed onset of pCMS and thus might provide a time window for taking precautionary measures to prevent pCMS or reduce its severity. The study was focused specifically on children who had undergone surgery for medulloblastoma. METHODS In this single-center retrospective cohort study, the authors included 71 children with medulloblastoma, 28 of whom developed pCMS after primary resection. Clinical and laboratory data were collected prospectively and analyzed systematically. Variables were included for univariate and multivariate analysis. RESULTS Univariate regression analysis revealed 7 variables that had a significant influence on pCMS onset, namely, tumor size, maximum tumor diameter > 5 cm, tumor infiltration or compression of the brainstem, significantly larger decreases in hemoglobin (p = 0.010) and hematocrit (p = 0.003) in the pCMS group after surgery than in the no-pCMS group, significantly more reported incidents of severe bleeding in the tumor bed during surgery in the pCMS group, preoperative hydrocephalus, and a mean body temperature rise of 0.5°C in the first 4 days after surgery in the pCMS group. Multiple regression analysis revealed that tumor size, tumor infiltration into or compression of the brainstem, and higher mean body temperature in the first 4 postoperative days were independent and highly significant predictors for pCMS. CONCLUSIONS The authors confirmed earlier findings that tumor-associated preoperative conditions, such as a maximum tumor diameter ≥ 5 cm and infiltration into or compression of the brainstem, are associated with a higher risk for the development of pCMS. Most importantly, the authors found that a 0.5°C higher mean body temperature in the first 4 postoperative days increased the odds ratio for the development of pCMS almost 5-fold. These data suggest that an important focus for the prevention of pCMS in children who have undergone medulloblastoma surgery might be rigorous maintenance of normothermia as standard care after surgery.

Specific combinations of ion channel inhibitors reduce excessive Ca2+ influx as a consequence of oxidative stress and increase neuronal and glial cell viability in vitro

Combinations of Ca²⁺ channel inhibitors have been proposed as an effective means to prevent excess Ca²⁺ flux and death of neurons and glia following neurotrauma in vivo. However, it is not yet known if beneficial outcomes such as improved viability have been due to direct effects on intracellular Ca²⁺ concentrations. Here, the effects of combinations of Lomerizine (Lom), 2,3-dioxo-7-(1H-imidazol-1-yl)6-nitro-1,2,3,4-tetrahydro-1-quinoxalinyl]acetic acid monohydrate (YM872), 3,5-dimethyl-1-adamantanamine (memantine (Mem)) and/or adenosine 5'-triphosphate periodate oxidized sodium salt (oxATP) to block voltage-gated Ca²⁺ channels, Ca²⁺ permeable α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, NMDA receptors and purinergic P2X₇ receptors (P2X₇R) respectively, on Ca²⁺ concentration and viability of rat primary mixed cortical (MC) cultures exposed to hydrogen peroxide (H₂O₂) insult, were assessed. The contribution of ryanodine-sensitive intracellular stores to intracellular Ca²⁺ concentration was also assessed. Live cell calcium imaging revealed that a 30min H₂O₂ insult induced a slow increase in intracellular Ca²⁺, in part from intracellular sources, associated with loss of cell viability by 6h. Most combinations of inhibitors that included oxATP significantly decreased Ca²⁺ influx and increased cell viability when administered simultaneously with H₂O₂. However, reductions in intracellular Ca²⁺ concentration were not always linked to improved cell viability. Examination of the density of specific cell subpopulations demonstrated that most combinations of inhibitors that included oxATP preserved NG2+ non-oligodendroglial cells, but preservation of astrocytes and neurons required additional inhibitors. Olig2⁺ oligodendroglia and ED-1⁺ activated microglia/macrophages were not preserved by any of the inhibitor combinations. These data indicate that following H₂O₂ insult, limiting intracellular Ca²⁺ entry via P2X₇R is generally associated with increased cell viability. Protection of NG2+ non-oligodendroglial cells by Ca²⁺ channel inhibitor combinations may contribute to observed beneficial outcomes in vivo.

Transforming growth-beta 1 contributes to isoflurane postconditioning against cerebral ischemia-reperfusion injury by regulating the c-Jun N-terminal kinase signaling pathway

AIM

Cerebral ischemia-reperfusion (I/R) injury is a devastating complication in the perioperative period. Transforming growth factor beta (TGF-β) is a key protein that can participate in the repair and control process responses after I/R injury. Isoflurane is widely used in neurosurgery. Previous studies have shown that isoflurane preconditioning plays an important role in neuroprotection. However, the effects of isoflurane postconditioning on cerebral I/R injury have not yet been elucidated. In the present study, we evaluated the protective effect of isoflurane postconditioning against cerebral I/R injury and investigated the role of the TGF-β signaling pathway and the downstream c-Jun N-terminal kinase (JNK) signaling pathway in neuroprotective mechanism. In particular, the JNK signaling pathway emerges as a possible target for brain repair after stroke.

METHODS

Cerebral I/R injury was produced in SD rat by using the middle cerebral artery occlusion model for 90 min, followed by 24h reperfusion. Postconditioning by inhalation of isoflurane was performed at different concentrations (1.5%, 3.0%, and 4.5%) for 1h after ischemia at the starting time point of reperfusion. The protective effect was tested by neurological deficit scoring with 2,3,5-triphenyl tetrazolium chloride and propidium iodide (PI) staining. Apoptosis of CA1 cells in the hippocampus was detected by TUNEL method. Expression levels of TGF-β1, Smad 2/3, p-Smad2/3, JNK, and p-JNK were determined by immunostaining and Western blot.

RESULTS

Postconditioning by isoflurane at 1.5% and 3.0% concentrations significantly decreased the neurobehavioral deficit scores and infarct volume compared with the I/R group, but no significant difference in neurobehavioral deficit score was detected between the I/R and 4.5% isoflurane postconditioning groups. Additionally, 1.5% isoflurane postconditioning decreased the numbers of PI-positive cells at 24h after reperfusion compared with the I/R group. TGF-β1 and p-Smad2/3 protein gradually increased after I/R injury, with the highest values observed in the 1.5% and 3% isoflurane postconditioning groups. For Smad2/3 protein expression, no differences existed among all groups. After inducing the TGF-β/SMAD3 signaling pathway specific blocker (LY2157299), the neurological deficit scores increased, infarct volumes enlarged, apoptosis increased, and PI-positive CA1 cells in the hippocampus also increased. The expression levels of TGF-β1 and p-Smad2/3 proteins were downregulated. During the pre-injection of LY2157299, the expression levels of TGF-β1 and p-Smad2/3 decreased significantly, but compared with the sham group, the expression level of p-JNK significantly increased. When the injection of LY2157299 was abolished, the expression of p-JNK significantly decreased. The expression levels of p-JNK and TGF-β1 significantly decreased when LY2157299 and SP600125 were injected simultaneously. However, the protective effect mediated by SP600125 completely disappeared, and the role of LY2157299 became dominant. Compared with the sham group, the expression of TGF-β1 was almost unchanged by the injection of SP600125 alone, but the expression of p-JNK significantly decreased.

CONCLUSIONS

Up to 1.5% isoflurane can upregulate the expression of TGF-β1 and downregulate that of p-JNK, which significantly mitigated I/R injury, leading to cerebral injury. However, this protective effect was abrogated when the TGF-β1 signaling pathway was blocked by LY2157299. Overall, the present results provided valid evidence to demonstrate that TGF-β1 contributes to isoflurane postconditioning against cerebral I/R injury by inhibiting the JNK signaling pathway.

Remote ischemic preconditioning in the prevention of ischemic brain damage during intracranial aneurysm treatment (RIPAT): study protocol for a randomized controlled trial

BACKGROUND

The treatment of intracranial aneurysms may be associated with cerebral ischemia. We hypothesize that pre-interventional remote ischemic preconditioning (RIPC) reduces ischemic cerebral tissue damage in patients undergoing elective intracranial aneurysm treatment.

METHODS/DESIGN

This study is a single-center, prospective, randomized, double-blind explorative trial. Patients with an unruptured intracranial aneurysm admitted to Innsbruck Medical University Hospital for coiling or clipping will be consecutively randomized to either the intervention group (= RIPC by inflating an upper extremity blood-pressure cuff for 3 x 5 min to 200 mmHg) or the control group after induction of anesthesia. Participants will be randomized 1:1 to either the preconditioning group or the sham group using a random allocation sequence and block randomization. The precalculated sample size is n = 24 per group. The primary endpoint is the area-under-the-curve concentration of serum biomarkers (S100B, NSE, GFAP, MMP9, MBP, and cellular microparticles) in the first five days after treatment. Secondary endpoints are the number and volume of new ischemic lesions in magnetic resonance imaging and clinical outcome evaluated with the National Institutes of Health Stroke Scale, the modified Rankin Scale, and neuropsychological tests at six and twelve months. All outcome variables will be determined by observers blinded to group allocation. This study was approved by the local institutional Ethics Committee (UN5164), version 3.0 of the study protocol, dated 20 October 2013.

DISCUSSION

This study uses the elective treatment of intracranial aneurysms as a paradigmatic situation to explore the neuroprotective effects of RIPC. If effects are demonstrable in this pilot trial, a larger, prospective phase III trial will be considered.

Comparative analysis of gonadal steroid-mediated neuroprotection after transient focal ischemia in rats: route of application and substrate composition

Progesterone (P) and 17ß-estradiol (E2) mitigate neuronal damage after experimentally induced traumatic brain injury (TBI) and ischemic stroke. Fish oil components such as omega-3 polyunsaturated fatty acids (PUFA n3) also provide neuroprotection in these traumatic models. Steroids and PUFA n3 dampen neuroinflammatory processes and regulate glial function in the affected brain areas. Using a transient focal ischemic rat model, we demonstrate that the co-application of PUFA n3 and P/E2 and the choice of the application route have a clear impact on the prevention of ischemia-induced infarct volume and behavioral recovery. A combinatory PUFA n3 plus P/E2 emulsion intravenously administered was most effective in reducing the infarct size and in restoring behavioral reconstitution compared to other oil emulsions and subcutaneous depot medication. These data encourage to refining clinical treatment protocols for TBI and stroke with gonadal steroids and to establishing combinatory drugs of steroids and fish oil-enriched emulsions thereby creating a win-win situation with two effective components.

Three Ca2+ channel inhibitors in combination limit chronic secondary degeneration following neurotrauma

Following neurotrauma, cells beyond the initial trauma site undergo secondary degeneration, with excess Ca2+ a likely trigger for loss of neurons, compact myelin and function. Treatment using inhibitors of specific Ca2+ channels has shown promise in preclinical studies, but clinical trials have been disappointing and combinatorial approaches are needed. We assessed efficacy of multiple combinations of three Ca2+ channel inhibitors at reducing secondary degeneration following partial optic nerve transection in rat. We used lomerizine to inhibit voltage gated Ca2+ channels; oxidised adenosine-triphosphate (oxATP) to inhibit purinergic P2X7 receptors and/or 2-[7-(1H-imidazol-1-yl)-6-nitro-2,3-dioxo-1,2,3,4-tetrahydro quinoxalin-1-yl]acetic acid (INQ) to inhibit Ca2+ permeable α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. Only the three Ca2+ channel inhibitors delivered in combination significantly preserved visual function, as assessed using the optokinetic nystagmus visual reflex, at 3 months after injury. Preservation of retinal ganglion cells was partial and is unlikely to have accounted for differential effects on function. A range of the Ca2+ channel inhibitor combinations prevented swelling of optic nerve vulnerable to secondary degeneration. Each of the treatments involving lomerizine significantly increased the proportion of axons with normal compact myelin. Nevertheless, limiting decompaction of myelin was not sufficient for preservation of function in our model. Multiple combinations of Ca2+ channel inhibitors reduced formation of atypical node/paranode complexes; outcomes were not associated with preservation of visual function. However, prevention of lengthening of the paranodal gap that was only achieved by treatment with the three Ca2+ channel inhibitors in combination was an important additional effect that likely contributed to the associated preservation of the optokinetic reflex using this combinatorial treatment strategy.

Cognitive dysfunction after cardiac surgery: Pathophysiological mechanisms and preventive strategies

Despite improvements in surgical techniques and the implementation of effective brain protection strategies, the incidence of brain injury after cardiac surgery has remained relatively constant over the years as patients have become older and sicker. Cognitive dysfunction is the most common clinical manifestation of brain injury after cardiac surgery. Its occurrence is related to a combination of three factors that are often associated with cardiopulmonary bypass (CPB): embolism, hypoperfusion, and the inflammatory response. However, such factors and their potential cerebral consequences are not exclusive to CPB. Postoperative cognitive dysfunction also afflicts patients who undergo cardiac surgery without CPB as well as nonsurgery patients who undergo transcatheter interventions. There is growing evidence that patient-related factors such as the presence of (cerebro)vascular risk factors play an important role in both early and late postoperative cognitive dysfunction.

Pupil evaluation in addition to Glasgow Coma Scale components in prediction of traumatic brain injury and mortality

Background

Early diagnosis and prediction of traumatic brain injury (TBI) is essential for determining treatment strategies and allocating resources. This study evaluated the predictive accuracy of Glasgow Coma Scale (GCS) verbal, motor and eye components alone, or in addition to pupil size and reactivity, for TBI.

Methods

A retrospective cohort analysis of data from 51 425 severely injured patients registered in the Trauma Registry of the German Society for Trauma Surgery from 1993 to 2009 was undertaken. Only directly admitted patients alive on admission and with complete data on GCS, pupil size and pupil reactivity were included. The unadjusted predictive roles of GCS components and pupil parameters, alone or in combination, were modelled using area under the receiver operating characteristic (AUROC) curve analyses and multivariable logistic regression regarding presence of TBI and death.

Results

Some 24 115 patients fulfilled the study inclusion criteria. Best accuracy for outcome prediction was found for pupil reactivity (AUROC 0·770, 95 per cent confidence interval 0·761 to 0·779) and GCS motor component (AUROC 0·797, 0·788 to 0·805), with less accuracy for GCS eye and verbal components. The combination of pupil reactivity and GCS motor component (AUROC 0·822, 0·814 to 0·830) outmatched the predictive accuracy of GCS alone (AUROC 0·808, 0·800 to 0·815). Pupil reactivity and size were significantly correlated (rs = 0·56, P < 0·001). Patients displaying both unequal pupils and fixed pupils were most likely to have TBI (95·1 per cent of 283 patients). Good outcome (Glasgow Outcome Scale score 4 or more) was documented for only 1929 patients (8·0 per cent) showing fixed and bilateral dilated pupils.

Conclusion

The best predictive accuracy for presence of TBI was obtained using the GCS components. Pupil reactivity together with the GCS motor component performed best in predicting death.