Role of Anesthetics and Their Adjuvants in Neurovascular Protection in Secondary Brain Injury after Aneurysmal Subarachnoid Hemorrhage

Dexmedetomidine is Associated with Reduced In-Hospital Mortality Risk of Patients with Subarachnoid Hemorrhage Undergoing Surgery

BACKGROUND

Subarachnoid hemorrhage (SAH) is a severe neurologic event with high mortality. The choice of sedatives in SAH management may influence patient outcomes. This study aimed to investigate the association between sedatives and in-hospital mortality among patients with SAH.

METHODS

This study analyzed data from the MIMIC-IV database, and in-hospital mortality was the primary outcome. Key variables collected included sedatives, demographics, comorbidities, vital signs, laboratory tests, and severity scores. Univariate and multivariate logistic regression analyses were used to assess associations between sedative use and in-hospital mortality, with adjustments for confounding factors. Further stratified analyses explored the effects of dexmedetomidine across different patient subgroups, and mediation analysis evaluated the role of creatinine in the relationship between dexmedetomidine and mortality.

RESULTS

A total of 527 patients were included in this study, with 301 males. Compared with propofol and midazolam, the use of dexmedetomidine was significantly related to the reduction of in-hospital mortality in patients with SAH (odds ratio, 0.369; 95% confidence interval, 0.237-0.574; P < 0.001). After adjusting for variables such as demographics, comorbidities, and laboratory tests, dexmedetomidine remained associated with lower in-hospital mortality. In addition, our findings indicated that dexmedetomidine use was associated with a reduced risk of in-hospital mortality regardless of the presence of cerebrovascular disease. We discovered that creatinine acted as a mediator in the protective effect of dexmedetomidine on in-hospital mortality.

CONCLUSIONS

Dexmedetomidine is associated with significantly lower in-hospital mortality in patients with SAH. These findings underscore the importance of sedative choice for patients with SAH, suggesting that dexmedetomidine could enhance patient outcomes.

The Role of Desflurane in the Functional Outcomes Among Spinal Cord Injury Patients Undergoing Upper Extremity Nerve Transfer Procedures

Background and objective While several experimental studies have demonstrated the neuroprotective role of volatile anesthetics after spinal cord injury (SCI), the impact of volatile anesthetics on improving neurologic outcomes in spinal cord-injured patients is not known. Hence, this study aimed to examine the impact of volatile anesthetics on functional outcomes of chronic cervical SCI patients undergoing peripheral nerve transfer procedures. Methods We conducted a retrospective analysis involving adult patients with cervical SCI and upper extremity paralysis undergoing nerve transfer procedures between September 1, 2015, and January 31, 2019. The principal outcome measured was the motor strength of the reinnervated muscle targets assessed per the Medical Research Council (MRC) scale graded from 0 to 5. Secondary outcomes included Disabilities of Arm, Shoulder, and Hand (DASH); Sollerman Hand Function Test (SHFT); and Michigan Hand Questionnaire (MHQ) scores. Univariate analysis and logistic regression were performed to examine the association between the volatile anesthetics (sevoflurane, desflurane) used during the nerve transfer surgery with the improvement in muscle strength examined up to 48 months postoperatively. Results A total of 13 tetraplegic patients with a mean age of 39.2 ± 15.9 years were included in this study. We found that the desflurane group (n=22 muscles) had greater median motor strength than the sevoflurane group (n=60 muscles) towards the final follow-up when the desflurane group had median motor strength of 3 [interquartile range (IQR): 1-4] and sevoflurane group had a median motor strength of 1 (IQR: 0-2.25); p=0.014. However, there was no statistically significant difference between the two groups in the DASH, SHFT, and MHQ scores. Logistic regression analysis showed that type of nerve transfer and preop AIS (ASIA Impairment Scale) grade were significantly associated with higher odds of improvement of motor power by at least 2 grades. Conclusions Our preliminary data show an association between desflurane use and improved motor strength in SCI patients undergoing peripheral nerve transfers. The data suggest that volatile anesthetic conditioning-induced protection observed in preclinical studies may also exist in SCI patients. This will need to be validated in a larger sample size. Examining the therapeutic window, and identifying the molecular mechanisms underlying volatile anesthetic conditioning-induced protection are warranted to aid future translational studies.

Prospective Observational Study of Volatile Sedation with Sevoflurane After Aneurysmal Subarachnoid Hemorrhage Using the Sedaconda Anesthetic Conserving Device

BACKGROUND

Volatile sedation is still used with caution in patients with acute brain injury because of safety concerns. We analyzed the effects of sevoflurane sedation on systemic and cerebral parameters measured by multimodal neuromonitoring in patients after aneurysmal subarachnoid hemorrhage (aSAH) with normal baseline intracranial pressure (ICP).

METHODS

In this prospective observational study, we analyzed a 12-h period before and after the switch from intravenous to volatile sedation with sevoflurane using the Sedaconda Anesthetic Conserving Device with a target Richmond Agitation Sedation Scale score of - 5 to - 4. ICP, cerebral perfusion pressure (CPP), brain tissue oxygenation (PBrO2), metabolic values of cerebral microdialysis, systemic cardiopulmonary parameters, and the administered drugs before and after the sedation switch were analyzed.

RESULTS

We included 19 patients with a median age of 61 years (range 46-78 years), 74% of whom presented with World Federation of Neurosurgical Societies grade 4 or 5 aSAH. We observed no significant changes in the mean ICP (9.3 ± 4.2 vs. 9.7 ± 4.2 mm Hg), PBrO2 (31.0 ± 13.2 vs. 32.2 ± 12.4 mm Hg), cerebral lactate (5.0 ± 2.2 vs. 5.0 ± 1.9 mmol/L), pyruvate (136.6 ± 55.9 vs. 134.1 ± 53.6 µmol/L), and lactate/pyruvate ratio (37.4 ± 8.7 vs. 39.8 ± 9.2) after the sedation switch to sevoflurane. We found a significant decrease in mean arterial pressure (MAP) (88.6 ± 7.6 vs. 86.3 ± 5.8 mm Hg) and CPP (78.8 ± 8.5 vs. 76.6 ± 6.6 mm Hg) after the initiation of sevoflurane, but the decrease was still within the physiological range requiring no additional hemodynamic support.

CONCLUSIONS

Sevoflurane appears to be a feasible alternative to intravenous sedation in patients with aSAH without intracranial hypertension, as our study did not show negative effects on ICP, cerebral oxygenation, or brain metabolism. Nevertheless, the risk of a decrease of MAP leading to a consecutive CPP decrease should be considered.

Volatile Sedation in Neurointensive Care Patients After Aneurysmal Subarachnoid Hemorrhage: Effects on Delayed Cerebral Ischemia, Cerebral Vasospasm, and Functional Outcome

BACKGROUND

Volatile anesthetics have shown neuroprotective effects in preclinical studies, but clinical data on their use after aneurysmal subarachnoid hemorrhage (aSAH) are limited. This study aimed to analyze whether the use of volatile anesthetics for neurocritical care sedation affects the incidence of delayed cerebral ischemia (DCI), cerebral vasospasm (CVS), DCI-related infarction, or functional outcome.

METHODS

Data were retrospectively collected for ventilated aSAH patients (2016-2022), who received sedation for at least 180 hours. For comparative analysis, patients were assigned to a control and a study group according to the sedation used (intravenous vs. volatile sedation). Logistic regression analysis was performed to identify independent predictors of DCI, CVS, DCI-related infarction, and functional outcome.

RESULTS

Ninety-nine patients with a median age of 58 years (interquartile range: 52-65 years) were included. Forty-seven patients (47%) received intravenous sedation, while 52 patients (53%) received (additional) volatile sedation with isoflurane (n = 30, 58%) or sevoflurane (n = 22, 42%) for a median duration of 169 hours (range: 5-298 hours). There were no significant differences between the 2 groups regarding the occurrence of DCI, angiographic CVS, DCI-related infarction, or functional outcome. In a multivariable logistic regression analysis, the use of volatile anesthetics had no impact on the incidence of DCI-related infarction or the patients' functional outcome.

CONCLUSIONS

Volatile sedation in aSAH patients is not associated with the incidence of DCI, CVS, DCI-related infarction, or functional outcome. Although we could not demonstrate neuroprotective effects of volatile anesthetics, our results suggest that volatile sedation after aSAH has no negative effect on the patient's outcome.

Isoflurane conditioning improves functional outcomes after peripheral nerve injury in a sciatic cut repair murine model

Introduction

Anesthetic conditioning has been shown to provide neuroprotection in several neurological disorders. Whether anesthetic conditioning provides protection against peripheral nerve injuries remains unknown. The aim of our current study is to investigate the impact of isoflurane conditioning on the functional outcomes after peripheral nerve injury (PNI) in a rodent sciatic nerve injury model.

Methods

Adult male Lewis rats underwent sciatic nerve cut and repair and exposed to none (Group 1, sham), single isoflurane exposure (Group 2), three-time isoflurane exposure (Group 3), and six-time isoflurane exposure (Group 4). Isoflurane conditioning was established by administration of 2% isoflurane for 1 hour, beginning 1-hour post sciatic nerve cut and repair. Groups 3 and 4 were exposed to isoflurane for 1 hour, 3 and 6 consecutive days respectively. Functional outcomes assessed included compound muscle action potential (CMAP), evoked muscle force (tetanic and specific tetanic force), wet muscle mass, and axonal counting.

Results

We observed an increase in axons, myelin width and a decrease in G-ratio in the isoflurane conditioning groups (3- and 6-days). This correlated with a significant improvement in tetanic and specific tetanic forces, observed in both groups 3 and 4.

Discussion

Isoflurane conditioning (3- and 6-day groups) resulted in improvement in functional outcomes at 12 weeks post peripheral nerve injury and repair in a murine model. Future experiments should be focused on identifying the therapeutic window of isoflurane conditioning and exploring the underlying molecular mechanisms responsible for isoflurane conditioning induced neuroprotection in PNI.

Conditioning-based therapeutics for aneurysmal subarachnoid hemorrhage - A critical review

Aneurysmal subarachnoid hemorrhage (SAH) carries significant mortality and morbidity, with nearly half of SAH survivors having major cognitive dysfunction that impairs their functional status, emotional health, and quality of life. Apart from the initial hemorrhage severity, secondary brain injury due to early brain injury and delayed cerebral ischemia plays a leading role in patient outcome after SAH. While many strategies to combat secondary brain injury have been developed in preclinical studies and tested in late phase clinical trials, only one (nimodipine) has proven efficacious for improving long-term functional outcome. The causes of these failures are likely multitude, but include use of therapies targeting only one element of what has proven to be multifactorial brain injury process. Conditioning is a therapeutic strategy that leverages endogenous protective mechanisms to exert powerful and remarkably pleiotropic protective effects against injury to all major cell types of the CNS. The aim of this article is to review the current body of evidence for the use of conditioning agents in SAH, summarize the underlying neuroprotective mechanisms, and identify gaps in the current literature to guide future investigation with the long-term goal of identifying a conditioning-based therapeutic that significantly improves functional and cognitive outcomes for SAH patients.

Isoflurane Conditioning-Induced Delayed Cerebral Ischemia Protection in Subarachnoid Hemorrhage-Role of Inducible Nitric Oxide Synthase

Background Recent evidence implicates inflammation as a key driver in delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage (SAH). Inducible nitric oxide synthase (iNOS) is one of the known major mediators of inflammation. We previously showed that an inhalational anesthetic, isoflurane, provides strong protection against delayed cerebral ischemia after SAH. Our current study aims to define the role of iNOS in isoflurane conditioning-induced protection against delayed cerebral ischemia in a mouse model of SAH. Methods and Results The experiments used 10- to 14-week-old male wild-type (C57BL/6) and iNOS global knockout mice. Anesthetic conditioning was initiated 1 hour after SAH with isoflurane 2% for 1 hour. Isoflurane-induced changes in iNOS expression were measured. N-(3-(aminomethyl) benzyl) acetamidine, a highly selective iNOS inhibitor, was injected intraperitoneally immediately after SAH and then daily. Vasospasm, microvessel thrombosis, and neurological assessment was performed. Data were analyzed by 1-way ANOVA and 2-way repeated measures ANOVA followed by Student Newman Keuls comparison test. Statistical significance was set at P<0.05. Isoflurane conditioning downregulated iNOS expression in naïve and SAH mice. N-(3-(aminomethyl) benzyl) acetamidine attenuated large artery vasospasm and microvessel thrombosis and improved neurological deficits in wild-type animals. iNOS knockout mice were significantly resistant to vasospasm, microvessel thrombosis, and neurological deficits induced by SAH. Combining isoflurane with N-(3-(aminomethyl) benzyl) acetamidine did not offer extra protection, nor did treating iNOS knockout mice with isoflurane. Conclusions Isoflurane conditioning-induced delayed cerebral ischemia protection appears to be mediated by downregulating iNOS. iNOS is a potential therapeutic target to improve outcomes after SAH.

Neuronal ferroptosis after intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a devastating form of stroke with high rates of morbidity, mortality, and disability. It induces cell death that is responsible for the secondary brain injury (SBI). The underlying mechanism of SBI after ICH is still unclear, and whether it is related to iron overload is worthy to be discussed. Ferroptosis is an iron-dependent non-apoptotic modes of cell death and plays a particularly important role in the occurrence and progression of ICH. Many ICH-induced regulators and signalling pathways of ferroptosis have been reported as promising targets for treating ICH. In this article, we review the definition, characteristics, and inhibition methods of neuronal ferroptosis caused by iron deposition after ICH, and review the biomarkers for ferroptosis.

Mesenchymal stem cells-derived therapies for subarachnoid hemorrhage in preclinical rodent models: a meta-analysis

Background

Mesenchymal stem cells (MSCs) and MSCs-derived extracellular vesicles (EVs) have emerged as potential novel therapies for subarachnoid hemorrhage (SAH). However, their effects remain incompletely understood. We aim to comprehensively evaluate the effect of MSCs-derived therapies in rodent models of SAH.

Methods

We searched PubMed, EMBASE, and Web of Science up to September 2021 to identify studies that reported the effects of MSCs or MSCs-derived EVs in a rodent SAH model. Neurobehavioral score was extracted as the functional outcome, and brain water content was measured as the histopathological outcome. A random-effects model was used to calculate the standardized mean difference (SMD) and confidence interval (CI).

Results

Nine studies published from 2018 to 2021 met the inclusion criteria. Studies quality scores ranged from 5 to 10, with a mean value of 7.22. Our results revealed an overall positive effect of MSCs and MSCs-derived EVs on the neurobehavioral score with a SMD of − 2.21 (95% CI − 3.14, − 1.08; p < 0.0001). Meanwhile, we also found that MSCs and MSCs-derived EVs reduced brain water content by a SMD of − 2.09 (95% CI − 2.99, − 1.19; p < 0.00001). Significant heterogeneity among studies was observed, further stratified and sensitivity analyses did not identify the source of heterogeneity.

Conclusions

Our results suggested that MSCs-derived therapies prominently improved functional recovery and reduced brain edema in the rodent models of SAH. Notably, the limitations of small sample size should be considered when interpreting the results, and large animal studies and human trials are needed for further investigation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02725-2.

Cerebrospinal fluid metabolic profiling reveals divergent modulation of pentose phosphate pathway by midazolam, propofol and dexmedetomidine in patients with subarachnoid hemorrhage: a cohort study

BACKGROUND

Agitation is common in subarachnoid hemorrhage (SAH), and sedation with midazolam, propofol and dexmedetomidine is essential in agitation management. Previous research shows the tendency of dexmedetomidine and propofol in improving long-term outcome of SAH patients, whereas midazolam might be detrimental. Brain metabolism derangement after SAH might be interfered by sedatives. However, how sedatives work and whether the drugs interfere with patient outcome by altering cerebral metabolism is unclear, and the comprehensive view of how sedatives regulate brain metabolism remains to be elucidated.

METHODS

For cerebrospinal fluid (CSF) and extracellular space of the brain exchange instantly, we performed a cohort study, applying CSF of SAH patients utilizing different sedatives or no sedation to metabolomics. Baseline CSF metabolome was corrected by selecting patients of the same SAH and agitation severity. CSF components were analyzed to identify the most affected metabolic pathways and sensitive biomarkers of each sedative. Markers might represent the outcome of the patients were also investigated.

RESULTS

Pentose phosphate pathway was the most significantly interfered (upregulated) pathway in midazolam (p = 0.0000107, impact = 0.35348) and propofol (p = 0.00000000000746, impact = 0.41604) groups. On the contrary, dexmedetomidine decreased levels of sedoheptulose 7-phosphate (p = 0.002) and NADP (p = 0.024), and NADP is the key metabolite and regulator in pentose phosphate pathway. Midazolam additionally augmented purine synthesis (p = 0.00175, impact = 0.13481) and propofol enhanced pyrimidine synthesis (p = 0.000203, impact = 0.20046), whereas dexmedetomidine weakened pyrimidine synthesis (p = 0.000000000594, impact = 0.24922). Reduced guanosine diphosphate (AUC of ROC 0.857, 95%CI 0.617-1, p = 0.00506) was the significant CSF biomarker for midazolam, and uridine diphosphate glucose (AUC of ROC 0.877, 95%CI 0.631-1, p = 0.00980) for propofol, and succinyl-CoA (AUC of ROC 0.923, 95%CI 0.785-1, p = 0.000810) plus adenosine triphosphate (AUC of ROC 0.908, 95%CI 0.6921, p = 0.00315) for dexmedetomidine. Down-regulated CSF succinyl-CoA was also associated with favorable outcome (AUC of ROC 0.708, 95% CI: 0.524-0.865, p = 0.029333).

CONCLUSION

Pentose phosphate pathway was a crucial target for sedatives which alter brain metabolism. Midazolam and propofol enhanced the pentose phosphate pathway and nucleotide synthesis in poor-grade SAH patients, as presented in the CSF. The situation of dexmedetomidine was the opposite. The divergent modulation of cerebral metabolism might further explain sedative pharmacology and how sedatives affect the outcome of SAH patients.

Gap Junctions and Hemichannels Composed of Connexins and Pannexins Mediate the Secondary Brain Injury Following Intracerebral Hemorrhage

Simple Summary

Intracerebral hemorrhage (ICH) is a leading medical problem without effective treatment options. The poor prognosis is attributed to the primary brain injury of the mechanical compression caused by hematoma, and secondary brain injury (SBI) that includes inflammation, glutamate excitotoxicity, oxidative stress and disruption of the blood brain barrier (BBB). Evidences suggests that gap junctions and hemichannels composed of connexins and pannexins regulate the inflammation and excitotoxicity insult in the pathological process of central nervous system disease, such as cerebral ischemia and neurodegeneration disease. In this manuscript, we discuss the fact that connexins- and pannexins-based channels could be involved in secondary brain injury of ICH, particularly through mediating inflammation, oxidative stress, BBB disruption and cell death. The details provided in this manuscript may help develop potential targets for therapeutic intervention of ICH.

Abstract

Intracerebral hemorrhage (ICH) is a devastating disease with high mortality and morbidity; the mortality rate ranges from 40% at 1 month to 54% at 1 year; only 12–39% achieve good outcomes and functional independence. ICH affects nearly 2 million patients worldwide annually. In ICH development, the blood leakage from ruptured vessels generates sequelae of secondary brain injury (SBI). This mechanism involves activated astrocytes and microglia, generation of reactive oxygen species (ROS), the release of reactive nitrogen species (RNS), and disrupted blood brain barrier (BBB). In addition, inflammatory cytokines and chemokines, heme compounds, and products of hematoma are accumulated in the extracellular spaces, thereby resulting in the death of brain cells. Recent evidence indicates that connexins regulate microglial activation and their phenotypic transformation. Moreover, communications between neurons and glia via gap junctions have crucial roles in neuroinflammation and cell death. A growing body of evidence suggests that, in addition to gap junctions, hemichannels (composed of connexins and pannexins) play a key role in ICH pathogenesis. However, the precise connection between connexin and pannexin channels and ICH remains to be resolved. This review discusses the pathological roles of gap junctions and hemichannels in SBI following ICH, with the intent of discovering effective therapeutic options of strategies to treat ICH.