Effect of analgesics and sedatives on the occurrence of spreading depolarizations accompanying acute brain injury

The Impact of Sedative Choice in the Management of Aneurysmal Subarachnoid Hemorrhage: A Scoping Review

Aneurysmal subarachnoid hemorrhage (aSAH) is characterized by high mortality and morbidity. This scoping review assesses the current evidence regarding the use of sedatives and analgesics in the acute intensive care unit management of aSAH. We conducted a systematic search of Ovid MEDLINE, Ovid Embase, Ovid EmCare, APA PsycInfo, CINAHL, and the Cochrane Database of Systematic Reviews from inception to June 2023. Studies were included if they enrolled intensive care unit patients aged 18 or older with a significant proportion (> 20%) who had aSAH and evaluated the impact of one or more commonly used analgosedatives on physiological parameters in the management of aSAH. The methodological quality of the studies was assessed using the Methodological Index for Nonrandomized Studies score. Of 2,583 articles, 11 met the inclusion criteria. The median sample size was 47 (interquartile range 10-127), and the median Methodological Index for Nonrandomized Studies score was 9.5 (interquartile range 8-11). The studies' publication years ranged from 1980 to 2023. Dexmedetomidine and ketamine showed potential benefits in reducing the incidence of cortical spreading depolarization and delayed cerebral ischemia. Propofol and opioids appeared safe but lacked robust evidence for efficacy. Benzodiazepines were associated with increased delayed cerebral ischemia-related cerebral infarctions and cortical spreading depolarization events. The evidence available to guide the use of analgosedative medications in aSAH is critically inadequate. Dexmedetomidine and ketamine warrant further exploration in large-scale prospective studies because of their potential benefits. Improved study designs with consistent definitions and a focus on patient-centered outcomes are necessary to inform clinical practice.

Prevention of Delayed Cerebral Ischemia After Aneurysmal Subarachnoid Hemorrhage-Summary of Existing Clinical Evidence

The 2023 International Subarachnoid Hemorrhage Conference identified a need to provide an up-to-date review on prevention methods for delayed cerebral ischemia (DCI) following aneurysmal subarachnoid hemorrhage and highlight areas for future research. A PubMed search was conducted for key factors contributing to development of delayed cerebral ischemia: anesthetics, antithrombotics, cerebrospinal fluid (CSF) diversion, hemodynamic, endovascular, and medical management. It was found that there is still a need for prospective studies analyzing the best methods for anesthetics and antithrombotics, though inhaled anesthetics and antiplatelets were found to have some advantages. Lumbar drains should increasingly be considered the first line of CSF diversion when applicable. Finally, maintaining euvolemia before and during vasospasm is recommended as there is no evidence supporting prophylactic spasmolysis or angioplasty. There is accumulating observational evidence, however, that intra-arterial spasmolysis with refractory DCI might be beneficial in patients not responding to induced hypertension. Nimodipine remains the medical therapy with the most support for prevention.

Acute Management of Moderate to Severe Traumatic Brain Injury

The focus of this article is on the acute management of traumatic brain injury. The article focuses on the classification of traumatic brain injury, general acute management of traumatic brain injury, the role of the physiatrist on this team, and lastly, behavioral and family considerations in the acute care setting. The article includes a focus on physiologic systems, strategies for the management of various aspects of brain injury, and consideration of factors associated with the continuum of care. Overall, the article reviews this critical period of brain injury recovery and provides a primer for the physiatrist.

Ketamine for Critically Ill Patients with Severe Acute Brain Injury: A Systematic Review with Meta-analysis and Trial Sequential Analysis of Randomized Clinical Trials

BACKGROUND

Patients with severe acute brain injury have a high risk of a poor clinical outcome due to primary and secondary brain injury. Ketamine reportedly inhibits cortical spreading depolarization, an electrophysiological phenomenon that has been associated with secondary brain injury, making ketamine potentially attractive for patients with severe acute brain injury. The aim of this systematic review is to explore the current literature regarding ketamine for patients with severe acute brain injury.

METHODS

We systematically searched international databases for randomized clinical trials comparing ketamine by any regimen versus placebo, no intervention, or any control drug for patients with severe acute brain injury. Two authors independently reviewed and selected trials for inclusion, extracted data, assessed risk of bias, and performed analysis using Review Manager and Trial Sequential Analysis. Evidence certainty was assessed using Grading of Recommendations Assessment, Development and Evaluation. The primary outcomes were the proportion of participants with an unfavorable functional outcome, the proportion of participants with one or more serious adverse events, and quality of life.

RESULTS

We identified five randomized trials comparing ketamine versus sufentanil, fentanyl, other sedatives, or saline (total N = 149 participants). All outcomes were at overall high risk of bias. The proportions of participants with one or more serious adverse events did not differ between ketamine and sufentanil or fentanyl (relative risk 1.45, 95% confidence interval 0.81-2.58; very low certainty). Trial sequential analysis showed that further trials are needed.

CONCLUSIONS

The level of evidence regarding the effects of ketamine on functional outcome and serious adverse events in patients with severe acute brain injury is very low. Ketamine may markedly, modestly, or not at all affect these outcomes. Large randomized clinical trials at low risk of bias are needed.

Post-traumatic Transient Neurological Dysfunction: A Proposal for Pathophysiology

Unexplained neurological deterioration is occasionally observed in patients with traumatic brain injuries (TBIs). We aimed to describe the clinical features of post-traumatic transient neurological dysfunction and provide new insight into its pathophysiology. We retrospectively collected data from patients with focal neurological deterioration of unknown origin during hospitalization for acute TBI for 48 consecutive months. Brain imaging, including computed tomography, diffusion-weighted imaging and perfusion-weighted imaging, and electroencephalography were conducted during the episodes. Fourteen (2.0%) patients experienced unexplained focal neurological deterioration among 713 patients who were admitted for traumatic intracranial hemorrhage during the study period. Aphasia was the predominant symptom in all patients, and hemiparesis or hemianopia was accompanied in three patients. These symptoms developed within 14 days after trauma. Structural imaging did not show any significant interval change, and electroencephalography showed persistent arrhythmic slowing in the corresponding hemisphere in most patients. Perfusion imaging revealed increased cerebral blood flow in the symptomatic hemisphere. Surgical intervention and anti-seizure medications were ineffective in abolishing the symptoms. The symptoms disappeared spontaneously after 4 h to 1 month. Transient neurological dysfunction (TND) can occur during the acute phase of TBI. Although TND may last longer than a typical transient ischemic attack or seizure, it eventually resolves regardless of treatment. Based on our observation, we postulate that this is a manifestation of spreading depolarization occurring in the injured brain, which is analogous to migraine aura.

[Current Aspects of Intensive Medical Care for Traumatic Brain Injury - Part 1 - Primary Treatment Strategies, Haemodynamic Management and Multimodal Monitoring]

This two-part article deals with the intensive medical care of traumatic brain injury. Part 1 addresses the primary treatment strategy, haemodynamic management and multimodal monitoring, Part 2 secondary treatment strategies, long-term outcome, neuroprognostics and chronification. Traumatic brain injury is a complex clinical entity with a high mortality rate. The primary aim is to maintain homeostasis based on physiological targeted values. In addition, further therapy must be geared towards intracranial pressure. In addition to this, there are other monitoring options that appear sensible from a pathophysiological point of view with appropriate therapy adjustment. However, there is still a lack of data on their effectiveness. A further aspect is the inflammation of the cerebrum with the "cross-talk" of the organs, which has a significant influence on further intensive medical care.

From spreading depolarization to blood-brain barrier dysfunction: navigating traumatic brain injury for novel diagnosis and therapy

Considerable strides in medical interventions during the acute phase of traumatic brain injury (TBI) have brought improved overall survival rates. However, following TBI, people often face ongoing, persistent and debilitating long-term complications. Here, we review the recent literature to propose possible mechanisms that lead from TBI to long-term complications, focusing particularly on the involvement of a compromised blood-brain barrier (BBB). We discuss evidence for the role of spreading depolarization as a key pathological mechanism associated with microvascular dysfunction and the transformation of astrocytes to an inflammatory phenotype. Finally, we summarize new predictive and diagnostic biomarkers and explore potential therapeutic targets for treating long-term complications of TBI.

Duration of spreading depression is the electrophysiological correlate of infarct growth in malignant hemispheric stroke

Spreading depolarizations (SD) contribute to lesion progression after experimental focal cerebral ischemia while such correlation has never been shown in stroke patients. In this prospective, diagnostic study, we investigate the association of SDs and secondary infarct progression after malignant hemispheric stroke. SDs were continuously monitored for 3-9 days with electrocorticography after decompressive hemicraniectomy for malignant hemispheric stroke. To ensure valid detection and analysis of SDs, a threshold based on the electrocorticographic baseline activity was calculated to identify valid electrocorticographic recordings. Subsequently SD characteristics were analyzed in association to infarct progression based on serial MRI. Overall, 62 patients with a mean stroke volume of 289.6 ± 68 cm3 were included. Valid electrocorticographic recordings were found in 44/62 patients with a mean recording duration of 139.6 ± 26.5 hours and 52.5 ± 39.5 SDs per patient. Infarct progression of more than 5% was found in 21/44 patients. While the number of SDs was similar between patients with and without infarct progression, the SD-induced depression duration per day was significantly longer in patients with infarct progression (593.8 vs. 314.1 minutes; *p = 0.046). Therefore, infarct progression is associated with a prolonged SD-induced depression duration. Real-time analysis of electrocorticographic recordings may identify secondary stroke progression and help implementing targeted management strategies.

Inhibition of astroglial hemichannels prevents synaptic transmission decline during spreading depression

BACKGROUND

Spreading depression (SD) is an intriguing phenomenon characterized by massive slow brain depolarizations that affect neurons and glial cells. This phenomenon is repetitive and produces a metabolic overload that increases secondary damage. However, the mechanisms associated with the initiation and propagation of SD are unknown. Multiple lines of evidence indicate that persistent and uncontrolled opening of hemichannels could participate in the pathogenesis and progression of several neurological disorders including acute brain injuries. Here, we explored the contribution of astroglial hemichannels composed of connexin-43 (Cx43) or pannexin-1 (Panx1) to SD evoked by high-K+ stimulation in brain slices.

RESULTS

Focal high-K+ stimulation rapidly evoked a wave of SD linked to increased activity of the Cx43 and Panx1 hemichannels in the brain cortex, as measured by light transmittance and dye uptake analysis, respectively. The activation of these channels occurs mainly in astrocytes but also in neurons. More importantly, the inhibition of both the Cx43 and Panx1 hemichannels completely prevented high K+-induced SD in the brain cortex. Electrophysiological recordings also revealed that Cx43 and Panx1 hemichannels critically contribute to the SD-induced decrease in synaptic transmission in the brain cortex and hippocampus.

CONCLUSIONS

Targeting Cx43 and Panx1 hemichannels could serve as a new therapeutic strategy to prevent the initiation and propagation of SD in several acute brain injuries.

Isoflurane lowers the cerebral metabolic rate of oxygen and prevents hypoxia during cortical spreading depolarization in vitro: An integrative experimental and modeling study

Cortical spreading depolarization (SD) imposes a massive increase in energy demand and therefore evolves as a target for treatment following acute brain injuries. Anesthetics are empirically used to reduce energy metabolism in critical brain conditions, yet their effect on metabolism during SD remains largely unknown. We investigated oxidative metabolism during SD in brain slices from Wistar rats. Extracellular potassium ([K+]o), local field potential and partial tissue oxygen pressure (ptiO2) were measured simultaneously. The cerebral metabolic rate of oxygen (CMRO2) was calculated using a reaction-diffusion model. By that, we tested the effect of clinically relevant concentrations of isoflurane on CMRO2 during SD and modeled tissue oxygenation for different capillary pO2 values. During SD, CMRO2 increased 2.7-fold, resulting in transient hypoxia in the slice core. Isoflurane decreased CMRO2, reduced peak [K+]o, and prolonged [K+]o clearance, which indicates reduced synaptic transmission and sodium-potassium ATPase inhibition. Modeling tissue oxygenation during SD illustrates the need for increased capillary pO2 levels to prevent hypoxia. In the absence thereof, isoflurane could improve tissue oxygenation by lowering CMRO2. Therefore, isoflurane is a promising candidate for pre-clinical studies on neuronal survival in conditions involving SD.

Galanin diminishes cortical spreading depolarization across rodents - A candidate for treatment?

Galanin (Gal) is a neuropeptide with the potential to ameliorate cortical spreading depolarization (CSD), an electrophysiological phenomenon occurring after brain injury or in migraine aura. Gal is expressed in all cortical neurons both in rat and in mouse cortices. Here we investigated whether the effect of Gal on CSD previously described in the rat is conserved in the mouse cortex. In rats, the topical application of Gal to the cortex for 1 h did not induce any change in CSD amplitudes, propagation velocity, or threshold of elicitation. Rather, topical application of Gal for 3 h was necessary to obtain a significant decrease in these CSD parameters and to develop a remarkable increase in the KCl threshold to elicit a CSD in rat cortex. In contrast, the topical application of Gal on cortical surface for 1 h in mice was sufficient to significantly attenuate CSD amplitudes and increase threshold. A thinner cortex, a faster diffusion or different affinity/expression of receptors for Gal are possible reasons to explain this difference in the time course between rats and mice. Our data are relevant to postulate Gal as a potential target for inhibition of CSD under pathological situations such as stroke or ischemia. SIGNIFICANCE STATEMENT: The neuropeptide Galanin (Gal) is expressed in all neurons throughout the cerebral cortex, both in rats and mice, and is able to reduce or even inhibit Cortical Spreading Depolarization, thus, Gal has the potential to control neuronal excitability that may identify Gal as a target in drug development against CSD.

Ketamine improves neuronal recovery following spreading depolarization in peri-infarct tissues

Spreading depolarization (SD) has emerged as an important contributor to the enlargement of acute brain injuries. We previously showed that the N-methyl-D-aspartate receptor antagonist ketamine was able to prevent deleterious consequences of SD in brain slices, under conditions of metabolic compromise. The current study aimed to extend these observations into an in vivo stroke model, to test whether gradients of metabolic capacity lead to differential accumulation of calcium (Ca2+) following SD. In addition, we tested whether ketamine protects vulnerable tissuewhile allowing SD to propagate through surrounding undamaged tissue. Focal lesions were generated using a distal middle cerebral artery occlusion in mice, and clusters of SD were generated at 20 min intervals with remote microinjection of potassium chloride. SDs invading peri-infarct regions had significantly different consequences, depending on the distance from the infarct core. Proximal to the lesion, Ca2+ transients were extended, as compared with responses in better-perfused tissue more remote from the lesion. Extracellular potential shifts were also longer and hyperemia responses were reduced in proximal regions following SDs. Consistent with in vitro studies, ketamine, at concentrations that did not abolish the propagation of SD, reduced the accumulation of intracellular Ca2+ in proximal regions following an SD wave. These findings suggest that deleterious consequences of SD can be targeted in vivo, without requiring outright block of SD initiation and propagation.

Similarities in the Electrographic Patterns of Delayed Cerebral Infarction and Brain Death After Aneurysmal and Traumatic Subarachnoid Hemorrhage

While subarachnoid hemorrhage is the second most common hemorrhagic stroke in epidemiologic studies, the recent DISCHARGE-1 trial has shown that in reality, three-quarters of focal brain damage after subarachnoid hemorrhage is ischemic. Two-fifths of these ischemic infarctions occur early and three-fifths are delayed. The vast majority are cortical infarcts whose pathomorphology corresponds to anemic infarcts. Therefore, we propose in this review that subarachnoid hemorrhage as an ischemic-hemorrhagic stroke is rather a third, separate entity in addition to purely ischemic or hemorrhagic strokes. Cumulative focal brain damage, determined by neuroimaging after the first 2 weeks, is the strongest known predictor of patient outcome half a year after the initial hemorrhage. Because of the unique ability to implant neuromonitoring probes at the brain surface before stroke onset and to perform longitudinal MRI scans before and after stroke, delayed cerebral ischemia is currently the stroke variant in humans whose pathophysiological details are by far the best characterized. Optoelectrodes located directly over newly developing delayed infarcts have shown that, as mechanistic correlates of infarct development, spreading depolarizations trigger (1) spreading ischemia, (2) severe hypoxia, (3) persistent activity depression, and (4) transition from clustered spreading depolarizations to a negative ultraslow potential. Furthermore, traumatic brain injury and subarachnoid hemorrhage are the second and third most common etiologies of brain death during continued systemic circulation. Here, we use examples to illustrate that although the pathophysiological cascades associated with brain death are global, they closely resemble the local cascades associated with the development of delayed cerebral infarcts.

Synaptic Zn2+ contributes to deleterious consequences of spreading depolarizations

Spreading depolarizations (SDs) are profound waves of neuroglial depolarization that can propagate repetitively through injured brain. Recent clinical work has established SD as an important contributor to expansion of acute brain injuries and have begun to extend SD studies into other neurological disorders. A critical challenge is to determine how to selectively prevent deleterious consequences of SD. In the present study, we determined whether a wave of profound Zn2+ release is a key contributor to deleterious consequences of SD, and whether this can be targeted pharmacologically. Focal KCl microinjection was used to initiate SD in the CA1 region of the hippocampus in murine brain slices. An extracellular Zn2+ chelator with rapid kinetics (ZX1) increased SD propagation rates and improved recovery of extracellular DC potential shifts. Under conditions of metabolic compromise, tissues showed sustained impairment of functional and structural recovery following a single SD. ZX1 effectively improved recovery of synaptic potentials and intrinsic optical signals in these vulnerable conditions. Fluorescence imaging and genetic deletion of a presynaptic Zn2+ transporter confirmed synaptic release as the primary contributor to extracellular accumulation and deleterious consequences of Zn2+ during SD. These results demonstrate a role for synaptic Zn2+ release in deleterious consequences of SD and show that targeted extracellular chelation could be useful for disorders where repetitive SD enlarges infarcts in injured tissues.

Different vulnerability of fast and slow cortical oscillations to suppressive effect of spreading depolarization: state-dependent features potentially relevant to pathogenesis of migraine aura

BACKGROUND

Spreading depolarization (SD), underlying mechanism of migraine aura and potential activator of pain pathways, is known to elicit transient local silencing cortical activity. Sweeping across the cortex, the electrocorticographic depression is supposed to underlie spreading negative symptoms of migraine aura. Main information about the suppressive effect of SD on cortical oscillations was obtained in anesthetized animals while ictal recordings in conscious patients failed to detect EEG depression during migraine aura. Here, we investigate the suppressive effect of SD on spontaneous cortical activity in awake animals and examine whether the anesthesia modifies the SD effect.

METHODS

Spectral and spatiotemporal characteristics of spontaneous cortical activity following a single unilateral SD elicited by amygdala pinprick were analyzed in awake freely behaving rats and after induction of urethane anesthesia.

RESULTS

In wakefulness, SD transiently suppressed cortical oscillations in all frequency bands except delta. Slow delta activity did not decline its power during SD and even increased it afterwards; high-frequency gamma oscillations showed the strongest and longest depression under awake conditions. Unexpectedly, gamma power reduced not only during SD invasion the recording cortical sites but also when SD occupied distant subcortical/cortical areas. Contralateral cortex not invaded by SD also showed transient depression of gamma activity in awake animals. Introduction of general anesthesia modified the pattern of SD-induced depression: SD evoked the strongest cessation of slow delta activity, milder suppression of fast oscillations and no distant changes in gamma activity.

CONCLUSION

Slow and fast cortical oscillations differ in their vulnerability to SD influence, especially in wakefulness. In the conscious brain, SD produces stronger and spatially broader depression of fast cortical oscillations than slow ones. The frequency-specific effects of SD on cortical activity of awake brain may underlie some previously unexplained clinical features of migraine aura.

Memantine inhibits cortical spreading depolarization and improves neurovascular function following repetitive traumatic brain injury

Cortical spreading depolarization (CSD) is a promising target for neuroprotective therapy in traumatic brain injury (TBI). We explored the effect of NMDA receptor antagonism on electrically triggered CSDs in healthy and brain-injured animals. Rats received either one moderate or four daily repetitive mild closed head impacts (rmTBI). Ninety-three animals underwent craniectomy with electrocorticographic (ECoG) and local blood flow monitoring. In brain-injured animals, ketamine or memantine inhibited CSDs in 44 to 88% and 50 to 67% of cases, respectively. Near-DC/AC-ECoG amplitude was reduced by 44 to 75% and 52 to 67%, and duration by 39 to 87% and 61 to 78%, respectively. Daily memantine significantly reduced spreading depression and oligemia following CSD. Animals (N = 31) were randomized to either memantine (10 mg/kg) or saline with daily neurobehavioral testing. Memantine-treated animals had higher neurological scores. We demonstrate that memantine improved neurovascular function following CSD in sham and brain-injured animals. Memantine also prevented neurological decline in a blinded, preclinical randomized rmTBI trial.

Cortical spreading depolarization-induced constriction of penetrating arteries can cause watershed ischemia: A potential mechanism for white matter lesions

Periventricular white matter lesions (WMLs) are common MRI findings in migraine with aura (MA). Although hemodynamic disadvantages of vascular supply to this region create vulnerability, the pathophysiological mechanisms causing WMLs are unclear. We hypothesize that prolonged oligemia, a consequence of cortical spreading depolarization (CSD) underlying migraine aura, may lead to ischemia/hypoxia at hemodynamically vulnerable watershed zones fed by long penetrating arteries (PAs). For this, we subjected mice to KCl-triggered single or multiple CSDs. We found that post-CSD oligemia was significantly deeper at medial compared to lateral cortical areas, which induced ischemic/hypoxic changes at watershed areas between the MCA/ACA, PCA/anterior choroidal and at the tip of superficial and deep PAs, as detected by histological and MRI examination of brains 2-4 weeks after CSD. BALB-C mice, in which MCA occlusion causes large infarcts due to deficient collaterals, exhibited more profound CSD-induced oligemia and were more vulnerable compared to Swiss mice such that a single CSD was sufficient to induce ischemic lesions at the tip of PAs. In conclusion, CSD-induced prolonged oligemia has potential to cause ischemic/hypoxic injury at hemodynamically vulnerable brain areas, which may be one of the mechanisms underlying WMLs located at the tip of medullary arteries seen in MA patients.

Synaptic Zn2+ contributes to deleterious consequences of spreading depolarizations

Spreading depolarizations (SDs) are profound waves of neuroglial depolarization that can propagate repetitively through injured brain. Recent clinical work has established SD as an important contributor to expansion of acute brain injuries and have begun to extend SD studies into other neurological disorders. A critical challenge is to determine how to selectively prevent deleterious consequences of SD. In the present study, we determined whether a wave of profound Zn2+ release is a key contributor to deleterious consequences of SD, and whether this can be targeted pharmacologically. Focal KCl microinjection was used to initiate SD in the CA1 region of the hippocampus in murine brain slices. An extracellular Zn2+ chelator with rapid kinetics (ZX-1) increased SD propagation rates and improved recovery of extracellular DC potential shifts. Under conditions of metabolic compromise, tissues showed sustained impairment of functional and structural recovery following a single SD. ZX-1 effectively improved recovery of synaptic potentials and intrinsic optical signals in these vulnerable conditions. Fluorescence imaging and genetic deletion of a presynaptic Zn2+ transporter confirmed synaptic release as the primary contributor to extracellular accumulation and deleterious consequences of Zn2+ during SD. These results demonstrate a role for synaptic Zn2+ release in deleterious consequences of SD and show that targeted extracellular chelation could be useful for disorders where repetitive SD enlarges infarcts in injured tissues.

Improving Neurotrauma by Depolarization Inhibition With Combination Therapy: A Phase 2 Randomized Feasibility Trial

BACKGROUND AND OBJECTIVES

Spreading depolarizations (SDs) are a pathological mechanism that mediates lesion development in cerebral gray matter. They occur in ∼60% of patients with severe traumatic brain injury (TBI), often in recurring and progressive patterns from days 0 to 10 after injury, and are associated with worse outcomes. However, there are no protocols or trials suggesting how SD monitoring might be incorporated into clinical management. The objective of this protocol is to determine the feasibility and efficacy of implementing a treatment protocol for intensive care of patients with severe TBI that is guided by electrocorticographic monitoring of SDs.

METHODS

Patients who undergo surgery for severe TBI with placement of a subdural electrode strip will be eligible for enrollment. Those who exhibit SDs on electrocorticography during intensive care will be randomized 1:1 to either (1) standard care that is blinded to the further course of SDs or (2) a tiered intervention protocol based on efficacy to suppress further SDs. Interventions aim to block the triggering and propagation of SDs and include adjusted targets for management of blood pressure, CO 2 , temperature, and glucose, as well as ketamine pharmacotherapy up to 4 mg/kg/ hour. Interventions will be escalated and de-escalated depending on the course of SD pathology.

EXPECTED OUTCOMES

We expect to demonstrate that electrocorticographic monitoring of SDs can be used as a real- time diagnostic in intensive care that leads to meaningful changes in patient management and a reduction in secondary injury, as compared with standard care, without increasing medical complications or adverse events.

DISCUSSION

This trial holds potential for personalization of intensive care management by tailoring therapies based on monitoring and confirmation of the targeted neuronal mechanism of SD. Results are expected to validate the concept of this approach, inform refinement of the treatment protocol, and lead to larger-scale trials.

Spreading Depolarizations Suppress Hematoma Growth in Hyperacute Intracerebral Hemorrhage in Mice

BACKGROUND

Spreading depolarizations (SDs) occur in all types of brain injury and may be associated with detrimental effects in ischemic stroke and subarachnoid hemorrhage. While rapid hematoma growth during intracerebral hemorrhage triggers SDs, their role in intracerebral hemorrhage is unknown.

METHODS

We used intrinsic optical signal and laser speckle imaging, combined with electrocorticography, to investigate the effects of SD on hematoma growth during the hyperacute phase (0-4 hours) after intracortical collagenase injection in mice. Hematoma expansion, SDs, and cerebral blood flow were simultaneously monitored under normotensive and hypertensive conditions.

RESULTS

Spontaneous SDs erupted from the vicinity of the hematoma during rapid hematoma growth. We found that hematoma growth slowed down by >60% immediately after an SD. This effect was even stronger in hypertensive animals with faster hematoma growth. To establish causation, we exogenously induced SDs (every 30 minutes) at a remote site by topical potassium chloride application and found reduced hematoma growth rate and final hemorrhage volume (18.2±5.8 versus 10.7±4.1 mm3). Analysis of cerebral blood flow using laser speckle flowmetry revealed that suppression of hematoma growth by spontaneous or induced SDs coincided and correlated with the characteristic oligemia in the wake of SD, implicating the vasoconstrictive effect of SD as one potential mechanism of action.

CONCLUSIONS

Our findings reveal that SDs limit hematoma growth during the early hours of intracerebral hemorrhage and decrease final hematoma volume.

Management Strategies Based on Multi-Modality Neuromonitoring in Severe Traumatic Brain Injury

Secondary brain injury after neurotrauma is comprised of a host of distinct, potentially concurrent and interacting mechanisms that may exacerbate primary brain insult. Multimodality neuromonitoring is a method of measuring multiple aspects of the brain in order to understand the signatures of these different pathomechanisms and to detect, treat, or prevent potentially reversible secondary brain injuries. The most studied invasive parameters include intracranial pressure (ICP), cerebral perfusion pressure (CPP), autoregulatory indices, brain tissue partial oxygen tension, and tissue energy and metabolism measures such as the lactate pyruvate ratio. Understanding the local metabolic state of brain tissue in order to infer pathology and develop appropriate management strategies is an area of active investigation. Several clinical trials are underway to define the role of brain tissue oxygenation monitoring and electrocorticography in conjunction with other multimodal neuromonitoring information, including ICP and CPP monitoring. Identifying an optimal CPP to guide individualized management of blood pressure and ICP has been shown to be feasible, but definitive clinical trial evidence is still needed. Future work is still needed to define and clinically correlate patterns that emerge from integrated measurements of metabolism, pressure, flow, oxygenation, and electrophysiology. Pathophysiologic targets and precise critical care management strategies to address their underlying causes promise to mitigate secondary injuries and hold the potential to improve patient outcome. Advancements in clinical trial design are poised to establish new standards for the use of multimodality neuromonitoring to guide individualized clinical care.

Noninvasive and reliable automated detection of spreading depolarization in severe traumatic brain injury using scalp EEG

BACKGROUND

Spreading depolarizations (SDs) are a biomarker and a potentially treatable mechanism of worsening brain injury after traumatic brain injury (TBI). Noninvasive detection of SDs could transform critical care for brain injury patients but has remained elusive. Current methods to detect SDs are based on invasive intracranial recordings with limited spatial coverage. In this study, we establish the feasibility of automated SD detection through noninvasive scalp electroencephalography (EEG) for patients with severe TBI.

METHODS

Building on our recent WAVEFRONT algorithm, we designed an automated SD detection method. This algorithm, with learnable parameters and improved velocity estimation, extracts and tracks propagating power depressions using low-density EEG. The dataset for testing our algorithm contains 700 total SDs in 12 severe TBI patients who underwent decompressive hemicraniectomy (DHC), labeled using ground-truth intracranial EEG recordings. We utilize simultaneously recorded, continuous, low-density (19 electrodes) scalp EEG signals, to quantify the detection accuracy of WAVEFRONT in terms of true positive rate (TPR), false positive rate (FPR), as well as the accuracy of estimating SD frequency.

RESULTS

WAVEFRONT achieves the best average validation accuracy using Delta band EEG: 74% TPR with less than 1.5% FPR. Further, preliminary evidence suggests WAVEFRONT can estimate how frequently SDs may occur.

CONCLUSIONS

We establish the feasibility, and quantify the performance, of noninvasive SD detection after severe TBI using an automated algorithm. The algorithm, WAVEFRONT, can also potentially be used for diagnosis, monitoring, and tailoring treatments for worsening brain injury. Extension of these results to patients with intact skulls requires further study.

Effects of anesthetic adjunctive agents on postoperative cognitive dysfunction in elderly patients undergoing noncardiac surgery: A Bayesian network meta-analysis

BACKGROUND

Elderly patients are prone to postoperative cognitive dysfunction (POCD). The comparison of the effects of anesthetic adjuvant drugs on POCD in elderly patients undergoing noncardiac surgery remains controversial.

METHODS

The final search took place on June 10, 2023. Randomized controlled trials including ketamine, ulinastatin, dexmedetomidine, parecoxib, and midazolam on the prevention and treatment of POCD in elderly undergoing noncardiac surgery were collected. A Bayesian network meta-analysis was performed to quantitatively combine the evidence.

RESULTS

A total of 35 randomized trials were finally included in this systematic review, and the overall risk of bias is Allocation concealment. These anesthetic adjuvant drugs did not show significant differences in preventing POCD on postoperative days 1 and 7 compared with each other, but ulinastatin may be more effective in preventing POCD than dexmedetomidine [odds ratio (OR) = 0.28, 95% confidence interval (CI) = (0.10, 0.71)] and parecoxib [OR = 0.3, 95% CI = (0.10, 0.82 on postoperative day 3. The efficiency ranking results also find that ulinastatin and ketamine might provide better effects regarding POCD prevention.

CONCLUSIONS

Ketamine and ulinastatin might have better effects in preventing POCD in elderly patients undergoing noncardiac surgery. Our meta-analysis provided evidence for the use of ulinastatin and ketamine in the prevention of POCD in elderly patients undergoing noncardiac surgery.

The Impact of Sedative Choice on Intracranial and Systemic Physiology in Moderate to Severe Traumatic Brain Injury: A Scoping Review

Although sedative use is near-ubiquitous in the acute management of moderate to severe traumatic brain injury (m-sTBI), the evidence base for these agents is undefined. This review summarizes the evidence for analgosedative agent use in the intensive care unit management of m-sTBI. Clinical studies of sedative and analgosedative agents currently utilized in adult m-sTBI management (propofol, ketamine, benzodiazepines, opioids, and alpha-2 agonists) were identified and assessed for relevance and methodological quality. The primary outcome was the effect of the analgosedative agent on intracranial pressure (ICP). Secondary outcomes included intracranial hemodynamic and metabolic parameters, systemic hemodynamic parameters, measures of therapeutic intensity, and clinical outcomes. Of 594 articles identified, 61 met methodological review criteria, and 40 were included in the qualitative summary; of these, 33 were prospective studies, 18 were randomized controlled trials, and 8 were blinded. There was consistent evidence for the efficacy of sedative agents in the management of m-sTBI and raised ICP, but the overall quality of the evidence was poor, consisting of small studies (median sample size, 23.5) of variable methodological quality. Propofol and midazolam achieve the goals of sedation without notable differences in efficacy or safety, although high-dose propofol may disrupt cerebral autoregulation. Dexmedetomidine and propofol/ dexmedetomidine combination may cause clinically significant hypotension. Dexmedetomidine was effective to achieve a target sedation score. De novo opioid boluses were associated with increased ICP and reduced cerebral perfusion pressure. Ketamine bolus and infusions were not associated with increased ICP and may reduce the incidence of cortical spreading depolarization events. In conclusion, there is a paucity of high-quality evidence to inform the optimal use of analgosedative agents in the management of m-sTBI, inferring significant scope for further research.

A Spatial-Temporal Graph Attention Network for Automated Detection and Width Estimation of Cortical Spreading Depression Using Scalp EEG

We present an end-to-end Spatial-Temporal Graph Attention Network (STGAT) for non-invasive detection and width estimation of Cortical Spreading Depressions (CSDs) on scalp electroencephalography (EEG). Our algorithm, that we refer to as CSD Spatial-temporal graph attention network or CSD-STGAT, is trained and tested on simulated CSDs with varying width and speed ranges. Using high-density EEG, CSD-STGAT achieves less than 10.96% normalized width estimation error for narrow CSDs, with an average normalized error of 6.35%±3.08% across all widths, enabling non-invasive and automated estimation of the width of CSDs for the first time. In addition, CSD-STGAT learns the temporal and spatial features of CSDs simultaneously, which improves the "spatio-temporal tracking accuracy" (i.e., the defined detection performance metric at each electrode) of the narrow CSDs by up to 14%, compared to the state-of-the-art CSD-SpArC algorithm, with only one-tenth of the network size. CSD-STGAT achieves the best spatio-temporal tracking accuracy of 86.27%±0.53% for wide CSDs using high-density EEG, which is comparable to the performance of CSD-SpArC with less than 0.38% performance reduction. We further stitch the detections across all electrodes and over time to evaluate the "temporal accuracy". Our algorithm achieves less than 0.7% false positive rate in the simulated dataset with inter-CSD intervals ranging from 5 to 60 minutes. The lightweight architecture of CSD-STGAT paves the way towards real-time detection and parameter estimation of these waves in the brain, with significant clinical impact.

Nonpharmacological modulation of cortical spreading depolarization

AIMS

Cortical spreading depolarization (CSD) is a wave of pathologic neuronal dysfunction that spreads through cerebral gray matter, causing neurologic disturbance in migraine and promoting lesion development in acute brain injury. Pharmacologic interventions have been found to be effective in migraine with aura, but their efficacy in acutely injured brains may be limited. This necessitates the assessment of possible adjunctive treatments, such as nonpharmacologic methods. This review aims to summarize currently available nonpharmacological techniques for modulating CSDs, present their mechanisms of action, and provide insight and future directions for CSD treatment.

MAIN METHODS

A systematic literature review was performed, generating 22 articles across 3 decades. Relevant data is broken down according to method of treatment.

KEY FINDINGS

Both pharmacologic and nonpharmacologic interventions can mitigate the pathological impact of CSDs via shared molecular mechanisms, including modulating K⁺/Ca²⁺/Na⁺/Cl^- ion channels and NMDA, GABA_A, serotonin, and CGRP ligand-based receptors and decreasing microglial activation. Preclinical evidence suggests that nonpharmacologic interventions, including neuromodulation, physical exercise, therapeutic hypothermia, and lifestyle changes can also target unique mechanisms, such as increasing adrenergic tone and myelination and modulating membrane fluidity, which may lend broader modulatory effects. Collectively, these mechanisms increase the electrical initiation threshold, increase CSD latency, slow CSD velocity, and decrease CSD amplitude and duration.

SIGNIFICANCE

Given the harmful consequences of CSDs, limitations of current pharmacological interventions to inhibit CSDs in acutely injured brains, and translational potentials of nonpharmacologic interventions to modulate CSDs, further assessment of nonpharmacologic modalities and their mechanisms to mitigate CSD-related neurologic dysfunction is warranted.

A retrospect and outlook on the neuroprotective effects of anesthetics in the era of endovascular therapy

Studies on the neuroprotective effects of anesthetics were carried out more than half a century ago. Subsequently, many cell and animal experiments attempted to verify the findings. However, in clinical trials, the neuroprotective effects of anesthetics were not observed. These contradictory results suggest a mismatch between basic research and clinical trials. The Stroke Therapy Academic Industry Roundtable X (STAIR) proposed that the emergence of endovascular thrombectomy (EVT) would provide a proper platform to verify the neuroprotective effects of anesthetics because the haemodynamics of patients undergoing EVT is very close to the ischaemia–reperfusion model in basic research. With the widespread use of EVT, it is necessary for us to re-examine the neuroprotective effects of anesthetics to guide the use of anesthetics during EVT because the choice of anesthesia is still based on team experience without definite guidelines. In this paper, we describe the research status of anesthesia in EVT and summarize the neuroprotective mechanisms of some anesthetics. Then, we focus on the contradictory results between clinical trials and basic research and discuss the causes. Finally, we provide an outlook on the neuroprotective effects of anesthetics in the era of endovascular therapy.

NS1619 Alleviate Brain-Derived Extracellular Vesicle-Induced Brain Injury by Regulating BKca Channel and Nrf2/HO-1/NF-ĸB Pathway

Brain induced extracellular vesicle (BDEV) elevates after traumatic brain injury (TBI) and contributes to secondary brain injury. However, the role of BDEV in TBI remains unclear. In this study, we determined the mechanisms of BDEV in brain injury and explored whether neuroprotective drug BKca channel opener NS1619 may attenuate BDEV-induced brain injury. We injected BDEV and lactadherin, respectively, to mimic the up and downregulation of BDEV after TBI and illustrated the role of BDEV in vivo. In vitro, the membrane potential and calcium concentration of HT-22, bEnd3, and BV-2 were measured by fluorescent staining. The effects of BDEV and NS1619 on HT-22 were evaluated by CCK-8, LDH release assay, Na⁺/k⁺-ATPase activity, JC-1 staining, DHE staining, and 4-HNE staining, respectively. The role of BDEV and NS1619 on the Nrf2/HO-1/p65 pathway was also evaluated in HT-22. Finally, we administrated TBI mice with NS1619 to clarify the role of NS1619 against BDEV in vivo. Our results suggested that BDEV aggravated and lactadherin mitigated TBI-induced EB leakage, brain edema, neuronal degeneration, apoptosis, ROS level, microgliosis, MMP-9 activity, and NF-κB activation. In vitro, BDEV-caused depolarized membrane potential and calcium overload were significantly attenuated by NS1619 in HT-22, bEnd3, and BV-2. BDEV markedly decreased cell viability, Na⁺/k⁺-ATPase activity, and caused mitochondrial dysregulation, oxidative stress, and NF-ĸB activation. NS1619 pretreatment alleviated above process and enhanced antioxidant system Nrf2/HO-1 in HT-22. Finally, NS1619 administration significantly inhibited neuroinflammation response and improved TBI outcome after TBI. NS1619 treatment also reduced 4-HNE content and NF-ĸB activation and enhanced Nrf2/HO-1 pathway. Our data showed that BDEV aggravated brain injury by perturbing cell membrane potential, calcium homeostasis, oxidative stress, and neuroinflammation. The BKca channel opener NS1619 attenuated BDEV-induced pathological process in vitro and in vivo by modulating the BKca channel and Nrf2/HO-1/NF-ĸB pathway.

Targeting NMDA Receptor Complex in Management of Epilepsy

N-methyl-D-aspartate receptors (NMDARs) are widely distributed in the central nervous system (CNS) and play critical roles in neuronal excitability in the CNS. Both clinical and preclinical studies have revealed that the abnormal expression or function of these receptors can underlie the pathophysiology of seizure disorders and epilepsy. Accordingly, NMDAR modulators have been shown to exert anticonvulsive effects in various preclinical models of seizures, as well as in patients with epilepsy. In this review, we provide an update on the pathologic role of NMDARs in epilepsy and an overview of the NMDAR antagonists that have been evaluated as anticonvulsive agents in clinical studies, as well as in preclinical seizure models.

The use of ketamine as a neuroprotective agent following cardiac arrest: A scoping review of current literature

AIMS

The objective of this article is to summarize the state of the literature surrounding the use of ketamine as a neuroprotective agent following cardiac arrest.

METHODS

Five electronic databases were used to search for studies related to the use of ketamine for neuroprotection following cardiac arrest. This search was performed once in May 2020, and an updated search was conducted in May 2021 and March 2022.

RESULTS

All searches combined retrieved 181 results; no clinical trials were identified. As such, the authors were limited to writing a scoping review of the literature rather than a systematic review.

CONCLUSIONS

The current state of the literature describes the mechanism of action of ketamine as a neuroprotective agent through its action as an NMDA antagonist. There is evidence of its efficacy as a neuroprotective agent in preclinical models of cardiac arrest. Current published clinical work supports the use of ketamine ameliorating neurologic outcomes in other conditions such as epilepsy, traumatic brain injury, and depression. The current state of the literature is reflective of the notion that the use of ketamine following cardiac arrest may result in improved neurologic outcomes. Future research directions should focus on the use of ketamine as a possible clinical intervention following cardiac arrest.

Spreading Depolarization as a Therapeutic Target in Severe Ischemic Stroke: Physiological and Pharmacological Strategies

BACKGROUND

Spreading depolarization (SD) occurs nearly ubiquitously in malignant hemispheric stroke (MHS) and is strongly implicated in edema progression and lesion expansion. Due to this high burden of SD after infarct, it is of great interest whether SD in MHS patients can be mitigated by physiologic or pharmacologic means and whether this intervention improves clinical outcomes. Here we describe the association between physiological variables and risk of SD in MHS patients who had undergone decompressive craniectomy and present an initial case of using ketamine to target SD in MHS.

METHODS

We recorded SD using subdural electrodes and time-linked with continuous physiological recordings in five subjects. We assessed physiologic variables in time bins preceding SD compared to those with no SD.

RESULTS

Using multivariable logistic regression, we found that increased ETCO2 (OR 0.772, 95% CI 0.655-0.910) and DBP (OR 0.958, 95% CI 0.941-0.991) were protective against SD, while elevated temperature (OR 2.048, 95% CI 1.442-2.909) and WBC (OR 1.113, 95% CI 1.081-1.922) were associated with increased risk of SD. In a subject with recurrent SD, ketamine at a dose of 2 mg/kg/h was found to completely inhibit SD.

CONCLUSION

Fluctuations in physiological variables can be associated with risk of SD after MHS. Ketamine was also found to completely inhibit SD in one subject. These data suggest that use of physiological optimization strategies and/or pharmacologic therapy could inhibit SD in MHS patients, and thereby limit edema and infarct progression. Clinical trials using individualized approaches to target this novel mechanism are warranted.

Ketamine and Its Emergence in the Field of Neurology

The quest for a safe and effective anesthetic medication in the mid-20th century led to the discovery of CI-581, which was later named ketamine. Ketamine was labeled a “dissociative anesthetic” due to the state of sensory deprivation that it induces in the subjects receiving it. Although it enjoyed widespread use at the beginning of the Vietnam war, its use rapidly waned due to its psychedelic effect and it became more popular as a recreational drug, and in the field of veterinary medicine. However, as we gained more knowledge about its multiple sites of action, it has reemerged as a useful anesthetic/analgesic agent. In the last decade, the field of neurology has witnessed the growing use of ketamine for the treatment of several neurological conditions including migraine, status epilepticus, stroke, and traumatic brain injury (TBI). Ketamine acts primarily as a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist. The binding of ketamine to NMDA receptors leads to decreased frequency and duration of Ca⁺² channel opening and thus inhibits glutaminergic transmission. This mechanism has proven to be neuroprotective in several neurological conditions. Ketamine does not increase intracranial pressure (ICP), and it maintains cerebral perfusion pressure (CPP) by increasing cerebral blood flow. Ketamine has also been shown to inhibit massive slow waves of neurological depolarizations called cortical spreading depolarizations (CSD), usually seen during acute neurological injury and are responsible for further neurological deterioration. Unlike other anesthetic agents, ketamine does not cause cardiac or respiratory suppression. All these favorable mechanisms and cerebral/hemodynamic actions have led to increased interest among clinicians and researchers regarding the novel uses of ketamine. This review will focus on the use of ketamine for various neurological indications.

Mapping spreading depolarisations after traumatic brain injury: a pilot clinical study protocol

INTRODUCTION

Cortical spreading depolarisation (CSD) is characterised by a near-complete loss of the ionic membrane potential of cortical neurons and glia propagating across the cerebral cortex, which generates a transient suppression of spontaneous neuronal activity. CSDs have become a recognised phenomenon that imparts ongoing secondary insults after brain injury. Studies delineating CSD generation and propagation in humans after traumatic brain injury (TBI) are lacking. Therefore, this study aims to determine the feasibility of using a multistrip electrode array to identify CSDs and characterise their propagation in space and time after TBI.

METHODS AND ANALYSIS

This pilot, prospective observational study will enrol patients with TBI requiring therapeutic craniotomy or craniectomy. Subdural electrodes will be placed for continuous electrocorticography monitoring for seizures and CSDs as a research procedure, with surrogate informed consent obtained preoperatively. The propagation of CSDs relative to structural brain pathology will be mapped using reconstructed CT and electrophysiological cross-correlations. The novel use of multiple subdural strip electrodes in conjunction with brain morphometric segmentation is hypothesised to provide sufficient spatial information to characterise CSD propagation across the cerebral cortex and identify cortical foci giving rise to CSDs.

ETHICS AND DISSEMINATION

Ethical approval for the study was obtained from the Hennepin Healthcare Research Institute's ethics committee, HSR 17-4400, 25 October 2017 to present. Study findings will be submitted for publication in peer-reviewed journals and presented at scientific conferences.

TRIAL REGISTRATION NUMBER

NCT03321370.

Questioning Glutamate Excitotoxicity in Acute Brain Damage: The Importance of Spreading Depolarization

BACKGROUND

Within 2 min of severe ischemia, spreading depolarization (SD) propagates like a wave through compromised gray matter of the higher brain. More SDs arise over hours in adjacent tissue, expanding the neuronal damage. This period represents a therapeutic window to inhibit SD and so reduce impending tissue injury. Yet most neuroscientists assume that the course of early brain injury can be explained by glutamate excitotoxicity, the concept that immediate glutamate release promotes early and downstream brain injury. There are many problems with glutamate release being the unseen culprit, the most practical being that the concept has yielded zero therapeutics over the past 30 years. But the basic science is also flawed, arising from dubious foundational observations beginning in the 1950s METHODS: Literature pertaining to excitotoxicity and to SD over the past 60 years is critiqued.

RESULTS

Excitotoxicity theory centers on the immediate and excessive release of glutamate with resulting neuronal hyperexcitation. This instigates poststroke cascades with subsequent secondary neuronal injury. By contrast, SD theory argues that although SD evokes some brief glutamate release, acute neuronal damage and the subsequent cascade of injury to neurons are elicited by the metabolic stress of SD, not by excessive glutamate release. The challenge we present here is to find new clinical targets based on more informed basic science. This is motivated by the continuing failure by neuroscientists and by industry to develop drugs that can reduce brain injury following ischemic stroke, traumatic brain injury, or sudden cardiac arrest. One important step is to recognize that SD plays a central role in promoting early neuronal damage. We argue that uncovering the molecular biology of SD initiation and propagation is essential because ischemic neurons are usually not acutely injured unless SD propagates through them. The role of glutamate excitotoxicity theory and how it has shaped SD research is then addressed, followed by a critique of its fading relevance to the study of brain injury.

CONCLUSIONS

Spreading depolarizations better account for the acute neuronal injury arising from brain ischemia than does the early and excessive release of glutamate.

Ketamine in Acute Brain Injury: Current Opinion Following Cerebral Circulation and Electrical Activity

The use of ketamine in patients with TBI has often been argued due to its possible deleterious effects on cerebral circulation and perfusion. Early studies suggested that ketamine could increase intracranial pressure, decreasing cerebral perfusion pressure and thereby reducing oxygen supply to the damaged cerebral cortex. Some recent studies have refuted these conclusions relating to the role of ketamine, especially in patients with TBI, showing that ketamine should be the first-choice drug in this type of patient at induction. Our narrative review collects evidence on ketamine’s use in patients with TBI. Databases were examined for studies in which ketamine had been used in acute traumatic brain injury (TBI). The outcomes considered in this narrative review were: mortality of patients with TBI; impact on intracranial pressure and cerebral perfusion pressure; blood pressure and heart rate values; depolarization rate; and preserved neurological functions. 11 recent studies passed inclusion and exclusion criteria and were included in this review. Despite all the benefits reported in the literature, the use of ketamine in patients with brain injury still appears to be limited. A slight increase in intracranial pressure was found in only two studies, while two smaller studies showed a reduction in intracranial pressure after ketamine administration. There was no evidence of harm from the ketamine’s use in patients with TBI.

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.

Cortical Spreading Depolarizations in Aneurysmal Subarachnoid Hemorrhage: An Overview of Current Knowledge and Future Perspectives

Despite significant advances in the management of aneurysmal subarachnoid hemorrhage (SAH), morbidity and mortality remain devastating particularly for high-grade SAH. Poor functional outcome usually results from delayed cerebral ischemia (DCI). The pathogenesis of DCI during aneurysmal SAH has historically been attributed to cerebral vasospasm, but spreading depolarizations (SDs) are now considered to play a central role in DCI. During SAH, SDs may produce an inverse hemodynamic response leading to spreading ischemia. Several animal models have contributed to a better understanding of the pathogenesis of SDs during aneurysmal SAH and provided new therapeutic approaches including N-methyl-D-aspartate receptor antagonists and phosphodiesterase inhibitors. Herein we review the current knowledge in the field of SDs' pathogenesis and we detail the key experimental and clinical studies that have opened interesting new therapeutic approaches to prevent DCI in aneurysmal SAH.

The management of delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is a rare event affecting relatively young patients therefore leading to a high social impact. The management of SAH follows a biphasic course with early brain injuries in the first 72 hours followed by a phase at risk of secondary deterioration due to delayed cerebral ischemia (DCI) in 20 to 30% patients. Cerebral infarction from DCI is the most preventable cause of mortality and morbidity after SAH. DCI prevention, early detection and treatment is therefore advocated. Formerly limited to the occurrence of vasospasm, DCI is now associated with multiple pathophysiological processes involving for instance the macrocirculation, the microcirculation, neurovascular units, and inflammation. Therefore, the therapeutic targets and management strategies are also evolving and are not only focused on proximal vasospasm. In this review, we describe the current knowledge of DCI pathophysiology. We then discuss the diagnosis strategies that may guide physicians at the bedside with a multimodal approach in the unconscious patient. We will present the prevention strategies that have proven efficient as well as future targets and present the therapeutic approach that is currently being developed when a DCI occurs.

Ketamine for critically ill patients with severe acute brain injury: Protocol for a systematic review with meta-analysis and Trial Sequential Analysis of randomised clinical trials

INTRODUCTION

Intensive care for patients with severe acute brain injury aims both to treat the immediate consequences of the injury and to prevent and treat secondary brain injury to ensure a good functional outcome. Sedation may be used to facilitate mechanical ventilation, for treating agitation, and for controlling intracranial pressure. Ketamine is an N-methyl-D-aspartate receptor antagonist with sedative, analgesic, and potentially neuroprotective properties. We describe a protocol for a systematic review of randomised clinical trials assessing the beneficial and harmful effects of ketamine for patients with severe acute brain injury.

METHODS AND ANALYSIS

We will systematically search international databases for randomised clinical trials, including CENTRAL, MEDLINE, Embase, and trial registries. Two authors will independently review and select trials for inclusion, and extract data. We will compare ketamine by any regimen versus placebo, no intervention, or other sedatives or analgesics for patients with severe acute brain injury. The primary outcomes will be functional outcome at maximal follow up, quality of life, and serious adverse events. We will also assess secondary and exploratory outcomes. The extracted data will be analysed using Review Manager and Trials Sequential Analysis. Evidence certainty will be graded using GRADE.

ETHICS AND DISSEMINATION

The results of the systematic review will be disseminated through peer-reviewed publication. With the review, we hope to inform future randomised clinical trials and improve clinical practice.

PROSPERO NO

CRD42021210447.

Spreading Depolarization After Chronic Subdural Hematoma Evacuation: Associated Clinical Risk Factors and Influence on Clinical Outcome

BACKGROUND

Chronic subdural hematoma (cSDH) is a common neurosurgical condition responsible for excess morbidity, particularly in the geriatric population. Recovery after evacuation is complicated by fluctuating neurological deficits in a high proportion of patients. We previously demonstrated that spreading depolarizations (SDs) may be responsible for some of these events. In this study, we aim to determine candidate risk factors for probable SD and assess the influence of probable SD on outcome.

METHODS

We used two cohorts who underwent surgery for cSDH. The first cohort (n = 40) had electrocorticographic monitoring to detect SD. In the second cohort (n = 345), we retrospectively identified subjects with suspected SD based on the presence of transient neurological symptoms not explained by structural etiology or ictal activity on electroencephalography. We extracted standard demographic and outcome variables for comparisons and modeling.

RESULTS

Of 345 subjects, 80 (23%) were identified in the retrospective cohort as having probable SD. Potential risk factors included history of hypertension, worse clinical presentation on the Glasgow Coma Scale, and lower Hounsfield unit density and volume of the preoperative subdural hematoma. Probable SD was associated with multiple worse-outcome measures, including length of stay and clinical outcomes, but not increased mortality. On a multivariable analysis, probable SD was independently associated with worse outcome, determined by the Glasgow Outcome Scale score at the first clinic follow-up (odds ratio 1.793, 95% confidence interval 1.022-3.146) and longer hospital length of stay (odds ratio 7.952, 95% confidence interval 4.062-15.563).

CONCLUSIONS

Unexplained neurological deficits after surgery for cSDH occur in nearly a quarter of patients and may be explained by SD. We identified several potential candidate risk factors. Patients with probable SD have worse outcomes, independent of other baseline risk factors. Further data with gold standard monitoring are needed to evaluate for possible predictors of SD to target therapies to a high-risk population.

Development and Evaluation of a Method for Automated Detection of Spreading Depolarizations in the Injured Human Brain

BACKGROUND

Spreading depolarizations (SDs) occur in some 60% of patients receiving intensive care following severe traumatic brain injury and often occur at a higher incidence following serious subarachnoid hemorrhage and malignant hemisphere stroke (MHS); they are independently associated with worse clinical outcome. Detection of SDs to guide clinical management, as is now being advocated, currently requires continuous and skilled monitoring of the electrocorticogram (ECoG), frequently extending over many days.

METHODS

We developed and evaluated in two clinical intensive care units (ICU) a software routine capable of detecting SDs both in real time at the bedside and retrospectively and also capable of displaying patterns of their occurrence with time. We tested this prototype software in 91 data files, each of approximately 24 h, from 18 patients, and the results were compared with those of manual assessment ("ground truth") by an experienced assessor blind to the software outputs.

RESULTS

The software successfully detected SDs in real time at the bedside, including in patients with clusters of SDs. Counts of SDs by software (dependent variable) were compared with ground truth by the investigator (independent) using linear regression. The slope of the regression was 0.7855 (95% confidence interval 0.7149-0.8561); a slope value of 1.0 lies outside the 95% confidence interval of the slope, representing significant undersensitivity of 79%. R2 was 0.8415.

CONCLUSIONS

Despite significant undersensitivity, there was no additional loss of sensitivity at high SD counts, thus ensuring that dense clusters of depolarizations of particular pathogenic potential can be detected by software and depicted to clinicians in real time and also be archived.

Frequency selective neuronal modulation triggers spreading depolarizations in the rat endothelin-1 model of stroke

Ischemia is one of the most common causes of acquired brain injury. Central to its noxious sequelae are spreading depolarizations (SDs), waves of persistent depolarizations which start at the location of the flow obstruction and expand outwards leading to excitotoxic damage. The majority of acute stage of stroke studies to date have focused on the phenomenology of SDs and their association with brain damage. In the current work, we investigated the role of peri-injection zone pyramidal neurons in triggering SDs by optogenetic stimulation in an endothelin-1 rat model of focal ischemia. Our concurrent two photon fluorescence microscopy data and local field potential recordings indicated that a ≥ 60% drop in cortical arteriolar red blood cell velocity was associated with SDs at the ET-1 injection site. SDs were also observed in the peri-injection zone, which subsequently exhibited elevated neuronal activity in the low-frequency bands. Critically, SDs were triggered by low- but not high-frequency optogenetic stimulation of peri-injection zone pyramidal neurons. Our findings depict a complex etiology of SDs post focal ischemia and reveal that effects of neuronal modulation exhibit spectral and spatial selectivity.

Memantine Improves Recovery After Spreading Depolarization in Brain Slices and can be Considered for Future Clinical Trials

BACKGROUND

Spreading depolarization (SD) has been identified as a key mediator of secondary lesion progression after acute brain injuries, and clinical studies are beginning to pharmacologically target SDs. Although initial work has focused on the N-Methyl-D-aspartate receptor antagonist ketamine, there is also interest in alternatives that may be better tolerated. We recently showed that ketamine can inhibit mechanisms linked to deleterious consequences of SD in brain slices. The present study tested the hypothesis that memantine improves recovery of brain slices after SD and explored the effects of memantine in a clinical case targeting SD.

METHODS

For mechanistic studies, electrophysiological and optical recordings were made from hippocampal area CA1 in acutely prepared brain slices from mice. SDs were initiated by localized microinjection of K+ in conditions of either normal or reduced metabolic substrate availability. Memantine effects were assessed from intrinsic optical signals and extracellular potential recordings. For the clinical report, a subdural strip electrode was used for continuous electrocorticographic recording after the surgical evacuation of a chronic subdural hematoma.

RESULTS

In brain slice studies, memantine (10-300 µM) did not prevent the initiation of SD, but impaired SD propagation rate and recovery from SD. Memantine reduced direct current (DC) shift duration and improved recovery of synaptic potentials after SD. In brain slices with reduced metabolic substrate availability, memantine reduced the evidence of structural disruption after the passage of SD. In our clinical case, memantine did not noticeably immediately suppress SD; however, it was associated with a significant reduction of SD duration and a reduction in the electrocorticographic (ECoG) suppression that occurs after SD. SD was completely suppressed, with improvement in neurological examination with the addition of a brief course of ketamine.

CONCLUSIONS

These data extend recent work showing that N-Methyl-D-aspartate receptor antagonists can improve recovery from SD. These results suggest that memantine could be considered for future clinical trials targeting SD, and in some cases as an adjunct or alternative to ketamine.

Local Application of Magnesium Sulfate Solution Suppressed Cortical Spreading Ischemia and Reduced Brain Damage in a Rat Subarachnoid Hemorrhage-Mimicking Model

OBJECTIVE

Cortical spreading depolarization (CSD), cortical spreading ischemia (CSI), and early brain injury are involved in the occurrence of delayed brain ischemia after subarachnoid hemorrhage (SAH). We tested whether local application of magnesium (Mg) sulfate solution suppressed CSD and CSI, and decreased brain damage in a rat SAH-mimicking model.

METHODS

Nitric oxide synthase inhibitor L-NG-nitroarginine methyl ester (L-NAME) and high concentration potassium solution were topically applied to simulate the environment after SAH. We irrigated the parietal cortex with artificial cerebrospinal fluid (ACSF), containing L-NAME (1 mM), K⁺ (35 mM), and Mg²⁺ (5 mM). Forty-five rats were divided into 3 groups: sham surgery (sham group), L-NAME + [K⁺]_ACSF (control group), and L-NAME + [K⁺]_ACSF + [Mg²⁺] (Mg group). CSD was induced by topical application with 1 M KCl solution in 3 groups. The effects of Mg administration on CSD and cerebral blood flow were evaluated. Histological brain tissue damage, body weight, and neurological score were assessed at 2 days after insult.

RESULTS

Mg solution significantly shortened the total depolarization time, and reduced CSI, histological brain damage, and brain edema compared with those of the control group (P < 0.05). Body weight loss was significantly suppressed in the Mg group (P < 0.05), but neurological score did not improve.

CONCLUSIONS

Local application of Mg suppressed CSI and reduced brain damage in a rat SAH-mimicking model. Mg irrigation therapy may be beneficial to suppress brain damage due to CSI after SAH.

Cognitive Dysfunction After Analgesia and Sedation: Out of the Operating Room and Into the Pediatric Intensive Care Unit

In the midst of concerns for potential neurodevelopmental effects after surgical anesthesia, there is a growing awareness that children who require sedation during critical illness are susceptible to neurologic dysfunctions collectively termed pediatric post-intensive care syndrome, or PICS-p. In contrast to healthy children undergoing elective surgery, critically ill children are subject to inordinate neurologic stress or injury and need to be considered separately. Despite recognition of PICS-p, inconsistency in techniques and timing of post-discharge assessments continues to be a significant barrier to understanding the specific role of sedation in later cognitive dysfunction. Nonetheless, available pediatric studies that account for analgesia and sedation consistently identify sedative and opioid analgesic exposures as risk factors for both in-hospital delirium and post-discharge neurologic sequelae. Clinical observations are supported by animal models showing neuroinflammation, increased neuronal death, dysmyelination, and altered synaptic plasticity and neurotransmission. Additionally, intensive care sedation also contributes to sleep disruption, an important and overlooked variable during acute illness and post-discharge recovery. Because analgesia and sedation are potentially modifiable, understanding the underlying mechanisms could transform sedation strategies to improve outcomes. To move the needle on this, prospective clinical studies would benefit from cohesion with regard to datasets and core outcome assessments, including sleep quality. Analyses should also account for the wide range of diagnoses, heterogeneity of this population, and the dynamic nature of neurodevelopment in age cohorts. Much of the related preclinical evidence has been studied in comparatively brief anesthetic exposures in healthy animals during infancy and is not generalizable to critically ill children. Thus, complementary animal models that more accurately "reverse translate" critical illness paradigms and the effect of analgesia and sedation on neuropathology and functional outcomes are needed. This review explores the interactive role of sedatives and the neurologic vulnerability of critically ill children as it pertains to survivorship and functional outcomes, which is the next frontier in pediatric intensive care.

Ketamine as an Anesthetic for Patients with Acute Brain Injury: A Systematic Review

For years, the use of ketamine as an anesthetic to patients suffering from acute brain injury has been debated because of its possible deleterious effects on the cerebral circulation and thus on the cerebral perfusion. Early studies suggested that ketamine could increase the intracranial pressure thus lowering the cerebral perfusion and hence reduce the oxygen supply to the injured brain. However, more recent studies are less conclusive and might even indicate that patients with acute brain injury could benefit from ketamine sedation. This systematic review summarizes the evidence regarding the use of ketamine in patients suffering from traumatic brain injury. Databases were searched for studies using ketamine in acute brain injury. Outcomes of interest were mortality, intracranial pressure, cerebral perfusion pressure, blood pressure, heart rate, spreading depolarizations, and neurological function. In total 11 studies were included. The overall level of evidence concerning the use of ketamine in brain injury is low. Only two studies found a small increase in intracranial pressure, while two small studies found decreased levels of intracranial pressure following ketamine administration. We found no evidence of harm during ketamine use in patients suffering from acute brain injury.

Pathophysiology of Delayed Cerebral Ischemia After Subarachnoid Hemorrhage: A Review

Delayed cerebral ischemia is a major predictor of poor outcomes in patients who suffer subarachnoid hemorrhage. Treatment options are limited and often ineffective despite many years of investigation and clinical trials. Modern advances in basic science have produced a much more complex, multifactorial framework in which delayed cerebral ischemia is better understood and novel treatments can be developed. Leveraging this knowledge to improve outcomes, however, depends on a holistic understanding of the disease process. We conducted a review of the literature to analyze the current state of investigation into delayed cerebral ischemia with emphasis on the major themes that have emerged over the past decades. Specifically, we discuss microcirculatory dysfunction, glymphatic impairment, inflammation, and neuroelectric disruption as pathological factors in addition to the canonical focus on cerebral vasospasm. This review intends to give clinicians and researchers a summary of the foundations of delayed cerebral ischemia pathophysiology while also underscoring the interactions and interdependencies between pathological factors. Through this overview, we also highlight the advances in translational studies and potential future therapeutic opportunities.

A One-Day Prospective National Observational Study on Sedation-Analgesia of Patients with Brain Injury in French Intensive Care Units: The SEDA-BIP-ICU (Sedation-Analgesia in Brain Injury Patient in ICU) Study

BACKGROUND

Sedation/analgesia is a daily challenge faced by intensivists managing patients with brain injury (BI) in intensive care units (ICUs). The optimization of sedation in patients with BI presents particular challenges. A choice must be made between the potential benefit of a rapid clinical evaluation and the potential exacerbation of intracranial hypertension in patients with impaired cerebral compliance. In the ICU, a pragmatic approach to the use of sedation/analgesia, including the optimal titration, management of multiple drugs, and use of any type of brain monitor, is needed. Our research question was as follows: the aim of the study is to identify what is the current daily practice regarding sedation/analgesia in the management of patients with BI in the ICU in France?

METHODS

This study was composed of two parts. The first part was a descriptive survey of sedation practices and characteristics in 30 French ICUs and 27 academic hospitals specializing in care for patients with BI. This first step validates ICU participation in data collection regarding sedation-analgesia practices. The second part was a 1-day prospective cross-sectional snapshot of all characteristics and prescriptions of patients with BI.

RESULTS

On the study day, among the 246 patients with BI, 106 (43%) had a brain monitoring device and 74 patients (30%) were sedated. Thirty-nine of the sedated patients (53%) suffered from intracranial hypertension, 14 patients (19%) suffered from agitation and delirium, and 7 patients (9%) were sedated because of respiratory failure. Fourteen patients (19%) no longer had a formal indication for sedation. In 60% of the sedated patients, the sedatives were titrated by nurses based on sedation scales. The Richmond Agitation Sedation Scale was used in 80% of the patients, and the Behavioral Pain Scale was used in 92%. The common sedatives and opioids used were midazolam (58.1%), propofol (40.5%), and sufentanil (67.5%). The cerebral monitoring devices available in the participating ICUs were transcranial Doppler ultrasound (100%), intracranial and intraventricular pressure monitoring (93.3%), and brain tissue oxygenation (60%). Cerebral monitoring by one or more monitoring devices was performed in 62% of the sedated patients. This proportion increased to 74% in the subgroup of patients with intracranial hypertension, with multimodal cerebral monitoring in 43.6%. The doses of midazolam and sufentanil were lower in sedated patients managed based on a sedation/analgesia scale.

CONCLUSIONS

Midazolam and sufentanil are frequently used, often in combination, in French ICUs instead of alternative drugs. In our study, cerebral monitoring was performed in more than 60% of the sedated patients, although that proportion is still insufficient. Future efforts should stress the use of multiple monitoring modes and adherence to the indications for sedation to improve care of patients with BI. Our study suggests that the use of sedation and analgesia scales by nurses involved in the management of patients with BI could decrease the dosages of midazolam and sufentanil administered. Updated guidelines are needed for the management of sedation/analgesia in patients with BI.