EEG Characteristics of Successful Burst Suppression for Refractory Status Epilepticus

Utility and rationale for continuous EEG monitoring: a primer for the general intensivist

This review offers a comprehensive guide for general intensivists on the utility of continuous EEG (cEEG) monitoring for critically ill patients. Beyond the primary role of EEG in detecting seizures, this review explores its utility in neuroprognostication, monitoring neurological deterioration, assessing treatment responses, and aiding rehabilitation in patients with encephalopathy, coma, or other consciousness disorders. Most seizures and status epilepticus (SE) events in the intensive care unit (ICU) setting are nonconvulsive or subtle, making cEEG essential for identifying these otherwise silent events. Imaging and invasive approaches can add to the diagnosis of seizures for specific populations, given that scalp electrodes may fail to identify seizures that may be detected by depth electrodes or electroradiologic findings. When cEEG identifies SE, the risk of secondary neuronal injury related to the time-intensity "burden" often prompts treatment with anti-seizure medications. Similarly, treatment may be administered for seizure-spectrum activity, such as periodic discharges or lateralized rhythmic delta slowing on the ictal-interictal continuum (IIC), even when frank seizures are not evident on the scalp. In this setting, cEEG is utilized empirically to monitor treatment response. Separately, cEEG has other versatile uses for neurotelemetry, including identifying the level of sedation or consciousness. Specific conditions such as sepsis, traumatic brain injury, subarachnoid hemorrhage, and cardiac arrest may each be associated with a unique application of cEEG; for example, predicting impending events of delayed cerebral ischemia, a feared complication in the first two weeks after subarachnoid hemorrhage. After brief training, non-neurophysiologists can learn to interpret quantitative EEG trends that summarize elements of EEG activity, enhancing clinical responsiveness in collaboration with clinical neurophysiologists. Intensivists and other healthcare professionals also play crucial roles in facilitating timely cEEG setup, preventing electrode-related skin injuries, and maintaining patient mobility during monitoring.

Impact of an Interactive, Animation-Based Electroencephalography Curriculum on Learner Confidence and Knowledge

BACKGROUND

There is a national need for innovative electroencephalography (EEG) education with efficacy evaluated by rigorous statistical analysis. We created a dynamic, online resource that includes a series of animated videos at a single academic medical center.

METHODS

For the animations and interactive module, we used VideoScribe and Articulate, respectively. The module comprised three chapters: (1) Origin & Technical Aspects of EEG, (2) Normal Adult EEG in Wakefulness & Sleep, and (3) Abnormal EEG, with appendices on artifacts, variants, activation procedures, seizure/epilepsy classification, and neonatal/pediatric EEG. The curriculum and knowledge assessments were reviewed independently by two fellowship-trained physicians before distribution. Linear mixed-effects models with bootstrapping were used to compare paired pre- and post-tests as well as Likert scale questionnaires.

RESULTS

Forty-nine learners participated in the pretest survey; 38 matched participants completed post-tests (78%). Learners across fields perceived benefit (100% would recommend to colleagues), indicated improved self-efficacy (P < 0.0001), and performed better on post-test knowledge assessments (54.1 vs 88.2%, P < 0.0001). In the neurology providers subgroup (n = 20), pretest scores correlated with years in training (Spearman r = 0.52, P = 0.039), neurology rotations (r = 0.70, P = 0.003), epilepsy/EEG rotations (r = 0.6, P = 0.014), and EEG teaching hours (r = 0.62, P = 0.01); content knowledge and self-efficacy improvement for neurology providers remained significant in a multivariate model adjusting for these covariates.

CONCLUSIONS

This animation-based, interactive EEG module proved effective in elevating learner confidence and knowledge across several medical specialties and training levels. Further study across institutions and subspecialties is needed to substantiate broad applicability, but our data appear promising for early EEG learners.

Status epilepticus in the ICU

Status epilepticus (SE) is a common medical emergency associated with significant morbidity and mortality. Management that follows published guidelines is best suited to improve outcomes, with the most severe cases frequently being managed in the intensive care unit (ICU). Diagnosis of convulsive SE can be made without electroencephalography (EEG), but EEG is required to reliably diagnose nonconvulsive SE. Rapidly narrowing down underlying causes for SE is crucial, as this may guide additional management steps. Causes may range from underlying epilepsy to acute brain injuries such as trauma, cardiac arrest, stroke, and infections. Initial management consists of rapid administration of benzodiazepines and one of the following non-sedating intravenous antiseizure medications (ASM): (fos-)phenytoin, levetiracetam, or valproate; other ASM are increasingly used, such as lacosamide or brivaracetam. SE that continues despite these medications is called refractory, and most commonly treated with continuous infusions of midazolam or propofol. Alternatives include further non-sedating ASM and non-pharmacologic approaches. SE that reemerges after weaning or continues despite management with propofol or midazolam is labeled super-refractory SE. At this step, management may include non-sedating or sedating compounds including ketamine and barbiturates. Continuous video EEG is necessary for the management of refractory and super-refractory SE, as these are almost always nonconvulsive. If possible, management of the underlying cause of seizures is crucial particularly for patients with autoimmune encephalitis. Short-term mortality ranges from 10 to 15% after SE and is primarily related to increasing age, underlying etiology, and medical comorbidities. Refractoriness of treatment is clearly related to outcome with mortality rising from 10% in responsive cases, to 25% in refractory, and nearly 40% in super-refractory SE.

ACVIM Consensus Statement on the management of status epilepticus and cluster seizures in dogs and cats

BACKGROUND

Seizure emergencies (ie, status epilepticus [SE] and cluster seizures [CS]), are common challenging disorders with complex pathophysiology, rapidly progressive drug-resistant and self-sustaining character, and high morbidity and mortality. Current treatment approaches are characterized by considerable variations, but official guidelines are lacking.

OBJECTIVES

To establish evidence-based guidelines and an agreement among board-certified specialists for the appropriate management of SE and CS in dogs and cats.

ANIMALS

None.

MATERIALS AND METHODS

A panel of 5 specialists was formed to assess and summarize evidence in the peer-reviewed literature with the aim to establish consensus clinical recommendations. Evidence from veterinary pharmacokinetic studies, basic research, and human medicine also was used to support the panel's recommendations, especially for the interventions where veterinary clinical evidence was lacking.

RESULTS

The majority of the evidence was on the first-line management (ie, benzodiazepines and their various administration routes) in both species. Overall, there was less evidence available on the management of emergency seizure disorders in cats in contrast to dogs. Most recommendations made by the panel were supported by a combination of a moderate level of veterinary clinical evidence and pharmacokinetic data as well as studies in humans and basic research studies.

CONCLUSIONS AND CLINICAL RELEVANCE

Successful management of seizure emergencies should include an early, rapid, and stage-based treatment approach consisting of interventions with moderate to preferably high ACVIM recommendations; management of complications and underlying causes related to seizure emergencies should accompany antiseizure medications.

Electroencephalography as a Biomarker of Prognosis in Acute Brain Injury

Electroencephalography (EEG) is a noninvasive tool that allows the monitoring of cerebral brain function in critically ill patients, aiding with diagnosis, management, and prognostication. Specific EEG features have shown utility in the prediction of outcomes in critically ill patients with status epilepticus, acute brain injury (ischemic stroke, intracranial hemorrhage, subarachnoid hemorrhage, and traumatic brain injury), anoxic brain injury, and toxic-metabolic encephalopathy. Studies have also found an association between particular EEG patterns and long-term functional and cognitive outcomes as well as prediction of recovery of consciousness following acute brain injury. This review summarizes these findings and demonstrates the value of utilizing EEG findings in the determination of prognosis.

Diversity of electroencephalographic patterns during propofol-induced burst suppression

Burst suppression is a brain state consisting of high-amplitude electrical activity alternating with periods of quieter suppression that can be brought about by disease or by certain anesthetics. Although burst suppression has been studied for decades, few studies have investigated the diverse manifestations of this state within and between human subjects. As part of a clinical trial examining the antidepressant effects of propofol, we gathered burst suppression electroencephalographic (EEG) data from 114 propofol infusions across 21 human subjects with treatment-resistant depression. This data was examined with the objective of describing and quantifying electrical signal diversity. We observed three types of EEG burst activity: canonical broadband bursts (as frequently described in the literature), spindles (narrow-band oscillations reminiscent of sleep spindles), and a new feature that we call low-frequency bursts (LFBs), which are brief deflections of mainly sub-3-Hz power. These three features were distinct in both the time and frequency domains and their occurrence differed significantly across subjects, with some subjects showing many LFBs or spindles and others showing very few. Spectral-power makeup of each feature was also significantly different across subjects. In a subset of nine participants with high-density EEG recordings, we noted that each feature had a unique spatial pattern of amplitude and polarity when measured across the scalp. Finally, we observed that the Bispectral Index Monitor, a commonly used clinical EEG monitor, does not account for the diversity of EEG features when processing the burst suppression state. Overall, this study describes and quantifies variation in the burst suppression EEG state across subjects and repeated infusions of propofol. These findings have implications for the understanding of brain activity under anesthesia and for individualized dosing of anesthetic drugs.

Quantitative assessment of burst suppression as a predictor of seizure recurrence in refractory status epilepticus

OBJECTIVE

To determine whether quantitative EEG analysis of burst suppression can predict seizure recurrence in patients with refractory status epilepticus (RSE) being treated with anesthetic doses of continuous IV antiseizure medications (cIVASM).

METHODS

Quantitative assessment of burst suppression (including epileptiform discharges [EDs] and evolution) in 31 occasions (from 27 patients), and correlation with seizure recurrence up to 48 hours post sedative wean.

RESULTS

Occasions resulting in seizure recurrence (vs. no seizure recurrence) had lower burst (8.4 vs. 10.6 µV) and interburst interval (IBI) (4.2 vs. 4.8 µV) average amplitude, duration (bursts 2.8 vs. 3.6 s: IBIs 3.6 vs. 4.4 s); and burst total power (0.4 vs. 0.7 µV2). Bursts (0.86 vs. 0.60) and IBIs (0.28 vs. 0.07) with EDs, higher number of EDs within bursts (mean 2.1 vs. 1.4) and IBIs (0.6 vs. 0.2), and positive evolution measures all predicted seizure recurrence, although EDs had the greatest adjusted odds ratio on multivariate analysis.

CONCLUSIONS

For patients in burst suppression, successful wean of cIVASM was not determined by classical burst suppression measures, but instead how "epileptiform" bursts and IBIs were, as determined by EDs in both bursts and IBIs and surrogates for evolution within bursts.

SIGNIFICANCE

If confirmed, these objective measures could be used during clinical care to help determine when to wean cIVASM in patients with RSE.

Severity scores for status epilepticus in the ICU: systemic illness also matters

BACKGROUND

Current prognostic scores for status epilepticus (SE) may not be adequate for patients in ICU who usually have more severe systemic conditions or more refractory episodes of SE. We aimed to compare the prognostic performance of two SE scores, Status Epilepticus Severity Score (STESS) and Epidemiology-Based Mortality Score in Status Epilepticus (EMSE) score, with four systemic severity scores, Acute Physiology and Chronic Health Evaluation 2 (APACHE-2), Simplified Acute Physiology Score 2 (SAPS-2), Sequential Organ Failure Assessment (SOFA) score, and Inflammation, Nutrition, Consciousness, Neurologic function and Systemic condition (INCNS) score in critically ill patients with SE.

METHODS

This retrospective observational study of a prospectively identified SE cohort was conducted in the ICU at a tertiary-care center. The area under the receiver operating characteristic curve (AUC), sensitivity, specificity, positive predictive value, negative predictive value, accuracy, and associations with outcomes of STESS, EMSE, INCNS, APACHE-2, SAPS-2, and SOFA score for the prediction of in-hospital mortality and no return to baseline condition were assessed.

RESULTS

Between January 2015 and December 2020, 166 patients with SE in ICU were included in the study. In predicting in-hospital death, APACHE-2 (0.72), SAPS-2 (0.73), and SOFA score (0.71) had higher AUCs than STESS (0.58) and EMSE (0.69). In predicting no return to baseline condition, the AUC of APACHE-2 (0.75) was the highest, and the AUC of INCNS (0.55) was the lowest. When the specificity approached 90%, the sensitivity values of these scores were not quite acceptable (< 40%). Neither SE scores nor systemic severity scores had desirable prognostic power. In the multivariate logistic regression analyses, the best combinations of scores always included at least one or more systemic severity scores.

CONCLUSIONS

STESS and EMSE were insufficient in outcome prediction for SE patients in ICU, and EMSE was marginally better than STESS. Systemic illness matters in ICU patients with SE, and SE scores should be modified to achieve better accuracy in this severely ill population. This study mostly refers to severely ill patients in the ICU.

Prognostic scores in status epilepticus: A systematic review and meta-analysis

The performance of prognostic scores of status epilepticus (SE) has been reported in very heterogeneous cohorts. We aimed to provide a summary of the available evidence on their respective performance. PubMed and EMBASE were searched for relevant articles. Studies were reviewed for eligibility for meta-analysis of the area under the receiver-operating characteristic curve (AUC) and for meta-analysis of sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) in predicting in-hospital mortality with scores in which at least two external evaluations had been published. This study was registered with PROSPERO (international prospective register of systematic reviews) (CRD42022325766). Study quality was assessed using Prediction model Risk Of Bias ASsessment Tool (PROBAST). In the meta-analysis of AUC, 21 studies were pooled for STESS (Status Epilepticus Severity Score), five for EMSE-EAC (Epidemiology-based Mortality Score in Status Epilepticus - Etiology, Age, level of Consciousness), five for EMSE-EACE (EMSE - Etiology, Age, level of Consciousness, EEG), and two for ENDIT (Encephalitis, nonconvulsive status epilepticus, Diazepam resistance, Imaging abnormalities, Tracheal intubation). The pooled AUC of STESS, EMSE-EAC, EMSE-EACE, and ENDIT was 0.74 (95% CI: 0.71-0.78), 0.68 (95% CI 0.63-0.72), 0.77 (95% CI: 0.72-0.81), and 0.78 (95% CI: 0.70-0.87), respectively. The pooled sensitivity of STESS-3, STESS-4, EMSE-EACE-64, and ENDIT-4 was 0.83 (95% CI: 0.80-0.86), 0.60 (95% CI: 0.55-0.65), 0.76 (95% CI: 0.67-0.83), and 0.70 (95% CI: 0.55-0.82), respectively. Their pooled specificity was 0.50 (95% CI: 0.48-0.52), 0.74 (95% CI: 0.72-0.76), 0.63 (95% CI: 0.59-0.67), and 0.65 (95% CI: 0.61-0.70), respectively. Their pooled PPV was 0.27 (95% CI: 0.24-0.30), 0.35 (95% CI: 0.29-0.41), 0.33 (95% CI: 0.24-0.43), and 0.20 (95% CI: 0.13-0.27). Their pooled NPV was 0.94 (95% CI: 0.93-0.96), 0.90 (95% CI: 0.89-0.92), 0.89 (95% CI: 0.80-0.98), and 0.95 (95% CI: 0.92-0.98). Variations in performance were observed in patients' subgroups, such as critically ill patients and refractory cases. Investigated scores only have acceptable AUC, sensitivity, and specificity for predicting in-hospital mortality, with the EMSE-EAC having a lower discriminative power. STESS-3 has the highest sensitivity, and STESS-4 the highest specificity, but neither combines acceptable sensitivity and specificity. All these scores had high NPV but very low PPV. Caution should be exercised in their clinical use. Further studies are required to develop more accurate scores.

Therapeutically induced EEG burst-suppression pattern to treat refractory status epilepticus—what is the evidence?

Current guidelines advocate to treat refractory status epilepticus (RSE) with continuously administered anesthetics to induce an artificial coma if first- and second-line antiseizure drugs have failed to stop seizure activity. A common surrogate for monitoring the depth of the artificial coma is the appearance of a burst-suppression pattern (BS) in the EEG. This review summarizes the current knowledge on the origin and neurophysiology of the BS phenomenon as well as the evidence from the literature for the presumed benefit of BS as therapy in adult patients with RSE.

Processed Electroencephalogram-Based Monitoring to Guide Sedation in Critically Ill Adult Patients: Recommendations from an International Expert Panel-Based Consensus

BACKGROUND

The use of processed electroencephalography (pEEG) for depth of sedation (DOS) monitoring is increasing in anesthesia; however, how to use of this type of monitoring for critical care adult patients within the intensive care unit (ICU) remains unclear.

METHODS

A multidisciplinary panel of international experts consisting of 21 clinicians involved in monitoring DOS in ICU patients was carefully selected on the basis of their expertise in neurocritical care and neuroanesthesiology. Panelists were assigned four domains (techniques for electroencephalography [EEG] monitoring, patient selection, use of the EEG monitors, competency, and training the principles of pEEG monitoring) from which a list of questions and statements was created to be addressed. A Delphi method based on iterative approach was used to produce the final statements. Statements were classified as highly appropriate or highly inappropriate (median rating ≥ 8), appropriate (median rating ≥ 7 but < 8), or uncertain (median rating < 7) and with a strong disagreement index (DI) (DI < 0.5) or weak DI (DI ≥ 0.5 but < 1) consensus.

RESULTS

According to the statements evaluated by the panel, frontal pEEG (which includes a continuous colored density spectrogram) has been considered adequate to monitor the level of sedation (strong consensus), and it is recommended by the panel that all sedated patients (paralyzed or nonparalyzed) unfit for clinical evaluation would benefit from DOS monitoring (strong consensus) after a specific training program has been performed by the ICU staff. To cover the gap between knowledge/rational and routine application, some barriers must be broken, including lack of knowledge, validation for prolonged sedation, standardization between monitors based on different EEG analysis algorithms, and economic issues.

CONCLUSIONS

Evidence on using DOS monitors in ICU is still scarce, and further research is required to better define the benefits of using pEEG. This consensus highlights that some critically ill patients may benefit from this type of neuromonitoring.

Anesthesia-Associated Periodic Discharges

PURPOSE

Anesthetic agents have been widely used in the treatment of refractory status epilepticus and the medical management of increased intracranial pressure whenever the goal is therapeutic burst suppression. Periodic patterns typically consisting of generalized periodic discharges (GPDs) following emergence from anesthesia have been described in several case reports. However, their clinical significance and in particular whether these patterns are epileptiform remains unclear.

METHODS

This is a single-center, retrospective, observational study examining EEG patterns following emergence from pharmacologically induced burst suppression. Clinical and EEG data were collected. Patients who developed GPDs following anesthetic wean were compared with those who did not.

RESULTS

Over 4.5 years, 14 patients developed GPDs related to anesthetic withdrawal. The GPDs had a frequency between 0.5 and 2.5 Hz. Generalized periodic discharges related to anesthetic withdrawal were transient, with a median duration of 40 hours (interquartile range, 24-48 hours). Notably, in all patients, the pattern was stimulus dependent. When compared with a control group of 19 consecutive patients who did not develop a generalized periodic pattern in the context of the anesthetic wean, there was no significant difference in the status epilepticus relapse between the two groups (29% vs. 44%; P = 0.63). Patients in the GPD group were more likely to be on pentobarbital (93% vs. 58%; P = 0.05) and were more likely to have concomitant systemic infection treated with antibiotics compared with the control group (86% vs. 42%; P = 0.02).

CONCLUSIONS

Generalized periodic patterns are common following the wean of intravenous anesthetics (particularly pentobarbital) and likely represent a transitional encephalopathic state in a subset of patients. Their morphology is distinct and can be differentiated from the reemergence of status epilepticus (if the latter was the indication for anesthetic treatment). Failure to recognize this pattern may lead to prolonged unnecessary treatments if it is mistaken for the emergence of seizure activity. The presence of concomitant systemic infection and associated antibiotic treatment may be risk factors for the development of this pattern.

Quantitative burst suppression on serial intermittent EEG in refractory status epilepticus

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Quantitative burst suppression ratios (QBSR) represent depth of EEG suppression.

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Deeper QBSR on serial intermittent EEG did not affect survival in RSE.

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Non-suppressive continuous EEG effects on RSE mortality merits further research.

Objectives

In refractory status epilepticus (RSE), the optimal degree of suppression (EEG burst suppression or merely suppressing seizures) remains unknown. Many centers lacking continuous EEG must default to serial intermittent recordings where uncertainty from lack of data may prompt more aggressive suppression. In this study, we sought to determine whether the quantitative burst suppression ratio (QBSR) from serial intermittent EEG recording is associated with RSE patient outcome.

Methods

We screened the EEG database to identify non-anoxic adult RSE patients for EEG and chart review. QBSR was calculated per 10-second EEG epoch as the percentage of time during which EEG amplitude was <3 µV. Patients who survived 1–3 months after discharge from ICU and hospital comprised the favorable group. Further to initial unadjusted univariate analysis of all pooled QBSR, we conducted multivariate analyses to account for individual patient confounders (“per-capita analysis”), uneven number of EEG recordings (“per-session analysis”), and uneven number of epochs (“per-epoch analysis”). We analyzed gender, anesthetic number, and adjusted status epilepticus severity score (aSTESS) as confounders.

Results

In 135,765 QBSR values over 160 EEG recordings (median 2.17 h every ≥24 h) from 17 patients on Propofol, Midazolam, and/or Ketamine, QBSR was deeper in the favorable group (p < 0.001) on initial unadjusted analysis. However, on adjusted multivariate analysis, there was consistently no association between QBSR and outcome. Higher aSTESS consistently associated with unfavorable outcome on per-capita (p = 0.033), per-session (p = 0.048) and per-epoch (p < 0.001) analyses. Greater maximal number of non-barbiturate anesthetic associated with favorable outcome on per-epoch analysis (p < 0.001).

Conclusions

There was no association between depth of EEG suppression using non-barbiturate anesthetic and RSE patient outcome based on QBSR from serial intermittent EEG. A per-epoch association between non-barbiturate anesthetic and favorable outcome suggests an effect from non-suppressive time-varying EEG content.

Significance

Targeting and following deeper burst suppression through non-barbiturate anesthetics on serial intermittent EEG monitoring of RSE is of limited utility.

Seizure Management in the Intensive Care Unit

Purpose of this review

This review presents current therapy for seizures in the intensive care unit. The reader is provided with recent evidence regarding the use of EEG in determining treatment for acute seizures. Proposed treatment approaches for seizures and status epilepticus are provided. Controversies and complexity of selecting treatments are discussed.

Recent findings

Critical Care EEG Monitoring Research Consortium analyzed the association of periodic and rhythmic electroencephalographic patterns with seizures and found that lateralized and generalized periodic discharges and lateralized rhythmic delta were associated with increased seizure risk. Applications using modified EEG techniques have demonstrated more rapid feedback to the ICU than was previously possible.

Summary

Accurate diagnosis and efficient treatment of seizures in the ICU is challenging due to patient factors, complexities of antiepileptic drug therapy, and the required expertise for EEG interpretation. Selection of optimally effective therapy for seizures or status epilepticus depends on multiple factors, making collaboration between neurophysiologists and the ICU team of paramount importance.

Seizures, Status Epilepticus, and Continuous EEG in the Intensive Care Unit

PURPOSE OF REVIEW

This article discusses the evolving definitions of seizures and status epilepticus in the critical care environment and the role of critical care EEG in both diagnosing seizure activity and serving as a predictive biomarker of clinical trajectory.

RECENT FINDINGS

Initial screening EEG has been validated as a tool to predict which patients are at risk of future seizures. However, accepted definitions of seizures and nonconvulsive status epilepticus encourage a treatment trial when the diagnosis on EEG is indeterminate because of periodic or rhythmic patterns or uncertain clinical correlation. Similarly, recent data have demonstrated the diagnostic utility of intracranial EEG in increasing the yield of seizure detection. EEG has additionally been validated as a diagnostic biomarker of covert consciousness, a predictive biomarker of cerebral ischemia and impending neurologic deterioration, and a prognostic biomarker of coma recovery and status epilepticus resolution. A recent randomized trial concluded that patients allocated to continuous EEG had no difference in mortality than those undergoing intermittent EEG but could not demonstrate whether this lack of difference was because of studying heterogeneous conditions, examining a monitoring tool rather than a therapeutic approach, or examining an outcome measure (mortality) perhaps more strongly associated with early withdrawal of life-sustaining therapy than to a sustained response to pharmacotherapy.

SUMMARY

Seizures and status epilepticus are events of synchronous hypermetabolic activity that are either discrete and intermittent or, alternatively, continuous. Seizures and status epilepticus represent the far end of a continuum of ictal-interictal patterns that include lateralized rhythmic delta activity and periodic discharges, which not only predict future seizures but may be further classified as status epilepticus on the basis of intracranial EEG monitoring or a diagnostic trial of antiseizure medication therapy. In particularly challenging cases, neuroimaging or multimodality neuromonitoring may be a useful adjunct documenting metabolic crisis. Specialized uses of EEG as a prognostic biomarker have emerged in traumatic brain injury for predicting language function and covert consciousness, cardiac arrest for predicting coma recovery, and subarachnoid hemorrhage for predicting neurologic deterioration due to delayed cerebral ischemia.

Update on the management of status epilepticus

PURPOSE OF REVIEW

Randomized controlled trials investigating the initial pharmacological treatment of status epilepticus have been recently published. Furthermore, status epilepticus arising in comatose survivors after cardiac arrest has received increasing attention in the last years. This review offers an updated assessment of status epilepticus treatment in these different scenarios.

RECENT FINDINGS

Initial benzodiazepines underdosing is common and correlates with development of status epilepticus refractoriness. The recently published ESETT trial provides high-level evidence regarding the equivalence of fosphenytoin, valproate, and levetiracetam as a second-line option. Myoclonus or epileptiform transients on electroencephalography occur in up to 1/3 of patients surviving a cardiac arrest. Contrary to previous assumptions regarding an almost invariable association with death, at least 1/10 of them may awaken with reasonably good prognosis, if treated. Multimodal prognostication including clinical examination, EEG, somatosensory evoked potentials, biochemical markers, and neuroimaging help identifying patients with a chance to recover consciousness, in whom a trial with antimyoclonic compounds and at times general anesthetics is indicated.

SUMMARY

There is a continuous, albeit relatively slow progress in knowledge regarding different aspect of status epilepticus; recent findings refine some treatment strategies and help improving patients' outcomes. Further high-quality studies are clearly needed to further improve the management of these patients, especially those with severe, refractory status epilepticus forms.

Does electroencephalographic burst suppression still play a role in the perioperative setting?

With the widespread use of electroencephalogram [EEG] monitoring during surgery or in the Intensive Care Unit [ICU], clinicians can sometimes face the pattern of burst suppression [BS]. The BS pattern corresponds to the continuous quasi-periodic alternation between high-voltage slow waves [the bursts] and periods of low voltage or even isoelectricity of the EEG signal [the suppression] and is extremely rare outside ICU and the operative room. BS can be secondary to increased anesthetic depth or a marker of cerebral damage, as a therapeutic endpoint [i.e., refractory status epilepticus or refractory intracranial hypertension]. In this review, we report the neurophysiological features of BS to better define its role during intraoperative and critical care settings.

To Wean or Not to Wean: Machine Learning to the Rescue

[Box: see text]

Electrographic predictors of successful weaning from anaesthetics in refractory status epilepticus

Intravenous third-line anaesthetic agents are typically titrated in refractory status epilepticus to achieve either seizure suppression or burst suppression on continuous EEG. However, the optimum treatment paradigm is unknown and little data exist to guide the withdrawal of anaesthetics in refractory status epilepticus. Premature withdrawal of anaesthetics risks the recurrence of seizures, whereas the prolonged use of anaesthetics increases the risk of treatment-associated adverse effects. This study sought to measure the accuracy of features of EEG activity during anaesthetic weaning in refractory status epilepticus as predictors of successful weaning from intravenous anaesthetics. We prespecified a successful anaesthetic wean as the discontinuation of intravenous anaesthesia without developing recurrent status epilepticus, and a wean failure as either recurrent status epilepticus or the resumption of anaesthesia for the purpose of treating an EEG pattern concerning for incipient status epilepticus. We evaluated two types of features as predictors of successful weaning: spectral components of the EEG signal, and spatial-correlation-based measures of functional connectivity. The results of these analyses were used to train a classifier to predict wean outcome. Forty-seven consecutive anaesthetic weans (23 successes, 24 failures) were identified from a single-centre cohort of patients admitted with refractory status epilepticus from 2016 to 2019. Spectral components of the EEG revealed no significant differences between successful and unsuccessful weans. Analysis of functional connectivity measures revealed that successful anaesthetic weans were characterized by the emergence of larger, more densely connected, and more highly clustered spatial functional networks, yielding 75.5% (95% confidence interval: 73.1-77.8%) testing accuracy in a bootstrap analysis using a hold-out sample of 20% of data for testing and 74.6% (95% confidence interval 73.2-75.9%) testing accuracy in a secondary external validation cohort, with an area under the curve of 83.3%. Distinct signatures in the spatial networks of functional connectivity emerge during successful anaesthetic liberation in status epilepticus; these findings are absent in patients with anaesthetic wean failure. Identifying features that emerge during successful anaesthetic weaning may allow faster and more successful anaesthetic liberation after refractory status epilepticus.

Successful Wean Despite Emergence of Ictal-Interictal EEG Patterns During the Weaning of Prolonged Burst-Suppression Therapy for Super-Refractory Status Epilepticus

BACKGROUND

Management of refractory status epilepticus (SE) commonly involves the induction of burst suppression using intravenous anesthetic agents. However, the endpoints of these therapies are not well defined. Weaning anesthetic agents are complicated by the emergence of electroencephalogram (EEG) patterns along the ictal-interictal continuum (IIC), which have uncertain significance given that IIC patterns may worsen cerebral metabolism and oxygenation, have a dissociation between scalp and depth EEG recordings, or may indicate a late stage of SE itself. Determining the significance of IIC patterns in the unique context of anesthetic weaning is important to prevent the potential for unnecessarily prolonging anesthetic coma.

METHODS

Among 118 individuals with SE, we retrospectively identified a series of patients who underwent at least 24 h of burst-suppression therapy, experienced two or more weaning trials, and developed IIC patterns during anesthetic weaning. Anesthetic titration strategies during the emergence of these patterns were examined.

RESULTS

Each of the six individuals who met inclusion criteria experienced aggressive weaning despite the emergence of IIC patterns. The IIC patterns that were encountered during anesthetic weaning (including generalized and lateralized periodic discharges) are described in detail. Favorable outcomes were reported in each subject.

CONCLUSION

IIC patterns encountered during anesthetic weaning may be transitional and warrant observation, allowing for the emergence of more definitive clinical or electrographic results. The metabolic impact of these IIC patterns on brain activity is uncertain, but weaning strategies that treat IIC as a surrogate of recurrent SE risk further prolonging anesthetic management and its known toxicity. We speculate that these patterns may have a context-specific association with SE relapse, with less-risk conferred when these patterns are observed during the weaning of anesthetic agents after prolonged burst-suppression therapy. Other electrographic features aside from this clinical context may discriminate the risk of SE relapse, such as EEG background activity.

A pragmatic approach to intravenous anaesthetics and electroencephalographic endpoints for the treatment of refractory and super-refractory status epilepticus in critical care

Status epilepticus is a common neurological emergency, with overall mortality around 20%. Over half of cases are first time presentations of seizures. The pathological process by which spontaneous seizures are generated arises from an imbalance in excitatory and inhibitory neuronal networks, which if unchecked, can result in alterations in intracellular signalling pathways and electrolyte shifts, which bring about changes in the blood brain barrier, neuronal cell death and eventually cerebral atrophy. This narrative review focusses on the treatment of status epilepticus in adults. Anaesthetic agents interrupt neuronal activity by enhancing inhibitory or decreasing excitatory transmission, primarily via GABA and NMDA receptors. Intravenous anaesthetic agents are commonly used as second or third line drugs in the treatment of refractory status epilepticus, but the optimal timing and choice of anaesthetic drug has not yet been established by high quality evidence. Titration of antiepileptic and anaesthetic drugs in critically ill patients presents a particular challenge, due to alterations in drug absorbtion and metabolism as well as changes in drug distrubution, which arise from fluid shifts and altered protein binding. Furthermore, side effects associated with prolonged infusions of anaesthetic drugs can lead to multi-organ dysfunction and a need for critical care support. Electroencelography can identify patterns of burst suppression, which may be a target to guide weaning of intravenous therapy. Continuous elctroencephalography has the potential to directly impact clinical care, but despite its utility, major barriers exist which have limited its widespread use in clinical practice. A flow chart outlining the timing and dosage of anaesthetic agents used at our institution is provided.

Duration of therapeutic coma and outcome of refractory status epilepticus

OBJECTIVE

Examine the association of duration of therapeutic coma (TC) with seizure recurrence, morbidity, and mortality in refractory status epilepticus (RSE). Define an optimal window for TC that provides sustained seizure control and minimizes complications.

METHODS

Retrospective, observational cohort study involving patients who presented with RSE to the University of Alabama at Birmingham or the University of California at San Francisco from 2010 to 2016. Relationship of duration of TC with primary and secondary outcomes was evaluated using two-sample t tests, simple linear regression, and chi-square tests. Multivariable linear and logistic regression models were used to identify independent predictors. Predictive ability of TC for seizure recurrence was quantified using a receiver-operating characteristic curve. Youden index was used to determine an optimal cutoff value.

RESULTS

Multivariable analysis of clinical and treatment characteristics of 182 patients who were treated predominantly with propofol as anesthetic agent showed that longer duration of the first trial of TC (27.2 vs 15.6 hours) was independently associated with a higher chance of seizure recurrence following the first weaning attempt (P = 0.038) but not with poor functional neurologic outcome upon discharge, in-hospital complications, or mortality. Furthermore, higher doses of anesthetic utilized during the first trial of TC were independently associated with fewer in-hospital complications (P = 0.003) and associated with a shorter duration of mechanical ventilation and total length of stay. Duration of TC was identified as an independent predictor of seizure recurrence with an optimal cutoff point at 35 hours.

SIGNIFICANCE

This study suggests that a shorter duration yet deeper TC as treatment for RSE may be more effective and safer than the currently recommended TC duration of 24-48 hours. Prospective and randomized trials should be conducted to validate these assertions.

External validation of the epidemiology-based mortality score in status epilepticus in an American intensive care population

INTRODUCTION

Although overall mortality of status epilepticus is high, baseline patient characteristics and co-morbidities may be helpful to predict outcomes and shape treatment decisions. Two previously published scoring systems exist to predict outcomes: the Status Epilepticus Severity Score (STESS) and the Epidemiology-based Mortality Score in Status Epilepticus (EMSE). However, a comparison of the two scores has not previously been completed in an American intensive care unit. We hypothesize that both scores will adequately predict the primary outcome of in-hospital death, but that the EMSE may more accurately predict functional outcomes, and significantly impact treatment decisions for both clinicians and families.

METHODS

We performed a retrospective analysis of all cases of status epilepticus admitted to the Neuro-Critical Care Unit (NCCU) at the Ohio State University Wexner Medical Center from 6/1/2014 - 8/31/2015. We collected data on age, comorbidities, EEG findings, and seizure history. The primary outcome measured was in-hospital death; secondary outcomes included length of stay in the NCCU, placement of a tracheostomy and/or a percutaneous endoscopic gastrostomy upon discharge, and discharge location were used as surrogate markers for outcome severity. A sensitivity and specificity analysis was carried out, in addition to a student's t-test for a comparison of the two scores. ANOVA was completed to compare secondary outcomes RESULTS: Forty-six patients were admitted to the NCCU for management of status epilepticus during June 2014 and January 2016, thirteen of which experienced in-hospital death. The median age of the sample was 60, with approximately half of the sample (52.63%) having 3 or more comorbidities. The sensitivity of both EMSE and STESS were very high (100% and 90% respectively); however, the specificities were very low (28.6% and 42.9% respectively). A student's t-test between those who experienced in-hospital death and those who did not was only significant for EMSE at the p < 0.1 level (p = 0.055). Additionally, mean EMSE scores but not STESS scores, were significantly higher (p < 0.001) for those patients who were discharged to skilled nursing facilities or with hospice than compared to those who were discharged to home or to acute inpatient rehabilitation.

CONCLUSIONS

The EMSE and STESS may be useful to predict outcomes of status epilepticus in populations with few comorbid conditions, but are less helpful when patients have multiple medical problems. Secondly, while neither score may be specific enough to differentiate for the primary outcome of death, their utility may be helpful to predict secondary outcomes that strongly affect clinical decisions. Based on these results, we believe a prospective trial of EMSE and STESS should be carried out to obtain more information on their utility, especially in American patients who may have more relevant comorbidities than in other countries.

Updates in Refractory Status Epilepticus

Refractory status epilepticus is defined as persistent seizures despite appropriate use of two intravenous medications, one of which is a benzodiazepine. It can be seen in up to 40% of cases of status epilepticus with an acute symptomatic etiology as the most likely cause. New-onset refractory status epilepticus (NORSE) is a recently coined term for refractory status epilepticus where no apparent cause is found after initial testing. A large proportion of NORSE cases are eventually found to have an autoimmune etiology needing immunomodulatory treatment. Management of refractory status epilepticus involves treatment of an underlying etiology in addition to intravenous anesthetics and antiepileptic drugs. Alternative treatment options including diet therapies, electroconvulsive therapy, and surgical resection in case of a focal lesion should be considered. Short-term and long-term outcomes tend to be poor with significant morbidity and mortality with only one-third of patients reaching baseline neurological status.

Does burst-suppression achieve seizure control in refractory status epilepticus?

Background

The general principles in the administration of anesthetic drugs entail not only the suppression of seizure activity but also the achievement of electroencephalography burst suppression (BS). However, previous studies have reported conflicting results, possibly owing to the inclusion of various anesthetic agents, not all patients undergoing continuous electroencephalography (cEEG), and the inclusion of anoxic encephalopathy. This study aimed to analyze the effects of midazolam-induced BS on the occurrence outcomes in refractory status epilepticus patients.

Methods

Based on a prospective database of patients who had been diagnosed with status epilepticus via cEEG, multivariate Poisson regression modules were used to estimate the effect of midazolam-induced BS on breakthrough seizure, withdrawal seizure, intra-hospital complications, functional outcome at 3 months, and mortality. Modules were based on a pre-compiled directed acyclic graph (DAG).

Results

We included 51 non-anoxic encephalopathy, refractory status epilepticus patients. Burst suppression was achieved in 26 patients (51%); 25 patients (49%) had non-burst suppression on their cEEG. Breakthrough seizure was less often seen in the burst suppression group than in the non-burst suppression group. The incidence risk ratio [IRR] was 0.30 (95% confidence interval = 0.13–0.74). There was weak evidence of an association between BS and increased withdrawal seizure, but no association between BS and intra-hospital complications, mortality or functional outcomes was observed.

Conclusion

This study provides evidence that BS is safe and associated with less breakthrough seizures. Additionally, it was not associated with an increased rate of intra-hospital complications or long-term outcomes.

High dose phenobarbitone coma in pediatric refractory status epilepticus; a retrospective case record analysis, a proposed protocol and review of literature

BACKGROUND

Ongoing refractory status epilepticus is associated with significant morbidity and mortality. Therapeutic coma induction with midazolam, thiopentone, phenobarbitone or propofol is indicated when conventional antiepileptics fail to abort seizure. Of these, the most extensively studied is midazolam. Amongst the remaining three, phenobarbitone has the most favourable pharmacological profile, but has not been studied adequately, more so in the pediatric age group. The current retrospective case records analysis is an attempt to describe use of phenobarbitone coma in pediatric refractory status epilepticus.

METHODS

Case records of patients, admitted with status epilepticus to the pediatric inpatient services of a tertiary care teaching hospital of North India between January 2014 and December 2016 were reviewed. Those with refractory status epilepticus who failed to respond to midaolam infusion and phenobarbitone coma was used were included for analysis.

RESULTS

Overall, 108 children presented in status, of which 34 developed refractory status epilepticus. Of these 34, 21 responded to midazolam infusion and in 13 high dose phenobarbitone coma following a standardised protocol was used. Amongst these 13 (8 males and 5 females, median age 6 years, IQR: 2.5-9.5), 12 responded and 1 succumbed. The median time to clinical seizure resolution and desired electroencephalographic changes post phenobarbitone initiation were 16 (IQR: 12-25) and 72 h (IQR: 48-120) respectively.

CONCLUSION

High dose phenobarbitone appears to be an effective therapeutic modality in pediatric refractory status epilepticus. The current study provides a protocol for its use which can be validated in future studies with larger sample size.

The state of everyday quantitative EEG use in Canada: A national technologist survey

PURPOSE

This study sought to determine the state of quantitative EEG (QEEG) use in Canada, as QEEG may provide a partial solution to the issue of escalating EEG demand against insufficient health care resources.

METHODS

A 10-item survey questionnaire was administered to participants at the annual meeting of the Canadian Association of Electroneurophysiology Technologists, which was held in parallel with the annual meeting of the Canadian Neurological Sciences Federation.

RESULTS

At least 70% of the Canadian population has QEEG access through academic medical institutions with applicability to adults and children. QEEG was clinically used 50% in real-time and 50% retrospectively in the critical care and epilepsy monitoring units for long-term monitoring and automated seizure detection. QEEG trend use, montage use, and duration were variable.

CONCLUSION

To cope with insufficient health care resources, QEEG is in surprisingly frequent clinical use across Canada. There is no consensus on optimal QEEG trends and montages. The relative ubiquity of QEEG affords an excellent opportunity for research as increasing EEG demand outpaces dwindling health care resources into the foreseeable future.

Periodic Lateralized Epileptiform Discharges can Survive Anesthesia and Result in Asymmetric Drug-induced Burst Suppression

Drug-induced burst suppression (DIBS) is bihemispheric and bisymmetric in adults and older children. However, asymmetric DIBS may occur if a pathological process is affecting one hemisphere only or both hemispheres disproportionately. The usual suspect is a destructive lesion; an irritative or epileptogenic lesion is usually not invoked to explain DIBS asymmetry. We report the case of a 66-year-old woman with new-onset seizures who was found to have a hemorrhagic cavernoma and periodic lateralized epileptiform discharges (PLEDs) in the right temporal region. After levetiracetam and before anesthetic antiepileptic drugs (AEDs) were administered, the electroencephalogram (EEG) showed continuous PLEDs over the right hemisphere with maximum voltage in the posterior temporal region. Focal electrographic seizures also occurred occasionally in the same location. Propofol resulted in bihemispheric, but not in bisymmetric, DIBS. Remnants or fragments of PLEDs that survived anesthesia increased the amplitude and complexity of the bursts in the right hemisphere leading to asymmetric DIBS. Phenytoin, lacosamide, ketamine, midazolam, and topiramate were administered at various times in the course of EEG monitoring, resulting in suppression of seizures but not of PLEDs. Ketamine and midazolam reduced the rate, amplitude, and complexity of PLEDs but only after producing substantial attenuation of all burst components. When all anesthetics were discontinued, the EEG reverted to the original preanesthesia pattern with continuous non-fragmented PLEDs. The fact that PLEDs can survive anesthesia and affect DIBS symmetry is a testament to the robustness of the neurodynamic processes underlying PLEDs.