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

The Origin of the Burst-Suppression Paradigm in Treatment of Status Epilepticus

After electroencephalography (EEG) was introduced in hospitals, early literature recognized burst-suppression pattern (BSP) as a distinctive EEG pattern characterized by intermittent high-power oscillations alternating with isoelectric periods in coma and epileptic encephalopathies of childhood or the pattern could be induced by general anesthesia and hypothermia. The term was introduced by Swank and Watson in 1949 but was initially described by Derbyshire et al. in 1936 in their study about the anesthetic effects of tribromoethanol. Once the EEG/BSP pattern emerged in the literature as therapeutic goal in refractory status epilepticus, researchers began exploring whether the depth of EEG suppression correlated with improved seizure control and clinical outcomes. We can conclude that, from a historical perspective, the evidence to suppress the brain to a BSP when treating status epilepticus is inconclusive.

Treatment of Refractory Status Epilepticus With Continuous Intravenous Anesthetic Drugs: A Systematic Review

Importance

Multiple continuous intravenous anesthetic drugs (CIVADs) are available for the treatment of refractory status epilepticus (RSE). There is a paucity of data comparing the different types of CIVADs used for RSE.

Objective

To systematically review and compare outcome measures associated with the initial CIVAD choice in RSE in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

Evidence Review

Data sources included English and non-English articles using Embase, MEDLINE, PubMed, and Web of Science (January 1994-June 2023) as well as manual search. Study selection included peer-reviewed studies of 5 or more patients and at least 1 patient older than 12 years with status epilepticus refractory to a benzodiazepine and at least 1 standard antiseizure medication, treated with continuously infused midazolam, ketamine, propofol, pentobarbital, or thiopental. Independent extraction of articles was performed using prespecified data items. The association between outcome variables and CIVAD was examined with an analysis of variance or χ2 test where appropriate. Binary logistic regressions were used to examine the association between outcome variables and CIVAD with etiology, change in mortality over time, electroencephalography (EEG) monitoring (continuous vs intermittent), and treatment goal (seizure vs burst suppression) included as covariates. Risk of bias was addressed by listing the population and type of each study.

Findings

A total of 66 studies with 1637 patients were included. Significant differences among CIVAD groups in short-term failure, hypotension, and CIVAD substitution during treatment were observed. Non-epilepsy-related RSE (vs epilepsy-related RSE) was associated with a higher rate of CIVAD substitution (60 of 120 [50.0%] vs 11 of 43 [25.6%]; odds ratio [OR], 3.11; 95% CI, 1.44-7.11; P = .006) and mortality (98 of 227 [43.2%] vs 7 of 63 [11.1%]; OR, 17.0; 95% CI, 4.71-109.35; P < .001). Seizure suppression was associated with mortality (OR, 7.72; 95% CI, 1.77-39.23; P = .005), but only a small subgroup was available for analysis (seizure suppression: 17 of 22 [77.3%] from 3 publications vs burst suppression: 25 of 98 [25.5%] from 12 publications). CIVAD choice and EEG type were not predictors of mortality. Earlier publication year was associated with mortality, although the observation was no longer statistically significant after adjusting SEs for clustering.

Conclusions and Relevance

Epilepsy-related RSE was associated with lower mortality compared with other RSE etiologies. A trend of decreasing mortality over time was observed, which may suggest an effect of advances in neurocritical care. The overall data are heterogeneous, which limits definitive conclusions on the choice of optimal initial CIVAD in RSE treatment.

Electroencephalographic features of elderly patients during anesthesia induction with remimazolam: a sub-study of a randomized controlled trial

BACKGROUND

Although remimazolam is used as a general anesthetic in elderly patients due to its hemodynamic stability, the electroencephalogram (EEG) characteristics of remimazolam are not well-known. The purpose of this study was to identify the EEG features of remimazolam-induced unconsciousness in elderly patients and compare them with propofol.

METHODS

Remimazolam (n=26) or propofol (n=26) were randomly administered for anesthesia induction in surgical patients. The hypnotic agent was blinded only to the patients. During the induction of anesthesia, remimazolam was administered at a rate of 6 mg/kg/h, and propofol was administered at a target effect-site concentration of 3.5 μg/ml. The EEG signals from 8 channels (Fp1,Fp2,Fz,F3,F4,Pz,P3,P4, referenced to A2, using the 10-20 system) were acquired during the induction of anesthesia and in the postoperative care unit. Power spectrum analysis was performed, and directed functional connectivity between frontal and parietal regions was evaluated using normalized symbolic transfer entropy. Functional connectivity in unconscious processes induced by remimazolam or propofol was compared with baseline. To compare each power of frequency over time of the two hypnotic agents, a permutation test with t statistic was conducted.

RESULTS

Compared to the baseline in the alpha band, the feedback connectivity decreased by an average of 46% and 43%, respectively, after the loss of consciousness induced by remimazolam and propofol (95% CI for the mean difference:-0.073 to -0.044 for remimazolam, P<0.001,-0.068 to -0.042 for propofol,P<0.001). Asymmetry in the feedback and feedforward connectivity in the alpha band was suppressed after the loss of consciousness induced by remimazolam and propofol. There were no significant differences in the power of each frequency over time between the two hypnotic agents (minimum q-value=0.4235).

CONCLUSIONS

Both regimens showed a greater decrease in feedback connectivity compared to a decrease in feedforward connectivity after loss of consciousness, leading to a disruption of asymmetry between the frontoparietal connectivity.

Correlation between burst suppression and postoperative delirium in elderly patients: a prospective study

OBJECTIVE

To explore the correlation between intraoperative burst suppression (BS) and postoperative delirium (POD) in elderly patients, and provide more ideas for reducing POD in clinical.

METHODS

Ninety patients, aged over 60 years, who underwent lumbar internal fixation surgery in our hospital were selected. General information of patients was obtained and informed consent was signed during preoperative visits. Patients were divided into burst suppression (BS) group and non-burst suppression (NBS) group by intraoperative electroencephalogram monitoring. Intraoperative systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and heart rate (HR) were recorded, and the variation and minimum value were obtained by calculating. Hemoglobin (HGB), C-reactive protein (CRP), system immune inflammatory index (SII) at 24 and 72 h after surgery, the incidence of postoperative adverse reactions, postoperative hospital stay, and total cost were recorded after operation. POD assessment was performed using CAM within 7 days after surgery or until discharge. SPSS25.0 was used for statistical analysis.

RESULTS

Compared with the NBS group, the number of elderly patients with high frailty level in BS group was more (P = 0.048). There is correlation between BS and POD (OR: 4.954, 95%CI 1.034-23.736, P = 0.045), and most of the POD patients in BS group behave as hyperactive type.

CONCLUSION

The occurrence of intraoperative BS is associated with POD, and elderly patients with frailty are more likely to have intraoperative BS. BS can be used as a predictor of POD.

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.

Association Between Induced Burst Suppression and Clinical Outcomes in Patients With Refractory Status Epilepticus: A 9-Year Cohort Study

BACKGROUND AND OBJECTIVES

To investigate the frequency of induced EEG burst suppression pattern during continuous IV anesthesia (IVAD) and associated outcomes in adult patients treated for refractory status epilepticus (RSE).

METHODS

Patients with RSE treated with anesthetics at a Swiss academic care center from 2011 to 2019 were included. Clinical data and semiquantitative EEG analyses were assessed. Burst suppression was categorized as incomplete burst suppression (with ≥20% and <50% suppression proportion) or complete burst suppression (with ≥50% suppression proportion). The frequency of induced burst suppression and association of burst suppression with outcomes (persistent seizure termination, in-hospital survival, and return to premorbid neurologic function) were the endpoints.

RESULTS

We identified 147 patients with RSE treated with IVAD. Among 102 patients without cerebral anoxia, incomplete burst suppression was achieved in 14 (14%) with a median of 23 hours (interquartile range [IQR] 1-29) and complete burst suppression was achieved in 21 (21%) with a median of 51 hours (IQR 16-104). Age, Charlson comorbidity index, RSE with motor symptoms, the Status Epilepticus Severity Score and arterial hypotension requiring vasopressors were identified as potential confounders in univariable comparisons between patients with and without any burst suppression. Multivariable analyses revealed no associations between any burst suppression and the predefined endpoints. However, among 45 patients with cerebral anoxia, induced burst suppression was associated with persistent seizure termination (72% without vs 29% with burst suppression, p = 0.004) and survival (50% vs 14% p = 0.005).

DISCUSSION

In adult patients with RSE treated with IVAD, burst suppression with ≥50% suppression proportion was achieved in every fifth patient and not associated with persistent seizure termination, in-hospital survival, or return to premorbid neurologic function.

Balancing the risks and benefits of anesthetics in status epilepticus

PURPOSE

According to international guidelines, status epilepticus refractory to first- and second-line antiseizure medication should be treated with anesthetics. Therefore, continuously delivered intravenous midazolam, propofol, or barbiturates are recommended as third-line therapy. While electroencephalographically (EEG)-controlled titration of anesthetics to seizure termination or to the emergence of an EEG burst-suppression pattern makes sense, evidence of the efficacy and tolerability of such third-line treatment is limited and concerns regarding the risks of anesthesia remain. The lack of treatment alternatives and persistent international discord reflecting contradictory results from some studies leave clinicians on their own when deciding to escalate treatment. In this conference-accompanying narrative review, we highlight the challenges of EEG-monitored third-line treatment and discuss recent studies that examined earlier administration of anesthetics.

RESULTS

Based on the literature, maintaining continuous burst suppression is difficult despite the constant administration of anesthetics, and the evidence for burst suppression as an adequate surrogate target is limited by methodological shortcomings as acknowledged by international guidelines. In our Swiss cohort including 102 patients with refractory status epilepticus, burst suppression as defined by the American Clinical Neurophysiology Society's Critical Care EEG Terminology 2021 was established in only 21%. Besides case reports suggesting that rapid but short-termed anesthesia can be sufficient to permanently stop seizures, a study including 205 patients revealed that anesthesia as second-line treatment was associated with a shorter median duration of status epilepticus (0.5 versus 12.5 days, p < 0.001), median ICU (2 versus 5.5 days, p < 0.001) and hospital stay (8 versus 17 days, p < 0.001) with equal rates of complications when compared to anesthesia as third-line treatment.

CONCLUSIONS

Recent investigations have led to important findings and new insights regarding the use of anesthetics in refractory status epilepticus. However, numerous methodological limitations and remaining questions need to be considered when it comes to the translation into clinical practice, and, in consequence, call for prospective randomized studies. This paper was presented at the 8th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures held in September 2022.

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.

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.

Long-term prognosis related to deep sedation in refractory status Epilepticus

OBJECTIVE

To evaluate long-term prognosis in patients with refractory status epilepticus according to the level of sedation reached during drug-induced coma.

MATERIALS AND METHODS

Longitudinal study of patients with status epilepticus who received anesthetics to induce therapeutic coma. Demographic data, clinical, and electroencephalographic characteristics were collected, as well as variables related to sedation. We considered as deep sedation the EEG burst-suppression patterns (suppression ratio > 50%). A GOSE (Glasgow Outcome Scale Extended) score of 7 or 8 was considered as good prognosis. A comparative study was carried out to identify predictors of good or poor prognosis at discharge, at 1 and 2 years of follow-up.

RESULTS

We included 61 patients: 63.9% were men; mean age 53.5 ± 16.8 years (range 16-86 years), 39.3% reached deep sedation; 62.3% had > 48 h induced coma. The median hospital stay was 21 days, while 10 days in the intensive care unit (ICU). In the multiple regression analysis, an ICU length of stay ≥ 7 days was associated with poor prognosis at discharge and at long-term (P < .05), while deep sedation was associated only with poor long-term prognosis (1 and 2 years, P < .05). The Kaplan-Meier curve showed higher survival in the group that did not undergo deep sedation (P < .05).

CONCLUSIONS

In refractory status epilepticus, deep sedation is associated with poor prognosis at long-term.

Allopregnanolone and perampanel as adjuncts to midazolam for treating diisopropylfluorophosphate-induced status epilepticus in rats

Combinations of midazolam, allopregnanolone, and perampanel were assessed for antiseizure activity in a rat diisopropylfluorophosphate (DFP) status epilepticus model. Animals receiving DFP followed by atropine and pralidoxime exhibited continuous high-amplitude rhythmical electroencephalography (EEG) spike activity and behavioral seizures for more than 5 hours. Treatments were administered intramuscularly 40 min after DFP. Seizures persisted following midazolam (1.8 mg/kg). The combination of midazolam with either allopregnanolone (6 mg/kg) or perampanel (2 mg/kg) terminated EEG and behavioral status epilepticus, but the onset of the perampanel effect was slow. The combination of midazolam, allopregnanolone, and perampanel caused rapid and complete suppression of EEG and behavioral seizures. In the absence of DFP, animals treated with the three-drug combination were sedated but not anesthetized. Animals that received midazolam alone exhibited spontaneous recurrent EEG seizures, whereas those that received the three-drug combination did not, demonstrating antiepileptogenic activity. All combination treatments reduced neurodegeneration as assessed with Fluoro-Jade C staining to a greater extent than midazolam alone, and most reduced astrogliosis as assessed by GFAP immunoreactivity but had mixed effects on markers of microglial activation. We conclude that allopregnanolone, a positive modulator of the GABAA receptor, and perampanel, an AMPA receptor antagonist, are potential adjuncts to midazolam in the treatment of benzodiazepine-refractory organophosphate nerve agent-induced status epilepticus.

Burst suppression uncovers rapid widespread alterations in network excitability caused by an acute seizure focus

Burst suppression is an electroencephalogram pattern of globally symmetric alternating high amplitude activity and isoelectricity that can be induced by general anaesthetics. There is scattered evidence that burst suppression may become spatially non-uniform in the setting of underlying pathology. Here, we induced burst suppression with isoflurane in rodents and then created a neocortical acute seizure focus with injection of 4-aminopyridine (4-AP) in somatosensory cortex. Burst suppression events were recorded before and after creation of the focus using bihemispheric wide-field calcium imaging and multielectrode arrays. We find that the seizure focus elicits a rapid alteration in triggering, initiation, and propagation of burst suppression events. Compared with the non-seizing brain, bursts are triggered from the thalamus, initiate in regions uniquely outside the epileptic focus, elicit marked increases of multiunit activity and propagate towards the seizure focus. These findings support the rapid, widespread impact of focal epilepsy on the extended brain network.

Thiamylal anaesthetic therapy for febrile refractory status epilepticus in children

PURPOSE

To evaluate barbiturate anaesthetic therapy using thiamylal for febrile refractory status epilepticus (fRSE) in children.

METHODS

This was a review of a prospectively-collected database between April 2012-March 2016 for fRSE cases treated with thiamylal anaesthetic therapy in a single paediatric hospital in Japan. The sample comprised 23 children (median age, 23 months) with fRSE that underwent thiamylal anaesthetic therapy for convulsive seizures lasting longer than 60 min, sustained after intravenous administration of benzodiazepine and non-benzodiazepine anticonvulsants. The intervention comprised protocol-based thiamylal anaesthetic therapy with bolus administration. We measured the dose and time required to achieve the burst suppression pattern (BSP) on electroencephalography, seizure recurrence, death, neurological sequelae, and complications.

RESULTS

All patients except one reached the BSP. The thiamylal median dose until reaching the BSP was 27.5 mg/kg, and the median time from thiamylal administration to reaching the BSP was 109.5 min. There was one case of immediate treatment failure and one of withdrawal seizure, but no breakthrough seizure. No deaths occurred during treatment, and neurological sequelae occurred in four cases (17%). Vasopressors were administered in all cases. Other complications included 11 cases of pneumonia and one of enterocolitis.

CONCLUSION

We revealed the time and dose required to reach the BSP with thiamylal anaesthetic therapy using bolus administration in children. Our results suggested that reaching the BSP with bolus administration requires markedly less time than without bolus administration, rarely causes seizure recurrence in paediatric fRSE, and causes haemodynamic dysfunction and infections as often as observed without bolus administration.

[Management of refractory and super-refractory status epilepticus]

If status epilepticus continues despite the use of intravenous antiepileptic drugs or narcotics, it is called "refractory" or "super-refractory" status epilepticus (RSE, SRSE). Prolonged seizure activity is associated with neuronal damage, systemic complications and mortality rates of up to 50%, especially in generalized tonic clonic seizure types. In order to terminate the status, several rescue interventions with drugs and other measures are available. However, their evidence base is low because the effectiveness of the measures was almost exclusively derived from case reports and case series. In individual cases, a good outcome is possible even after several months of ongoing SRSE.

Pharmacology and clinical applications of flupirtine: Current and future options

Flupirtine is the first representative in a class of triaminopyridines that exhibits pharmacological properties leading to the suppression of over-excitability of neuronal and non-neuronal cells. Consequently, this drug has been used as a centrally acting analgesic in patients with a range of acute and persistent pain conditions without the adverse effects characteristic of opioids and non-steroidal anti-inflammatory drug and is well tolerated. The pharmacological profile exhibited involves actions on several cellular targets, including Kv7 channels, G-protein-regulated inwardly rectifying K channels and γ-aminobutyric acid type A receptors, but also there is evidence of additional as yet unidentified mechanisms of action involved in the effects of flupirtine. Flupirtine has exhibited effects in a range of cells and tissues related to the locations of these targets. In additional to analgesia, flupirtine has demonstrated pharmacological properties consistent with use as an anticonvulsant, a neuroprotectant, skeletal and smooth muscle relaxant, in treatment of auditory and visual disorders, and treatment of memory and cognitive impairment. Flupirtine is providing important information and clues regarding novel mechanistic approaches to the treatment of a range of clinical conditions involving hyper-excitability of cells. Identification of molecules exhibiting specificity for the pharmacological targets (e.g., Kv7 isoforms) involved in the actions of flupirtine will provide further insight into clinical applications. Whether the broad-spectrum pharmacology of flupirtine or target-specific actions is preferential to gain benefit, especially in complex clinical conditions, requires further investigation. This review will consider recent advancement in understanding of the pharmacological profile and related clinical applications of flupirtine.