The treatment of status epilepticus

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.

Status epilepticus: Role for etiology in determining response to benzodiazepines

OBJECTIVE

Clinical factors contributing to benzodiazepine failure in treating status epilepticus (SE) include suboptimal dosing and seizure duration. As many benzodiazepine-refractory episodes of SE arise from acute etiologies, we sought to determine whether etiology impacts SE treatment.

METHODS

The potency of diazepam to terminate SE induced by lithium-pilocarpine (LiPilo-SE) or kainic acid (KA-SE) in 3-week-old rats was studied by video-electroencephalography. Synaptic γ-aminobutyric acid type A receptor (GABAR)-mediated currents were recorded from dentate granule cells using voltage-clamp electrophysiology. Surface expression of γ2 subunit-containing GABARs and Kv4.2 potassium channels in hippocampal slices was determined using a biotinylation assay. Expression of phosphorylated forms of β2/3 and γ2 subunits was determined using phosphospecific antibodies and Western blotting.

RESULTS

Diazepam failed to terminate late SE in LiPilo-SE animals but was successful in terminating KA-SE of 1- and 3-hour duration. One hour after SE onset, GABAR-mediated synaptic inhibition and γ2 subunit-containing GABAR surface expression were reduced in LiPilo-SE animals. These were unchanged in KA-SE animals at 1 and 3 hours. Phosphorylation of γ2 subunit residue S327 was unchanged in both models, although GABAR β3 subunit S408/409 residues were dephosphorylated in the LiPilo-SE animals. Kv4.2 potassium channel surface expression was increased in LiPilo-SE animals but reduced in KA-SE animals.

INTERPRETATION

SE-model-dependent differences support a novel hypothesis that the development of benzodiazepine pharmacoresistance may be etiologically predetermined. Further studies are required to investigate the mechanisms that underlie such etiological differences during SE and whether etiology-dependent protocols for the treatment of SE need to be developed. Ann Neurol 2018;83:830-841.

Feasibility Study Evaluating Therapeutic Hypothermia for Refractory Status Epilepticus in Children

Pediatric refractory status epilepticus (RSE) is a neurological emergency with significant morbidity and mortality, which lacks consensus regarding diagnosis and treatment(s). Therapeutic hypothermia (TH) is an effective treatment for RSE in preclinical models and small series. In addition, TH is a standard care for adults after cardiac arrest and neonates with hypoxic-ischemic encephalopathy. The purpose of this study was to identify the feasibility of a study of pediatric RSE within a research group (Pediatric Neurocritical Care Research Group [PNCRG]). Pediatric intensive care unit (PICU) admissions at seven centers were prospectively screened from October 2012 to July 2013 for RSE. Experts within the PNCRG estimated that clinicians would be unwilling to enroll a child, unless the child required at least two different antiepileptic medications and a continuous infusion of another antiepileptic medication with ongoing electrographic seizure activity for ≥2 hours after continuous infusion initiation. Data for children meeting the above inclusion criteria were collected, including the etiology of RSE, history of epilepsy, and maximum dose of continuous antiepileptic infusions. There were 8113 PICU admissions over a cumulative 52 months (October 2012-July 2013) at seven centers. Of these, 69 (0.85%) children met inclusion criteria. Twenty children were excluded due to acute diagnoses affected by TH, contraindications to TH, or lack of commitment to aggressive therapies. Sixteen patients had seizure cessation within 2 hours, resulting in 33 patients who had inadequate seizure control after 2 hours and a continuous antiepileptic infusion. Midazolam (21/33, 64%) and pentobarbital (5/33, 15%) were the most common infusions with a wide maximum dose range. More than one infusion was required for seizure control in four patients. There are substantial numbers of subjects at clinical sites within the PNCRG with RSE that would meet the proposed inclusion criteria for a study of TH. The true feasibility of such a study depends on the sample size necessary to achieve therapeutic effects on justifiable clinical outcomes.

Neonatal status epilepticus: differences between preterm and term newborns

BACKGROUND

Despite the many studies on neonatal seizures, neonatal status epilepticus (NSE) remains a controversial entity, with no general consensus about its definition. We report the characteristics of newborns with NSE in order to assess whether they showed homogeneous features or displayed clinical and/or instrumental differences depending on gestational age (GA). Preterm and term neonates were compared and risk factors for adverse outcome evaluated.

METHODS

From 154 newborns with video-EEG confirmed neonatal seizures admitted to the NICU of Parma University Hospital between January 1999 and December 2012, we collected a cohort of 47 newborns (19 preterm, 28 full-term) with NSE. NSE was defined as continuous seizure activity for at least 30 min or recurrent seizures lasting a total of 30 min without definite return to the baseline neurologic condition between seizures. Outcome was assessed at least at one year. We applied the χ(2) test to compare nominal data, and multivariate logistic regression analysis to determine independent risk factors for adverse outcome.

RESULTS

Only Apgar scores and neurologic examination (p ≤ .02) were different between the groups. None of the preterm newborns had a favourable outcome compared to 25% of the full-term ones (p = .032). Moreover, 52.6% of preterm neonates died compared to 17.8% of the full-term newborns (p = .01; OR = 5.11). The only variable related to outcome was Apgar score at 5 min (p = .02).

CONCLUSION

Newborns with NSE represented a quite homogeneous group regardless of the GA. Outcome was unfavourable in most of the subjects; however adverse outcome and death were more represented in preterm newborns.

Status epilepticus in childhood

Status epilepticus (SE) remains a life-threatening condition that afflicts both adults and children, and may occur at onset of epilepsy, especially in children. Febrile SE is the most common cause in children, while other symptomatic causes are less frequent compared to adults. The aetiological workup that must be undertaken in all cases includes neuroimaging and electroencephalography. The various electroencephalographic patterns seen in patients with SE along with the out-of-hospital treatment for SE in children and treatment strategies in cases that are refractory to first-line medical treatments are discussed. Medically induced coma may be necessary in refractory cases, although the optimal agents to use and degree of electroencephalographic suppression in children remain unclear. Neurosurgery is not a well-known treatment option that could be considered for refractory cases. Although the prognosis has probably improved over the years, it remains a potential life-threatening emergency.

Guidelines for the evaluation and management of status epilepticus

Status epilepticus (SE) treatment strategies vary substantially from one institution to another due to the lack of data to support one treatment over another. To provide guidance for the acute treatment of SE in critically ill patients, the Neurocritical Care Society organized a writing committee to evaluate the literature and develop an evidence-based and expert consensus practice guideline. Literature searches were conducted using PubMed and studies meeting the criteria established by the writing committee were evaluated. Recommendations were developed based on the literature using standardized assessment methods from the American Heart Association and Grading of Recommendations Assessment, Development, and Evaluation systems, as well as expert opinion when sufficient data were lacking.

Status Epilepticus in Children

Status epilepticus (SE) is a life-threatening emergency that requires prompt treatment, including basic neuroresuscitation principles (the ABCs), antiepileptic drugs to stop the seizure and identification of etiology. It results from an inability to normally abort an isolated seizure either due to ineffective inhibition, or due to abnormally persistent excessive excitation. Symptomatic SE is more common in younger children and the likely etiology depends on the age of the child. Treating the precipitating cause may prevent ongoing neurologic injury and facilitates seizure control. Benzodiapenes, phenytoin and phenobarbital form the mainstay of treatment. A systematic treatment regimen, planned in advance, is needed, including one for refractory status epilepticus (RSE). Patient education and home management of seizures is important to reduce the morbidity and mortality associated with SE.

Seizures in the context of acute illness

PURPOSE OF REVIEW

Seizures during an acute illness demand immediate evaluation, as they indicate an acute central nervous system insult. There are three goals: identify and treat the precipitating cause; determine the need for antiepileptic drug therapy; and recognize nonconvulsive seizures. Management depends upon whether there is a primary or secondary central nervous system insult. Seizures may persist despite antiepileptic drugs if the precipitating cause is untreated.

RECENT FINDINGS

Seizures and epilepsy and children with neurodevelopmental disabilities comprise a significant percentage of acute care in children. A continuum exists from a single seizure and escalating seizures to status epilepticus. Seizure treatment is more successful when given earlier, and prognosis depends on the cause. Guidelines for the diagnostic evaluation and treatment of status epilepticus have been produced. Continuous electroencephalographic monitoring reveals frequent nonconvulsive seizures and nonconvulsive status epilepticus in the sick child.

SUMMARY

The recognition and rapid treatment of clinical and electrographic seizures is important during acute illness.

Intravenous midazolam in convulsive status epilepticus in children with pharmacoresistant epilepsy

Although the efficacy of midazolam in refractory status epilepticus and as a first-line agent in children with established status epilepticus has been reported, differences in starting doses, continuation method, timing of efficacy assessment, and discontinuation pose limitations in deriving a specific protocol for midazolam use. An audit of clinical experience with a protocol of midazolam as first-line agent for impending status epilepticus (defined as a continuous, generalized, convulsive seizure lasting >5 minutes) in 76 episodes of unprovoked convulsive status epilepticus in children 1-15 years old with treatment-refractory epilepsy demonstrated that: (1) repeated bolus midazolam 0.1mg/kg (every 5 minutes, maximum 5) controlled 91% of events; (2) three bolus doses controlled 89% of the episodes, with minimal chance of response beyond that; (3) treating impending status resulted in lower doses (mean 0.17 mg/kg) than reported and infrequent utilization of additional anticonvulsants (9%); and (4) adverse events were infrequent (respiratory depression 13%, assisted ventilation 3%).

Effect of TTX suppression of hippocampal activity following status epilepticus

Status epilepticus (SE) is a severe neurological condition that can result in brain damage. In animals, SE is associated with cell loss and aberrant synaptogenesis. These pathological processes appear to be activity-dependent and may continue after the SE has ended. We postulated that suppression of electrical activity following SE at the site of the epileptic focus will reduce seizure-induced damage. To achieve this goal, tetrodotoxin (TTX) was used to suppress electrical activity in the hippocampi bilaterally following SE. Adult rats experienced lithium-pilocarpine-induced SE for 2h while controls underwent sham-SE with saline injections. Starting 12h after the SE or sham-SE rats received either continuous TTX (1 microM) or saline infusions through cannulas implanted in the bilateral hippocampi for 5h daily for 4 days. TTX resulted in significant EEG suppression and reduction in spikes and sharp waves. Rats were sacrificed 2 weeks after SE and the brains examined for cell loss and sprouting. Rats receiving TTX following SE had significantly more cell loss as well as a trend toward more mossy fiber sprouting than saline-treated rats following SE. TTX injection in sham-SE rats caused no cell loss or mossy fiber sprouting. These results suggest that suppression of electrical activity following SE is detrimental.

Subunit-specific trafficking of GABA(A) receptors during status epilepticus

It is proposed that a reduced surface expression of GABA(A) receptors (GABARs) contributes to the pathogenesis of status epilepticus (SE), a condition characterized by prolonged seizures. This hypothesis was based on the finding that prolonged epileptiform bursting (repetitive bursts of prolonged depolarizations with superimposed action potentials) in cultures of dissociated hippocampal pyramidal neurons (dissociated cultures) results in the increased intracellular accumulation of GABARs. However, it is not known whether this rapid modification in the surface-expressed GABAR pool results from selective, subunit-dependent or nonselective, subunit-independent internalization of GABARs. In hippocampal slices obtained from animals undergoing prolonged SE (SE-treated slices), we found that the surface expression of the GABAR beta2/3 and gamma2 subunits was reduced, whereas that of the delta subunit was not. Complementary electrophysiological recordings from dentate granule cells in SE-treated slices demonstrated a reduction in GABAR-mediated synaptic inhibition, but not tonic inhibition. A reduction in the surface expression of the gamma2 subunit, but not the delta subunit was also observed in dissociated cultures and organotypic hippocampal slice cultures when incubated in an elevated KCl external medium or an elevated KCl external medium supplemented with NMDA, respectively. Additional studies demonstrated that the reduction in the surface expression of the gamma2 subunit was independent of direct ligand binding of the GABAR. These findings demonstrate that the regulation of surface-expressed GABAR pool during SE is subunit-specific and occurs independent of ligand binding. The differential modulation of the surface expression of GABARs during SE has potential implications for the treatment of this neurological emergency.

Anesthesia for epilepsy surgery in children

BACKGROUND

The perioperative management of infants and children for epilepsy surgery should focus on the specific problems unique to the state of the disease, age of the child, and operative conditions. A basic understanding of age-dependent variables and the interaction of anesthetic and surgical procedures are essential in minimizing perioperative morbidity and mortality. Specific medical conditions that impact the conduct of anesthesia include congenital anomalies, chronic anticonvulsant therapies, and evolving coagulopathies. The neurosurgical procedure and neurophysiological monitoring will determine the type of anesthetic technique to be utilized during surgery.

OBJECTIVE

This review will provide a systematic approach to pediatric patients undergoing epilepsy surgery.

Update on the acute management of status epilepticus in children

PURPOSE OF REVIEW

Status epilepticus is the most common neurologic emergency in children. The understanding of its less recognizable forms, its pharmacologic management, the role of electroencephalography and the long-term morbidity and mortality as a result of status epilepticus are consistently evolving. This review frames the current understanding of several issues as they apply to acute management in the emergency department.

RECENT FINDINGS

Researchers are working to define less recognizable forms of status epilepticus such as nonconvulsive, autonomic and psychogenic. Buccal and intranasal forms of midazolam are emerging as suitable alternatives to rectal diazepam in the initial treatment of status epilepticus. Valproic acid, chloral hydrate and newer-generation antiepileptics are being proposed as safe and effective alternatives to the traditional drugs used to treat status epilepticus. The role of electroencephalography in diagnosis is being elucidated. Risk factors for neurologic sequelae and mortality after status epilepticus remain an area of research with conflicting findings and no real consensus.

SUMMARY

The understanding of different types of status epilepticus, the options for pharmacologic treatment, the tools for diagnosis and the morbidity and mortality of the disease are still evolving. As a result, several areas for further research remain that will help clinicians in their approach to this complex condition.

Status epilepticus: pathophysiology and management in adults

As in Clark and Prout's classic work, we identify three phases of generalised convulsive status epilepticus, which we call impending, established, and subtle. We review physiological and subcellular changes that might play a part in the transition from single seizures to status epilepticus and in the development of time-dependent pharmacoresistance. We review the principles underlying the treatment of status epilepticus and suggest that prehospital treatment is beneficial, that therapeutic drugs should be used in rapid sequence according to a defined protocol, and that refractory status epilepticus should be treated with general anaesthesia. We comment on our preference for drugs with a short elimination half-life and discuss some therapeutic choices.