Effect of temperature on kainic acid-induced seizures

Temperature Control in Acute Brain Injury: An Update

Temperature control in severe acute brain injury (SABI) is a key component of acute management. This manuscript delves into the complex role of temperature management in SABI, encompassing conditions like traumatic brain injury (TBI), acute ischemic stroke (AIS), intracerebral hemorrhage (ICH), aneurysmal subarachnoid hemorrhage (aSAH), and hypoxemic/ischemic brain injury following cardiac arrest. Fever is a common complication in SABI and is linked to worse neurological outcomes due to increased inflammatory responses and intracranial pressure (ICP). Temperature management, particularly hypothermic temperature control (HTC), appears to mitigate these adverse effects primarily by reducing cerebral metabolic demand and dampening inflammatory pathways. However, the effectiveness of HTC varies across different SABI conditions. In the context of post-cardiac arrest, the impact of HTC on neurological outcomes has shown inconsistent results. In cases of TBI, HTC seems promising for reducing ICP, but its influence on long-term outcomes remains uncertain. For AIS, clinical trials have yet to conclusively demonstrate the benefits of HTC, despite encouraging preclinical evidence. This variability in efficacy is also observed in ICH, aSAH, bacterial meningitis, and status epilepticus. In pediatric and neonatal populations, while HTC shows significant benefits in hypoxic-ischemic encephalopathy, its effectiveness in other brain injuries is mixed. Although the theoretical basis for employing temperature control, especially HTC, is strong, the clinical outcomes differ among various SABI subtypes. The current consensus indicates that fever prevention is beneficial across the board, but the application and effectiveness of HTC are more nuanced, underscoring the need for further research to establish optimal temperature management strategies. Here we provide an overview of the clinical evidence surrounding the use of temperature control in various types of SABI.

Isoflurane treatment for refractory and super-refractory status epilepticus in dogs

Introduction

Resistant epileptic episodes, such as refractory status epilepticus (RSE) and super-refractory status epilepticus (SRSE), are neurological emergencies that require immediate medical treatment. Although inhalational anesthetics, such as isoflurane (ISO), have been proposed as a means of seizure control in dogs, there is currently a lack of both experimental and clinical studies on this subject.

Study design

This is a retrospective clinical study.

Methods

Records of dogs that received ISO for the management of RSE and SRSE during their intensive care unit (ICU) hospitalization at the Companion Animal Clinic of the Aristotle University of Thessaloniki were included in the present study. The study period spanned from February 2013 to March 2023. Dogs were identified as responders (R) when RSE/SRSE ceased after ISO administration, and the dogs were successfully discharged from the ICU after ISO discontinuation. Dogs were identified as non-responders (NR) when RSE/SRSE ceased after ISO administration, but RSE/SRSE reoccurred after ISO discontinuation. Additional data about the number and time of ISO cycles, the time of ICU hospitalization, the side effects of ISO administration, and an additional administration of antiepileptic drugs (AEDs) and anesthetic drugs were also recorded.

Results

A total of 20 dogs with 26 recorded RSE/SRSE episodes and 26 anesthetic cycles with ISO were included in the present study. The clinical termination of seizure activity was achieved 100% (26/26) in all episodes. In 73.1% (19/26) of the episodes, ISO administration resulted in successful RSE/SRSE treatment. Poor outcome was recorded in 26.9% (7/26) of the episodes because RSE/SRSE reoccurred after ISO discontinuation, and the dogs were euthanatized or died due to cardiac arrest. Inspiratory ISO ranged between 0.5 and 4.0%. The median time of the anesthetic cycles with ISO was 12.67 h (4.00-62.00). The median duration of the ICU hospitalization was 48.00 h (24.00-120.00). At least one ISO-related side effect was recorded in 23 out of 26 (88.5%) episodes.

Conclusion

To the authors' knowledge, this is the first clinical study that addresses the administration of ISO for RSE/SRSE treatment in dogs. The use of ISO may be beneficial in terminating RSE/SRSE; however, further prospective studies are necessary to confirm this observation.

Targeted temperature management with hypothermia for comatose patients after cardiac arrest

Targeted temperature management with mild hypothermia (TTM-hypothermia; 32-34 °C) is a treatment strategy for adult patients who are comatose after cardiac arrest. Robust preclinical data support the beneficial effects of hypothermia beginning within 4 hours of reperfusion and maintained during the several days of postreperfusion brain dysregulation. TTM-hypothermia increased survival and functional recovery after adult cardiac arrest in several trials and in realworld implementation studies. TTM-hypothermia also benefits neonates with hypoxic-ischemic brain injury. However, larger and methodologically more rigorous adult trials do not detect benefit. Reasons for inconsistency of adult trials include the difficulty delivering differential treatment between randomized groups within 4 hours and the use of shorter durations of treatment. Furthermore, adult trials enrolled populations that vary in illness severity and brain injury, with individual trials enriched for higher or lower illness severity. There are interactions between illness severity and treatment effect. Current data indicate that TTM-hypothermia implemented quickly for adult patients after cardiac arrest, may benefit select patients at risk of severe brain injury but not benefit other patients. More data are needed on how to identify treatment-responsive patients and on how to titrate the timing and duration of TTM-hypothermia.

The outcome of early life status epilepticus—lessons from laboratory animals

Status epilepticus (SE) is the most common neurologic emergency in children. Both clinical and laboratory studies have demonstrated that SE in early life can cause brain damage and permanent behavioral abnormalities, trigger epileptogenesis, and interfere with normal brain development. In experimental rodent models, the consequences of seizures are dependent upon age, the model used, and seizure duration. In studies involving neonatal and infantile animals, the model used, experimental design, conditions during the experiment, and manipulation of animals can significantly affect the course of the experiments as well as the results obtained. Standardization of laboratory approaches, harmonization of scientific methodology, and improvement in data collection can improve the comparability of data among laboratories.

Focal Cooling for Drug-Resistant Epilepsy: A Review

Importance

Epilepsy affects at least 1.2% of the population, with one-third of cases considered to be drug-resistant epilepsy (DRE). For these cases, focal cooling therapy may be a potential avenue for treatment, offering hope to people with DRE for freedom from seizure. The therapy leverages neuroscience and engineering principles to deliver a reversible treatment unhindered by pharmacology.

Observations

Analogous to (but safer than) the use of global cooling in postcardiac arrest and neonatal ischemic injury, extensive research supports the premise that focal cooling as a long-term treatment for epilepsy could be effective. The potential advantages of focal cooling are trifold: stopping epileptiform discharges, seizures, and status epilepticus safely across species (including humans).

Conclusions and Relevance

This Review presents the most current evidence supporting focal cooling in epilepsy. Cooling has been demonstrated as a potentially safe and effective treatment modality for DRE, although it is not yet ready for use in humans outside of randomized clinical trials. The Review will also offer a brief overview of the technical challenges related to focal cooling in humans, including the optimal device design and cooling parameters.

Tetrodotoxin prevents heat-shock induced granule cell dispersion in hippocampal slice cultures

Granule cell dispersion (GCD) has been associated as a pathological feature of temporal lobe epilepsy (TLE). Early-life epileptiform activity such as febrile seizures has been proposed to have a causal link to developing chronic TLE. During postnatal development, the hippocampus may be particularly vulnerable to hyperexcitability-induced insults since neuronal migration and differentiation are still ongoing in the hippocampus. Further, the extracellular matrix (ECM), here in particular the protein reelin, has been implicated in the pathophysiology of GCD. Thus, loss of reelin-expressing cells, Cajal-Retzius cells and subsets of interneurons, may be related to GCD. To study the possible role of febrile seizures, we previously induced GCD in vitro by subjecting hippocampal slice cultures to a transient heat-shock, which was not accompanied by loss of Cajal-Retzius cells. In order to examine the mechanisms involved in heat-shock induced GCD, the present study aimed to determine whether such dispersion could be prevented by blocking cellular electrical activity. Here we show that the extent of heat-shock induced GCD could be significantly reduced by treatment with the sodium channel blocker tetrodotoxin (TTX), suggesting that electrical activity is an important factor involved in heat-shock induced GCD.

Climate change and epilepsy: Insights from clinical and basic science studies

Climate change is with us. As professionals who place value on evidence-based practice, climate change is something we cannot ignore. The current pandemic of the novel coronavirus, SARS-CoV-2, has demonstrated how global crises can arise suddenly and have a significant impact on public health. Global warming, a chronic process punctuated by acute episodes of extreme weather events, is an insidious global health crisis needing at least as much attention. Many neurological diseases are complex chronic conditions influenced at many levels by changes in the environment. This review aimed to collate and evaluate reports from clinical and basic science about the relationship between climate change and epilepsy. The keywords climate change, seasonal variation, temperature, humidity, thermoregulation, biorhythm, gene, circadian rhythm, heat, and weather were used to search the published evidence. A number of climatic variables are associated with increased seizure frequency in people with epilepsy. Climate change-induced increase in seizure precipitants such as fevers, stress, and sleep deprivation (e.g. as a result of more frequent extreme weather events) or vector-borne infections may trigger or exacerbate seizures, lead to deterioration of seizure control, and affect neurological, cerebrovascular, or cardiovascular comorbidities and risk of sudden unexpected death in epilepsy. Risks are likely to be modified by many factors, ranging from individual genetic variation and temperature-dependent channel function, to housing quality and global supply chains. According to the results of the limited number of experimental studies with animal models of seizures or epilepsy, different seizure types appear to have distinct susceptibility to seasonal influences. Increased body temperature, whether in the context of fever or not, has a critical role in seizure threshold and seizure-related brain damage. Links between climate change and epilepsy are likely to be multifactorial, complex, and often indirect, which makes predictions difficult. We need more data on possible climate-driven altered risks for seizures, epilepsy, and epileptogenesis, to identify underlying mechanisms at systems, cellular, and molecular levels for better understanding of the impact of climate change on epilepsy. Further focussed data would help us to develop evidence for mitigation methods to do more to protect people with epilepsy from the effects of climate change.

Recent antiepileptic and neuroprotective applications of brain cooling

Hypothermia is a widely used clinical practice for neuroprotection and is a well-established method to mitigate the adverse effects of some clinical conditions such as reperfusion injury after cardiac arrest and hypoxic ischemic encephalopathy in newborns. The discovery, that lowering the core temperature has a therapeutic potential dates back to the early 20th century, but the underlying mechanisms are actively researched, even today. Especially, in the area of neural disorders such as epilepsy and traumatic brain injury, cooling has promising prospects. It is well documented in animal models, that the application of focal brain cooling can effectively terminate epileptic discharges. There is, however, limited data regarding human clinical trials. In this review article, we will discuss the main aspects of therapeutic hypothermia focusing on its use in treating epilepsy. The various experimental approaches and device concepts for focal brain cooling are presented and their potential for controlling and suppressing seizure activity are compared.

Hypothermia as an adjuvant treatment in paediatric refractory or super-refractory status epilepticus

Therapeutic hypothermia is among the adjuvant therapies suggested for refractory or super-refractory status epilepticus (R/SR-SE) in paediatric patients. Experimental evidence of neuroprotective and antiseizure effects provides a strong rationale for using therapeutic hypothermia in patients with status epilepticus. Thus, hypothermia between 20°C and 33°C in animals with status epilepticus is associated not only with significantly less neuronal damage, predominantly in the hippocampal CA1, CA2, and CA3 areas, but also with increased seizure latency and decreased seizure frequency and duration. Therapeutic hypothermia has rarely been used in paediatric R/SR-SE. In the few reported cases, seizure control was markedly improved but nearly half the patients experienced recurrences after rewarming. Studies are needed to clarify the modalities and indications of therapeutic hypothermia in paediatric patients with R/SR-SE. WHAT THIS PAPER ADDS: Hypothermia at 20°C to 33°C is neuroprotective and has antiseizure effects in experimental status epilepticus. In children, antiseizure effects are marked but recurrences after rewarming are common.

The Role of Secondary Brain Insults in Status Epilepticus: A Systematic Review

(1) Background: Little is known about the impact of pathophysiological mechanisms that underlie the enhancement of excitotoxicity and the neuronal consequences of status epilepticus (SE), as well as the clinical consequences of secondary brain insults (SBI) in patients with SE on outcome; (2) Methods: Electronic searches were conducted in May 2020 using Medline via PubMed, Embase, and Google Scholar (#CRD42019139092). Experimental studies of animals or randomized, observational, controlled trials of patients with SE in indexed journals were included. There were no language or date restrictions for the published literature included in this review. Information was extracted on study design, sample size, SBI characteristics, and primary and secondary outcomes, including the timing of evaluation; (3) Results: Among the 2209 articles responding to our inclusion criteria, 56 were included in this systematic review. There are numerous experimental data reporting the deleterious effects associated with each of the SBI in animals exposed to SE. In humans, only the effect of target temperature management in hypothermia (32-34 °C) has been explored. (4) Conclusions: There is little experimental evidence that favors the control of secondary brain insult after SE. Further studies are required to assess the neuroprotective interest of secondary brain insult control after SE in humans.

Recommandations Formalisées d’Experts SRLF/SFMU : Prise en charge des états de mal épileptiques en préhospitalier, en structure d’urgence et en réanimation dans les 48 premières heures (A l’exclusion du nouveau-né et du nourrisson)

La Société de réanimation de langue française et la Société française de médecine d’urgence ont décidé d’élaborer de nouvelles recommandations sur la prise en charge de l’état mal épileptique (EME) avec l’ambition de répondre le plus possible aux nombreuses questions pratiques que soulèvent les EME : diagnostic, enquête étiologique, traitement non spécifique et spécifique. Vingt-cinq experts ont analysé la littérature scientifique et formulé des recommandations selon la méthodologie GRADE. Les experts se sont accordés sur 96 recommandations. Les recommandations avec le niveau de preuve le plus fort ne concernent que l’EME tonico-clonique généralisé (EMTCG) : l’usage des benzodiazépines en première ligne (clonazépam en intraveineux direct ou midazolam en intramusculaire) est recommandé, répété 5 min après la première injection (à l’exception du midazolam) en cas de persistance clinique. En cas de persistance 5 min après cette seconde injection, il est proposé d’administrer la seconde ligne thérapeutique : valproate de sodium, (fos-)phénytoïne, phénobarbital ou lévétiracétam. La persistance avérée de convulsions 30 min après le début de l’administration du traitement de deuxième ligne signe l’EMETCG réfractaire. Il est alors proposé de recourir à un coma thérapeutique au moyen d’un agent anesthésique intraveineux de type midazolam ou propofol. Des recommandations spécifiques à l’enfant et aux autres EME sont aussi énoncées.

Secondary hypothermia in patients with super-refractory status epilepticus managed with propofol and ketamine

BACKGROUND

Therapeutic hypothermia as a potent nonpharmacologic antiseizure therapy has been investigated experimentally in animal models and humans. Although induced hypothermia has been shown to be neuroprotective in acute convulsive status epilepticus, whether its use will translate into improved outcomes for patients with super-refractory nonconvulsive status epilepticus (SRNCSE) has been debated. No clinical data are available on the occurrence and prognostic impact of secondary hypothermia (s-HT) in patients with SRNCSE. With the possibility of core to periphery redistribution of heat with propofol and a centrally mediated dose-dependent fall in body temperature with ketamine, we aimed to investigate the incidence of s-HT events in patients with SRNCSE managed with propofol and ketamine and their impact on clinical outcomes.

METHODS

We performed a retrospective observational analysis of consecutive patients with SRNCSE managed with propofol and/or ketamine in a single-center neurological intensive care unit between December 1, 2012 and December 31, 2015. Patients were divided according to the occurrence of hypothermia (temperature < 35.0 °C) into an s-HT group and a nonhypothermia (n-HT) group. Patients who received targeted temperature management therapy were excluded. We compared the demographics, comorbidities, treatment characteristics, and outcomes between groups.

RESULTS

Ninety-nine consecutive patients with SRNCSE managed with propofol and/or ketamine were identified during the study period. Twenty patients who received targeted temperature management were excluded, leaving a total of 79 patients for analysis. Hypothermia was observed in 52% (41/79) of the study population. Ketamine was used in 63/79 patients (80%). Ketamine infusion rates were higher and of longer duration among patients who developed s-HT compared with those who did not (mean dosage: 57.35 ± 26.6 mcg/kg/min vs 37.17 ± 15 mcg/kg/min, P = 0.001; duration: 116.36 ± 81.9 h vs 88 ± 89.7 h, P = 0.048). Propofol was used in 78/79 patients (99%), with no significant differences in characteristics between groups (mean dosage: 46.44 ± 20.2 mcg/kg/min vs 36.9 ± 12.9 mcg/kg/min, P = 0.058; duration: 125.43 ± 96.4 h vs 102.3 ± 87.1 h, P = 0.215). No significant differences in demographics, comorbidities, status epilepticus duration and resolution rates, and outcomes were observed between groups.

CONCLUSION

In this single-center retrospective analysis of patients whose SRNCSE is being treated, higher doses and longer durations of ketamine were associated with the occurrence of s-HT. Further investigation is warranted to clarify the thermogenic effects of ketamine and its effect on status epilepticus outcomes.

Hypothermia as a treatment in status epilepticus: A narrative review

Status epilepticus (SE) is associated with high mortality and morbidity rates, notably in its refractory and super-refractory forms. This narrative review discusses recent data on the potential benefits of targeted temperature management. In studies of patients with cerebral injury due to various factors, therapeutic hypothermia had variable effects on survival and functional outcomes. Sources of this variability may include the underlying etiology, whether hypothermia was used for prophylaxis or treatment, the degree and duration of hypothermia, and the hypothermia application modalities. Data from animal studies strongly suggest benefits from therapeutic hypothermia in SE. In humans, beneficial effects have been described in anecdotal case reports and small case series, but the level of evidence is low. A randomized controlled trial found no evidence that moderate hypothermia (32-34 °C) was neuroprotective in critically ill patients with convulsive SE. Nevertheless, some promising effects were noted, suggesting that therapeutic hypothermia might have a role as an adjuvant to anticonvulsant drug therapy in patients with refractory or super-refractory SE. This article is part of a Special Issue entitled "Status Epilepticus". This article is part of the Special Issue "Proceedings of the 7th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures".

Pharmacotherapy for Refractory and Super-Refractory Status Epilepticus in Adults

Patients with prolonged seizures that do not respond to intravenous benzodiazepines and a second-line anticonvulsant suffer from refractory status epilepticus and those with seizures that do not respond to continuous intravenous anesthetic anticonvulsants suffer from super-refractory status epilepticus. Both conditions are associated with significant morbidity and mortality. A strict pharmacological treatment regimen is urgently required, but the level of evidence for the available drugs is very low. Refractory complex focal status epilepticus generally does not require anesthetics, but all intravenous non-anesthetizing anticonvulsants may be used. Most descriptive data are available for levetiracetam, phenytoin and valproate. Refractory generalized convulsive status epilepticus is a life-threatening emergency, and long-term clinical consequences are eminent. Administration of intravenous anesthetics is mandatory, and drugs acting at the inhibitory gamma-aminobutyric acid (GABA)_A receptor such as midazolam, propofol and thiopental/pentobarbital are recommended without preference for one of those. One in five patients with anesthetic treatment does not respond and has super-refractory status epilepticus. With sustained seizure activity, excitatory N-methyl-d-aspartate (NMDA) receptors are increasingly expressed post-synaptically. Ketamine is an antagonist at this receptor and may prove efficient in some patients at later stages. Neurosteroids such as allopregnanolone increase sensitivity at GABA_A receptors; a Phase 1/2 trial demonstrated safety and tolerability, but randomized controlled data failed to demonstrate efficacy. Adjunct ketogenic diet may contribute to termination of difficult-to-treat status epilepticus. Randomized controlled trials are needed to increase evidence for treatment of refractory and super-refractory status epilepticus, but there are multiple obstacles for realization. Hitherto, prospective multicenter registries for pharmacological treatment may help to improve our knowledge.

Thermoregulation in epilepsy

Several aspects of thermoregulation play a role in epilepsy. Circuitries involved in thermoregulation are affected by seizures and epilepsy, hyperthermia may be both cause and result of seizures, and hypothermia may prevent or abort seizures. Autonomic manifestations of seizures including thermoregulatory disturbances are common in a variety of clinical epilepsy syndromes. Experimental hyperthermia has been studied extensively, predominantly to investigate febrile seizures of childhood. In particular prolonged or complex febrile seizures have been associated with the later development of epilepsy in adulthood and the pathophysiology of how febrile seizures cause epilepsy is of tremendous interest. Febrile seizures represent an opportunity to potentially intervene early in life in susceptible individuals and affect epileptogenesis. The pathophysiologic underpinnings of how hyperthermia induces seizures and how this in turn results in epilepsy are controversial, but likely involve multiple factors. Both glutamatergic and GABAergic neurotransmission is affected, and numerous mutations in genes encoding ion channels have been identified. Cytokines such as interleukin-1β have been implicated in febrile seizures as well as susceptibility to provoked seizures later in life. Hyperthermia is a common feature of generalized convulsive status epilepticus, but may also be seen with nonconvulsive seizures, indicating involvement of thermoregulatory centers.

Biosynthesis and biotechnological application of non-canonical amino acids: Complex and unclear

Compared with the better-studied canonical amino acids, the distribution, metabolism and functions of natural non-canonical amino acids remain relatively obscure. Natural non-canonical amino acids have been mainly discovered in plants as secondary metabolites that perform diversified physiological functions. Due to their specific characteristics, a broader range of natural and artificial non-canonical amino acids have recently been applied in the development of functional materials and pharmaceutical products. With the rapid development of advanced methods in biotechnology, non-canonical amino acids can be incorporated into peptides, proteins and enzymes to improve the function and performance relative to their natural counterparts. Therefore, biotechnological application of non-canonical amino acids in artificial bio-macromolecules follows the central goal of synthetic biology to: create novel life forms and functions. However, many of the non-canonical amino acids are synthesized via chemo- or semi-synthetic methods, and few non-canonical amino acids can be synthesized using natural in vivo pathways. Therefore, further research is needed to clarify the metabolic pathways and key enzymes of the non-canonical amino acids. This will lead to the discovery of more candidate non-canonical amino acids, especially for those that are derived from microorganisms and are naturally bio-compatible with chassis strains for in vivo biosynthesis. In this review, we summarize representative natural and artificial non-canonical amino acids, their known information regarding associated metabolic pathways, their characteristics and their practical applications. Moreover, this review summarizes current barriers in developing in vivo pathways for the synthesis of non-canonical amino acids, as well as other considerations, future trends and potential applications of non-canonical amino acids in advanced biotechnology.

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.

Targeted temperature management in the ICU: Guidelines from a French expert panel

Over the recent period, the use of induced hypothermia has gained an increasing interest for critically ill patients, in particular in brain-injured patients. The term "targeted temperature management" (TTM) has now emerged as the most appropriate when referring to interventions used to reach and maintain a specific level temperature for each individual. TTM may be used to prevent fever, to maintain normothermia, or to lower core temperature. This treatment is widely used in intensive care units, mostly as a primary neuroprotective method. Indications are, however, associated with variable levels of evidence based on inhomogeneous or even contradictory literature. Our aim was to conduct a systematic analysis of the published data in order to provide guidelines. We present herein recommendations for the use of TTM in adult and paediatric critically ill patients developed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) method. These guidelines were conducted by a group of experts from the French Intensive Care Society (Société de réanimation de langue française [SRLF]) and the French Society of Anesthesia and Intensive Care Medicine (Société francaise d'anesthésie réanimation [SFAR]) with the participation of the French Emergency Medicine Association (Société française de médecine d'urgence [SFMU]), the French Group for Pediatric Intensive Care and Emergencies (Groupe francophone de réanimation et urgences pédiatriques [GFRUP]), the French National Association of Neuro-Anesthesiology and Critical Care (Association nationale de neuro-anesthésie réanimation française [ANARLF]), and the French Neurovascular Society (Société française neurovasculaire [SFNV]). Fifteen experts and two coordinators agreed to consider questions concerning TTM and its practical implementation in five clinical situations: cardiac arrest, traumatic brain injury, stroke, other brain injuries, and shock. This resulted in 30 recommendations: 3 recommendations were strong (Grade 1), 13 were weak (Grade 2), and 14 were experts' opinions. After two rounds of rating and various amendments, a strong agreement from voting participants was obtained for all 30 (100%) recommendations, which are exposed in the present article.

Targeted temperature management in the ICU: guidelines from a French expert panel

Over the recent period, the use of induced hypothermia has gained an increasing interest for critically ill patients, in particular in brain-injured patients. The term “targeted temperature management” (TTM) has now emerged as the most appropriate when referring to interventions used to reach and maintain a specific level temperature for each individual. TTM may be used to prevent fever, to maintain normothermia, or to lower core temperature. This treatment is widely used in intensive care units, mostly as a primary neuroprotective method. Indications are, however, associated with variable levels of evidence based on inhomogeneous or even contradictory literature. Our aim was to conduct a systematic analysis of the published data in order to provide guidelines. We present herein recommendations for the use of TTM in adult and paediatric critically ill patients developed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) method. These guidelines were conducted by a group of experts from the French Intensive Care Society (Société de Réanimation de Langue Française [SRLF]) and the French Society of Anesthesia and Intensive Care Medicine (Société Francaise d’Anesthésie Réanimation [SFAR]) with the participation of the French Emergency Medicine Association (Société Française de Médecine d’Urgence [SFMU]), the French Group for Pediatric Intensive Care and Emergencies (Groupe Francophone de Réanimation et Urgences Pédiatriques [GFRUP]), the French National Association of Neuro-Anesthesiology and Critical Care (Association Nationale de Neuro-Anesthésie Réanimation Française [ANARLF]), and the French Neurovascular Society (Société Française Neurovasculaire [SFNV]). Fifteen experts and two coordinators agreed to consider questions concerning TTM and its practical implementation in five clinical situations: cardiac arrest, traumatic brain injury, stroke, other brain injuries, and shock. This resulted in 30 recommendations: 3 recommendations were strong (Grade 1), 13 were weak (Grade 2), and 14 were experts’ opinions. After two rounds of rating and various amendments, a strong agreement from voting participants was obtained for all 30 (100%) recommendations, which are exposed in the present article.

Status Epilepticus and Beyond: A Clinical Review of Status Epilepticus and an Update on Current Management Strategies in Super-refractory Status Epilepticus

Status epilepticus and refractory status epilepticus represent some of the most complex conditions encountered in the neurological intensive care unit. Challenges in management are common as treatment options become limited and prolonged hospital courses are accompanied by complications and worsening patient outcomes. Antiepileptic drug treatments have become increasingly complex. Rational polytherapy should consider the pharmacodynamics and kinetics of medications. When seizures cannot be controlled with medical therapy, alternative treatments, including early surgical evaluation can be considered; however, evidence is limited. This review provides a brief overview of status epilepticus, and a recent update on the management of refractory status epilepticus based on evidence from the literature, evidence-based guidelines, and experiences at our institution.

Management of status epilepticus

Status epilepticus is a neurologic and medical emergency manifested by prolonged seizure activity or multiple seizures without return to baseline. It is associated with substantial medical cost, morbidity, and mortality. There is a spectrum of severity dependent on the type of seizure, underlying pathology, comorbidities, and appropriate and timely medical management. This chapter discusses the evolving definitions of status epilepticus and multiple patient and clinical factors which influence outcome. The pathophysiology of status epilepticus is reviewed to provide a better understanding of the mechanisms which contribute to status epilepticus, as well as the potential long-term effects. The clinical presentations of different types of status epilepticus in adults are discussed, with emphasis on the hospital course and management of the most dangerous type, generalized convulsive status epilepticus. Strategies for the evaluation and management of status epilepticus are provided based on available evidence from clinical trials and recommendations from the Neurocritical Care Society and the European Federation of Neurological Societies.

Hypothermia for Neuroprotection in Convulsive Status Epilepticus

BACKGROUND

Convulsive status epilepticus often results in permanent neurologic impairment. We evaluated the effect of induced hypothermia on neurologic outcomes in patients with convulsive status epilepticus.

METHODS

In a multicenter trial, we randomly assigned 270 critically ill patients with convulsive status epilepticus who were receiving mechanical ventilation to hypothermia (32 to 34°C for 24 hours) in addition to standard care or to standard care alone; 268 patients were included in the analysis. The primary outcome was a good functional outcome at 90 days, defined as a Glasgow Outcome Scale (GOS) score of 5 (range, 1 to 5, with 1 representing death and 5 representing no or minimal neurologic deficit). The main secondary outcomes were mortality at 90 days, progression to electroencephalographically (EEG) confirmed status epilepticus, refractory status epilepticus on day 1, "super-refractory" status epilepticus (resistant to general anesthesia), and functional sequelae on day 90.

RESULTS

A GOS score of 5 occurred in 67 of 138 patients (49%) in the hypothermia group and in 56 of 130 (43%) in the control group (adjusted common odds ratio, 1.22; 95% confidence interval [CI], 0.75 to 1.99; P=0.43). The rate of progression to EEG-confirmed status epilepticus on the first day was lower in the hypothermia group than in the control group (11% vs. 22%; odds ratio, 0.40; 95% CI, 0.20 to 0.79; P=0.009), but there were no significant differences between groups in the other secondary outcomes. Adverse events were more frequent in the hypothermia group than in the control group.

CONCLUSIONS

In this trial, induced hypothermia added to standard care was not associated with significantly better 90-day outcomes than standard care alone in patients with convulsive status epilepticus. (Funded by the French Ministry of Health; HYBERNATUS ClinicalTrials.gov number, NCT01359332 .).

Neuroprotective effect of therapeutic hypothermia versus standard care alone after convulsive status epilepticus: protocol of the multicentre randomised controlled trial HYBERNATUS

Convulsive status epilepticus (CSE) is a major medical emergency associated with a 50 % morbidity rate. CSE guidelines have recommended prompt management for many years, but there is no evidence to date that they have significantly improved practices or outcomes. Developing neuroprotective strategies for use after CSE holds promise for diminishing morbidity and mortality rates. Hypothermia has been shown to afford neuroprotection in various health conditions. We therefore designed a trial to determine whether 90-day outcomes in mechanically ventilated patients with CSE requiring management in the intensive care unit (ICU) are improved by early therapeutic hypothermia (32-34 °C) for 24 h with propofol sedation. We are conducting a multicentre, open-label, parallel-group, randomised, controlled trial (HYBERNATUS) of potential neuroprotective effects of therapeutic hypothermia and routine propofol sedation started within 8 h after CSE onset in ICU patients requiring mechanical ventilation. Included patients are allocated to receive therapeutic hypothermia (32-34 °C) plus standard care or standard care alone. We plan to enrol 270 patients in 11 ICUs. An interim analysis is scheduled after the inclusion of 135 patients. The main study objective is to evaluate the effectiveness of therapeutic hypothermia (32-34 °C) for 24 h in diminishing 90-day morbidity and mortality (defined as a Glasgow Outcome Scale score <5). The HYBERNATUS trial is expected to a decreased proportion of patients with a Glasgow Outcome Scale score lower than 5 after CSE requiring ICU admission and mechanical ventilation. Trial registration Clinicaltrials.gov identifier NCT01359332 (registered on 23 May 2011).

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.

Neuroprotective effects of deep hypothermia in refractory status epilepticus

Objective

Pharmacoresistance develops quickly during repetitive seizures, and refractory status epilepticus (RSE) remains a therapeutic challenge. The outcome of RSE is poor, with high mortality and morbidity. New treatments are needed. Deep hypothermia (20°C) is used clinically during reconstructive cardiac surgery and neurosurgery, and has proved safe and effective in those indications. We tested the hypothesis that deep hypothermia reduces RSE and its long‐term consequences.

Methods

We used a model of SE induced by lithium and pilocarpine and refractory to midazolam. Several EEG measures were recorded in both hypothermic (n = 17) and normothermic (n = 20) animals. Neuronal injury (by Fluoro‐Jade B), cell‐mediated inflammation, and breakdown of the blood–brain barrier (BBB) (by immunohistochemistry) were studied 48 h following SE onset.

Results

Normothermic rats in RSE seized for 4.1 ± 1.1 h, and at 48 h they displayed extensive neuronal injury in many brain regions, including hippocampus, dentate gyrus, amygdala, entorhinal and pyriform cortices, thalamus, caudate/putamen, and the frontoparietal neocortex. Deep hypothermia (20°C) of 30 min duration terminated RSE within 12 min of initiation of hypothermia, reduced EEG power and seizure activity upon rewarming, and eliminated SE‐induced neuronal injury in most animals. Normothermic rats showed widespread breakdown of the BBB, and extensive macrophage infiltration in areas of neuronal injury, which were completely absent in animals treated with hypothermia.

Interpretation

These results suggest that deep hypothermia may open a new therapeutic avenue for the treatment of RSE and for the prevention of its long‐term consequences.

Hyperthermia aggravates status epilepticus-induced epileptogenesis and neuronal loss in immature rats

This study tightly controlled seizure duration and severity during status epilepticus (SE) in postnatal day 10 (P10) rats, in order to isolate hyperthermia as the main variable and to study its consequences. Body temperature was maintained at 39 ± 1 °C in hyperthermic SE rats (HT+SE) or at 35 ± 1 °C in normothermic SE animals (NT+SE) during 30 min of SE, which was induced by lithium-pilocarpine (3 mEq/kg, 60 mg/kg) and terminated by diazepam and cooling to NT. All video/EEG measures of SE severity were similar between HT+SE and NT+SE pups. At 24h, neuronal injury was present in the amygdala in the HT+SE group only, and was far more severe in the hippocampus in HT+SE than NT+SE pups. Separate groups of animals were monitored four months later for spontaneous recurrent seizures (SRS). Only HT+SE animals developed convulsive SRS. Both HT+SE and NT+SE animals developed electrographic SRS (83% vs. 55%), but SRS frequency and severity were higher in hyperthermic animals (12.5 ± 3.5 vs. 4.2 ± 2.0 SRS/day). The density of hilar neurons was lower, thickness of the amygdala and perirhinal cortex was reduced, and lateral ventricles were enlarged in HT+SE over NT+SE littermates and HT/NT controls. In this model, hyperthermia greatly increased the epileptogenicity of SE and its neuropathological sequelae.

Deep hypothermia for the treatment of refractory status epilepticus

In a rat model of status epilepticus (SE) induced by lithium and pilocarpine and refractory to midazolam, deep hypothermia (20 °C for 30 min) reduced EEG power over 50-fold, stopped SE within 12 min, and reduced EEG spikes by 87%. Hypothermia deserves further investigation as a treatment of last resort for refractory SE. This article is part of a Special Issue entitled "Status Epilepticus".

Therapeutic hypothermia for status epilepticus: A report, historical perspective, and review

Refractory status epilepticus is a disease associated with high morbidity and mortality, which does not always respond to standard treatments, and when they fail, alternative modalities become crucial. Therapeutic hypothermia slows nerve conduction in vitro, and has been shown to abort seizures in animal models. Therapeutic hypothermia has been experimentally used in humans since 1963 for a variety of intracranial pathologies. More recently there have been multiple reports demonstrating the effectiveness of therapeutic hypothermia in treating refractory status epilepticus. We report a case of super-refractory status epilepticus successfully treated with therapeutic hypothermia, complimented by a historical and literature review of this modality. While there is limited evidence, and some risks associated with therapeutic hypothermia, it should be considered as a reasonable and potentially effective treatment option for refractory status epilepticus.

Therapeutic hypothermia for refractory status epilepticus in a child with malignant migrating partial seizures of infancy and SCN1A mutation: a case report

Status epilepticus (SE) is a common indication for neurocritical care and can be refractory to standard measures. Refractory SE (RSE) is associated with high morbidity and mortality. Unconventional therapies may be utilized in certain cases, including therapeutic hypothermia (TH), bumetanide, and the ketogenic diet. However, the literature describing the use of such therapies in RSE is limited. Details of a case of TH for RSE in an infant with malignant migrating partial seizures of infancy were obtained from the medical record. A 4-month-old child developed SE that was refractory to treatment with concurrent midazolam, phenobarbital, fosphenytoin, topiramate, levetiracetam, folinic acid, and pyridoxal-5-phosphate. This led to progressive implementation of three unconventional therapies: TH, bumetanide, and the ketogentic diet. Electrographic seizures ceased for the entirety of a 43-hour period of TH with a target rectal temperature of 33.0°C–34.0°C. No adverse effects of hypothermia were noted other than a single episode of asymptomatic hypokalemia. Seizures recurred 10 hours after rewarming was begun and did not abate with reinstitution of hypothermia. No effect was seen with administration of bumetanide. Seizures were controlled long-term within 48 hours of institution of the ketogenic diet. TH and the ketogenic diet may be effective for treating RSE in children.

Therapeutic brain hypothermia, its mechanisms of action, and its prospects as a treatment for epilepsy

Cooling the core body temperature to 32-35°C, is almost standard practice for conditions such as cardiac arrest in adults, and perinatal hypoxic ischemic encephalopathy in neonates. Limited clinical data, and more extensive animal experiments, indicate that hypothermia could help control seizures, and could be applied directly to the brain using implantable devices. These data have fostered further research to evaluate whether cooling would be a viable means to treat refractory epilepsy. Although the effect of temperature on cellular physiology has long been recognized, with possibly dual effects on pyramidal cells and interneurons, the exact mechanisms underlying its beneficial effects, in particular in epilepsy, are yet to be discovered. This article reviews currently available clinical and laboratory data with a focus on cellular mechanisms of action and prospects of hypothermia as a treatment for intractable seizures.

Use of hypothermia in the intensive care unit

Used for over 3600 years, hypothermia, or targeted temperature management (TTM), remains an ill defined medical therapy. Currently, the strongest evidence for TTM in adults are for out-of-hospital ventricular tachycardia/ventricular fibrillation cardiac arrest, intracerebral pressure control, and normothermia in the neurocritical care population. Even in these disease processes, a number of questions exist. Data on disease specific therapeutic markers, therapeutic depth and duration, and prognostication are limited. Despite ample experimental data, clinical evidence for stroke, refractory status epilepticus, hepatic encephalopathy, and intensive care unit is only at the safety and proof-of-concept stage. This review explores the deleterious nature of fever, the theoretical role of TTM in the critically ill, and summarizes the clinical evidence for TTM in adults.

Status epilepticus: a review, with emphasis on refractory cases

Status epilepticus is among the most dramatic of clinical presentations encountered by emergency room physicians, neurologists, neurosurgeons and intensivists. While progress in its management has been aided significantly with an increasing number of effective treatment options, improved diagnostic methods and more effective monitoring, poor outcomes and diagnostic failures are still frequently encountered. Refractory cases still carry significant morbidity and mortality rates, including poor cognitive outcomes. This review discusses basic pathophysiology and management of status epilepticus, neuroimaging findings, the role of continuous electroencephalogram monitoring and nonconvulsive status epilepticusas well as recent developments in treatment options for refractory cases.

Deep hypothermia terminates status epilepticus--an experimental study

In search for novel treatment approaches in status epilepticus, the anticonvulsant effect of moderate and deep hypothermia was assessed in a rodent model. Self-sustaining status epilepticus (SSSE) characterized by spontaneous high-amplitude discharges recorded from the dentate gyrus was induced in male adult rats by electrical stimulation of the perforant path. After the end of stimulation, rats underwent cooling to 30 °C (n=7) and 20 °C (n=10) for 120 min and rewarming to 37 °C for another 60 min. Control SSSE animals (n=6) remained untreated for 180 min. Frequency of epileptiform discharges was assessed every 10 min. At the target temperature of 20 °C, SSSE was completely suppressed in four rats, this effect was not observed in any animal of the other two groups (p=0.043). On rewarming, seizure activity did not reoccur. Discharge frequency was significantly lower in the 20 °C group at most time points after 60 min of cooling. Following deep hypothermia, eight animals were rewarmed, all survived and moved spontaneously at 37 °C. These experimental data indicate the strong and enduring anticonvulsant and obviously safe properties of cooling down to 20 °C. Patients with status epilepticus refractory to first- and second-line anticonvulsants may benefit from deep cooling as an effective non-pharmacological adjunct to anesthetic anticonvulsants.

Early EEG monitoring for detecting postanoxic status epilepticus during therapeutic hypothermia: a pilot study

OBJECTIVE

To determine whether routine electroencephalography (EEG) detected electrical status epilepticus (ESE), masked by neuromuscular blockade, in comatose cardiac-arrest survivors receiving therapeutic hypothermia.

DESIGN

Prospective 3-year study.

SETTING

Medical ICU.

PATIENTS

Fifty-one consecutive comatose cardiac-arrest patients treated between May 2005 and May 2008 using a standardized protocol of hypothermia with neuromuscular blockade.

INTERVENTION

EEG was performed routinely as soon as possible after starting therapeutic hypothermia. EEG recordings were read by an independent neurophysiologist who was blinded to patient data.

MEASUREMENTS AND MAIN RESULTS

Median body temperature at EEG recording was 33.0°C (range 32.4-33.8). ESE was found on 5 (10%) of the 51 EEG recordings: three patients had continuous rhythmic generalized spikes and two patients had continuous rhythmic focal spike-waves. Of the 17 (33%) patients who were discharged alive, 8 (8/51, 16%) had a CPC score of 1, 4 (8%) of 2, and 5 (10%) of 3. All patients with ESE died during their ICU stay.

CONCLUSION

These preliminary results indicate that postanoxic status epilepticus can be masked by neuromuscular blockade during our protocol of therapeutic hypothermia. Routine EEG monitoring might be helpful in cardiac-arrest survivors receiving therapeutic hypothermia. Further studies including continuous EEG monitoring are needed to determine whether early diagnosis and treatment of ESE during therapeutic hypothermia improves the outcome.

Temperature management in acute neurologic injury: to cool or not to cool

Therapeutic hypothermia is becoming an important intervention following acute neurologic injury despite inconclusive results concerning efficacy. This enthusiasm primarily stems from a lack of other effective interventions in this population. With the increase in the use of therapeutic hypothermia, several practical issues must be considered when initiating this intervention. Clinical pharmacists can play an important role in anticipating and addressing some complications such as shivering, slow drug metabolism, and infection. This review will discuss the available literature concerning the efficacy of therapeutic hypothermia in various neurologic injuries, as well as the most common adverse events associated with it.

Video-EEG monitoring in newborns with hypoxic-ischemic encephalopathy treated with hypothermia

BACKGROUND

Therapeutic hypothermia (TH) is becoming standard of care in newborns with hypoxic-ischemic encephalopathy (HIE). The prognostic value of the EEG and the incidence of seizures during TH are uncertain.

OBJECTIVE

To describe evolution of EEG background and incidence of seizures during TH, and to identify EEG patterns predictive for MRI brain injury.

METHODS

A total of 41 newborns with HIE underwent TH. Continuous video-EEG was performed during hypothermia and rewarming. EEG background and seizures were reported in a standardized manner. Newborns underwent MRI after rewarming. Sensitivity and specificity of EEG background for moderate to severe MRI brain injury was assessed at 6-hour intervals during TH and rewarming.

RESULTS

EEG background improved in 49%, remained the same in 38%, and worsened in 13%. A normal EEG had a specificity of 100% upon initiation of monitoring and 93% at later time points. Burst suppression and extremely low voltage patterns held the greatest prognostic value only after 24 hours of monitoring, with a specificity of 81% at the beginning of cooling and 100% at later time points. A discontinuous pattern was not associated with adverse outcome in most patients (73%). Electrographic seizures occurred in 34% (14/41), and 10% (4/41) developed status epilepticus. Seizures had a clinical correlate in 57% (8/14) and were subclinical in 43% (6/14).

CONCLUSIONS

Continuous video-EEG monitoring in newborns with HIE undergoing TH provides prognostic information about early MRI outcome and accurately identifies electrographic seizures, nearly half of which are subclinical.

Treatment of refractory convulsive status epilepticus in children: other therapies

Refractory convulsive status epilepticus occurs when seizures are not controlled with initial benzodiazepine therapy or a subsequent anticonvulsant drug. Typically drug-induced anesthesia is then pursued with midazolam or a barbiturate. This results in prolonged, intensive care, which requires meticulous attention to medical management to minimize complications. When seizures persist other options must be considered. These include (1) other medications, (2) surgery, (3) the ketogenic diet, (4) hypothermia, (5) inhalational anesthetic agents, and (6) immune modulating therapy. This review addresses the literature related to the use of the latter (4) treatment options. I will discuss the role of each treatment and review the evidence for it's use, along with possible side-effects.

Central nervous system activity of the proanthocyanidin-rich fraction obtained from Croton celtidifolius in rats

Objectives

The aim of the present study was to evaluate the possible neurobehavioural effects in rats of the proanthocyanidin-rich fraction (PRF) isolated from the bark of Croton celtidifolius (Euphorbiaceae).

Methods

Adult Wistar rats were treated with the PRF (0.3–30 mg/kg) and evaluated in different behavioural paradigms classically used for the screening of drugs with psychoactive effects.

Key findings

Acute intraperitoneal (i.p.) administration of PRF decreased spontaneous locomotor activity (open field arena and activity cage), enhanced the duration of ethyl ether-induced hypnosis, increased the latency to the first convulsion induced by pentylenetetrazole (60 mg/kg, i.p.) and attenuated apomorphine-induced (0.5 mg/kg, i.p.) stereotyped behaviour. In lower doses, PRF (0.3 or 3 mg/kg, i.p.) increased the frequency of open arm entries in the elevated plus-maze test.

Conclusions

The present findings suggest that the systemic administration of PRF induces a wide spectrum of behavioural alterations in rats, consistent with the putative existence of hypnosedative, anticonvulsant and anxiolytic compounds.

Prevention of hypoglycemia-induced neuronal death by hypothermia

Hypothermia reduces neuronal damage after cerebral ischemia and traumatic brain injury, while hyperthermia exacerbates damage from these insults. Previously we have shown that temperature-dependent modulation of excitotoxic neuronal death is mediated in part by temperature-dependent changes in the synaptic release/translocation of Zn(2+). In this study, we hypothesize that brain temperature also affects hypoglycemia-induced neuronal death by modulation of vesicular Zn(2+) release from presynaptic terminals. To test our hypothesis, we used a rat model of insulin-induced hypoglycemia. Here we found that hypoglycemia-induced neuronal injury was significantly affected by brain temperature, that is, hypothermia inhibited while hyperthermia aggravated neuronal death. To investigate the mechanism of temperature-dependent neuronal death after hypoglycemia, we measured zinc release/translocation, reactive oxygen species (ROS) production, and microglia activation. Here we found that hypoglycemia-induced Zn(2+) release/translocation, ROS production, and microglia activation were inhibited by hypothermia but aggravated by hyperthermia. Even when the insult was accompanied by hyperthermic conditions, zinc chelation inhibited ROS production and microglia activation. Zinc chelation during hyperthermia reduced neuronal death, superoxide production, and microglia activation, which was comparable to the protective effects of hypothermia. We conclude that neuronal death after hypoglycemia is temperature-dependent and is mediated by increased Zn(2+) release, superoxide production, and microglia activation.

Mechanisms of action, physiological effects, and complications of hypothermia

BACKGROUND

Mild to moderate hypothermia (32-35 degrees C) is the first treatment with proven efficacy for postischemic neurological injury. In recent years important insights have been gained into the mechanisms underlying hypothermia's protective effects; in addition, physiological and pathophysiological changes associated with cooling have become better understood.

OBJECTIVE

To discuss hypothermia's mechanisms of action, to review (patho)physiological changes associated with cooling, and to discuss potential side effects.

DESIGN

Review article.

INTERVENTIONS

None.

MAIN RESULTS

A myriad of destructive processes unfold in injured tissue following ischemia-reperfusion. These include excitotoxicty, neuroinflammation, apoptosis, free radical production, seizure activity, blood-brain barrier disruption, blood vessel leakage, cerebral thermopooling, and numerous others. The severity of this destructive cascade determines whether injured cells will survive or die. Hypothermia can inhibit or mitigate all of these mechanisms, while stimulating protective systems such as early gene activation. Hypothermia is also effective in mitigating intracranial hypertension and reducing brain edema. Side effects include immunosuppression with increased infection risk, cold diuresis and hypovolemia, electrolyte disorders, insulin resistance, impaired drug clearance, and mild coagulopathy. Targeted interventions are required to effectively manage these side effects. Hypothermia does not decrease myocardial contractility or induce hypotension if hypovolemia is corrected, and preliminary evidence suggests that it can be safely used in patients with cardiac shock. Cardiac output will decrease due to hypothermia-induced bradycardia, but given that metabolic rate also decreases the balance between supply and demand, is usually maintained or improved. In contrast to deep hypothermia (<or=30 degrees C), moderate hypothermia does not induce arrhythmias; indeed, the evidence suggests that arrhythmias can be prevented and/or more easily treated under hypothermic conditions.

CONCLUSIONS

Therapeutic hypothermia is a highly promising treatment, but the potential side effects need to be properly managed particularly if prolonged treatment periods are required. Understanding the underlying mechanisms, awareness of physiological changes associated with cooling, and prevention of potential side effects are all key factors for its effective clinical usage.

ICU management of acute liver failure

Survival of patients presenting with acute liver failure (ALF) has improved because of earlier disease recognition, better understanding of pathophysiology of various insults leading to ALF, and advances in supportive measures including a team approach, better ICU care, and liver transplantation. This article focuses on patient management and evaluation that takes place in the ICU for patients who have acute liver injury. An organized team approach to decision making about critical care delivered during this period of time is important for achieving a good patient outcome.

Systemic cooling to treat status epilepticus: an old idea becomes a hot topic

Hypothermia for Refractory Status Epilepticus. Corry JJ, Dhar R, Murphy T, Diringer MN. Neurocrit Care 2008;9(2): 189–197. INTRODUCTION: Status epilepticus (SE) can be refractory to conventional anticonvulsants, requiring anesthetic doses of medications to suppress seizures. This approach carries significant morbidity, is associated with a high fatality rate, and may not always control SE. Hypothermia has been shown to suppress epileptiform activity experimentally, but has not previously been used as a primary modality to control SE in humans. METHODS: Four patients with SE refractory to benzodiazepine and/or barbiturate infusions were treated with hypothermia (target temperature: 31–35°C) using an endovascular cooling system. All received continuous EEG monitoring, three were on midazolam infusions and one had recurrent seizures on weaning from pentobarbital. RESULTS: Therapeutic hypothermia was successful in aborting seizure activity in all four patients, allowing midazolam infusions to be discontinued; three achieved a burst-suppression pattern on EEG. After controlled rewarming, two patients remained seizure-free, and all four demonstrated a marked reduction in seizure frequency. Adverse events included shivering, coagulopathy without bleeding, and venous thromboembolism. Two death occurred, neither directly related to hypothermia; however, immunosuppression related to the use of barbiturates and hypothermia may have contributed to an episode of fatal sepsis in one patient. CONCLUSIONS: Hypothermia was able to suppress seizure activity in patients with SE refractory to traditional therapies with minimal morbidity. It appears promising as an alternative or an adjunct to anesthetic doses of other agents, but requires further study to better evaluate its safety and efficacy.

Hypothermia for refractory status epilepticus

INTRODUCTION

Status epilepticus (SE) can be refractory to conventional anticonvulsants, requiring anesthetic doses of medications to suppress seizures. This approach carries significant morbidity, is associated with a high fatality rate, and may not always control SE. Hypothermia has been shown to suppress epileptiform activity experimentally, but has not previously been used as a primary modality to control SE in humans.

METHODS

Four patients with SE refractory to benzodiazepine and/or barbiturate infusions were treated with hypothermia (target temperature: 31-35 degrees C) using an endovascular cooling system. All received continuous EEG monitoring, three were on midazolam infusions and one had recurrent seizures on weaning from pentobarbital.

RESULTS

Therapeutic hypothermia was successful in aborting seizure activity in all four patients, allowing midazolam infusions to be discontinued; three achieved a burst-suppression pattern on EEG. After controlled rewarming, two patients remained seizure-free, and all four demonstrated a marked reduction in seizure frequency. Adverse events included shivering, coagulopathy without bleeding, and venous thromboembolism. Two death occurred, neither directly related to hypothermia; however, immunosuppression related to the use of barbiturates and hypothermia may have contributed to an episode of fatal sepsis in one patient.

CONCLUSIONS

Hypothermia was able to suppress seizure activity in patients with SE refractory to traditional therapies with minimal morbidity. It appears promising as an alternative or an adjunct to anesthetic doses of other agents, but requires further study to better evaluate its safety and efficacy.