Electroencephalography in Survivors of Cardiac Arrest: Comparing Pre- and Post-therapeutic Hypothermia Eras

Hyperthermia-Induced Changes in EEG of Anesthetized Mice Subjected to Passive Heat Exposure

Currently, the role of hypothermia in electroencephalography (EEG) is well-established. However, few studies have investigated the effect of hyperthermia on EEG, an important physiological parameter governing brain function. The aim of this work was to determine how neuronal activity in anesthetized mice is affected when the temperature rises above the physiological threshold mandatory to maintain the normal body functions. In this study, a temperature-elevation protocol, from 37 to 42°C, was applied to four female mice of 2–3 months old while EEG was recorded simultaneously. We found that hyperthermia reduces EEG amplitude by 4.36% when rising from 37 to 38 degrees and by 24.33% when it is increased to 42 degrees. Likewise, increasing the body temperature produces a very large impact on the EEG spectral parameters, reducing the frequency power at the delta, theta, alpha, and beta bands. Our results show that hyperthermia has a global effect on the EEG, being able to change the electrical activity of the brain.

Management of temperature control in post-cardiac arrest care: an expert report

Targeted temperature management (TTM) through induced hypothermia (between 32-36 ^oC) is currently regarded as a first-line treatment during the management of post-cardiac arrest patients admitted to the Intensive Care Unit (ICU). The aim of TTM is to afford neuroprotection and reduce secondary neurological damage caused by anoxia. Despite the large body of evidence on its benefits, the TTM is still little used in Spain. There are controversial issues referred to its implementation, such as the optimal target body temperature, timing, duration and the rewarming process. The present study reviews the best available scientific evidence and the current recommendations contained in the international guidelines. In addition, the study focuses on the practical implementation of TTM in post-cardiac arrest patients in general and cardiological ICUs, with a discussion of the implementation strategies, protocols, management of complications and assessment of the neurological prognosis.

Epileptiform Discharge and Electrographic Seizures during the Hypothermia Phase as Predictors of Rewarming Seizures in Children after Resuscitation

The aim of this study was to determine the frequency, timing, and predictors of rewarming seizures in a cohort of children undergoing therapeutic hypothermia after resuscitation. We retrospectively reviewed consecutive pediatric patients undergoing therapeutic hypothermia after resuscitation admitted to our pediatric intensive care unit between January 2000 and December 2019. Continuous electroencephalographic monitoring was performed during hypothermia (24 h for cardiac aetiologies and 72 h for asphyxial aetiologies), rewarming (72 h), and then an additional 12 h of normothermia. Thirty comatose children undergoing therapeutic hypothermia after resuscitation were enrolled, of whom 10 (33.3%) had rewarming seizures. Two (20%) of these patients had their first seizure during the rewarming phase. Four (40%) patients had electroclinical seizures, and six (60%) had nonconvulsive seizures. The median time from starting rewarming to the onset of rewarming seizures was 37.3 h (range 6 to 65 h). The patients with interictal epileptiform activity and electrographic seizures during the hypothermia phase were more likely to have rewarming seizures compared to those without interictal epileptiform activity or electrographic seizures (p = 0.019 and 0.019, respectively). Therefore, in high-risk patients, continuous electroencephalographic monitoring for a longer duration may help to detect rewarming seizures and guide clinical management.

Otoacoustic Emissions for Outcome Prediction in Postanoxic Brain Injury

Background: Non-invasive, easy-to-use bedside tools to estimate prognosis in unresponsive patients with postanoxic brain injury are needed. We assessed the usefulness of otoacoustic emissions as outcome markers after cardiac arrest. Methods: Distortion product otoacoustic emissions (DPOAE) and transient evoked otoacoustic emissions (TEOAE) were measured in cardiac arrest patients whose prognosis was deemed to be poor following standard neurological assessment (n = 10). Ten patients with myocardial infarction without prior loss of consciousness served as controls. Results: Compared to controls with myocardial infarction, cardiac arrest patients with poor neurological prognosis had significantly less often preserved DPOAE (9.2 vs. 40.8% positive measurements; OR 0.15 (CI 0.07-0.30); p < 0.0001). Partially preserved DPOAE were noted in 4 cardiac arrest patients. TEOAE were not statistically different between the two groups. Conclusions: Despite their convenience, otoacoustic emissions cannot be used as reliable prognostic markers in cardiac arrest survivors. This is because we identified 4 cases with partially preserved otoacoustic emissions in a sample of 10 unresponsive post-cardiac arrest patients whose neurological condition was so poor that active treatment was withdrawn. However, we suggest that future research should address if decaying outer hair cell function over time may serve as a proxy for evolving ischemic brain damage.

EEG Characteristics in Cooled and Rewarmed Periods in Post-cardiac Arrest Therapeutic Hypothermia Patients

PURPOSE

Continuous video EEG is a tool to assess brain function in injuries, including cardiac arrest (CA). In post-CA therapeutic hypothermia (TH) studies, some EEG features are linked to poor prognosis, but the evolvement of EEG characteristics during two temperature phases and its significance is unclear. We systematically analyzed EEG characteristics in cooled and rewarmed phases of post-CA therapeutic hypothermia patients and investigated their correlation to patient outcome.

METHODS

This is a retrospective study of EEG analyses, from a single academic center, of 20 patients who underwent CA and therapeutic hypothermia. For each patient, three 30-minute EEG segments in cooled and rewarmed phases were analyzed for continuity, frequency, interictal epileptiform discharges, and seizures. Mortality at the time of discharge was used as outcome.

RESULTS

Rewarming was associated with the emergence of interictal epileptiform discharges, 2.6 times as likely compared with the cooled period (P = 0.03), and was not affected by systemic factors. Continuity, frequency, and discrete seizures were unaffected by temperature and did not show variance within each temperature phase. There was a trend toward the emergence of interictal epileptiform discharges upon rewarming and mortality, but it was not statistically significant.

CONCLUSIONS

Increased interictal epileptiform discharges with rewarming in post-CA therapeutic hypothermia patients may suggest poor prognosis, but a larger scale prospective study is needed.

EEG as an Indicator of Cerebral Functioning in Postanoxic Coma

Postanoxic coma after cardiac arrest is one of the most serious acute cerebral conditions and a frequent cause of admission to critical care units. Given substantial improvement of outcome over the recent years, a reliable and timely assessment of clinical evolution and prognosis is essential in this context, but may be challenging. In addition to the classic neurologic examination, EEG is increasingly emerging as an important tool to assess cerebral functions noninvasively. Although targeted temperature management and related sedation may delay clinical assessment, EEG provides accurate prognostic information in the early phase of coma. Here, the most frequently encountered EEG patterns in postanoxic coma are summarized and their relations with outcome prediction are discussed. This article also addresses the influence of targeted temperature management on brain signals and the implication of the evolution of EEG patterns over time. Finally, the article ends with a view of the future prospects for EEG in postanoxic management and prognostication.

Case Studies in Neurocritical Care

The practice of neurocritical care encompasses multiple acute neurologic and neurosurgical diseases and requires detailed knowledge of neurology and critical care. This article presents 5 cases that illustrate just some of the conditions encountered in the daily practice of neurocritical care and exemplify some of the common diagnostic, therapeutic, and prognostic challenges facing the neurointensivist. Life-threatening medical complications after severe acute ischemic stroke, seizures and extreme agitation from autoimmune encephalitis, refractory seizures after subdural hemorrhage, neurologic and systemic complications related to aneurysmal subarachnoid hemorrhage, and status epilepticus after cardiac arrest are discussed in this article.

Medical management of epileptic seizures: challenges and solutions

Epilepsy is one of the most common neurologic illnesses. This condition afflicts 2.9 million adults and children in the US, leading to an economic impact amounting to $15.5 billion. Despite the significant burden epilepsy places on the population, it is not very well understood. As this understanding continues to evolve, it is important for clinicians to stay up to date with the latest advances to provide the best care for patients. In the last 20 years, the US Food and Drug Administration has approved 15 new antiepileptic drugs (AEDs), with many more currently in development. Other advances have been achieved in terms of diagnostic modalities like electroencephalography technology, treatment devices like vagal nerve and deep-brain stimulators, novel alternate routes of drug administration, and improvement in surgical techniques. Specific patient populations, such as the pregnant, elderly, those with HIV/AIDS, and those with psychiatric illness, present their own unique challenges, with AED side effects, drug interactions, and medical-psychiatric comorbidities adding to the conundrum. The purpose of this article is to review the latest literature guiding the management of acute epileptic seizures, focusing on the current challenges across different practice settings, and it discusses studies in various patient populations, including the pregnant, geriatric, those with HIV/AIDS, comatose, psychiatric, and "pseudoseizure" patients, and offers possible evidence-based solutions or the expert opinion of the authors. Also included is information on newer AEDs, routes of administration, and significant AED-related drug-interaction tables. This review has tried to address only some of these issues that any practitioner who deals with the acute management of seizures may encounter. The document also highlights the numerous avenues for new research that would help practitioners optimize epilepsy management.