EEG patterns and their correlations with short- and long-term mortality in patients with hypoxic encephalopathy.

OBJECTIVE: To analyze the association between electroencephalographic (EEG) patterns and overall, short- and long-term mortality in patients with hypoxic encephalopathy (HE). METHODS: Retrospective, mono-center analysis of 199 patients using univariate log-rank tests (LR) and multivariate cox regression (MCR). RESULTS: Short-term mortality, defined as death within 30-days post-discharge was 54.8%. Long-term mortality rates were 69.8%, 71.9%, and 72.9%, at 12-, 24-, and 36-months post-HE, respectively. LR revealed a significant association between EEG suppression (SUP) and short-term mortality, and identified low voltage EEG (LV), burst suppression (BSP), periodic discharges (PD) and post-hypoxic status epilepticus (PSE) as well as missing (aBA) or non-reactive background activity (nrBA) as predictors for overall, short- and long-term mortality. MCR indicated SUP, LV, BSP, PD, aBA and nrBA as significantly associated with overall and short-term mortality to varying extents. LV and BSP were significant predictors for long-term mortality in short-term survivors. Rhythmic delta activity, stimulus induced rhythmic, periodic or ictal discharges and sharp waves were not significantly associated with a higher mortality. CONCLUSION: The presence of several specific EEG patterns can help to predict overall, short- and long-term mortality in HE patients. SIGNIFICANCE: The present findings may help to improve the challenging prognosis estimation in HE patients.

EEG in the Pediatric Intensive Care Unit: An Irish Experience.

INTRODUCTION: Evidence for continuous EEG monitoring in the pediatric intensive care unit (PICU) is increasing. However, 24/7 access to EEG is not routinely available in most centers, and clinical management is often informed by more limited EEG resources. The experience of EEG was reviewed in a tertiary PICU where 24/7 EEG cover is unavailable. METHODS: Retrospective EEG and clinical review of 108 PICU patients. Correlations were carried out between EEG and clinical variables including mortality. The role of EEG in clinical decision making was documented. RESULTS: One hundred ninety-six EEGs were carried out in 108 PICU patients over 2.5 years (434 hours of recording). After exclusion of 1 outlying patient with epileptic encephalopathy, 136 EEGs (median duration, 65 minutes; range, 20 minutes to 4 hours 40 minutes) were included. Sixty-two patients (57%) were less than 12 months old. Seizures were detected in 18 of 107 patients (17%); 74% of seizures were subclinical; 72% occurred within the first 30 minutes of recording. Adverse EEG findings were associated with high mortality. Antiepileptic drug use was high in the studied population irrespective of EEG seizure detection. Prevalence of epileptiform discharges and EEG seizures diminished with increasing levels of sedation. CONCLUSIONS: EEG provides important diagnostic information in a large proportion of PICU patients. In the absence of 24/7 EEG availability, empirical antiepileptic drug utilization is high.

The cumulative duration of bispectral index less than 40 concurrent with hypotension is associated with 90-day postoperative mortality: a retrospective study.

BACKGROUND: The relationship between intraoperative low bispectral index (BIS) values and poor clinical outcomes has been controversial. Intraoperative hypotension is associated with postoperative complication. The purpose of this study was to investigate the influence of intraoperative low BIS values and hypotension on postoperative mortality in patients undergoing major abdominal surgery. METHODS: This retrospective study analyzed 1862 cases of general anesthesia. We collected the cumulative time of BIS values below 20 and 40 as well as electroencephalographic suppression and documented the incidences in which these states were maintained for at least 5 min. Durations of intraoperative mean arterial pressures (MAP) less than 50 mmHg were also recorded. Multivariable logistic regression was used to evaluate the association between suspected risk factors and postoperative mortality. RESULTS: Ninety-day mortality and 180-day mortality were 1.5 and 3.2% respectively. The cumulative time in minutes for BIS values falling below 40 coupled with MAP falling below 50 mmHg was associated with 90-day mortality (odds ratio, 1.26; 95% confidence interval, 1.04-1.53; P = .019). We found no association between BIS related values and 180-day mortality. CONCLUSIONS: The cumulative duration of BIS values less than 40 concurrent with MAP less than 50 mmHg was associated with 90-day postoperative mortality, not 180-day postoperative mortality.

Sudden unexpected death in epilepsy. A nationwide population-based study.

OBJECTIVE: The incidence of sudden unexpected death in epilepsy (SUDEP) varies between studies. We determined the incidence of SUDEP in the entire Icelandic population during a 20-year period. METHODS: All individuals in Iceland with epilepsy who died unexpectedly from January 1, 1991 through December 31, 2010 were included. Case ascertainment was based on autopsies, reimbursement for antiepileptic drugs, death certificates, information from neurologists, and medical records. The incidence of SUDEP was calculated according to the total number of residents in Iceland during the study period and an estimated epilepsy population of Iceland. RESULTS: We identified 37 individuals (26 men, 11 women) with definite SUDEP (n = 29), definite SUDEP plus (n = 4), and probable SUDEP (n = 4). Incidence of SUDEP was 0.6 per 100 000 person-years for the general population, and higher among men. The estimated incidence of SUDEP in the epilepsy population was 1.3 per 1000 person-years. SUDEP accounted for 0.1% of all deaths in Iceland during the study period. SIGNIFICANCE: SUDEP is an important cause of death in working-age people. This study provides the incidence of SUDEP in an unselected population of an entire country. The SUDEP incidence in the epilepsy population is comparable to that of previous studies.

Early EEG Features for Outcome Prediction After Cardiac Arrest in Children.

PURPOSE: We aimed to determine which early EEG features and feature combinations most accurately predicted short-term neurobehavioral outcomes and survival in children resuscitated after cardiac arrest. METHODS: This was a prospective, single-center observational study of infants and children resuscitated from cardiac arrest who underwent conventional EEG monitoring with standardized EEG scoring. Logistic regression evaluated the marginal effect of each EEG variable or EEG variable combinations on the outcome. The primary outcome was neurobehavioral outcome (Pediatric Cerebral Performance Category score), and the secondary outcome was mortality. The authors identified the models with the highest areas under the receiver operating characteristic curve (AUC), evaluated the optimal models using a 5-fold cross-validation approach, and calculated test characteristics maximizing specificity. RESULTS: Eighty-nine infants and children were evaluated. Unfavorable neurologic outcome (Pediatric Cerebral Performance Category score 4-6) occurred in 44 subjects (49%), including mortality in 30 subjects (34%). A model incorporating a four-level EEG Background Category (normal, slow-disorganized, discontinuous or burst-suppression, or attenuated-flat), stage 2 Sleep Transients (present or absent), and Reactivity-Variability (present or absent) had the highest AUC. Five-fold cross-validation for the optimal model predicting neurologic outcome indicated a mean AUC of 0.75 (range, 0.70-0.81) and for the optimal model predicting mortality indicated a mean AUC of 0.84 (range, 0.76-0.97). The specificity for unfavorable neurologic outcome and mortality were 95% and 97%, respectively. The positive predictive value for unfavorable neurologic outcome and mortality were both 86%. CONCLUSIONS: The specificity of the optimal model using a combination of early EEG features was high for unfavorable neurologic outcome and mortality in critically ill children after cardiac arrest. However, the positive predictive value was only 86% for both outcomes. Therefore, EEG data must be considered in overall clinical context when used for neuroprognostication early after cardiac arrest.

Long-Term Prognosis of Patients With Takotsubo Syndrome.

BACKGROUND: Prognosis of Takotsubo syndrome (TTS) remains controversial due to scarcity of available data. Additionally, the effect of the triggering factors remains elusive. OBJECTIVES: This study compared prognosis between TTS and acute coronary syndrome (ACS) patients and investigated short- and long-term outcomes in TTS based on different triggers. METHODS: Patients with TTS were enrolled from the International Takotsubo Registry. Long-term mortality of patients with TTS was compared to an age- and sex-matched cohort of patients with ACS. In addition, short- and long-term outcomes were compared between different groups according to triggering conditions. RESULTS: Overall, TTS patients had a comparable long-term mortality risk with ACS patients. Of 1,613 TTS patients, an emotional trigger was detected in 485 patients (30%). Of 630 patients (39%) related to physical triggers, 98 patients (6%) had acute neurologic disorders, while in the other 532 patients (33%), physical activities, medical conditions, or procedures were the triggering conditions. The remaining 498 patients (31%) had no identifiable trigger. TTS patients related to physical stress showed higher mortality rates than ACS patients during long-term follow-up, whereas patients related to emotional stress had better outcomes compared with ACS patients. CONCLUSIONS: Overall, TTS patients had long-term outcomes comparable to age- and sex-matched ACS patients. Also, we demonstrated that TTS can either be benign or a life-threating condition depending on the inciting stress factor. We propose a new classification based on triggers, which can serve as a clinical tool to predict short- and long-term outcomes of TTS. (International Takotsubo Registry [InterTAK Registry]; NCT01947621).

EEG-Annotate: Automated identification and labeling of events in continuous signals with applications to EEG.

BACKGROUND: In controlled laboratory EEG experiments, researchers carefully mark events and analyze subject responses time-locked to these events. Unfortunately, such markers may not be available or may come with poor timing resolution for experiments conducted in less-controlled naturalistic environments. NEW METHOD: We present an integrated event-identification method for identifying particular responses that occur in unlabeled continuously recorded EEG signals based on information from recordings of other subjects potentially performing related tasks. We introduce the idea of timing slack and timing-tolerant performance measures to deal with jitter inherent in such non-time-locked systems. We have developed an implementation available as an open-source MATLAB toolbox (http://github.com/VisLab/EEG-Annotate) and have made test data available in a separate data note. RESULTS: We applied the method to identify visual presentation events (both target and non-target) in data from an unlabeled subject using labeled data from other subjects with good sensitivity and specificity. The method also identified actual visual presentation events in the data that were not previously marked in the experiment. COMPARISON WITH EXISTING METHODS: Although the method uses traditional classifiers for initial stages, the problem of identifying events based on the presence of stereotypical EEG responses is the converse of the traditional stimulus-response paradigm and has not been addressed in its current form. CONCLUSIONS: In addition to identifying potential events in unlabeled or incompletely labeled EEG, these methods also allow researchers to investigate whether particular stereotypical neural responses are present in other circumstances. Timing-tolerance has the added benefit of accommodating inter- and intra- subject timing variations.

Persistent generalized periodic discharges: A specific marker of fatal outcome in cerebral hypoxia.

OBJECTIVES: Electroencephalography (EEG) is one of the methods used in predicting the outcome after cerebral hypoxia. In this study we aim to evaluate the significance of generalized periodic discharges (GPD) as a prognostic marker. METHODS: We retrospectively analyzed the medical histories of patients, who underwent an EEG after cardiac arrest during the time period from 2005 to 2013 at the University Hospital Zurich. All EEGs were re-interpreted using the 2012 American Clinical Neurophysiology Society (ACNS) classification for intensive care unit (ICU) EEGs. RESULTS: Out of 131 patients, in which an EEG was recorded after cardiopulmonary resuscitation, 119 were included in our study. The average interval between cardiac arrest and EEG-recording was 3.8±3.0days (range: 0-14days). Persistent GPDs (i.e. GPDs more than 24h after the event) were found in thirty-two (26.9%) of the patients initial EEGs. The appearance of persistent GPDs preceded fatal outcome in 100% of all cases (vs. 69.0% in the non-GPD-group, p<0.0001). CONCLUSION: Among other encephalopathic markers in EEG persistent GPDs are a highly specific prognostic marker of fatal outcome in patients with hypoxic encephalopathy. SIGNIFICANCE: Using standardized EEG interpretation, this study identified persistent GPDs as a specific prognostic marker in post cardiac arrest syndrome.

Continuous and routine EEG in intensive care: utilization and outcomes, United States 2005-2009.

OBJECTIVES: To evaluate the effect of intensive care unit continuous EEG (cEEG) monitoring on inpatient mortality, hospital charges, and length of stay. METHODS: A retrospective cross-sectional study was conducted using the Nationwide Inpatient Sample, a dataset representing 20% of inpatient discharges in nonfederal US hospitals. Adult discharge records reporting mechanical ventilation and EEG (routine EEG or cEEG) were included. cEEG was compared with routine EEG alone in association with the primary outcome of in-hospital mortality and secondary outcomes of total hospital charges and length of stay. Demographics, hospital characteristics, and medical comorbidity were used for multivariate adjustments of the primary and secondary outcomes. RESULTS: A total of 40,945 patient discharges in the weighted sample met inclusion criteria, of which 5,949 had reported cEEG. Mechanically ventilated patients receiving cEEG were younger than routine EEG patients (56 vs 61 years; p < 0.001). There was no difference in the 2 groups in income or medical comorbidities. cEEG was significantly associated with lower in-hospital mortality in both univariate (odds ratio = 0.54, 95% confidence interval 0.45-0.64; p < 0.001) and multivariate (odds ratio = 0.63, 95% confidence interval 0.51-0.76; p < 0.001) analyses. There was no significant difference in costs or length of stay for patients who received cEEG relative to those receiving only routine EEG. Sensitivity analysis showed that adjusting for diagnosis-related groups (DRGs) for any neurologic diagnoses, DRGs for neurologic procedures, and specific DRGs for epilepsy/convulsions did not substantially alter the association of cEEG with reduced inpatient mortality. CONCLUSIONS: cEEG is favorably associated with inpatient survival in mechanically ventilated patients, without adding significant charges to the hospital stay.

Emergency EEG: study of survival.

OBJECTIVE: To determine the survival rate according to the main findings of emergency electroencephalography (EEGs) of patients treated in a tertiary hospital. METHOD: In this prospective study, the findings of consecutive emergency EEGs performed on inpatients in Hospital de Base in São José do Rio Preto, Brazil were correlated with survival utilizing Kaplan-Meyer survival curves. RESULTS: A total of 681 patients with an average age of 42 years old (1 day to 96 years) were evaluated, of which 406 were male. The main reasons for EEGs were epileptic seizures (221 cases), hepatic encephalopathy [116 cases of which 85 (73.3%) were men, p-value=0.001], status epilepticus (104 cases) and impaired consciousness (78 cases). The underlying disease was confirmed in 578 (84.3%) cases with 119 (17.5%) having liver disease [91 (76.0%) were men, p-value=0.001], 105 (15.4%) suffering strokes, 67 (9.9%) having metabolic disorders, 51 (7.5%) central nervous system infections and 49 (7.2%) epilepsy. In the three months following EEG, a survival rate of 75% was found in patients with normal, discreet slow activity or intermittent rhythmic delta activity EEGs, of 50% for those with continuous delta activity and generalized epileptiform discharges, and of 25% for those with burst-suppression, diffuse depression, and in alpha/theta-pattern coma. Death was pronounced immediately in patients with isoelectric EEGs. CONCLUSION: The main findings of EEGs, differentiated different survival rates and are thus a good prognostic tool for patients examined in emergencies.

Association of perioperative risk factors and cumulative duration of low bispectral index with intermediate-term mortality after cardiac surgery in the B-Unaware Trial.

BACKGROUND: Current data suggest that mortality after noncardiac surgery may be associated with persistent hypotension and the cumulative duration of low processed electroencephalogram-based bispectral index (BIS). This study assessed the relationships among cumulative duration of low BIS (BIS < 45), intermediate-term mortality, and anesthetic dose after cardiac surgery. METHODS: The authors studied 460 patients (mean age, 63.0 +/- 13.1 yr; 287 men) who underwent cardiac surgery between September 2005 and October 2006 at Washington University Medical Center, St Louis, Missouri. By using multivariable Cox regression analysis, perioperative factors were evaluated for their potential association with intermediate-term all-cause mortality. RESULTS: A total of 82 patients (17.8%) died during a median follow-up of 3 yr (interquartile range, 2.7-3.3 yr). Comparing patients who died with those who survived, there was no statistically significant difference in the relationship between end-tidal anesthetic gas concentrations during the anesthetic maintenance phase and the BIS. Cumulative duration of low BIS was independently associated with intermediate-term mortality. The 1.29 adjusted hazard ratio (95% CI, 1.12-1.49) for intermediate-term mortality with cumulative duration of low BIS translated into a 29% increased risk of death for every cumulative hour spent with a BIS less than 45. The final multivariable Cox regression model showed a good discriminative ability (c-index of 0.78). CONCLUSIONS: This study found an association between cumulative duration of low BIS and mortality in the setting of cardiac surgery. Notably, this association was independent of both volatile anesthetic concentration and duration of anesthesia, suggesting that intermediate-term mortality after cardiac surgery was not causally related to excessive anesthetic dose.

Emergency EEG: study of survival / EEG de urgência: taxa de sobrevivência

OBJECTIVE: To determine the survival rate according to the main findings of emergency electroencephalography (EEGs) of patients treated in a tertiary hospital. METHOD: In this prospective study, the findings of consecutive emergency EEGs performed on inpatients in Hospital de Base in São José do Rio Preto, Brazil were correlated with survival utilizing Kaplan-Meyer survival curves. RESULTS: A total of 681 patients with an average age of 42 years old (1 day to 96 years) were evaluated, of which 406 were male. The main reasons for EEGs were epileptic seizures (221 cases), hepatic encephalopathy [116 cases of which 85 (73.3 percent) were men, p-value=0.001], status epilepticus (104 cases) and impaired consciousness (78 cases). The underlying disease was confirmed in 578 (84.3 percent) cases with 119 (17.5 percent) having liver disease [91 (76.0 percent) were men, p-value=0.001], 105 (15.4 percent) suffering strokes, 67 (9.9 percent) having metabolic disorders, 51 (7.5 percent) central nervous system infections and 49 (7.2 percent) epilepsy. In the three months following EEG, a survival rate of 75 percent was found in patients with normal, discreet slow activity or intermittent rhythmic delta activity EEGs, of 50 percent for those with continuous delta activity and generalized epileptiform discharges, and of 25 percent for those with burst-suppression, diffuse depression, and in alpha/theta-pattern coma. Death was pronounced immediately in patients with isoelectric EEGs. CONCLUSION: The main findings of EEGs, differentiated different survival rates and are thus a good prognostic tool for patients examined in emergencies.

OBJETIVO: Determinar a taxa de sobrevivência (TS), segundo os principais achados de eletrencefalograma de urgência (E-EEG), dos pacientes atendidos nas emergências de hospital de alta complexidade. MÉTODO: Estudo prospectivo, por ordem de chegada, da correlação entre os achados de E-EEG, feitos nos pacientes à beira do leito, com TS, utilizando-se as curvas de sobrevidas de Kaplan Meyer no Hospital de Base de São José do Rio Preto, São Paulo/Brasil. RESULTADOS: Foram estudados 681 pacientes, dos quais 406 (59,6 por cento) masculinos, com idade média de 42 anos (1 dia a 96 anos). As principais motivações para o E-EEG foram crises epilépticas (221 casos), encefalopatia hepática [(116 casos, dos quais 85 masculinos (73,3 por cento), p= 0,001]; estado de mal epiléptico 104 e rebaixamento de consciência 78. O diagnóstico da doença de base foi confirmado em 578 (84,3 por cento), sendo 119 (17,5 por cento) hepatopatia, dos quais 91 (76, por cento) masculinos, p= 0,001; 105 (15,4 por cento) acidente vascular encefálico; 67 (9,9 por cento) distúrbio metabólico; 51 (7,5 por cento) infecção do sistema nervoso central e 49 (7,2 por cento) epilepsia. TS de 75 por cento nos três primeiros meses foi encontrada nos pacientes com E-EEG com alentecimento discreto ou com atividade delta rítmica intermitente. TS por volta de 50 por cento nos três meses foi encontrado nos pacientes com E-EEG com delta contínuo, crítico e com descargas periódicas. A TS foi menor que 25 por cento nos dois primeiros meses após E-EEG, nos pacientes com E-EEG com surto/supressão, com depressão difusa e com comas alfa/teta e 0 por cento nos E-EEG iselétricos. CONCLUSÃO: O E-EEG, com seus principais achados, foi capaz de diferenciar as diversas taxas de sobrevivências na amostra estudada, constituindo-se, portanto, bom instrumento de prognóstico para pacientes atendidos nas unidades de emergência hospitalar.

Depth of anesthesia monitoring.

Depth-of-anesthesia monitoring with EEG or EEG combined with mLAER is becoming widely used in anesthesia practice. Evidence shows that this monitoring improves outcome by reducing the incidence of intra-operative awareness while reducing the average amount of anesthesia that is administered, resulting in faster wake-up and recovery, and perhaps reduced nausea and vomiting. As with any monitoring device, there are limitations in the use of the monitors and the anesthesiologist must be able to interpret the data accordingly. The limitations include the following. The currently available monitoring algorithms do not account for all anesthetic drugs, including ketamine, nitrous oxide and halothane. EMG and other high-frequency electrical artifacts are common and interfere with EEG interpretation. Data processing time produces a lag in the computation of the depth-of-anesthesia monitoring index. Frequently the EEG effects of anesthetic drugs are not good predictors of movement in response to a surgical stimulus because the main site of action for anesthetic drugs to prevent movement is the spinal cord. The use of depth-of-anesthesia monitoring in children is not as well understood as in adults. Several monitoring devices are commercially available. The BIS monitor is the most thoroughly studied and most widely used, but the amount of information about other monitors is growing. In the future, depth-of-anesthesia monitoring will probably help in further refining and better understanding the process of administering anesthesia.

How the self controls its "automatic pilot" when processing subliminal information.

Human performance may be primed by information not consciously available. Can such priming become so overwhelming that observers cannot help but act accordingly? In the present study, well-visible stimuli were preceded by whole series of unidentifiable stimuli. These series had strong, additive priming effects on behavior. However, their effect depended on the frequency with which they provided information conflicting to the visible main stimuli. Thus, effects of subliminal priming are under observers' strategic control, with the criterion presumably set as a function of the openly observable error frequency. Electrical brain potentials show that this criterion acts simultaneously at the level of visual discrimination of the primes and at motor activation evoked by the primes, thereby shielding observers from unwanted information.

Flexible polyimide-based intracortical electrode arrays with bioactive capability.

The promise of advanced neuroprosthetic systems to significantly improve the quality of life for a segment of the deaf, blind, or paralyzed population hinges on the development of an efficacious, and safe, multichannel neural interface for the central nervous system. The candidate implantable device that is to provide such an interface must exceed a host of exacting design parameters. We present a thin-film, polyimide-based, multichannel intracortical Bio-MEMS interface manufactured with standard planar photo-lithographic CMOS-compatible techniques on 4-in silicon wafers. The use of polyimide provides a mechanically flexible substrate which can be manipulated into unique three-dimensional designs. Polyimide also provides an ideal surface for the selective attachment of various important bioactive species onto the device in order to encourage favorable long-term reactions at the tissue-electrode interface. Structures have an integrated polyimide cable providing efficient contact points for a high-density connector. This report details in vivo and in vitro device characterization of the biological, electrical and mechanical properties of these arrays. Results suggest that these arrays could be a candidate device for long-term neural implants.