Continuous electroencephalogram monitoring in the intensive care unit

Intensive Care Management of Subarachnoid Haemorrhage

Aneurysmal subarachnoid haemorrhage (SAH) is a devastating disease associated with high mortality and poor outcome in many survivors. Aggressive treatment by a comprehensive multidisciplinary team is associated with improved outcome, but the intensive care management of SAH presents significant challenges. Multimodal neuromonitoring may detect secondary insults before irreversible neuronal damage has occurred, and is increasingly being used to guide treatment. This article reviews current trends in the intensive care management of SAH from aspects of initial resuscitation to recent developments in the prevention and management of complications, including delayed cerebral ischaemia. Evidence from clinical trials and recent consensus guidance is reviewed.

Frequency of non-convulsive seizures and non-convulsive status epilepticus in subarachnoid hemorrhage patients in need of controlled ventilation and sedation

BACKGROUND

Non-convulsive seizures (NCSZ) can be more prevalent than previously recognized among comatose neuro-intensive care patients. The aim of this study was to evaluate the frequency of NCSZ and non-convulsive status epilepticus (NCSE) in sedated and ventilated subarachnoid hemorrhage (SAH) patients.

METHODS

Retrospective study at a university hospital neuro-intensive care unit, from January 2008 until June 2010. Patients were treated according to a local protocol, and were initially sedated with midazolam or propofol or combinations of these sedative agents. Thiopental was added for treatment of intracranial hypertension. No wake-up tests were performed. Using NicoletOne(®) equipment (VIASYS Healthcare Inc., USA), continuous EEG recordings based on four electrodes and a reference electrode was inspected at full length both in a two electrode bipolar and a four-channel referential montage.

RESULTS

Approximately 5,500 h of continuous EEG were registered in 28 SAH patients (33 % of the patients eligible for inclusion). The median Glasgow Coma scale was 8 (range 3-14) and the median Hunt and Hess score was 4 (range 1-4). During EEG registration, no clinical seizures were observed. In none of the patients inter ictal epileptiform activity was seen. EEG seizures were recorded only in 2/28 (7 %) patients. One of the patients experienced 4 min of an NCSZ and one had a 5 h episode of an NCSE.

CONCLUSION

Continuous EEG monitoring is important in detecting NCSZ in sedated patients. Continuous sedation, without wake-up tests, was associated with a low frequency of subclinical seizures in SAH patients in need of controlled ventilation.

Absence of early epileptiform abnormalities predicts lack of seizures on continuous EEG

OBJECTIVE

To determine whether the absence of early epileptiform abnormalities predicts absence of later seizures on continuous EEG monitoring of hospitalized patients.

METHODS

We retrospectively reviewed 242 consecutive patients without a prior generalized convulsive seizure or active epilepsy who underwent continuous EEG monitoring lasting at least 18 hours for detection of nonconvulsive seizures or evaluation of unexplained altered mental status. The findings on the initial 30-minute screening EEG, subsequent continuous EEG recordings, and baseline clinical data were analyzed. We identified early EEG findings associated with absence of seizures on subsequent continuous EEG.

RESULTS

Seizures were detected in 70 (29%) patients. A total of 52 patients had their first seizure in the initial 30 minutes of continuous EEG monitoring. Of the remaining 190 patients, 63 had epileptiform discharges on their initial EEG, 24 had triphasic waves, while 103 had no epileptiform abnormalities. Seizures were later detected in 22% (n = 14) of studies with epileptiform discharges on their initial EEG, vs 3% (n = 3) of the studies without epileptiform abnormalities on initial EEG (p < 0.001). In the 3 patients without epileptiform abnormalities on initial EEG but with subsequent seizures, the first epileptiform discharge or electrographic seizure occurred within the first 4 hours of recording.

CONCLUSIONS

In patients without epileptiform abnormalities during the first 4 hours of recording, no seizures were subsequently detected. Therefore, EEG features early in the recording may indicate a low risk for seizures, and help determine whether extended monitoring is necessary.

Interrater reliability of ICU EEG research terminology

BACKGROUND

Standardized research terminology critical to the establishment of a multicenter intensive care unit (ICU) electroencephalogram (EEG) database was originally proposed in 2005 and has been modified many times since. However, interrater agreement (IRA) of the revised terminology has not been investigated.

METHODS

After a brief tutorial, investigators of ICU EEG research centers (n = 16) took an 82-question EEG certification test comprising 10-second EEG samples, which assessed the use of main term 1 (pattern location), main term 2 (pattern type), and modifiers from the most recently revised terminology.

RESULTS

Kappa values for main terms 1 and 2 were 0.87 and 0.92, respectively. Agreement was 93% for determination of amplitude and 80% for determination of frequency. Kappa values for each of the "plus" modifiers (fast, rhythmic, and sharp/spike activity) were 0.54, 0.62, and 0.16 respectively.

CONCLUSIONS

Main terms 1 and 2 have high IRA and are reasonable for use in multicenter research. There is a suggestion that assessment of amplitude has good reliability, while assessment of frequency may have less reliability. The fast and rhythmic "plus" modifiers have moderate IRA, while sharp/spike modifier has only slight IRA implying that further refinement and assessment of terminology modifiers may be necessary.

Status epilepticus and the use of continuous EEG monitoring in the intensive care unit

PURPOSE OF REVIEW

Status epilepticus (SE) is one of the major neurologic emergencies. Newer data about the genesis and treatment of this condition are available to help improve our understanding and management.

RECENT FINDINGS

Approximately 150,000 cases of generalized convulsive SE occur in the United States each year. Clinically apparent seizures complicate about 8% of intensive care unit admissions, and another 10% of ICU patients suffer electrographic seizures in the course of another critical illness. Some of these cases result from previously under-recognized epileptogenic effects of commonly used drugs, such as cefepime. Continuous EEG (cEEG) recording is necessary for both diagnosis and management in these patients, especially since anticonvulsant drugs may abolish motor activity without stopping seizures. Recent studies have underscored the utility of benzodiazepines as the first-line agents for SE termination. The recently published Rapid Anticonvulsant Medication Prior to Arrival Trial (RAMPART) demonstrates that the more rapidly treatment is administered, the more effective it will be. When SE fails to respond to usual doses of benzodiazepines, it should be considered refractory to conventional anticonvulsants, and a general anesthetic approach is likely to be necessary.

SUMMARY

While definitions have varied, patients should be managed for SE after 5 minutes of seizure activity. Management of a patient with SE involves three phases: termination of SE, prevention of recurrence, and treatment of complications. The typical anticonvulsants have limited ability to terminate SE; lorazepam is the most useful, controlling SE in 65% of patients experiencing generalized convulsive SE. If the first conventional anticonvulsant fails, others are unlikely to be useful, and one of the newer anticonvulsants or a general anesthetic agent should be considered. EEG is crucial in the diagnosis and classification of potential seizures. cEEG monitoring helps to guide anticonvulsant therapy in patients with SE and those with frequent seizures. In addition, cEEG has the potential for presymptomatic diagnosis of delayed neurologic deterioration in patients with subarachnoid hemorrhage and for the differential diagnosis of stroke subtypes, especially when cEEG is subjected to signal processing.

The safety of controlled hypotension for shoulder arthroscopy in the beach-chair position

BACKGROUND

The safety of controlled hypotension during arthroscopic shoulder procedures with the patient in the beach-chair position is controversial. Current practice for the management of intraoperative blood pressure is derived from expert opinion among anesthesiologists, but there is a paucity of clinical data validating their practice. The purpose of this study was to evaluate the effect of controlled hypotension on cerebral perfusion with use of continuous electroencephalographic monitoring in patients undergoing shoulder arthroscopy in the beach-chair position.

METHODS

Fifty-two consecutive patients who had undergone shoulder arthroscopy in the beach-chair position were enrolled prospectively in this study. All patients underwent preoperative blood pressure measurements, assignment of an American Society of Anesthesiologists (ASA) grade, and a preoperative and postoperative neurological and Mini-Mental State Examination (MMSE). The target systolic blood pressure for all patients was 90 to 100 mm Hg during surgery. Continuous intraoperative monitoring was performed with standard ASA monitors and a ten-lead portable electroencephalography monitor. Real-time electroencephalographic monitoring was performed by an attending-level neurophysiologist.

RESULTS

All patients violated at least one recommended limit for blood pressure reduction. The average decrease in systolic blood pressure and mean arterial pressure from baseline was 36% and 42%, respectively. Three patients demonstrated ischemic changes on electroencephalography that resolved with an increase in blood pressure. No adverse neurological sequelae were observed in any patient on the basis of the MMSE.

CONCLUSIONS

This study provides the first prospective data on global cerebral perfusion during shoulder arthroscopy in the beach-chair position with use of controlled hypotension. Our study suggests that patients may be able to safely tolerate a reduction in blood pressure greater than current recommendations. In the future, intraoperative cerebral monitoring may play a role in preventing neurological injury in patients undergoing shoulder arthroscopy in the beach-chair position.

[EEG in intensive care unit: which indications, which material?]

There is a growing development of continuous EEG monitoring (cEEG) in the intensive care unit (ICU) management of neurological patients. Its main objective is the detection of epileptic seizures or status epilepticus because the sensitivity of standard short-duration EEG recording in the ICU is poor. The aim of monitoring is to allow rapid recognition and treatment of epileptic complications in order to decrease secondary insults to the brain and improve outcome. Several studies have demonstrated that a large proportion of patients has epileptic crisis after subarachnoid haemorrhage, stroke or brain trauma, without any clinical manifestation. The EEG feature has also demonstrated a prognosis value but its value for clinical management needs further studies. Another application of EEG in the ICU is monitoring depth of anaesthesia or barbiturate treatment. Due to artifacts contamination, this is possible only in deeply sedated of paralyzed patients. The impact or cEEG monitoring on clinical management and its indications have to be further defined.

Multimodal intracranial monitoring: implications for clinical practice

This article presents an overview of intracranial monitoring techniques during the perioperative and intensive care management of neurologic patients. Various regional and global brain monitors are available; some modalities are well established whereas others are new to the clinical arena and their indications are still being evaluated. Indications for monitoring are reviewed, modalities critically evaluated, and future directions identified.

Initial EEG predicts outcomes in a trial of levetiracetam vs. fosphenytoin for seizure prevention

Continuous electroencephalography (cEEG) is increasingly used to detect both clinical and subclinical seizures in patients with traumatic brain injury (TBI) or subarachnoid hemorrhage (SAH). We assess whether EEG findings predict outcomes in TBI/SAH patients enrolled in a levetiracetam (LEV) vs. fosphenytoin (fos-PHT) seizure prevention trial (NCT00618436). This prospective, single-blinded, comparative trial randomized 52 patients with TBI or SAH to receive prophylactic LEV or fos-PHT. Continuous video EEG monitoring was conducted for the initial 72 h of medication administration. The association between EEG findings (degree of generalized and focal slowing, presence and frequency of epileptiform discharges and seizures) and outcomes (Glasgow Outcomes Scale-Extended (GOS-E) and Disability Rating Scale (DRS)) at discharge, 3 and 6 months was assessed using a generalized linear model. Severity of generalized slowing tended to be associated with outcomes in both treatment groups (discharge DRS, p=0.042; discharge GOS-E, p=0.026; 3 month DRS, p=0.051). The presence of focal slowing, the presence and frequency of epileptiform discharges and the presence of seizures were not predictive of outcome in either treatment group (all p>0.15). While it has been shown that LEV is associated with better outcome than fos-PHT when used as seizure prophylaxis in brain injury, aside from severity of generalized slowing, electrographic findings of focal slowing, epileptiform discharges, and seizures were not themselves associated with outcomes in patients with TBI or SAH enrolled in a randomized clinical trial.

A tunable support vector machine assembly classifier for epileptic seizure detection

Automating the detection of epileptic seizures could reduce the significant human resources necessary for the care of patients suffering from intractable epilepsy and offer improved solutions for closed-loop therapeutic devices such as implantable electrical stimulation systems. While numerous detection algorithms have been published, an effective detector in the clinical setting remains elusive. There are significant challenges facing seizure detection algorithms. The epilepsy EEG morphology can vary widely among the patient population. EEG recordings from the same patient can change over time. EEG recordings can be contaminated with artifacts that often resemble epileptic seizure activity. In order for an epileptic seizure detector to be successful, it must be able to adapt to these different challenges. In this study, a novel detector is proposed based on a support vector machine assembly classifier (SVMA). The SVMA consists of a group of SVMs each trained with a different set of weights between the seizure and non-seizure data and the user can selectively control the output of the SVMA classifier. The algorithm can improve the detection performance compared to traditional methods by providing an effective tuning strategy for specific patients. The proposed algorithm also demonstrates a clear advantage over threshold tuning. When compared with the detection performances reported by other studies using the publicly available epilepsy dataset hosted by the University of BONN, the proposed SVMA detector achieved the best total accuracy of 98.72%. These results demonstrate the efficacy of the proposed SVMA detector and its potential in the clinical setting.

Electroencephalogram monitoring in critically ill children: indications and strategies

Continuous electroencephalographic monitoring often detects nonconvulsive seizures in critically ill children, but it is resource-intense and has not been demonstrated to improve outcomes. As institutions develop clinical pathways for monitoring, they should consider how seemingly minor variations may exert substantial impacts on resource utilization and cost. In our 1-month prospective observational study, each patient in a 45-bed pediatric intensive care unit was screened for potential monitoring indications. We screened 247 patients. Minor differences in monitoring indications would exert substantial impact on resource utilization. We then calculated the number of monitoring days required each month, based on two strategies that differed in monitoring duration. The prolonged-targeted and brief-targeted strategies would have required 106 and 33 monitoring days, respectively. Based on nonconvulsive seizure occurrence data, these strategies would detect 0.14, and 0.43 patients with seizures per monitoring day performed, respectively. A brief-targeted strategy provides a high yield for nonconvulsive seizure identification, but would fail to diagnose some patients with seizures.

Pediatric neurocritical care

Pediatric neurocritical care is an emerging multidisciplinary field of medicine and a new frontier in pediatric critical care and pediatric neurology. Central to pediatric neurocritical care is the goal of improving outcomes in critically ill pediatric patients with neurological illness or injury and limiting secondary brain injury through optimal critical care delivery and the support of brain function. There is a pressing need for evidence based guidelines in pediatric neurocritical care, notably in pediatric traumatic brain injury and pediatric stroke. These diseases have distinct clinical and pathophysiological features that distinguish them from their adult counterparts and prevent the direct translation of the adult experience to pediatric patients. Increased attention is also being paid to the broader application of neuromonitoring and neuroprotective strategies in the pediatric intensive care unit, in both primary neurological and primary non-neurological disease states. Although much can be learned from the adult experience, there are important differences in the critically ill pediatric population and in the circumstances that surround the emergence of neurocritical care in pediatrics.

Critical care neurology: Five new things

Critical care neurology has generated interest both because of the urgency to understand acute brain injury and because acute interventions could improve outcomes. Unifying themes include intervention without delay and early recognition of the potential for deterioration of the patient. While monitoring devices offer useful prognostic indicators, conducting a thorough clinical neurologic examination is paramount in determining the most effective course of patient management. Recent progress has been made in acute brain injury monitoring, more effective reversal of anticoagulation after cerebral hemorrhage, use of hypothermia as a therapeutic intervention, and in the management of severe Guillain-Barré syndrome.

Quantitative EEG analysis for automated detection of nonconvulsive seizures in intensive care units

Because of increased awareness of the high prevalence of nonconvulsive seizures in critically ill patients, use of continuous EEG (cEEG) monitoring is rapidly increasing in ICUs. However, cEEG monitoring is labor intensive, and manual review and interpretation of the EEG are impractical in most ICUs. Effective methods to assist in rapid and accurate detection of nonconvulsive seizures would greatly reduce the cost of cEEG monitoring and enhance the quality of patient care. In this study, we report a preliminary investigation of a novel ICU EEG analysis and seizure detection algorithm. Twenty-four prolonged cEEG recordings were included in this study. Seizure detection sensitivity and specificity were assessed for the new algorithm and for the two commercial seizure detection software systems. The new algorithm performed with a mean sensitivity of 90.4% and a mean false detection rate of 0.066/hour. The two commercial detection products performed with low sensitivities (12.9 and 10.1%) and false detection rates of 1.036/hour and 0.013/hour, respectively. These findings suggest that the novel algorithm has potential to be the basis of clinically useful software that can assist ICU staff in timely identification of nonconvulsive seizures. This study also suggests that currently available seizure detection software does not perform sufficiently in detection of nonconvulsive seizures in critically ill patients. This article is part of a Supplemental Special Issue entitled The Future of Automated Seizure Detection and Prediction.

Artifact: recording EEG in special care units

Artifacts may be obtained during routine recording but are more common in special care units (SCUs) outside of the EEG laboratory, where complex electrical currents are present that create a "hostile" environment. Special care units include the epilepsy monitoring unit, neurologic intensive care unit, and operating room, where artifact is present in virtually every recording, increasing with prolonged use. Nonepileptic attacks treated as epileptic seizures have been incorrectly diagnosed and treated due to a misinterpreted EEG. The recent emergence of continuous EEG as a neurophysiologic surrogate for brain function in the neurologic intensive care unit and operating room has also brought a greater amount and new types of EEG artifact. The artifacts encountered in special care units during continuous EEG are becoming more complex and may have adverse therapeutic implications. Our knowledge of artifact needs to parallel our growth in technology to avoid the pitfalls that may be incurred during visual analysis of the EEG.

Impact of continuous EEG monitoring on clinical management in critically ill children

BACKGROUND

Continuous EEG (cEEG) monitoring is being used with increasing frequency in critically ill patients, most often to detect non-convulsive seizures. While cEEG is non-invasive and feasible in the critical care setting, it is also expensive and labor intensive, and there has been little study of its impact on clinical care. We aimed to determine prospectively the impact of cEEG on clinical management in critically ill children.

METHODS

Critically ill children (non-neonates) with acute encephalopathy underwent cEEG. Study enrollment and data collection were prospective.

RESULTS

100 children were studied. EEG monitoring led to specific clinical management changes in 59 children. These included initiating or escalating anti-seizure medications in 43 due to seizure detection, demonstrating that a specific event (subtle movement or vital sign change) was not a seizure in 21, or obtaining urgent neuroimaging that led to a clinical change in 3. In the remaining 41 children, cEEG ruled out the presence of non-convulsive seizures but did not lead to a specific change in clinical management.

CONCLUSIONS

EEG monitoring led to changes in clinical management in the majority of patients, suggesting it may have an important role in management of critically ill children. Further study is needed to determine whether the management changes elicited by cEEG improve outcome.

Early suppression of intracranial EEG signals predicts ischemic outcome in adult mice following hypoxia-ischemia

The objective of this study is to determine whether early alterations in intracranial EEG activity predict overall outcome in non-anesthetized adult mice following hypoxia-ischemia (HI). Adult C57BL/6 mice received surgical implantation of bilateral intracranial EEG electrodes in the hippocampus and cerebral cortex. Animals were subjected to a hypoxic-ischemic (HI) episode consisting of permanent occlusion of the right common carotid artery and subsequent systemic hypoxia (8% O(2) for 30 min). EEG activities were sorted based on the observance of motor seizures, poor physical outcome, brain injury, and mortality. EEG signals were quantified as amplitude, variance, and root mean square, and early alterations in these parameters were compared. Animals with poor-HI outcome exhibited longer and more profound suppression of EEG signals in the hippocampus ipsilateral to the carotid artery occlusion during HI. Of the parameters chosen to quantify EEG activity, root mean square demonstrated the greatest sensitivity in predicting subsequent outcome. Thus, ipsilateral hippocampal EEG signals are a reliable early marker for assessing HI outcome in adult mice, and further characterization of ischemic EEG signals may aid in the development of novel quantitative variables for use in animal models of experimental cerebral ischemia.

Dynamic monitors of brain function: a new target in neurointensive care unit

Introduction

Somatosensory evoked potential (SEP) recordings and continuous electroencephalography (EEG) are important tools with which to predict Glasgow Outcome Scale (GOS) scores. Their combined use may potentially allow for early detection of neurological impairment and more effective treatment of clinical deterioration.

Methods

We followed up 68 selected comatose patients between 2007 and 2009 who had been admitted to the Neurosurgical Intensive Care Unit of Treviso Hospital after being diagnosed with subarachnoid haemorrhage (51 cases) or intracerebral haemorrhage (17 cases). Quantitative brain function monitoring was carried out using a remote EEG-SEP recording system connected to a small amplification head box with 28 channels and a multimodal stimulator (NEMO; EBNeuro, Italy NeMus 2; EBNeuro S.p.A., Via P. Fanfani 97/A - 50127 Firenze, Italy). For statistical analysis, we fit a binary logistic regression model to estimate the effect of brain function monitoring on the probability of GOS scores equal to 1. We also designed a proportional odds model for GOS scores, depending on amplitude and changes in both SEPs and EEG as well as on the joint effect of other related variables. Both families of models, logistic regression analysis and proportional odds ratios, were fit by using a maximum likelihood test and the partial effect of each variable was assessed by using a likelihood ratio test.

Results

Using the logistic regression model, we observed that progressive deterioration on the basis of EEG was associated with an increased risk of dying by almost 24% compared to patients whose condition did not worsen according to EEG. SEP decreases were also significant; for patients with worsening SEPs, the odds of dying increased to approximately 32%. In the proportional odds model, only modifications of Modified Glasgow Coma Scale scores and SEPs during hospitalisation statistically significantly predicted GOS scores. Patients whose SEPs worsened during the last time interval had an approximately 17 times greater probability of a poor GOS score compared to the other patients.

Conclusions

The combined use of SEPs and continuous EEG monitoring is a unique example of dynamic brain monitoring. The temporal variation of these two parameters evaluated by continuous monitoring can establish whether the treatments used for patients receiving neurocritical care are properly tailored to the neurological changes induced by the lesions responsible for secondary damage.

Urgent continuous EEG (cEEG) monitoring leads to changes in treatment in half of cases

How Seizure Detection by Continuous Electroencephalographic Monitoring Affects the Prescribing of Antiepileptic Medications. Kilbride RD, Costello DJ, Chiappa KH. Arch Neurol 2009;66(6):723–728.

Objectives

To assess the effect of continuous electroencephalographic monitoring on the decision to treat seizures in the inpatient setting, particularly in the intensive care unit.

Design

Retrospective cohort study.

Setting

Medical and neuroscience intensive care units and neurological wards.

Patients

Three hundred consecutive nonelective continuous electroencephalographic monitoring studies, performed on 287 individual inpatients over a 27-month period.

Main Outcome Measures

Epileptiform electroencephalographic abnormalities and changes in antiepileptic drug (AED) therapy based on the electroencephalographic findings.

Results

The findings from the continuous electroencephalographic monitoring led to a change in AED prescribing in 52% of all studies with initiation of an AED therapy in 14%, modification of AED therapy in 33%, and discontinuation of AED therapy in 5% of all studies. Specifically, the detection of electrographic seizures led to a change in AED therapy in 28% of all studies.

Conclusions

The findings of continuous electroencephalographic monitoring resulted in a change in AED prescribing during or after half of the studies performed. Most AED changes were made as a result of the detection of electrographic seizures.

Nonconvulsive status epilepticus: a diagnostic and therapeutic challenge in the intensive care setting

Nonconvulsive status epilepticus (NCSE) comprises a group of syndromes that display a great diversity regarding response to anticonvulsants ranging from virtually self-limiting variants to entirely refractory forms. Therefore, treatment on intensive care units (ICUs) is required only for a selection of cases. The aetiology and clinical form of NCSE are strong predictors for the overall prognosis. Absence status epilepticus is commonly seen in patients with idiopathic generalized epilepsy and is rapidly terminated by low-dose of benzodiazepines. The management of complex partial status epilepticus is straightforward in patients with pre-existing epilepsy, but poses major problems if occurring in the context of acute brain lesions. Subtle status epilepticus represents the late stage of undertreated previous overt generalized convulsive status epilepticus and always requires aggressive ICU treatment. Within the intensive care setting, the diagnostic challenge may be seen in the difficulty in delineating nonepileptic conditions such as posthypoxic, metabolic or septic encephalopathies from NCSE. Although all important forms are considered, the focus of this review lies on clinical presentations and electroencephalogram features of comatose patients treated on ICUs and possible diagnostic pitfalls.

A novel approach for computer assisted EEG monitoring in the adult ICU

OBJECTIVE

The implementation of a computer assisted system for real-time classification of the electroencephalogram (EEG) in critically ill patients.

METHODS

Eight quantitative features were extracted from the raw EEG and combined into a single classifier. The system was trained with 41 EEG recordings and subsequently evaluated using an additional 20 recordings. Through visual analysis, each recording was assigned to one of the following categories: normal, iso-electric, low voltage, burst suppression, slowing, and EEGs with generalized periodic discharges or seizure activity.

RESULTS

36 (88%) recordings from the training set and 17 (85%) recordings from the test set were classified correctly. A user interface was developed to present both trend-curves and a diagnostic output in text form. Implementation in a dedicated EEG monitor allowed real-time analysis in the intensive care unit (ICU) during pilot measurements in four patients.

CONCLUSIONS

We present the first results from a computer assisted EEG interpretation system, based on a combination of eight quantitative features. Our system provided an initial, reasonably accurate interpretation by non-experts of the most common EEG patterns observed in neurological patients in the adult ICU.

SIGNIFICANCE

Computer assisted EEG monitoring may improve early detection of seizure activity and ischemia in critically ill patients.

Multimodal Cerebral Monitoring in Traumatic Brain Injury

Traumatic brain injury presents a significant impact on patients in terms of morbidity and mortality. Pathology is heterogeneous and is often associated with secondary deterioration. This paper reviews both clinical and research modes of monitoring to detect deterioration and compares what is available to the ideal. Intracranial pressure measurement, jugular venous oxygen saturation, microdialysis and cerebral oxygen monitoring are among the variables described and future research-based modalities are explored.

Continuous video-EEG monitoring increases detection rate of nonconvulsive status epilepticus in the ICU

PURPOSE

Status epilepticus (SE) is an important neurologic emergency requiring treatment on an intensive care unit (ICU). Although convulsive SE is self-evident, the diagnosis of nonconvulsive SE (NCSE) depends on electroencephalography (EEG) confirmation. Previous work showed that 82% of patients with SE had NCSE in our ICU. We hypothesize that continuous video-EEG monitoring (CVEM) may increase the diagnostic yield in patients with SE, especially NCSE, and leave fewer patients undiagnosed.

METHODS

We retrospectively assessed the EEG reports of 537 patients with suspected SE during three comparable 9-month periods, two groups before (groups 1 and 2) and one (group 3) after CVEM introduction. Differences in monthly rates of SE between groups were assessed using the Mann-Whitney U-test.

KEY FINDINGS

The rates of diagnosis increased significantly after implementation of CVEM (p = 0.0546). There was no significant difference in monthly rates of NCSE diagnosis between groups 2 and 1 (difference = 0.78 new diagnosis/month; p = 0.374). Differences between groups 3 and 2 (2.89; p = 0.0173), between groups 3 and 1 (3.67; p = 0.006) and between group 3 and pooled groups 1 and 2 (3.28; p = 0.002) were statistically significant.

SIGNIFICANCE

Frequency of NCSE diagnosis increased significantly after implementation of CVEM and was higher than the increment of performed investigations alone. Such an effect may result from the combination of longer observation periods during CVEM, greater and permanent availability of EEG recordings, and heightened awareness of NCSE. Future studies may corroborate improvement of diagnosis and outcomes in patients with disorders of consciousness by CVEM.

Prognostic value of continuous EEG monitoring during therapeutic hypothermia after cardiac arrest

Introduction

Continuous EEG (cEEG) is increasingly used to monitor brain function in neuro-ICU patients. However, its value in patients with coma after cardiac arrest (CA), particularly in the setting of therapeutic hypothermia (TH), is only beginning to be elucidated. The aim of this study was to examine whether cEEG performed during TH may predict outcome.

Methods

From April 2009 to April 2010, we prospectively studied 34 consecutive comatose patients treated with TH after CA who were monitored with cEEG, initiated during hypothermia and maintained after rewarming. EEG background reactivity to painful stimulation was tested. We analyzed the association between cEEG findings and neurologic outcome, assessed at 2 months with the Glasgow-Pittsburgh Cerebral Performance Categories (CPC).

Results

Continuous EEG recording was started 12 ± 6 hours after CA and lasted 30 ± 11 hours. Nonreactive cEEG background (12 of 15 (75%) among nonsurvivors versus none of 19 (0) survivors; P < 0.001) and prolonged discontinuous "burst-suppression" activity (11 of 15 (73%) versus none of 19; P < 0.001) were significantly associated with mortality. EEG seizures with absent background reactivity also differed significantly (seven of 15 (47%) versus none of 12 (0); P = 0.001). In patients with nonreactive background or seizures/epileptiform discharges on cEEG, no improvement was seen after TH. Nonreactive cEEG background during TH had a positive predictive value of 100% (95% confidence interval (CI), 74 to 100%) and a false-positive rate of 0 (95% CI, 0 to 18%) for mortality. All survivors had cEEG background reactivity, and the majority of them (14 (74%) of 19) had a favorable outcome (CPC 1 or 2).

Conclusions

Continuous EEG monitoring showing a nonreactive or discontinuous background during TH is strongly associated with unfavorable outcome in patients with coma after CA. These data warrant larger studies to confirm the value of continuous EEG monitoring in predicting prognosis after CA and TH.

Seizure identification in the ICU using quantitative EEG displays

OBJECTIVE

To evaluate the diagnostic accuracy of 2 quantitative EEG display tools, color density spectral array (CDSA) and amplitude-integrated EEG (aEEG), for seizure identification in the intensive care unit (ICU).

METHODS

A set of 27 continuous EEG recordings performed in pediatric ICU patients was transformed into 8-channel CDSA and aEEG displays. Three neurophysiologists underwent 2 hours of training to identify seizures using these techniques. They were then individually presented with a series of CDSA and aEEG displays, blinded to the raw EEG, and asked to mark any events suspected to be seizures. Their performance was compared to seizures identified on the underlying conventional EEG.

RESULTS

The 27 EEG recordings contained 553 discrete seizures over 487 hours. The median sensitivity for seizure identification across all recordings was 83.3% using CDSA and 81.5% using aEEG. However, among individual recordings, the sensitivity ranged from 0% to 100%. Factors reducing the sensitivity included low-amplitude, short, and focal seizures. False-positive rates were generally very low, with misidentified seizures occurring once every 17-20 hours.

CONCLUSIONS

Both CDSA and aEEG demonstrate acceptable sensitivity and false-positive rates for seizure identification among critically ill children. Accuracy of these tools would likely improve during clinical use, when findings can be correlated in real-time with the underlying raw EEG. In the hands of neurophysiologists, CDSA and aEEG displays represent useful screening tools for seizures during continuous EEG monitoring in the ICU. The suitability of these tools for bedside use by ICU nurses and physicians requires further study.

A case of frontal lobe epilepsy in which amplitude-integrated EEG combined with conventional EEG was useful for evaluating clusters of seizures

Accurate evaluation of status epilepticus or clusters of seizures in patients with epilepsy is a critical issue in epilepsy care units. Although the need for continuous electroencephalographic monitoring has been recognized, it has been difficult to evaluate the frequency of ictal changes in electroencephalography (EEG) data in real time. Amplitude-integrated EEG (aEEG) has been reported to be useful for neuromonitoring, particularly in newborn infants. However, few reports of the utility of aEEG in older children with epilepsy have been published. We employed aEEG in combination with conventional EEG in an 11-year old boy presenting with clusters of seizures and were able to accurately evaluate the frequency of seizures in real time. The combination of aEEG and conventional EEG may be a useful tool in both neonatal intensive care units and epilepsy care units.

Use of EEG monitoring and management of non-convulsive seizures in critically ill patients: a survey of neurologists

BACKGROUND

Continuous EEG monitoring (cEEG) of critically ill patients is frequently utilized to detect non-convulsive seizures (NCS) and status epilepticus (NCSE). The indications for cEEG, as well as when and how to treat NCS, remain unclear. We aimed to describe the current practice of cEEG in critically ill patients to define areas of uncertainty that could aid in designing future research.

METHODS

We conducted an international survey of neurologists focused on cEEG utilization and NCS management.

RESULTS

Three-hundred and thirty physicians completed the survey. 83% use cEEG at least once per month and 86% manage NCS at least five times per year. The use of cEEG in patients with altered mental status was common (69%), with higher use if the patient had a prior convulsion (89%) or abnormal eye movements (85%). Most respondents would continue cEEG for 24 h. If NCS or NCSE is identified, the most common anticonvulsants administered were phenytoin/fosphenytoin, lorazepam, or levetiracetam, with slightly more use of levetiracetam for NCS than NCSE.

CONCLUSIONS

Continuous EEG monitoring (cEEG) is commonly employed in critically ill patients to detect NCS and NCSE. However, there is substantial variability in current practice related to cEEG indications and duration and to management of NCS and NCSE. The fact that such variability exists in the management of this common clinical problem suggests that further prospective study is needed. Multiple points of uncertainty are identified that require investigation.

Status epilepticus

Status epilepticus (SE) is one of the most commonly occurring neurologic emergencies. About 40% of SE cases occur in people with epilepsy. Convulsive SE is easily recognized, but nonconvulsive SE is not and requires both a high index of suspicion and EEG confirmation. SE has a high mortality risk and requires rapid effective treatment for optimal response to therapy and outcome. The goal of treatment is to stop all clinical and electrographic seizures while maintaining vital functions. If seizures continue after initial treatment with a benzodiazepine, additional antiepileptic therapy should be administered. When SE is refractory to these treatments, continuous IV infusion with midazolam, propofol, or a barbiturate suppresses seizure activity. Standard treatment protocols are useful in promoting rapid intervention with appropriate medications.

How I treat patients with EEG patterns on the ictal-interictal continuum in the neuro ICU

Refractory status epilepticus (RSE) is associated with a high risk of poor outcome and treated by most neurointensivists with continuous intravenous antiepileptic medications (cIV-AEDs). Continuous EEG monitoring has allowed us to unveil a number of epileptiform patterns of less certain significance. These have been labeled ictal to interictal continuum (IIC), many of which are associated with poor outcome. It is unclear to which extent individual patterns are epiphenomena or lead to additional brain injury. The treatment of these patterns is highly controversial and guidelines how to manage them are non existent. In this review of a challenging case, I will discuss a number of approaches to determine the ictal nature of the IIC in an effort to minimize neuronal injury from epileptiform brain activity on the one hand and from the treatment on the other hand. Ultimately it will be most important to replace the dichotomy of ictal versus non-ictal patterns by differentiating between harmful and non-harmful patterns.