Predictors of neurologic outcome in hypothermia after cardiac arrest

Surviving refractory out-of-hospital ventricular fibrillation cardiac arrest: Critical care and extracorporeal membrane oxygenation management

BACKGROUND

Resuscitation of refractory out-of-hospital ventricular fibrillation/ventricular tachycardia (VF/VT) cardiac arrest using extracorporeal membrane oxygenation (ECMO) establishes a complex patient population. We aimed to describe the critical care strategies and outcomes in this population.

METHODS

Between December 1, 2015 and January 1, 2018, 100 consecutive adult patients with refractory VF/VT out-of-hospital cardiac arrest and ongoing CPR were transported to the cardiac catheterization laboratory. ECMO, coronary angiography, and percutaneous coronary intervention were performed. Patients achieving an organized cardiac rhythm were admitted to the cardiac intensive care unit (CICU). All patients were considered eligible for necessary intervention/surgery until declaration of death.

RESULTS

Of 100 appropriately transported patients, 83 achieved CICU admission. 40/83 (48%) discharged functionally intact. Multi-system organ failure occurred in all patients. Cardiac, pulmonary, renal, and liver injury improved within 3-4 days. Neurologic injury caused death in 26/37 (70%) patients. Poor neurologic outcomes were associated with anoxic injury or cerebral edema on admission head CT, decline in cerebral oximetry over the first 48 h, and elevated neuron specific enolase on CICU admission. For survivors, mean time to ECMO decannulation was 3.5 ± 0.2 days, following commands at 5.7 ± 0.8 days, and hospital discharge at 21 ± 3.2 days. 41/83 (49%) patients developed infections. CPR caused traumatic injury requiring procedural/surgical intervention in 22/83 (27%) patients.

CONCLUSIONS

Multi-system organ failure is ubiquitous but treatable with adequate hemodynamic support. Neurologic recovery was prolonged requiring delayed prognostication. Immediate 24/7 availability of surgical and medical specialty expertise was required to achieve 48% functionally intact survival.

The neuron specific enolase (NSE) ratio offers benefits over absolute value thresholds in post-cardiac arrest coma prognosis

INTRODUCTION

Serum neuron-specific enolase (NSE) levels have been shown to correlate with neurologic outcome in comatose survivors of cardiac arrest but use of absolute NSE thresholds is limited. This study describes and evaluates a novel approach to analyzing NSE, the NSE ratio, and evaluates the prognostic utility of NSE absolute value thresholds and trends over time.

METHODS

100 consecutive adult comatose cardiac arrest survivors were prospectively enrolled. NSE levels were assessed at 24, 48, and 72 h post-arrest. Primary outcome was the Glasgow Outcome Score (GOS) at 6 months post-arrest; good outcome was defined as GOS 3-5. Absolute and relative NSE values (i.e. the NSE ratio), peak values, and the trend in NSE over 72 h were analyzed.

RESULTS

98 patients were included. 42 (43%) had a good outcome. Five good outcome patients had peak NSE >33 µg/L (34.9-46.4 µg/L). NSE trends between 24 and 48 h differed between outcome groups (decrease by 3.0 µg/L (0.9-7.0 µg/L) vs. increase by 13.4 µg/L (-3.7 to 69.4 µg/L), good vs. poor, p = 0.004). The 48:24 h NSE ratio differed between the good and poor outcome groups (0.8 (0.6-0.9) vs. 1.4 (0.8-2.5), p = 0.001), and a 48:24 h ratio of ≥1.7 was 100% specific for poor outcome.

CONCLUSIONS

The NSE ratio is a unique method to quantify NSE changes over time. Values greater than 1.0 indicate increasing NSE and may be reflective of ongoing neuronal injury. The NSE ratio obviates the need for an absolute value cut-off.

SSEP in Therapeutic Hypothermia Era

PURPOSE

The reliability of somatosensory evoked potentials (SSEPs) in predicting outcome in comatose survivors of cardiac arrest treated with therapeutic hypothermia (TH) has been questioned. We investigated whether the absence of cortical (N20) responses was a reliable predictor of a nonawakening in the setting of TH.

METHODS

A retrospective review was conducted in cardiac arrest survivors treated with TH admitted to a single tertiary care hospital from April, 2010 to March, 2013 who underwent SSEP testing at various time points after cardiac arrest. N20 responses were categorized as normal, present but abnormal, bilaterally absent, or inadequate for interpretation. Neurologic outcome was assessed at discharge by the Cerebral Performance Category Scale (CPC).

RESULTS

Ninety-three SSEP studies were performed in 73 patients. Fourteen patients had absent N20 responses; all had poor outcome (CPC 4-5). Eleven patients had absent N20 s during hypothermia, three of whom had follow-up SSEPs after rewarming and cortical responses remained absent. Fifty-seven patients had N20 peaks identified and had variable outcomes. Evaluation of 1 or more N20 peaks was limited or inadequate in 11.4% of SSEPs performed during the cooling because of artifact.

CONCLUSIONS

Somatosensory evoked potentials remain a reliable prognostic indicator in patients undergoing TH. The limited sample size of patients who had SSEP performed during TH and repeated after normothermia added to the effect of self-fulfilling prophecy limit the interpretation of the reliability of this testing when performed during cooling. Further prospective, multicenter, large scale studies correlating cortical responses in SSEPs during and after TH are warranted. Technical challenges are commonplace during TH and caution is advised in the interpretation of suboptimal recordings.

Anoxic-Ischemic Brain Injury

Improvements in cardiopulmonary resuscitation and intensive care medicine have led to declining mortality rates for patients with out-of-hospital cardiac arrest, but overall it is still a minority that achieves good outcomes. Estimating neurologic prognosis for patients that remain comatose after resuscitation remains a challenge and the need for accurate and early prognostic predictors is crucial. A thoughtful approach is required and should take into account information acquired from multiple tests in association with neurologic examination. No decision should be made based on a single predictor. In addition to clinical examination, somatosensory evoked potentials, electroencephalogram, serum biomarkers, and neuroimaging provide complimentary information to inform prognosis.

Long-term risk of seizures among cardiac arrest survivors

INTRODUCTION

The long-term risk of seizures in cardiac arrest survivors is not established. We hypothesized that survivors of cardiac arrest face an increased long-term risk for seizures.

METHODS

We performed a retrospective cohort study using 2008-2015 claims data from a nationally representative 5% sample of Medicare beneficiaries ≥66 years-old. Our exposure of interest was a hospital diagnosis code of cardiac arrest, defined by previously validated ICD-9-CM codes. Since we were interested in long-term risk, we excluded patients with a history of seizure, and those who were diagnosed with a seizure during hospitalization or died during the index hospitalization. Our outcome was a diagnosis of seizure. Survival statistics were used to calculate seizure incidence and Cox proportional hazards models were used to determine the association between cardiac arrest and long-term seizures after adjustment for demographics and Charlson comorbidities.

RESULTS

Among 1,764,508 beneficiaries with a mean 4.5 years of follow-up, we identified 57,437 patients with cardiac arrest who survived to discharge without a seizure. The annual incidence of seizures was 1.26% (95% confidence interval [CI], 1.20-1.33%) compared to 0.61% (95% CI, 0.61-0.62%) in other Medicare patients. In unadjusted analysis, cardiac arrest was associated with an increased risk of post-discharge seizures (hazard ratio [HR], 1.8; 95% CI, 1.7-1.9), but the association was lost after adjustment for demographics and comorbidities (HR 0.9; 95% CI, 0.9-1.0; P = 0.12).

CONCLUSION

The long-term risk of seizures was not elevated in patients with cardiac arrest who survived to hospital discharge without a seizure.

Accuracy of the first interpretation of early brain CT images for predicting the prognosis of post-cardiac arrest syndrome patients at the emergency department

Background

Early brain CT is one of the most useful tools for estimating the prognosis in patients with post-cardiac arrest syndrome (PCAS) at the emergency department (ED). The aim of this study was to evaluate the prognosis-prediction accuracy of the emergency physicians' interpretation of the findings on early brain CT in PCAS patients treated by targeted temperature management (TTM).

Methods

This was a double-center, retrospective, observational study. Eligible subjects were cardiac arrest patients admitted to the intensive care unit (ICU) for TTM between April 2011 and March 2017. We performed the McNemar test to compare the predictive accuracies of the interpretation by emergency physicians and radiologists and calculated the kappa statistic for determining the concordance rate between the interpretations by these two groups.

Results

Of the 122 eligible patients, 106 met the inclusion criteria for this study. The predictive accuracies (sensitivity, specificity) of the interpretations by the emergency physicians and radiologists were (0.34, 1.00) and (0.41, 0.93), respectively, with no significant difference in either the sensitivity or specificity as assessed by the McNemar test. The kappa statistic calculated to determine the concordance between the two interpretations was 0.66 (0.48-0.83), which showed a good conformity.

Conclusions

The emergency physicians' interpretation of the early brain CT findings in PCAS patients treated by TTM was as reliable as that of radiologists, in terms of prediction of the prognosis.

Effect of regional cerebral oximetry to estimate neurologic prognostic outcomes in patients administered targeted temperature management

PURPOSE

The aim of our study is to research the role and efficacy of cerebral oximetry in predicting neurologic prognosis when applied during TTM to patients experiencing coma after CA.

METHODS

This study was performed on surviving adult comatose patients after CA treated with TTM. The average scores of rSO₂ was measured at 6h intervals for the first 2days and once a day for the following 3days with a NIRS device during TTM. The CPC scale was used to define the neurologic outcomes of patients. We compared the correlations of rSO₂ values between good (CPC 1-2) and poor (CPC 3-5) neurologic outcomes in CA patients.

RESULTS

There was no statistically significant difference identified between the prognosis groups in terms of rSO₂, CPR durations, hemoglobin values and admission body temperature (p>0.05). When the variation in rSO₂ values over time is investigated, though there was no significant difference between the good and poor prognosis groups, it appeared to fall in the first 6h in both prognosis groups. The median NT-proBNP and lactate values were observed to be higher in the poor prognosis group.

CONCLUSION

There is no significant correlation between rSO₂ values and neurologic outcomes. Multimodal monitoring methods may be useful and further studies with a larger patient population are necessary in this area.

Prognostic performance of early absence of pupillary light reaction after recovery of out of hospital cardiac arrest

INTRODUCTION

Loss of pupillary light reactivity (PLR) three days after a cardiorespiratory arrest is a prognostic factor. Its predictive value upon hospital admission remains unclear. Our objective was to determine the prognostic value of the absence of PLR upon hospital admission in patients with out-of-hospital cardiac arrest.

METHODS

We prospectively included all out-of-hospital cardiac arrests occurring between July 2011 and July 2017 treated by a mobile medical team (MMT) based on data from a French cardiac arrest registry database. PLR was evaluated upon hospital admission and the outcome on day 30. The prognosis was classified as good for Cerebral Performance Category (CPC) 1 or 2, and poor for CPC 3-5 or in case of death.

RESULTS

Data from 10151 patients was analysed. The sensitivity and specificity of the absence of PLR for a poor outcome were 72.2% (71.2-73.2) and 68.8% (66.7-70.1), respectively. We identified several variables modifying the sensitivity values and the false positive fraction of a factor, ranging from 0.49 (0.35-0.69) for the Glasgow Coma Scale to 2.17 (1.09-2.48) for pupillary asymmetry. Among those living with CPC 1 or 2 on day 30 (n = 1990; 19.6%), 621 (31.2% (29.2-33.3)) had no PLR upon hospital admission. In the multivariate analysis, loss of PLR was associated with a poor outcome (OR = 3.1 (2.7-3.5)).

CONCLUSIONS

Loss of pupillary light reactivity upon hospital admission is predictive of a poor outcome after out-of-hospital cardiac arrest. However, it does not have sufficient accuracy to determine prognosis and decision making.

Postanoxic alpha, theta or alpha-theta coma: Clinical setting and neurological outcome

AIM

The aim of this study was to determine the prognosis of 26 consecutive adults with alpha coma (AC), theta coma (TC) or alpha-theta coma (ATC) following CRA and to describe the clinical setting and EEG features of these patients.

METHODS

We retrospective analyzed a prospectively collected cohort of adult patients diagnosed as having AC, TC or ATC after CRA between January 2008 and June 2016. None of patients included in this analysis underwent therapeutic hypothermia (TH). Neurological outcome was expressed as the best score 6 months after CRA using the five-point Glasgow-Pisttsburgh Cerebral Performance Categories (CPC) RESULTS: Twenty-six patients were identified with a diagnosis of postanoxic AC, TC or ATC coma. There were 20 (77%) men and 6 (23%) women. The mean age was 63 ± 16 years. The most frequent EEG pattern was TC (21 patients, 80%), followed by AC (3 patients, 12%) and ATC (2 patients, 8%). The cardiac rhythm as primary origin of the CRA was ventricular fibrillation (VF) in 16 patients (61.5%), asystole in 8 patients (34.6%) and ventricular tachycardia (VT) in one patient (3.8%). The presence of EEG reactivity was present in 8 patients (30%). The mortality rate was 85%. Of the 4 surviving patients, two (3.8%) had moderate disability (CPC 2), one (3.8%) had severe disability (CPC 3) and one (3.8%) reached a good recovery. The age was significantly lower in survivors 46.2 ± 10.8 versus nonsurvivors 63.3 ± 15.5 (p = 0.04). There was increased association of EEG reactivity with survival (p = 0.07).

CONCLUSION

Hypoxic-ischemic AC, TC and ATC are associated with a poor prognosis and a high rate of mortality. In younger patients with AC, TC and ATC and incomplete forms showing reactivity on the EEG, there is a greater probability of clinical recovery.

Effect of sedation on quantitative electroencephalography after cardiac arrest

BACKGROUND

Electroencephalography (EEG) has clinical and prognostic importance after cardiac arrest (CA). Recently, interest in quantitative EEG (qEEG) analysis has grown. The qualitative effects of sedation on EEG are well known, but potentially confounding effects of sedatives on qEEG after anoxic injury are poorly characterized. We hypothesize that sedation increases suppression ratio (SR) and decreases alpha/delta ratio (ADR) and amplitude-integrated EEG (aEEG), and that the magnitude of sedation effects will be associated with outcome.

METHODS

We routinely monitor comatose post-arrest patients with EEG for 48-72h. We included comatose EEG-monitored patients after CA who had protocolized daily sedation interruptions. We used Persyst v12 to quantify qEEG parameters and calculated medians for 10min immediately prior to sedation interruption and for the last 5min of interruption. We used paired t-tests to determine whether qEEG parameters changed with sedation cessation, and logistic regression to determine whether these changes predicted functional recovery or survival at discharge.

RESULTS

78 subjects were included (median age 56, 65% male). Interruptions occurred a median duration of 34h post-arrest and lasted a median duration of 60min. Prior to interruption, higher aEEG predicted survival, while lower SR predicted both survival and favorable outcome. During interruption, SR decreased (p<0.001), aEEG increased (p=0.002), and ADR did not change. Larger decreases in SR predicted decreased survival (OR=1.04 per percent change; 95% CI 1.00-1.09).

CONCLUSION

Higher aEEG and lower SR predict survival after CA. Sedation alters aEEG and SR, but importantly does not appear to affect the relationship between these parameter values and outcome.

Occurrence of overt seizures in comatose survivor patients treated with targeted temperature

BACKGROUND

Unconscious patients after out-of-hospital cardiac arrest have a high risk of death. Therapeutic hypothermia is recommended by international resuscitation guidelines in order to attenuate secondary destructive physiological processes such as reperfusion injury, apoptosis, and cerebral edema. The target temperature to reach ranges between 32 and 34°C for at least 24 hr. Hypothermia can induce metabolic disturbances. There are some reports in the literature indicating the presence of seizures during targeted temperature management. On the other hand, postanoxic seizures are a sign of unfavorable neurological outcome. The purpose of this study was to evaluate the occurrence of overt seizures in comatose survivor patients treated with targeted temperature in respect to overt seizures in a normal temperature group of comatose patients.

METHODS

This was a retrospective study of unconscious adults post cardiopulmonary resuscitation, hospitalized in the intensive care unit during the years 2008-2015. The patients were divided into two groups: those treated with hypothermia and those with normal body temperature. Both groups were evaluated for the appearance of overt seizures during their hospitalization which was the primary outcome of the study.

RESULTS

The data of 88 consecutive unconscious patients after out-of-hospital cardiac arrest were collected. Twenty-six patients were treated with targeted temperature (32-34°C) and 62 patients with normal temperature. In the hypothermic group, 6 (23%) patients developed overt seizures during hospitalization compared to 11 (17%) in the normothermic group. The mortality rate was similar in both groups, 16 (61%) in the hypothermic group and 38 (61%) in the conservative group. According to the present study, overt seizures were more common in the group treated with hypothermia.

Accuracy of Limited-Montage Electroencephalography in Monitoring Postanoxic Comatose Patients

BACKGROUND

Continuous EEG (cEEG) monitoring may help to identify the small percentage of adults with hypoxic-ischemic encephalopathy (HIE) who will regain consciousness if allowed sufficient time. However, the limited yield in this population has led some to question the cost-effectiveness cEEG monitoring in this population. We hypothesized that limited-montage cEEG could provide essentially the same neurophysiologic information at lower cost. In this proof of concept study, we aim to demonstrate the potentials of limited channel EEG in prognostication in postanoxic patients.

METHODS

We retrospectively reviewed cEEG data from cases monitored at our institution with conventional 21-channel EEG over a 6-month period. Twenty-eight cases were identified in which patients with HIE underwent cEEG for at least 24 hours. Gold-standard findings were determined by conventional visual analysis of the full cEEG, and 2 independent electroencephalographers scored the same data using only limited-montage (4-channel) views. The sensitivity and specificity of limited-montage cEEG review were compared with conventional analysis. We also compared the relative costs of conventional and limited-montage EEG.

RESULTS

Using 4-channel limited montage cEEG, reviewers were able to classify accurately background continuity (in 88%), background amplitude (in 81%), maximum background frequency (in 70%), periodic epileptiform discharges, including a seizure (in 92%) and sporadic discharges (in 91%). All epileptiform features were detected with greater than 90% sensitivity and specificity. Eye movement artifact seen over bifrontal electrodes gave false positive detections of periodic epileptiform discharges in 31% of cases.

CONCLUSIONS

Limited-channel continuous EEG monitoring can provide meaningful electrophysiological data that can be used for prognostication in postanoxic comatose patients. Limited channel EEG can be a cost-effective alternative to conventional EEG monitoring in post-anoxic comatose patients.

Early Withdrawal Decision-Making in Patients with Coma After Cardiac Arrest: A Qualitative Study of Intensive Care Clinicians

INTRODUCTION

Neurologists are often asked to define prognosis in comatose patients. However, comatose patients following cardiac arrest are usually cared for by cardiologists or intensivists, and it is their approach that will influence decisions regarding withdrawal of life-sustaining interventions (WLSI). We observed that factors leading to these decisions vary across specialties and considered whether they could result in self-fulfilling prophecies and early WLSI. We conducted a hypothesis-generating qualitative study to identify factors used by non-neurologists to define prognosis in these patients and construct an explanatory model for how early WLSI might occur.

METHODS

This was a single-center qualitative study of intensivists caring for cardiac arrest patients with hypoxic-ischemic coma. Thirty attending physicians (n = 16) and fellows (n = 14) from cardiac (n = 8), medical (n = 6), surgical (n = 10), and neuro (n = 6) intensive care units underwent semi-structured interviews. Interview transcripts were analyzed using grounded theory techniques.

RESULTS

We found three components of early WLSI among non-neurointensivists: (1) development of fixed negative opinions; (2) early framing of poor clinical pictures to families; and (3) shortened windows for judging recovery potential. In contrast to neurointensivists, non-neurointensivists' negative opinions were frequently driven by patients' lack of consciousness and cardiopulmonary resuscitation circumstances. Both groups were influenced by age and comorbidities.

CONCLUSIONS

The results demonstrate that factors influencing prognostication differ across specialties. Some differ from those recommended by published guidelines and may lead to self-fulfilling prophecies and early WLSI. Better understanding of this framework would facilitate educational interventions to mitigate this phenomenon and its implications on patient care.

Post-ischemic Myoclonic Status Following Cardiac Arrest in Young Drug Users

BACKGROUND

Myoclonic status may be observed following cardiac arrest and has previously been identified as a poor prognostic indicator in regard to return of neurologic function. We describe a unique situation in post-cardiac arrest patients with myoclonic status and hypothesize possible predictors of a good neurologic outcome.

METHODS

Case series.

RESULTS

We illustrate two cases of cardiac arrest due to a respiratory cause in young patients with evidence of illicit drug use at the time of hospital admission that suffered post-ischemic myoclonic status. These patients subsequently recovered with good neurologic outcomes.

CONCLUSIONS

On rare occasions, myoclonic status does not imply a poor functional outcome following cardiac arrest. Other clinical and demographic characteristics including young age, presence of illicit substances, and primary respiratory causes of arrest may contribute to a severe clinical presentation, with a subsequent good neurologic outcome in a small subset of patients.

Prognostic Value of the Neurological Examination in Cardiac Arrest Patients After Therapeutic Hypothermia

Objectives

Current prognostication guidelines for cardiac arrest (CA) survivors predate the use of therapeutic hypothermia (TH). The prognostic value and ideal timing of the neurological examination remain unknown in the setting of TH.

Design

Patients (N = 291) admitted between 2007 and 2015 to Columbia University intensive care units for TH following CA had neurological examinations performed on days 1, 3, 5, and 7 postarrest. Absent pupillary light response (PLR), absent corneal reflexes (CRs), and Glasgow coma scores motor (GCS-M) no better than extension were considered poor examinations. Poor outcome was recorded as cerebral performance category score ≥3 at discharge and 1 year. Predictive values of examination maneuvers were calculated for each time point.

Main Results

Among the 137 survivors to day 7, sensitivities and negative predictive values were low at all time points. The PLR had false positive rates (FPRs) of 0% and positive predictive values (PPV) of 100% from day 3 onward. For the CR and GCS-M, the FPRs decreased from day 3 to 5 (9% vs 3%; 21% vs 9%), while PPVs increased (91% vs 96%; 90% vs 95%). Excluding patients who died due to withdrawal of life-sustaining therapy (WLST) did not significantly affect FPRs or PPVs, nor did assessing outcome at 1 year.

Conclusions

A poor neurological examination remains a strong predictor of poor outcome, both at hospital discharge and at 1 year, independent of WLST. Following TH, the predictive value of the examination is insufficient at day 3 and should be delayed until at least day 5, with some additional benefit beyond day 5.

The potential role of auditory evoked potentials to assess prognosis in comatose survivors from cardiac arrest

AIM

Few data are available on the use of brainstem auditory evoked potentials (BAEPs) in combination with other electrophysiological tools to assess prognosis of comatose survivors from cardiac arrest (CA).

METHODS

Retrospective analysis of data from all adult patients (>18years of age) admitted to our Dept of Intensive Care after CA over a 6-year period who were comatose (Glasgow Coma Scale <9) on admission, had been treated with targeted temperature management and had BAEP testing. We collected variables related to CA, as well as electroencephalography (EEG) findings, N20 somatosensory evoked potentials, and the presence of I, III and/or V waves on BAEP testing. Outcome was assessed at 3 months using the Cerebral Performance Categories (3-5=poor outcome).

RESULTS

We studied 65 patients; 48 (74%) had a poor neurological outcome. BAEP assessment was performed day 3 [3,4] after the CA. At least one of the three waves was absent bilaterally in 34 patients (52%); of these patients, 29 (85%) had a poor neurological outcome (sensitivity 60%, specificity 71%, positive predictive value [PPV] 85% and negative predictive value [NPV] 39%). Three patients (5%) had bilateral absence of all three waves, all of whom had a poor neurological outcome.

CONCLUSIONS

In this series of patients after CA, at least one of the BAEP waves was absent bilaterally in half the survivors; however, their use for prediction of poor neurological outcome remains limited.

Myoclonus After Cardiac Arrest: Where Do We Go From Here?

Prognostication after cardiac arrest often depends primarily on neurological function, and characterizing the extent of neurological injury hinges on neurophysiological testing and clinical neurological examination. The presence of early posthypoxic myoclonus (PHM) following cardiac arrest had been invariably associated with poor outcome, but more recent studies have shown that those with early PHM may survive with good neurological function. Electroencephalographic patterns suggestive of severe brain injury may be more valuable than the presence of PHM itself in portending poor functional status, and phenotyping PHM may also be useful in delineating benign and malignant forms. Patients with early PHM should be evaluated similarly to others who suffer cardiac arrest by using a multimodal approach in determining prognosis until further studies are performed that better characterize early PHM subtypes and their outcomes.

Neuron-Specific Enolase Predicts Poor Outcome After Cardiac Arrest and Targeted Temperature Management: A Multicenter Study on 1,053 Patients

OBJECTIVE

Outcome prediction after cardiac arrest is important to decide on continuation or withdrawal of intensive care. Neuron-specific enolase is an easily available, observer-independent prognostic biomarker. Recent studies have yielded conflicting results on its prognostic value after targeted temperature management.

DESIGN, SETTING, AND PATIENTS

We analyzed neuron-specific enolase serum concentrations 3 days after nontraumatic in-hospital cardiac arrest and out-of-hospital cardiac arrest and outcome of patients from five hospitals in Germany, Austria, and Italy. Patients were treated at 33°C for 24 hours. Cerebral Performance Category was evaluated upon ICU discharge. We performed case reviews of good outcome patients with neuron-specific enolase greater than 90 μg/L and poor outcome patients with neuron-specific enolase less than or equal to 17 μg/L (upper limit of normal).

MEASUREMENTS AND MAIN RESULTS

A neuron-specific enolase serum concentration greater than 90 μg/L predicted Cerebral Performance Category 4-5 with a positive predictive value of 99%, false positive rate of 0.5%, and a sensitivity of 48%. All three patients with neuron-specific enolase greater than 90 μg/L and Cerebral Performance Category 1-2 had confounders for neuron-specific enolase elevation. An neuron-specific enolase serum concentration less than or equal to 17 μg/L excluded Cerebral Performance Category 4-5 with a negative predictive value of 92%. The majority of 14 patients with neuron-specific enolase less than or equal to 17 μg/L who died had a cause of death other than hypoxic-ischemic encephalopathy. Specificity and sensitivity for prediction of poor outcome were independent of age, sex, and initial rhythm but higher for out-of-hospital cardiac arrest than for in-hospital cardiac arrest patients.

CONCLUSION

High neuron-specific enolase serum concentrations reliably predicted poor outcome at ICU discharge. Prediction accuracy differed and was better for out-of-hospital cardiac arrest than for in-hospital cardiac arrest patients. Our "in-the-field" data indicate 90 μg/L as a threshold associated with almost no false positives at acceptable sensitivity. Confounders of neuron-specific enolase elevation should be actively considered: neuron-specific enolase-producing tumors, acute brain diseases, and hemolysis. We strongly recommend routine hemolysis quantification. Neuron-specific enolase serum concentrations less than or equal to 17 μg/L argue against hypoxic-ischemic encephalopathy incompatible with reawakening.

Performing the Brain Death Examination and the Declaration of Pediatric Brain Death

Declaration of brain death is a clinical diagnosis made by the absence of neurological function in a comatose patient secondary to a known irreversible cause. Brain death determination is not an infrequent process in pediatric intensive care units. It is important that pediatric intensive care providers understand the definition of brain death and intensivists are able to implement brain death testing. The following is a narration detailing the process of brain death determination by physical examination. First, the prerequisites that determine patients' eligibility for brain death testing will be outlined. Next, each part of the physical exam, including the apnea test, will be described in detail. Finally, how the declaration of brain death is made is stated. In addition, special considerations and ancillary testing will be briefly highlighted.

Post-anoxic quantitative MRI changes may predict emergence from coma and functional outcomes at discharge

BACKGROUND

Traditional predictors of neurological prognosis after cardiac arrest are unreliable after targeted temperature management. Absence of pupillary reflexes remains a reliable predictor of poor outcome. Diffusion-weighted imaging has emerged as a potential predictor of recovery, and here we compare imaging characteristics to pupillary exam.

METHODS

We identified 69 patients who had MRIs within seven days of arrest and used a semi-automated algorithm to perform quantitative volumetric analysis of apparent diffusion coefficient (ADC) sequences at various thresholds. Area under receiver operating characteristic curves (ROC-AUC) were estimated to compare predictive values of quantitative MRI with pupillary exam at days 3, 5 and 7 post-arrest, for persistence of coma and functional outcomes at discharge. Cerebral Performance Category scores of 3-4 were considered poor outcome.

RESULTS

Excluding patients where life support was withdrawn, ≥2.8% diffusion restriction of the entire brain at an ADC of ≤650×10^-6m²/s was 100% specific and 68% sensitive for failure to wake up from coma before discharge. The ROC-AUC of ADC changes at ≤450×10^-6mm²/s and ≤650×10^-6mm²/s were significantly superior in predicting failure to wake up from coma compared to bilateral absence of pupillary reflexes. Among survivors, >0.01% of diffusion restriction of the entire brain at an ADC ≤450×10^-6m²/s was 100% specific and 46% sensitive for poor functional outcome at discharge. The ROC curve predicting poor functional outcome at ADC ≤450×10^-6mm²/s had an AUC of 0.737 (0.574-0.899, p=0.04).

CONCLUSION

Post-anoxic diffusion changes using quantitative brain MRI may aid in predicting persistent coma and poor functional outcomes at hospital discharge.

Early prediction of coma recovery after cardiac arrest with blinded pupillometry

OBJECTIVE

Prognostication studies on comatose cardiac arrest (CA) patients are limited by lack of blinding, potentially causing overestimation of outcome predictors and self-fulfilling prophecy. Using a blinded approach, we analyzed the value of quantitative automated pupillometry to predict neurological recovery after CA.

METHODS

We examined a prospective cohort of 103 comatose adult patients who were unconscious 48 hours after CA and underwent repeated measurements of quantitative pupillary light reflex (PLR) using the Neurolight-Algiscan device. Clinical examination, electroencephalography (EEG), somatosensory evoked potentials (SSEP), and serum neuron-specific enolase were performed in parallel, as part of standard multimodal assessment. Automated pupillometry results were blinded to clinicians involved in patient care. Cerebral Performance Categories (CPC) at 1 year was the outcome endpoint.

RESULTS

Survivors (n = 50 patients; 32 CPC 1, 16 CPC 2, 2 CPC 3) had higher quantitative PLR (median = 20 [range = 13-41] vs 11 [0-55] %, p < 0.0001) and constriction velocity (1.46 [0.85-4.63] vs 0.94 [0.16-4.97] mm/s, p < 0.0001) than nonsurvivors. At 48 hours, a quantitative PLR < 13% had 100% specificity and positive predictive value to predict poor recovery (0% false-positive rate), and provided equal performance to that of EEG and SSEP. Reduced quantitative PLR correlated with higher serum neuron-specific enolase (Spearman r = -0.52, p < 0.0001).

INTERPRETATION

Reduced quantitative PLR correlates with postanoxic brain injury and, when compared to standard multimodal assessment, is highly accurate in predicting long-term prognosis after CA. This is the first prognostication study to show the value of automated pupillometry using a blinded approach to minimize self-fulfilling prophecy. Ann Neurol 2017;81:804-810.

Neurophysiological prediction of neurological good and poor outcome in post-anoxic coma

OBJECTIVE

Investigation of the utility of association between electroencephalogram (EEG) and somatosensory-evoked potentials (SEPs) for the prediction of neurological outcome in comatose patients resuscitated after cardiac arrest (CA) treated with therapeutic hypothermia, according to different recording times after CA.

METHODS

Glasgow Coma Scale, EEG and SEPs performed at 12, 24 and 48-72 h after CA were assessed in 200 patients. Outcome was evaluated by Cerebral Performance Category 6 months after CA.

RESULTS

Within 12 h after CA, grade 1 EEG predicted good outcome and bilaterally absent (BA) SEPs predicted poor outcome. Because grade 1 EEG and BA-SEPs were never found in the same patient, the recording of both EEG and SEPs allows us to correctly prognosticate a greater number of patients with respect to the use of a single test within 12 h after CA. At 48-72 h after CA, both grade 2 EEG and BA-SEPs predicted poor outcome with FPR=0.0%. When these neurophysiological patterns are both present in the same patient, they confirm and strengthen their prognostic value, but because they also occurred independently in eight patients, poor outcome is predictable in a greater number of patients.

SIGNIFICANCE

The combination of EEG/SEP findings allows prediction of good and poor outcome (within 12 h after CA) and of poor outcome (after 48-72 h). Recording of EEG and SEPs in the same patients allows always an increase in the number of cases correctly classified, and an increase of the reliability of prognostication in a single patient due to concordance of patterns.

C-GRApH: A Validated Scoring System for Early Stratification of Neurologic Outcome After Out-of-Hospital Cardiac Arrest Treated With Targeted Temperature Management

Background

Out‐of‐hospital cardiac arrest (OHCA) results in significant morbidity and mortality, primarily from neurologic injury. Predicting neurologic outcome early post‐OHCA remains difficult in patients receiving targeted temperature management.

Methods and Results

Retrospective analysis was performed on consecutive OHCA patients receiving targeted temperature management (32–34°C) for 24 hours at a tertiary‐care center from 2008 to 2012 (development cohort, n=122). The primary outcome was favorable neurologic outcome at hospital discharge, defined as cerebral performance category 1 to 2 (poor 3–5). Patient demographics, pre‐OHCA diagnoses, and initial laboratory studies post‐resuscitation were compared between favorable and poor neurologic outcomes with multivariable logistic regression used to develop a simple scoring system (C‐GRApH). The C‐GRApH score ranges 0 to 5 using equally weighted variables: (C): coronary artery disease, known pre‐OHCA; (G): glucose ≥200 mg/dL; (R): rhythm of arrest not ventricular tachycardia/fibrillation; (A): age >45; (pH): arterial pH ≤7.0. A validation cohort (n=344) included subsequent patients from the initial site (n=72) and an external quaternary‐care health system (n=272) from 2012 to 2014. The c‐statistic for predicting neurologic outcome was 0.82 (0.74–0.90, P<0.001) in the development cohort and 0.81 (0.76–0.87, P<0.001) in the validation cohort. When subdivided by C‐GRApH score, similar rates of favorable neurologic outcome were seen in both cohorts, 70% each for low (0–1, n=60), 22% versus 19% for medium (2–3, n=307), and 0% versus 2% for high (4–5, n=99) C‐GRApH scores in the development and validation cohorts, respectively.

Conclusions

C‐GRApH stratifies neurologic outcomes following OHCA in patients receiving targeted temperature management (32–34°C) using objective data available at hospital presentation, identifying patient subsets with disproportionally favorable (C‐GRApH ≤1) and poor (C‐GRApH ≥4) prognoses.

Early predictors of poor outcome after out-of-hospital cardiac arrest

Background

Early identification of predictors for a poor long-term outcome in patients who survive the initial phase of out-of-hospital cardiac arrest (OHCA) may facilitate future clinical research, the process of care and information provided to relatives. The aim of this study was to determine the association between variables available from the patient’s history and status at intensive care admission with outcome in unconscious survivors of OHCA.

Methods

Using the cohort of the Target Temperature Management trial, we performed a post hoc analysis of 933 unconscious patients with OHCA of presumed cardiac cause who had a complete 6-month follow-up. Outcomes were survival and neurological function as defined by the Cerebral Performance Category (CPC) scale at 6 months after OHCA. After multiple imputations to compensate for missing data, backward stepwise multivariable logistic regression was applied to identify factors independently predictive of a poor outcome (CPC 3–5). On the basis of these factors, a risk score for poor outcome was constructed.

Results

We identified ten independent predictors of a poor outcome: older age, cardiac arrest occurring at home, initial rhythm other than ventricular fibrillation/tachycardia, longer duration of no flow, longer duration of low flow, administration of adrenaline, bilateral absence of corneal and pupillary reflexes, Glasgow Coma Scale motor response 1, lower pH and a partial pressure of carbon dioxide in arterial blood value lower than 4.5 kPa at hospital admission. A risk score based on the impact of each of these variables in the model yielded a median (range) AUC of 0.842 (0.840–0.845) and good calibration. Internal validation of the score using bootstrapping yielded a median (range) AUC corrected for optimism of 0.818 (0.816–0.821).

Conclusions

Among variables available at admission to intensive care, we identified ten independent predictors of a poor outcome at 6 months for initial survivors of OHCA. They reflected pre-hospital circumstances (six variables) and patient status on hospital admission (four variables). By using a simple and easy-to-use risk scoring system based on these variables, patients at high risk for a poor outcome after OHCA may be identified early.

Minimal EEG montage with high yield for the detection of status epilepticus in the setting of postanoxic brain damage

For the diagnosis of electrographic seizures or status epilepticus, we reduced the number of EEG-electrodes to make urgent EEG monitoring more feasible. Unlike the current existing research, with mixed results, we studied a specific population with postanoxic brain damage, expecting a higher yield of detection of ictal EEG patterns. In a population treated with therapeutic hypothermia post-cardiac arrest, the initial EEGs were reformatted in a longitudinal, a hairline and an 8-lead montage, and independently reviewed by two investigators. The EEGs were categorized into three categories: one without ictal EEG activity, one with interictal activity and one with probable electrographic seizure(s). Generalized ictal EEG activity was the most frequently observed EEG pattern. The average sensitivity for the detection of probable electrographic seizure(s) was 100 % for the 8-lead montage and 92 % in the hairline montage. In comparison to the routine longitudinal montage, the 8-lead montage proved to be reliable for the detection of electrographic seizure activity in a postanoxic population even with limited training in EEG interpretation. The hairline montage did not suffice with regard to the differential diagnosis of triphasic waves associated with metabolic encephalopathy and generalized nonconvulsive status epilepticus, but nonetheless detected the vast majority of probable electrographic seizure(s). Our results support the use of EEG monitoring with fewer electrodes for the detection of ictal EEG activity in the postanoxic population.

Neuroprognostication after adult cardiac arrest treated with targeted temperature management: task force for Belgian recommendations

The prognosis of patients who are admitted to the hospital after cardiac arrest often relies on neurological examination, which could be significantly influenced by the use of sedative drugs or the implementation of targeted temperature management. The need for early and accurate prognostication is crucial as up to 15-20% of patients could be considered as having a poor outcome and may undergo withdrawal of life-sustaining therapies while a complete neurological recovery is still possible. As current practice in Belgium is still based on a very early assessment of neurological function in these patients, the Belgian Society of Intensive Care Medicine created a multidisciplinary Task Force to provide an optimal approach for monitoring and refine prognosis of CA survivors. This Task Force underlined the importance to use a multimodal approach using several additional tools (e.g., electrophysiological tests, neuroimaging, biomarkers) and to refer cases with uncertain prognosis to specialized centers to better evaluate the extent of brain injury in these patients.

Neurology of cardiopulmonary resuscitation

This chapter aims to provide an up-to-date review of the science and clinical practice pertaining to neurologic injury after successful cardiopulmonary resuscitation. The past two decades have seen a major shift in the science and practice of cardiopulmonary resuscitation, with a major emphasis on postresuscitation neurologic care. This chapter provides a nuanced and thoughtful historic and bench-to-bedside overview of the neurologic aspects of cardiopulmonary resuscitation. A particular emphasis is made on the anatomy and pathophysiology of hypoxic-ischemic encephalopathy, up-to-date management of survivors of cardiopulmonary resuscitation, and a careful discussion on neurologic outcome prediction. Guidance to practice evidence-based clinical care when able and thoughtful, pragmatic suggestions for care where evidence is lacking are also provided. This chapter serves as both a useful clinical guide and an updated, thorough, and state-of-the-art reference on the topic for advanced students and experienced practitioners in the field.

Electroencephalographic reactivity testing in unconscious patients: a systematic review of methods and definitions

Electroencephalographic (EEG) reactivity testing is often presented as a clear-cut element of electrophysiological testing. Absence of EEG reactivity is generally considered an indicator of poor outcome, especially in patients after cardiac arrest. However, guidelines do not clearly describe how to test for reactivity and how to evaluate the results. In a quest for clear guidelines, we performed a systematic review aimed at identifying testing methods and definitions of EEG reactivity. We systematically searched the literature between 1970 and May 2016. Methodological quality of the studies was assessed using the QUality In Prognostic Studies tool. Quality of the descriptions of stimulus protocol and reactivity definition was rated on a four-category grading scale based on reproducibility. We found that protocols for EEG reactivity testing vary greatly and descriptions of protocols are almost never replicable. Furthermore, replicable definitions of presence or absence of EEG reactivity are never provided. In order to draw firm conclusions on EEG reactivity as a prognostic factor, future studies should include a precise stimulation protocol and reactivity definition to facilitate guideline formation.

Therapeutic hypothermia after cardiac arrest: outcome predictors

OBJECTIVE

The determination of coma patient prognosis after cardiac arrest has clinical, ethical and social implications. Neurological examination, imaging and biochemical markers are helpful tools accepted as reliable in predicting recovery. With the advent of therapeutic hypothermia, these data need to be reconfirmed. In this study, we attempted to determine the validity of different markers, which can be used in the detection of patients with poor prognosis under hypothermia.

METHODS

Data from adult patients admitted to our intensive care unit for a hypothermia protocol after cardiac arrest were recorded prospectively to generate a descriptive and analytical study analyzing the relationship between clinical, neurophysiological, imaging and biochemical parameters with 6-month outcomes defined according to the Cerebral Performance Categories scale (good 1-2, poor 3-5). Neuron-specific enolase was collected at 72 hours. Imaging and neurophysiologic exams were carried out in the 24 hours after the rewarming period.

RESULTS

Sixty-seven patients were included in the study, of which 12 had good neurological outcomes. Ventricular fibrillation and electroencephalographic theta activity were associated with increased likelihood of survival and improved neurological outcomes. Patients who had more rapid cooling (mean time of 163 versus 312 minutes), hypoxic-ischemic brain injury on magnetic resonance imaging or neuron-specific enolase > 58ng/mL had poor neurological outcomes (p < 0.05).

CONCLUSION

Hypoxic-ischemic brain injury on magnetic resonance imaging and neuron-specific enolase were strong predictors of poor neurological outcomes. Although there is the belief that early achievement of target temperature improves neurological prognoses, in our study, there were increased mortality and worse neurological outcomes with earlier target-temperature achievement.

Continuous EEG monitoring enhances multimodal outcome prediction in hypoxic-ischemic brain injury

OBJECTIVE

Hypoxic brain injury is the largest contributor to disability and mortality after cardiac arrest. We aim to identify electroencephalogram (EEG) characteristics that can predict outcome on cardiac arrest patients treated with targeted temperature management (TTM).

METHODS

We retrospectively examined clinical, EEG, functional outcome at discharge, and in-hospital mortality for 373 adult subjects with return of spontaneous circulation after cardiac arrest. Poor outcome was defined as a Cerebral Performance Category score of 3-5. Pure suppression-burst (SB) was defined as SB not associated with status epilepticus (SE), seizures, or generalized periodic discharges.

RESULTS

In-hospital mortality was 68.6% (N=256). Presence of both unreactive EEG background and SE was associated with a positive predictive value (PPV) of 100% (95% confidence interval: 0.96-1) and a false-positive rate (FPR) of 0% (95% CI: 0-0.11) for poor functional outcome. A prediction model including demographics data, admission exam, presence of status epilepticus, pure SB, and lack of EEG reactivity had an area under the curve of 0.92 (95% CI: 0.87-0.95) for poor functional outcome prediction, and 0.96 (95% CI: 0.94-0.98) for in-hospital mortality. Presence of pure SB (N=87) was confounded by anesthetics use in 83.9% of the cases, and was not an independent predictor of poor functional outcome, having a FPR of 23% (95% CI: 0.19-0.28).

CONCLUSIONS

An unreactive EEG background and SE predicted poor functional outcome and in-hospital mortality in cardiac arrest patients undergoing TTM. Prognostic value of pure SB is confounded by use of sedative agents, and its use on prognostication decisions should be made with caution.

EEG utilization in Canadian intensive care units: A multicentre prospective observational study

PURPOSE

We have previously shown that electroencephalography (EEG) may be an underutilized monitoring modality in a single general medical-surgical ICU, that does not have a specific neurocritical care consultation service or neurocritical care unit. The present study was designed to describe the pattern of EEG utilization across 3 academic ICUs in Ontario, Canada that use different models of neurocritical care.

METHOD

In this prospective multicentre observational study, ICU patients were screened weekly for 6 non-consecutive weeks to determine if they met the ESICM's recommendations or suggestions for EEG monitoring. If EEGs were performed, the results were recorded. Three models of neurocritical care provision were examined in 3 academic tertiary ICUs. Site 1 is an intensivist-led, medical-surgical ICU with no specific neurocritical care consultation service. The second site is also an intensivist led medical-surgical ICU, but with a formal neurocritical care consultation service. The third site is a virtual neurological and neurotrauma ICU within a medical-surgical ICU, staffed by rotating neurointensivists and general intensivists.

RESULTS

Of the 375 patients who were screened, 127 patients (34%) met at least one ESICM indication for EEG monitoring. Among the 127 patients, 46 patients (37%) had an EEG performed. Site 1 had the highest proportion of EEGs performed. The most common indication for EEG monitoring was for patients with unexplained altered level of consciousness, in the absence of primary brain injury. For the EEGs performed per ESICM indication, the majority of epileptiform abnormalities were found in patients admitted with status epilepticus.

CONCLUSIONS

EEG may be underutilized in Canadian ICUs. The impact on patient management and outcomes are unknown.

Combination of initial neurologic examination, quantitative brain imaging and electroencephalography to predict outcome after cardiac arrest

BACKGROUND

Prognosticating outcome following cardiac arrest is challenging and requires a multimodal approach. We tested the hypothesis that the combination of initial neurologic examination, quantitative analysis of head computed tomography (CT) and continuous EEG (cEEG) improve outcome prediction after cardiac arrest.

METHODS

Review of consecutive patients receiving head CT within 24h and cEEG monitoring between April 2010 and May 2013. Initial neurologic examination (Full Outline of UnResponsiveness_Brainstem reflexes (FOUR_B) score and initial Pittsburgh Post-Cardiac Arrest Category (PCAC)), gray matter to white matter attenuation ratio (GWR) on head CT and cEEG patterns were evaluated. The primary outcome was in-hospital mortality.

RESULTS

Of 240 subjects, 70 (29%) survived and 22 (9%) had a good neurologic outcome at hospital discharge. Combined determination of GW ratio and malignant cEEG had an incremental predictive value (AUC: 0.776 for mortality and 0.792 for poor neurologic outcome), with 0% false positive rate when compared with either test alone (AUC of GW ratio: 0.683 for mortality and 0.726 for poor outcome, AUC of malignant cEEG: 0.650 for mortality and 0.647 for poor outcome). Addition of FOUR_B or PCAC to this model improved prediction of mortality (p=0.014 for FOUR_B and 0.001 for PCAC) but not of poor outcome (p=0.786 for FOUR_B and 0.099 for PCAC).

CONCLUSIONS

Combining GWR with cEEG was superior to any individual test for predicting mortality and neurologic outcome. Addition of clinical variables further improved prognostication for mortality but not neurologic outcome. These preliminary data support a multi-modal prognostic workup in this population.

EEG power as a biomarker to predict the outcome after cardiac arrest and cardiopulmonary resuscitation induced global ischemia

AIMS

Cardiac arrest (CA) is a major cause of mortality and survivors often develop neurologic deficits. The objective of this study was to determine the effect of CA and cardiopulmonary resuscitation (CPR) in mice on the EEG and neurologic outcomes, and identify biomarkers that can prognosticate poor outcomes.

MAIN METHODS

Video-EEG records were obtained at various periods following CA-CPR and examined manually to determine the presence of spikes and sharp-waves, and seizures. EEG power was calculated using a fast Fourier transform (FFT) algorithm.

KEY FINDINGS

Fifty percent mice died within 72h following CA and successful CPR. Universal suppression of the background EEG was observed in all mice following CA-CPR, however, a more severe and sustained reduction in EEG power occurred in the mice that did not survive beyond 72h than those that survived until sacrificed. Spikes and sharp wave activity appeared in the cortex and hippocampus of all mice, but only one out of eight mice developed a purely electrographic seizure in the acute period after CA-CPR. Interestingly, none of the mice that died experienced any acute seizures. At 10days after the CA-CPR, 25% of the mice developed spontaneous convulsive and nonconvulsive seizures that remained restricted to the hippocampus. The frequency of nonconvulsive seizures was higher than that of convulsive seizures.

SIGNIFICANCE

A strong association between changes in EEG power and mortality following CA-CPR were observed in our study. Therefore, we suggest that the EEG power can be used to prognosticate mortality following CA-CPR induced global ischemia.

Should Postanoxic Status Epilepticus be Treated Aggressively?-No!

Electrographic status epilepticus and myoclonus represent frequent findings in patients surviving cardiac arrest; both features have been related to poor clinical outcome. Recent data have outlined that status epilepticus appearing during therapeutic hypothermia and sedation is practically and invariably related to a fatal issue, as opposed to some patients presenting status epilepticus and/or myoclonus after return to normothermic conditions. Although it seems reasonable to give a chance of awakening to the latter patients by administering consequent antiepileptic treatment, especially if other favorable prognostic markers are observed, an aggressive treatment of status epilepticus arising during hypothermia seems futile in view of the existing evidence.

Clinical Applications for EPs in the ICU

In critically ill patients, evoked potential (EP) testing is an important tool for measuring neurologic function, signal transmission, and secondary processing of sensory information in real time. Evoked potential measures conduction along the peripheral and central sensory pathways with longer-latency potentials representing more complex thalamocortical and intracortical processing. In critically ill patients with limited neurologic exams, EP provides a window into brain function and the potential for recovery of consciousness. The most common EP modalities in clinical use in the intensive care unit include somatosensory evoked potentials, brainstem auditory EPs, and cortical event-related potentials. The primary indications for EP in critically ill patients are prognostication in anoxic-ischemic or traumatic coma, monitoring for neurologic improvement or decline, and confirmation of brain death. Somatosensory evoked potentials had become an important prognostic tool for coma recovery, especially in comatose survivors of cardiac arrest. In this population, the bilateral absence of cortical somatosensory evoked potentials has nearly 100% specificity for death or persistent vegetative state. Historically, EP has been regarded as a negative prognostic test, that is, the absence of cortical potentials is associated with poor outcomes while the presence cortical potentials are prognostically indeterminate. In recent studies, the presence of middle-latency and long-latency potentials as well as the amplitude of cortical potentials is more specific for good outcomes. Event-related potentials, particularly mismatch negativity of complex auditory patterns, is emerging as an important positive prognostic test in patients under comatose. Multimodality predictive algorithms that combine somatosensory evoked potentials, event-related potentials, and clinical and radiographic factors are gaining favor for coma prognostication.

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.

Optic nerve sheath diameter on computed tomography not predictive of neurological status post-cardiac arrest

OBJECTIVE

Optic nerve sheath diameter (ONSD) measured on a head computed tomography (CT) has been suggested as a potential prognostic factor for poor neurological outcome after cardiac arrest. We performed a single centre retrospective cohort analysis to further investigate this relationship.

METHODS

All patients >18 years of age admitted to St. Paul's Hospital in Vancouver, Canada who survived a cardiac arrest and had a CT scan of the head within 48 hours were included in the analysis.

RESULTS

A total of 72 patients met inclusion criteria for the study; 54 (75.0%) of the patients had a poor neurological outcome, whereas 18 (25.0%) patients were discharged from the hospital with a good outcome. A CT head was obtained for patients in the good outcome group in a mean time of 9.3 hours (SD 10.0) compared to 10.2 hours (SD 11.2) for the poor outcome group (p=0.75). There was no difference in average ONSD observed between the two outcome groups (6.66 mm SD 0.78 v. 6.60 mm SD 0.82, p=0.77). Multiple logistic regression failed to show any association between ONSD and neurological outcome when adjusted for all other covariates (OR 1.32 95% CI 0.40-4.34, p=0.65). Setting an ONSD threshold of >8 mm (OR 2.32, 95% CI 0.14-39.40, p=0.55) or >7 mm (OR 0.28, 95% CI 0.03-2.77, p=0.28) also failed to show any association on neurological outcome.

CONCLUSION

There was no observed difference in ONSD between those with a good neurological outcome and those with a poor outcome. ONSD was not an independent predictor of poor neurological outcome.

Predicting neurologic outcome after targeted temperature management for cardiac arrest: systematic review and meta-analysis

OBJECTIVES

Targeted temperature management improves survival and neurologic outcomes for adult out-of-hospital cardiac arrest survivors but may alter the accuracy of tests for predicting neurologic outcome after cardiac arrest.

DATA SOURCES

We systematically searched Medline, Embase, CINAHL, and CENTRAL from database inception to September 2012.

STUDY SELECTION

Citations were screened for studies that examined diagnostic tests to predict poor neurologic outcome or death following targeted temperature management in adult cardiac arrest survivors.

DATA EXTRACTION

Data on study outcomes and quality were abstracted in duplicate. We constructed contingency tables for each diagnostic test and calculated sensitivity, specificity, and positive and negative likelihood ratios.

DATA SYNTHESIS

Of 2,737 citations, 20 studies (n = 1,845) met inclusion criteria. Meta-analysis showed that three tests accurately predicted poor neurologic outcome with low false-positive rates: bilateral absence of pupillary reflexes more than 24 hours after a return of spontaneous circulation (false-positive rate, 0.02; 95% CI, 0.01-0.06; summary positive likelihood ratio, 10.45; 95% CI, 3.37-32.43), bilateral absence of corneal reflexes more than 24 hours (false-positive rate, 0.04; 95% CI, 0.01-0.09; positive likelihood ratio, 6.8; 95% CI, 2.52-18.38), and bilateral absence of somatosensory-evoked potentials between days 1 and 7 (false-positive rate, 0.03; 95% CI, 0.01-0.07; positive likelihood ratio, 12.79; 95% CI, 5.35-30.62). False-positive rates were higher for a Glasgow Coma Scale motor score showing extensor posturing or worse (false-positive rate, 0.09; 95% CI, 0.06-0.13; positive likelihood ratio, 7.11; 95% CI, 5.01-10.08), unfavorable electroencephalogram patterns (false-positive rate, 0.07; 95% CI, 0.04-0.12; positive likelihood ratio, 8.85; 95% CI, 4.87-16.08), myoclonic status epilepticus (false-positive rate, 0.05; 95% CI, 0.02-0.11; positive likelihood ratio, 5.58; 95% CI, 2.56-12.16), and elevated neuron-specific enolase (false-positive rate, 0.12; 95% CI, 0.06-0.23; positive likelihood ratio, 4.14; 95% CI, 1.82-9.42). The specificity of available tests improved when these were performed beyond 72 hours. Data on neuroimaging, biomarkers, or combination testing were limited and inconclusive.

CONCLUSION

Simple bedside tests and somatosensory-evoked potentials predict poor neurologic outcome for survivors of cardiac arrest treated with targeted temperature management, and specificity improves when performed beyond 72 hours. Clinicians should use caution with these predictors as they carry the inherent risk of becoming self-fulfilling.