Prognosis after cardiac arrest and hypothermia: a new paradigm

Clinical value of miR-191-5p in predicting the neurological outcome after out-of-hospital cardiac arrest

BACKGROUND

The diagnostic and prognostic value of microRNAs (miRNA) in human disease has been confirmed in a number of clinical studies.

AIMS

The purpose of this study was to investigate the predictive value of miR-191-5p in the neurological outcome of patients recovering from out-of-hospital cardiac arrest (OHCA).

METHODS

A total of 260 patients undergoing the target temperature management trial were analyzed. The expression level of serum miR-191-5p was detected by qRT-PCR at 48 h after return of spontaneous circulation (ROSC). ROC curve was established to evaluate the ability of miR-191-5p as a biomarker for predicting adverse neurological outcomes after OHCA. Kaplan-Meier curve and Cox regression analysis were used for survival analysis.

RESULTS

One hundred eighteen patients (45%) had poor neurological outcomes at 6 months. The expression level of serum miR-191-5p in patients with poor neurological outcomes was significantly lower than that in patients with good neurological prognosis (P < 0.001) and was not associated with TTM trial. The AUC, sensitivity, and specificity of the ROC curve were 0.899, 84.7%, and 82.4%, respectively, suggesting that the level of miR-191-5p had the ability to predict neurological outcome. By the end of the experiment, 88 patients (34%) were dead. Results of survival analysis showed that lower miR-191-5p expression level was significantly associated with lower survival rate (HR: 0.344, 95% CI = 0.208-0.567, P < 0.001).

CONCLUSIONS

The level of miR-191-5p was down-regulated in patients with poor neurological outcomes, and it could be used as a promising novel biomarker for prediction of neurological outcome and survival after OHCA.

Prognostic value of diffusion-weighted MRI for post-cardiac arrest coma

OBJECTIVE

To validate quantitative diffusion-weighted imaging (DWI) MRI thresholds that correlate with poor outcome in comatose cardiac arrest survivors, we conducted a clinician-blinded study and prospectively obtained MRIs from comatose patients after cardiac arrest.

METHODS

Consecutive comatose post-cardiac arrest adult patients were prospectively enrolled. MRIs obtained within 7 days after arrest were evaluated. The clinical team was blinded to the DWI MRI results and followed a prescribed prognostication algorithm. Apparent diffusion coefficient (ADC) values and thresholds differentiating good and poor outcome were analyzed. Poor outcome was defined as a Glasgow Outcome Scale score of ≤2 at 6 months after arrest.

RESULTS

Ninety-seven patients were included, and 75 patients (77%) had MRIs. In 51 patients with MRI completed by postarrest day 7, the prespecified threshold of >10% of brain tissue with an ADC <650 ×10^-6 mm²/s was highly predictive for poor outcome with a sensitivity of 0.63 (95% confidence interval [CI] 0.42-0.80), a specificity of 0.96 (95% CI 0.77-0.998), and a positive predictive value (PPV) of 0.94 (95% CI 0.71-0.997). The mean whole-brain ADC was higher among patients with good outcomes. Receiver operating characteristic curve analysis showed that ADC <650 ×10^-6 mm²/s had an area under the curve of 0.79 (95% CI 0.65-0.93, p < 0.001). Quantitative DWI MRI data improved prognostication of both good and poor outcomes.

CONCLUSIONS

This prospective, clinician-blinded study validates previous research showing that an ADC <650 ×10^-6 mm²/s in >10% of brain tissue in an MRI obtained by postarrest day 7 is highly specific for poor outcome in comatose patients after cardiac arrest.

Prognostication of neurological outcome after cardiac arrest using wavelet phase coherence analysis of cerebral oxygen

BACKGROUND

The prognosis for cardiac arrest (CA) is associated with the degree of cerebral ischemia. We investigated the relationship between the wavelet coherence of cerebral oxyhemoglobin (HbO₂) among different channels and outcomes after CA. Moreover, we aimed to develop a prognostication method after CA.

METHODS

Eighty-three post-resuscitation patients were included. The HbO₂ data were collected during the post-resuscitation period (median day, 1) using functional near-infrared spectroscopy. The coherence between sections of prefrontal HbO₂ oscillations in five frequency intervals (I, 0.6-2 Hz; II, 0.15-0.6 Hz; III, 0.05-0.15 Hz; IV, 0.02-0.05 Hz; and V, 0.0095-0.02 Hz) were analyzed. We evaluated the outcomes using cerebral performance category (CPC) scores (good outcome, CPC ≤ 2 and poor outcome, CPC ≥ 3) at 3 months after CA. Additionally, the predictive method was developed using the biomarker and coherence value after CA.

RESULTS

Among the included patients, 19 patients (22.9%) had a good outcome. Poor outcome group had significantly lower phase coherence in the myogenic frequency interval III compared to good outcome group (0.36 ± 0.14 vs. 0.54 ± 0.18, P < 0.001). The predictive method using neuron-specific enolase (NSE) and interval III value demonstrated good discrimination (area under the curve 0.919; 95% confidence interval, 0.850-0.989).

CONCLUSIONS

The predictive method using NSE and phase coherence of HbO₂ in the interval III from the vascular smooth muscle cells could be a useful tool for prognosticating after CA. This suggests that evaluating cerebral ischemia using phase coherence of HbO₂ might be a helpful outcome predictor following CA.

Prediction of poor outcome after hypoxic-ischemic brain injury by diffusion-weighted imaging: A systematic review and meta-analysis

Accurate prediction of the neurological outcome following hypoxic-ischemic brain injury (HIBI) remains difficult. Diffusion-weighted imaging (DWI) can detect acute and subacute brain abnormalities following global cerebral hypoxia. Therefore, DWI can be used to predict the outcomes of HIBI. To this end, we searched the PubMed, EMBASE, and Cochrane Library databases for studies that examine the diagnostic accuracy of DWI in predicting HIBI outcomes in adult patients between January1995 and September 2019. Next, we conducted a comprehensive meta-analysis using the Meta-DiSc and several complementary techniques. Following the application of inclusion and exclusion criteria, a total of 28 studies were included with 98 data subsets. The overall sensitivity and specificity, with 95% confidence interval, were 0.613(0.599-0.628) and 0.958(0.947-0.967), respectively, and the area under the curve was 0.9090. Significant heterogeneity among the included studies and a threshold effect were observed (p<0.001). Different positive indices were the major sources for the heterogeneity, followed by the anatomical region examined, both of which significantly affected the prognostic accuracy. In conclusion, we demonstrated that DWI can be an instrumental modality in predicting the outcome of HIBI with good prognostic accuracy. However, the lack of clear and generally accepted positive indices limits its clinical application. Therefore, using more reliable positive indices and combining DWI with other clinical predictors may improve the diagnostic accuracy of HIBI.

Quantitative EEG Metrics Differ Between Outcome Groups and Change Over the First 72 h in Comatose Cardiac Arrest Patients

BACKGROUND

Forty to sixty-six percent of patients resuscitated from cardiac arrest remain comatose, and historic outcome predictors are unreliable. Quantitative spectral analysis of continuous electroencephalography (cEEG) may differ between patients with good and poor outcomes.

METHODS

Consecutive patients with post-cardiac arrest hypoxic-ischemic coma undergoing cEEG were enrolled. Spectral analysis was conducted on artifact-free contiguous 5-min cEEG epochs from each hour. Whole band (1-30 Hz), delta (δ, 1-4 Hz), theta (θ, 4-8 Hz), alpha (α, 8-13 Hz), beta (β, 13-30 Hz), α/δ power ratio, percent suppression, and variability were calculated and correlated with outcome. Graphical patterns of quantitative EEG (qEEG) were described and categorized as correlating with outcome. Clinical outcome was dichotomized, with good neurologic outcome being consciousness recovery.

RESULTS

Ten subjects with a mean age = 50 yrs (range = 18-65) were analyzed. There were significant differences in total power (3.50 [3.30-4.06] vs. 0.68 [0.52-1.02], p = 0.01), alpha power (1.39 [0.66-1.79] vs 0.27 [0.17-0.48], p < 0.05), delta power (2.78 [2.21-3.01] vs 0.55 [0.38-0.83], p = 0.01), percent suppression (0.66 [0.02-2.42] vs 73.4 [48.0-97.5], p = 0.01), and multiple measures of variability between good and poor outcome patients (all values median [IQR], good vs. poor). qEEG patterns with high or increasing power or large power variability were associated with good outcome (n = 6). Patterns with consistently low or decreasing power or minimal power variability were associated with poor outcome (n = 4).

CONCLUSIONS

These preliminary results suggest qEEG metrics correlate with outcome. In some patients, qEEG patterns change over the first three days post-arrest.

Increased Heat Generation in Postcardiac Arrest Patients During Targeted Temperature Management Is Associated With Better Outcomes

OBJECTIVES

Assess if amount of heat generated by postcardiac arrest patients to reach target temperature (Ttarget) during targeted temperature management is associated with outcomes by serving as a proxy for thermoregulatory ability, and whether it modifies the relationship between time to Ttarget and outcomes.

DESIGN

Retrospective cohort study.

SETTING

Urban tertiary-care hospital.

PATIENTS

Successfully resuscitated targeted temperature management-treated adult postarrest patients between 2008 and 2015 with serial temperature data and Ttarget less than or equal to 34°C.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Time to Ttarget was defined as time from targeted temperature management initiation to first recorded patient temperature less than or equal to 34°C. Patient heat generation ("heat units") was calculated as inverse of average water temperature × hours between initiation and Ttarget × 100. Primary outcome was neurologic status measured by Cerebral Performance Category score; secondary outcome was survival, both at hospital discharge. Univariate analyses were performed using Wilcoxon rank-sum tests; multivariate analyses used logistic regression. Of 203 patients included, those with Cerebral Performance Category score 3-5 generated less heat before reaching Ttarget (median, 8.1 heat units [interquartile range, 3.6-21.6 heat units] vs median, 20.0 heat units [interquartile range, 9.0-33.5 heat units]; p = 0.001) and reached Ttarget quicker (median, 2.3 hr [interquartile range, 1.5-4.0 hr] vs median, 3.6 hr [interquartile range, 2.0-5.0 hr]; p = 0.01) than patients with Cerebral Performance Category score 1-2. Nonsurvivors generated less heat than survivors (median, 8.1 heat units [interquartile range, 3.6-20.8 heat units] vs median, 19.0 heat units [interquartile range, 6.5-33.5 heat units]; p = 0.001) and reached Ttarget quicker (median, 2.2 hr [interquartile range, 1.5-3.8 hr] vs median, 3.6 hr [interquartile range, 2.0-5.0 hr]; p = 0.01). Controlling for average water temperature between initiation and Ttarget, the relationship between outcomes and time to Ttarget was no longer significant. Controlling for location, witnessed arrest, age, initial rhythm, and neuromuscular blockade use, increased heat generation was associated with better neurologic (adjusted odds ratio, 1.01 [95% CI, 1.00-1.03]; p = 0.039) and survival (adjusted odds ratio, 1.01 [95% CI, 1.00-1.03]; p = 0.045) outcomes.

CONCLUSIONS

Increased heat generation during targeted temperature management initiation is associated with better outcomes at hospital discharge and may affect the relationship between time to Ttarget and outcomes.

Intensive care for organ preservation: A four-stage pathway

Objective

Intensive care for organ preservation (ICOP) is defined as the initiation or pursuit of intensive care not to save the patient's life, but to protect and optimize organs for transplantation.

Analysis

When a patient has devastating brain injury that might progress to organ donation this can be conceptualized as evolving through four consecutive stages: (1) instability, (2) stability, (3) futility and (4) finality. ICOP might be applied at any of these stages, raising different ethical issues. Only in the stage of finality is the switch from neurointensive care to ICOP ethically justified.

Conclusion

The difference between the stages is that during instability, stability and futility the focus must be neurointensive care which seeks the patient's recovery or an accurate neurological prognostication, while finality focuses on withdrawal of life-sustaining therapy and commencement of comfort care, which may include ICOP for deceased donation.

Targeted Temperature Management and Multimodality Monitoring of Comatose Patients After Cardiac Arrest

Out-of-hospital cardiac arrest (CA) remains a leading cause of sudden morbidity and mortality; however, outcomes have continued to improve in the era of targeted temperature management (TTM). In this review, we highlight the clinical use of TTM, and provide an updated summary of multimodality monitoring possible in a modern ICU. TTM is neuroprotective for survivors of CA by inhibiting multiple pathophysiologic processes caused by anoxic brain injury, with a final common pathway of neuronal death. Current guidelines recommend the use of TTM for out-of-hospital CA survivors who present with a shockable rhythm. Further studies are being completed to determine the optimal timing, depth and duration of hypothermia to optimize patient outcomes. Although a multidisciplinary approach is necessary in the CA population, neurologists and neurointensivists are central in selecting TTM candidates and guiding patient care and prognostic evaluation. Established prognostic tools include clinal exam, SSEP, EEG and MR imaging, while functional MRI and invasive monitoring is not validated to improve outcomes in CA or aid in prognosis. We recommend that an evidence-based TTM and prognostication algorithm be locally implemented, based on each institution's resources and limitations. Given the high incidence of CA and difficulty in predicting outcomes, further study is urgently needed to determine the utility of more recent multimodality devices and studies.

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.

Acute brain lesions on magnetic resonance imaging in relation to neurological outcome after cardiac arrest

BACKGROUND

Magnetic resonance imaging (MRI) of the brain including diffusion-weighted imaging (DWI) is reported to have high prognostic accuracy in unconscious post-cardiac arrest (CA) patients. We documented acute MRI findings in the brain in both conscious and unconscious post-CA patients treated with target temperature management (TTM) at 32-34°C for 24 h as well as the relation to patients' neurological outcome after 6 months.

METHODS

A prospective observational study with MRI was performed regardless of the level of consciousness in post-CA patients treated with TTM. Neurological outcome was assessed using the Cerebral Performance Categories scale and dichotomized into good and poor outcome.

RESULTS

Forty-six patients underwent MRI at 3-5 days post-CA. Patients with good outcome had minor, mainly frontal and parietal, lesions. Acute hypoxic/ischemic lesions on MRI including DWI were more common in patients with poor outcome (P = 0.007). These lesions affected mostly gray matter (deep or cortical), with or without involvement of the underlying white matter. Lesions in the occipital and temporal lobes, deep gray matter and cerebellum showed strongest associations with poor outcome. Decreased apparent diffusion coefficient, was more common in patients with poor outcome.

CONCLUSIONS

Extensive acute hypoxic/ischemic MRI lesions in the cortical regions, deep gray matter and cerebellum detected by visual analysis as well as low apparent diffusion coefficient values from quantitative measurements were associated with poor outcome. Patients with good outcome had minor hypoxic/ischemic changes, mainly in the frontal and parietal lobes.

Clinical neurophysiology for neurological prognostication of comatose patients after cardiac arrest

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A multimodal prognostic approach is recommended after cardiac arrest.

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EEG (background and, reactivity, repetitive epileptiform features) and SSEP are core assessments.

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Some outlook into long-latency evoked potentials is offered.

Early prognostication of outcome in comatose patients after cardiac arrest represents a daunting task for clinicians, also considering the nowadays commonly used targeted temperature management with sedation in the first 24–48 h. A multimodal approach is currently recommended, in order to minimize the risks of false-positive prediction of poor outcome, including clinical examination off sedation, EEG (background characterization and reactivity, occurrence of repetitive epileptiform features), and early-latency SSEP responses represent the core assessments in this setting; they may be complemented by biochemical markers and neuroimaging.

This paper, which relies on a recent comprehensive review, focuses on an updated review of EEG and SSEP, and also offers some outlook into long-latency evoked potentials, which seem promising in clinical use.

A major miss in prognostication after cardiac arrest: Burst suppression and brain healing

We report a case with therapeutic hypothermia after cardiac arrest where meaningful recovery far exceeded anticipated negative endpoints following cardiac arrest with loss of brainstem reflexes and subsequent status epilepticus. This man survived and recovered after an out-of-hospital cardiac arrest followed by a 6-week coma with absent motor responses and 5 weeks of burst suppression. Standard criteria suggested no chance of recovery. His recovery may relate to the effect of burst-suppression on EEG to rescue neurons near neuronal cell death. Further research to understand the mechanisms of therapeutic hypothermia and late restoration of neuronal functional capacity may improve prediction and aid end-of-life decisions after cardiac arrest.

Cortical somatosensory evoked high-frequency (600Hz) oscillations predict absence of severe hypoxic encephalopathy after resuscitation

OBJECTIVE

Following cardiac arrest (CA), hypoxic encephalopathy (HE) frequently occurs and hence reliable neuroprognostication is crucial to decide on the extent of intensive care. Several investigations predict severe HE leading to persistent unresponsive wakefulness or death, with high specificity. Only few studies attempted to predict absence of severe HE. Cortical somatosensory evoked high-frequency (600Hz) oscillation (HFO) bursts indicate the presence of highly synchronized spiking activity in the primary somatosensory cortex. Since global neuronal damage characterizes severe HE preserved cortical HFOs may early exclude severe HE.

METHODS

We determined amplitudes of early and late HFO bursts in 302 comatose CA patients after median nerve somatosensory evoked potential (SSEPs) and clinical outcome upon intensive care unit discharge using the cerebral performance category (CPC) scale.

RESULTS

We detected significant early HFO bursts in 146 patients and late HFO bursts in 95 patients. Only one of 27 unresponsive wakefulness patients had a late HFO burst amplitude above 70nV and all seventeen patients who died despite higher amplitudes died from non-neurological causes.

CONCLUSIONS

High-frequency SSEP components can reliably be studied in comatose CA patients using standard equipment.

SIGNIFICANCE

Late HFO burst amplitudes above 70nV largely exclude severe HE incompatible with regaining consciousness.

Neurological prognostication of outcome in patients in coma after cardiac arrest

Management of coma after cardiac arrest has improved during the past decade, allowing an increasing proportion of patients to survive, thus prognostication has become an integral part of post-resuscitation care. Neurologists are increasingly confronted with raised expectations of next of kin and the necessity to provide early predictions of long-term prognosis. During the past decade, as technology and clinical evidence have evolved, post-cardiac arrest prognostication has moved towards a multimodal paradigm combining clinical examination with additional methods, consisting of electrophysiology, blood biomarkers, and brain imaging, to optimise prognostic accuracy. Prognostication should never be based on a single indicator; although some variables have very low false positive rates for poor outcome, multimodal assessment provides resassurance about the reliability of a prognostic estimate by offering concordant evidence.

Standardized EEG interpretation accurately predicts prognosis after cardiac arrest

Objective:

To identify reliable predictors of outcome in comatose patients after cardiac arrest using a single routine EEG and standardized interpretation according to the terminology proposed by the American Clinical Neurophysiology Society.

Methods:

In this cohort study, 4 EEG specialists, blinded to outcome, evaluated prospectively recorded EEGs in the Target Temperature Management trial (TTM trial) that randomized patients to 33°C vs 36°C. Routine EEG was performed in patients still comatose after rewarming. EEGs were classified into highly malignant (suppression, suppression with periodic discharges, burst-suppression), malignant (periodic or rhythmic patterns, pathological or nonreactive background), and benign EEG (absence of malignant features). Poor outcome was defined as best Cerebral Performance Category score 3–5 until 180 days.

Results:

Eight TTM sites randomized 202 patients. EEGs were recorded in 103 patients at a median 77 hours after cardiac arrest; 37% had a highly malignant EEG and all had a poor outcome (specificity 100%, sensitivity 50%). Any malignant EEG feature had a low specificity to predict poor prognosis (48%) but if 2 malignant EEG features were present specificity increased to 96% (p < 0.001). Specificity and sensitivity were not significantly affected by targeted temperature or sedation. A benign EEG was found in 1% of the patients with a poor outcome.

Conclusions:

Highly malignant EEG after rewarming reliably predicted poor outcome in half of patients without false predictions. An isolated finding of a single malignant feature did not predict poor outcome whereas a benign EEG was highly predictive of a good outcome.

Cardiac arrest and therapeutic hypothermia

Therapeutic hypothermia for patients who remain comatose following resuscitation from a cardiac arrest improves both survival and neurologic outcomes. Although this therapy has been incorporated into the guidelines for routine post-resuscitation care and has been in clinical use for over a decade, significant questions and controversies remain. In this review, we discuss these questions in the context of the current evidence and provide a practical framework to help guide clinicians.

Continuous Amplitude-Integrated Electroencephalographic Monitoring Is a Useful Prognostic Tool for Hypothermia-Treated Cardiac Arrest Patients

Supplemental Digital Content is available in the text.

Modern treatments have improved the survival rate following cardiac arrest, but prognostication remains a challenge. We examined the prognostic value of continuous electroencephalography according to time by performing amplitude-integrated electroencephalography on patients with cardiac arrest receiving therapeutic hypothermia.

Somatosensory evoked potentials aid prediction after hypoxic-ischaemic brain injury

Cardiopulmonary resuscitation, basic life support and early defibrillation are leading to more survivors of out-of-hospital cardiac arrest reaching hospital. Once stabilised on an intensive care unit, it can be difficult to predict the neurological outcome using clinical criteria alone, particularly with modern management using sedation, neuromuscular blockade and hypothermia. If we are to prevent ongoing futile life support, it is important to try to identify the majority of patients who, despite best efforts, will not make a meaningful recovery. Somatosensory evoked potentials are widely available electrophysiological tests that can provide an objective biomarker of a poor neurological outcome and assist in predicting the prognosis.

ED prognostication of comatose cardiac arrest patients undergoing therapeutic hypothermia is unreliable

BACKGROUND

Therapeutic hypothermia (TH) improves patient survival with good neurologic outcome after cardiac arrest. The value of early clinician prognostication in the emergency department (ED) has not been studied in this patient population.

OBJECTIVE

To determine if physicians can accurately predict survival and neurologic outcome at hospital discharge of resuscitated, comatose out-of-hospital cardiac arrest (OHCA) patients treated in a post-cardiac arrest clinical pathway that included TH.

METHODS

This was a prospective, observational study conducted at a tertiary referral center. Participants were physicians involved in the resuscitation of OHCA patients treated with a clinical pathway that included TH. Immediately after patient resuscitation in the ED, physicians recorded their prediction of patient survival and neurologic outcome on a standardized questionnaire. Neurologic outcome was assessed by the cerebral performance category.

RESULTS

Forty-two physicians completed questionnaires on 17 patients enrolled from October 2009 to March 2010. Sensitivity and specificity of physician prediction of patient survival were 0.67 (95% confidence interval [CI], 0.45-0.83) and 0.82 (95% CI, 0.59-0.94), respectively, with an area under the curve of 0.74 (95% CI, 0.61-0.88), a positive likelihood ratio (+LR) of 3.72 (95% CI, 1.30-11.02), and a -LR of 0.40 (95% CI, 0.21-0.77). Sensitivity and specificity of physician prediction of good neurologic outcome were 0.40 (95% CI, 0.20-0.64) and 0.69 (95% CI, 0.50-0.84), respectively, with an area under the curve of 0.55 (95% CI, 0.39-0.70), a +LR of 1.29 (95% CI, 0.56-3.03), and a -LR of 0.87 (95% CI, 0.53-1.41).

CONCLUSIONS

Physicians poorly prognosticate both survival and neurologic outcome in comatose OHCA patients undergoing TH. Premature prognostication in the ED is unreliable and should be avoided.

Efficacy of diffusion-weighted magnetic resonance imaging performed before therapeutic hypothermia in predicting clinical outcome in comatose cardiopulmonary arrest survivors

AIM OF THE STUDY

To develop a clinically relevant and qualitative brain magnetic resonance imaging (MRI) scoring system for acute stage comatose cardiac arrest patients.

METHODS

Consecutive comatose post-cardiopulmonary arrest patients were prospectively enrolled. Routine brain MRI sequences were scored by two independent and blinded experts. Predefined brain regions were qualitatively scored on diffusion-weighted imaging (DWI) sequences according to the severity of the abnormality on a scale from 0 to 4. The mean score provided by the raters determined poor outcome defined under the Cerebral Performance Categories 3, 4, or 5. DWI scans were repeated after therapeutic hypothermia (TH). The same qualitative scoring system was applied and results were compared to the initial scores.

RESULTS

Out of 24 recruited patients, 19 with brain MRI scans were included. Of the 19 included patients, seven showed a good outcome at hospital discharge and 12 patients showed poor neurologic outcome. Median time from the arrest to the initial DWI was 166min (IQR 114-240min). At 100% specificity, the overall, cortex, and cortex plus deep grey nuclei scores predicted poor patient outcome with a sensitivity of 91.7-100% (95% CI). Follow-up DWI scans after TH showed worse results than initial scans.

CONCLUSION

A qualitative MRI scoring system effectively assessed the severity of hypoxic-ischaemic brain injury following cardiopulmonary arrest. The scoring system may provide useful prognostic information in comatose cardiopulmonary arrest patients.

Effect of mild hypothermic cardiopulmonary bypass on the amplitude of somatosensory-evoked potentials

BACKGROUND

Several neurophysiological techniques are used to intraoperatively assess cerebral functioning during surgery and intensive care, but the introduction of hypothermia as a means of intraoperative neuroprotection has brought their reliability into question. The present study aimed to evaluate the effect of mild hypothermia on somatosensory-evoked potentials' (SSEPs) amplitude and latency in a cohort of cardiopulmonary bypass (CPB) patients as the temperature reached the steady-state.

MATERIALS AND METHODS

The amplitude and latency of 4 different SSEP signals--N9, N13, P14/N18 interpeak, and N20/P25--were evaluated retrospectively in 84 patients undergoing CPB during normothermic (36°C±0.43°C) and mild hypothermic (32°C±1.38°C) conditions. SSEPs were recorded in normothermia immediately after the induction of anesthesia and in hypothermia as the temperature reached its steady-state, specifically, when the nasopharyngeal temperature was equivalent to the rectal temperature (±0.5°C). A paired-samples t test was performed for each SSEP to test the differences in latencies and amplitudes between normothermic and hypothermic conditions.

RESULTS

Compared with normothermia, hypothermia not only significantly increased the latency of all SSEPs, N9 (P<0.001), N13 (P<0.001), P14/N18 (P<0.001), and N20/P25 (P<0.001), but also the amplitude of N9 (P<0.001) and N20/P25 (P<0.001).

CONCLUSIONS

The increased amplitude in particularly of cortical SSEPs (N20/P25), detected specifically during steady-state hypothermia, seems to support the clinical utility of this methodology in monitoring the brain function not only during cardiac surgery with CPB, but also in other settings like therapeutic hypothermia procedures in an intensive care unit.

Shorter time to target temperature is associated with poor neurologic outcome in post-arrest patients treated with targeted temperature management

INTRODUCTION

Time to achieve target temperature varies substantially for patients who undergo targeted temperature management (TTM) after cardiac arrest. The association between arrival at target temperature and neurologic outcome is poorly understood. We hypothesized that shorter time from initiation of cooling to target temperature ("induction") will be associated with worse neurologic outcome, reflecting more profound underlying brain injury and impaired thermoregulatory control.

METHODS

This was a multicenter retrospective study analyzing data from the Penn Alliance for Therapeutic Hypothermia (PATH) Registry. We examined the association between time from arrest to return of spontaneous circulation (ROSC) ("downtime"), ROSC to initiation of TTM ("pre-induction") and "induction" with cerebral performance category (CPC).

RESULTS

A total of 321 patients were analyzed, of whom 30.8% (99/321) had a good neurologic outcome. Downtime for survivors with good outcome was 11 (IQR 6-27) min vs. 21 (IQR 10-36) min (p=0.002) for those with poor outcome. Pre-induction did not vary between good and poor outcomes (98 (IQR 36-230) min vs. 114 (IQR 34-260) (p=ns)). Induction time in the good outcome cohort was 237 (IQR 142-361) min compared to 180 (IQR 100-276) min (p=0.004). Patients were categorized by induction time (<120min, 120-300min, >300min). Using multivariable logistic regression adjusted for age, initial rhythm, and downtime, induction time >300min was associated with good neurologic outcome when compared to those with an induction time <120min.

CONCLUSION

In this multicenter cohort of post-arrest TTM patients, shorter induction time was associated with poor neurologic outcome.

Electroencephalography (EEG) for neurological prognostication after cardiac arrest and targeted temperature management; rationale and study design

BACKGROUND

Electroencephalography (EEG) is widely used to assess neurological prognosis in patients who are comatose after cardiac arrest, but its value is limited by varying definitions of pathological patterns and by inter-rater variability. The American Clinical Neurophysiology Society (ACNS) has recently proposed a standardized EEG-terminology for critical care to address these limitations.

METHODS/DESIGN

In the TTM-trial, 399 post cardiac arrest patients who remained comatose after rewarming underwent a routine EEG. The presence of clinical seizures, use of sedatives and antiepileptic drugs during the EEG-registration were prospectively documented.

DISCUSSION

A well-defined terminology for interpreting post cardiac arrest EEGs is critical for the use of EEG as a prognostic tool.

TRIAL REGISTRATION

The TTM-trial is registered at ClinicalTrials.gov (NCT01020916).

Early prognostication in acute brain damage: where is the evidence?

PURPOSE OF REVIEW

Early prognostication in acute brain damage remains a challenge in the realm of critical care. There remains controversy over the most optimal methods that can be utilized to predict outcome. The utility of recently reported prognostic biomarkers and clinical methods will be reviewed.

RECENT FINDINGS

Recent guidelines touch upon prognostication techniques as part of management recommendations. In addition to novel laboratory values, there have been few reports on the use of clinical parameters, diagnostic imaging techniques, and electrophysiological techniques to assist in prognostication.

SUMMARY

Although encouraging, newer markers are not capable of providing accurate estimates on outcomes in acute injuries of the central nervous system. Traditional markers of prognostication may not be applicable in the light of newer and effective therapies (i.e. hypothermia). Substantial research in the field of outcome determination is in progress, but these studies need to be interpreted with caution.

Yield of intermittent versus continuous EEG in comatose survivors of cardiac arrest treated with hypothermia

Introduction

Electroencephalography (EEG) has a central role in the outcome prognostication in subjects with anoxic/hypoxic encephalopathy following a cardiac arrest (CA). Continuous EEG monitoring (cEEG) has been consistently developed and studied; however, its yield as compared to repeated standard EEG (sEEG) is unknown.

Methods

We studied a prospective cohort of comatose adults treated with therapeutic hypothermia (TH) after a CA. cEEG data regarding background activity and epileptiform components were compared to two 20-minute sEEGs extracted from the cEEG recording (one during TH, and one in early normothermia).

Results

Thirty-four recordings were studied. During TH, the agreement between cEEG and sEEG was 97.1% (95% CI: 84.6 to 99.9%) for background discontinuity and reactivity evaluation, while it was 94.1% (95% CI 80.3 to 99.2%) regarding epileptiform activity. In early normothermia, we did not find any discrepancies. Thus, concordance results were very good during TH (kappa 0.83), and optimal during normothermia (kappa = 1). The median delay between CA and the first EEG reactivity testing was 18 hours (range: 4.75 to 25) for patients with perfect agreement and 10 hours (range: 5.75 to 10.5) for the three patients with discordant findings (P = 0.02, Wilcoxon).

Conclusions

Standard intermittent EEG has comparable performance with continuous EEG both for variables important for outcome prognostication (EEG reactivity) and identification of epileptiform transients in this relatively small sample of comatose survivors of CA. This finding has an important practical implication, especially for centers where EEG resources are limited.

Clinical review: Continuous and simplified electroencephalography to monitor brain recovery after cardiac arrest

There has been a dramatic change in hospital care of cardiac arrest survivors in recent years, including the use of target temperature management (hypothermia). Clinical signs of recovery or deterioration, which previously could be observed, are now concealed by sedation, analgesia, and muscle paralysis. Seizures are common after cardiac arrest, but few centers can offer high-quality electroencephalography (EEG) monitoring around the clock. This is due primarily to its complexity and lack of resources but also to uncertainty regarding the clinical value of monitoring EEG and of treating post-ischemic electrographic seizures. Thanks to technical advances in recent years, EEG monitoring has become more available. Large amounts of EEG data can be linked within a hospital or between neighboring hospitals for expert opinion. Continuous EEG (cEEG) monitoring provides dynamic information and can be used to assess the evolution of EEG patterns and to detect seizures. cEEG can be made more simple by reducing the number of electrodes and by adding trend analysis to the original EEG curves. In our version of simplified cEEG, we combine a reduced montage, displaying two channels of the original EEG, with amplitude-integrated EEG trend curves (aEEG). This is a convenient method to monitor cerebral function in comatose patients after cardiac arrest but has yet to be validated against the gold standard, a multichannel cEEG. We recently proposed a simplified system for interpreting EEG rhythms after cardiac arrest, defining four major EEG patterns. In this topical review, we will discuss cEEG to monitor brain function after cardiac arrest in general and how a simplified cEEG, with a reduced number of electrodes and trend analysis, may facilitate and improve care.

Individualized correction of neuron-specific enolase (NSE) measurement in hemolyzed serum samples

BACKGROUND

Accuracy of serum neuron-specific enolase (NSE) measurement is paramount, particularly in the context of neurological outcome prognostication. However, NSE measurements are compromised by even slight hemolysis, as it is abundant in red blood cells (RBCs). We derived and validated an individualized hemolysis correction equation in an attempt to reduce the current rejection rate of 14% at our institution.

METHODS

Intracellular NSE was measured in RBC lysates to determine concentration variability. A correction equation was derived, accounting for both RBC-derived NSE false-elevation and hemoglobin-derived signal quenching. The performance of this individualized correction was evaluated in intentionally hemolyzed samples and accuracy was compared to a generalized correction.

RESULTS

Significant inter-individual variability of RBC NSE was observed, with an almost two-fold range (15.7-28.5 ng NSE/mg Hb, p<0.001); intra-individual variability was insignificant. The individualized hemolysis correction equation derived: NSE(corr)=NSE(meas)-(Hb(serum))(NSE(RBCs/Hb))+0.0844(Hb(serum))+1.1 corrected 95% of the intentionally hemolyzed samples to within ±5 ng/ml of corresponding baseline NSE concentrations, compared to 74% using a generalized formula.

CONCLUSIONS

The individualized hemolysis correction provides increased accuracy in the estimation of true serum NSE concentrations for hemolyzed samples, compared to a generalized approach, by accounting for inter-individual RBC NSE variability. Incorporating this correction should reduce sample rejection rates and overall health care costs.

A structured approach to neurologic prognostication in clinical cardiac arrest trials

Brain injury is the dominant cause of death for cardiac arrest patients who are admitted to an intensive care unit, and the majority of patients die after withdrawal of life sustaining therapy (WLST) based on a presumed poor neurologic outcome. Mild induced hypothermia was found to decrease the reliability of several methods for neurological prognostication. Algorithms for prediction of outcome, that were developed before the introduction of mild hypothermia after cardiac arrest, may have affected the results of studies with hypothermia-treated patients. In previous trials on neuroprotection after cardiac arrest, including the pivotal hypothermia trials, the methods for prognostication and the reasons for WLST were not reported and may have had an effect on outcome. In the Target Temperature Management trial, in which 950 cardiac arrest patients have been randomized to treatment at 33°C or 36°C, neuroprognostication and WLST-decisions are strictly protocolized and registered. Prognostication is delayed to at least 72 hours after the end of the intervention period, thus a minimum of 4.5 days after the cardiac arrest, and is based on multiple parameters to account for the possible effects of hypothermia.

Advances in pediatric neurocritical care

Because pediatric intensive care units (PICUs) improve survival for a range of acute diseases, attention has turned toward ensuring the best possible functional outcomes after critical illness. The neurocritical care of children is of increasing interest. However, the pediatric population encompasses a heterogeneous set of neurologic conditions, with several possible models of how best to address them. This article reviews the special challenges faced by PICUs with regards to diseases, technologies, and skills and the progress that has been made in treatment, monitoring, and prognostication. Recent advances in translational research expected to modify the field in the near-term are described.

Prognostic performance of diffusion-weighted MRI combined with NSE in comatose cardiac arrest survivors treated with mild hypothermia

BACKGROUND

MRI-based prognostication of comatose cardiac arrest survivors has shown promising results. However, the technique has not been validated in patients treated with therapeutic hypothermia and it is unknown how it might add to NSE-based prognostication. We sought to evaluate the prognostic performance of regional apparent diffusion coefficient (ADC) in comatose out-of-hospital cardiac arrest (OHCA) patients treated with mild hypothermia and its added value to NSE-based prognostication.

METHODS

An OHCA registry was analyzed to identify OHCA patients older than 15 who were treated with therapeutic hypothermia and underwent brain MRI between 2008 and 2011. Quantitative measurement of regional ADCs was performed by a radiologist blinded to the clinical outcome.

RESULTS

Of the 43 eligible patients, 11 (18.6 %) achieved a good outcome (6-month CPC of 1 or 2). The regional ADC of the occipital cortex showed the highest discriminatory power with an area under the curve of receiver operating characteristic (AUROC) of 0.943 (95 % CI, 0.872-1.000) and predicted poor outcomes with a sensitivity of 90.6 % and a specificity of 100 %. The AUROC for NSE levels (48-h) was 0.911 (95 % CI, 0.801-1.000) which was significantly correlated with the regional ADC (Pearson's r = -0.674, p < .001). The ADC-based predictions identified an additional 5 (35.7 %) poor outcome patients out of 14 with 48-h NSE levels less than 78.9 ng/mL, which is the cutoff point suggested in a previous study. However, additional prognostic information was not provided when the 48-h NSE levels were >78.9 ng/mL.

CONCLUSIONS

Regional ADC-based prognostication was accurate in OHCA patients who were treated with mild hypothermia. However, it only provided additional prognostic information when the 48-h NSE levels indicated a good prognosis (48-h NSE <78.9 ng/mL).

Continuous evaluation of neurological prognosis after cardiac arrest

Post-resuscitation care has changed in the last decade, and outcome after cardiac arrest has improved, thanks to several combined measures. Induced hypothermia has shown a treatment benefit in two randomized trials, but some doubts remain. General care has improved, including the use of emergency coronary intervention. Assessment of neurological function and prognosis in comatose cardiac arrest patient is challenging, especially when treated with hypothermia. In this review, we evaluate the recent literature and discuss the available evidence for prognostication after cardiac arrest in the era of temperature management. Relevant literature was identified searching PubMed and reading published papers in the field, but no standardized search strategy was used. The complexity of predicting outcome after cardiac arrest and induced hypothermia is recognized in the literature, and no single test can predict a poor prognosis with absolute certainty. A clinical neurological examination is still the gold standard, but the results need careful interpretation because many patients are affected by sedatives and by hypothermia. Common adjuncts include neurophysiology, brain imaging and biomarkers, and a multimodal strategy is generally recommended. Current guidelines for prediction of outcome after cardiac arrest and induced hypothermia are not sufficient. Based on our expert opinion, we suggest a multimodal approach with a continuous evaluation of prognosis based on repeated neurological examinations and electroencephalography. Somatosensory-evoked potential is an established method to help determine a poor outcome and is recommended, whereas biomarkers and magnetic resonance imaging are promising adjuncts. We recommend that a decisive evaluation of prognosis is performed at 72 h after normothermia or later in a patient free of sedative and analgetic drugs.

Therapeutic hypothermia and reliability of somatosensory evoked potentials in predicting outcome after cardiopulmonary arrest

The loss of the N20 component on testing median somatosensory evoked potentials (SSEP) has been established as the most reliable indicator of unfavorable prognosis in post-cardiopulmonary arrest patients. With the intervention of therapeutic hypothermia in the management of patients who remain comatose following cardiopulmonary arrest that association is now in dispute. Abandoning SSEP as a key prognostic indicator of neurologic outcome would be a serious loss and cannot be justified.