Serum neurofilament light levels are correlated to long-term neurocognitive outcome measures after cardiac arrest

OBJECTIVE: To explore associations between four methods assessing long-term neurocognitive outcome after out-of-hospital cardiac arrest and early hypoxic-ischemic neuronal brain injury assessed by the biomarker serum neurofilament light (NFL), and to compare the agreement for the outcome methods. METHODS: An explorative post-hoc study was conducted on survivor data from the international Target Temperature Management after Out-of-hospital Cardiac Arrest trial, investigating serum NFL sampled 48/72-hours post-arrest and neurocognitive outcome 6 months post-arrest. RESULTS: Among the long-term surviving participants (N = 457), serum NFL (n = 384) was associated to all outcome instruments, also when controlling for demographic and cardiovascular risk factors. Associations between NFL and the patient-reported Two Simple Questions (TSQ) were however attenuated when adjusting for vitality and mental health. NFL predicted results on the outcome instruments to varying degrees, with an excellent area under the curve for the clinician-report Cerebral Performance Category (CPC 1-2: 0.90). Most participants were classified as CPC 1 (79%). Outcome instrument correlations ranged from small (Mini-Mental State Examination [MMSE]-TSQ) to strong (CPC-MMSE). CONCLUSIONS: The clinician-reported CPC was mostly related to hypoxic-ischemic brain injury, but with a ceiling effect. These results may be useful when selecting methods and instruments for clinical follow-up models

Effects of Hypothermia vs Normothermia on Societal Participation and Cognitive Function at 6 Months in Survivors After Out-of-Hospital Cardiac Arrest

ImportanceThe Targeted Hypothermia vs Targeted Normothermia After Out-of-Hospital Cardiac Arrest (TTM2) trial reported no difference in mortality or poor functional outcome at 6 months after out-of-hospital cardiac arrest (OHCA). This predefined exploratory analysis provides more detailed estimation of brain dysfunction for the comparison of the 2 intervention regimens.ObjectivesTo investigate the effects of targeted hypothermia vs targeted normothermia on functional outcome with focus on societal participation and cognitive function in survivors 6 months after OHCA.Design, Setting, and ParticipantsThis study is a predefined analysis of an international multicenter, randomized clinical trial that took place from November 2017 to January 2020 and included participants at 61 hospitals in 14 countries. A structured follow-up for survivors performed at 6 months was by masked outcome assessors. The last follow-up took place in October 2020. Participants included 1861 adult (older than 18 years) patients with OHCA who were comatose at hospital admission. At 6 months, 939 of 1861 were alive and invited to a follow-up, of which 103 of 939 declined or were missing.InterventionsRandomization 1:1 to temperature control with targeted hypothermia at 33 °C or targeted normothermia and early treatment of fever (37.8 °C or higher).Main outcomes and measuresFunctional outcome focusing on societal participation assessed by the Glasgow Outcome Scale Extended ([GOSE] 1 to 8) and cognitive function assessed by the Montreal Cognitive Assessment ([MoCA] 0 to 30) and the Symbol Digit Modalities Test ([SDMT] z scores). Higher scores represent better outcomes.ResultsAt 6 months, 836 of 939 survivors with a mean age of 60 (SD, 13) (range, 18 to 88) years (700 of 836 male [84%]) participated in the follow-up. There were no differences between the 2 intervention groups in functional outcome focusing on societal participation (GOSE score, odds ratio, 0.91; 95% CI, 0.71-1.17; P = .46) or in cognitive function by MoCA (mean difference, 0.36; 95% CI,−0.33 to 1.05; P = .37) and SDMT (mean difference, 0.06; 95% CI,−0.16 to 0.27; P = .62). Limitations in societal participation (GOSE score less than 7) were common regardless of intervention (hypothermia, 178 of 415 [43%]; normothermia, 168 of 419 [40%]). Cognitive impairment was identified in 353 of 599 survivors (59%).ConclusionsIn this predefined analysis of comatose patients after OHCA, hypothermia did not lead to better functional outcome assessed with a focus on societal participation and cognitive function than management with normothermia. At 6 months, many survivors had not regained their pre-arrest activities and roles, and mild cognitive dysfunction was common.Trial RegistrationClinicalTrials.gov Identifier: NCT0290830

Biomarkers of brain injury after cardiac arrest; a statistical analysis plan from the TTM2 trial biobank investigators

Background: Several biochemical markers in blood correlate with the magnitude of brain injury and may be used to predict neurological outcome after cardiac arrest. We present a protocol for the evaluation of prognostic accuracy of brain injury markers after cardiac arrest. The aim is to define the best predictive marker and to establish clinically useful cut-off levels for routine implementation. Methods: Prospective international multicenter trial within the Targeted Hypothermia versus Targeted Normothermia after Out-of-Hospital Cardiac Arrest (TTM2) trial in collaboration with Roche Diagnostics International AG. Samples were collected 0, 24, 48, and 72 hours after randomisation (serum) and 0 and 48 hours after randomisation (plasma), and pre-analytically processed at each site before storage in a central biobank. Routine markers neuron-specific enolase (NSE) and S100B, and neurofilament light, total-tau and glial fibrillary acidic protein will be batch analysed using novel Elecsys® electrochemiluminescence immunoassays on a Cobas e601 instrument. Results: Statistical analysis will be reported according to the Standards for Reporting Diagnostic accuracy studies (STARD) and will include comparisons for prediction of good versus poor functional outcome at six months post-arrest, by modified Rankin Scale (0–3 vs. 4–6), using logistic regression models and receiver operating characteristics curves, evaluation of mortality at six months according to biomarker levels and establishment of cut-off values for prediction of poor neurological outcome at 95–100% specificities. Conclusions: This prospective trial may establish a standard methodology and clinically appropriate cut-off levels for the optimal biomarker of brain injury which predicts poor neurological outcome after cardiac arrest

The predictive value of highly malignant EEG patterns after cardiac arrest: evaluation of the ERC-ESICM recommendations

Purpose: The 2021 guidelines endorsed by the European Resuscitation Council (ERC) and the European Society of Intensive Care Medicine (ESICM) recommend using highly malignant electroencephalogram (EEG) patterns (HMEP; suppression or burst-suppression) at > 24 h after cardiac arrest (CA) in combination with at least one other concordant predictor to prognosticate poor neurological outcome. We evaluated the prognostic accuracy of HMEP in a large multicentre cohort and investigated the added value of absent EEG reactivity. Methods: This is a pre-planned prognostic substudy of the Targeted Temperature Management trial 2. The presence of HMEP and background reactivity to external stimuli on EEG recorded > 24 h after CA was prospectively reported. Poor outcome was measured at 6 months and defined as a modified Rankin Scale score of 4-6. Prognostication was multimodal, and withdrawal of life-sustaining therapy (WLST) was not allowed before 96 h after CA. Results: 845 patients at 59 sites were included. Of these, 579 (69%) had poor outcome, including 304 (36%) with WLST due to poor neurological prognosis. EEG was recorded at a median of 71 h (interquartile range [IQR] 52-93) after CA. HMEP at > 24 h from CA had 50% [95% confidence interval [CI] 46-54] sensitivity and 93% [90-96] specificity to predict poor outcome. Specificity was similar (93%) in 541 patients without WLST. When HMEP were unreactive, specificity improved to 97% [94-99] (p = 0.008). Conclusion: The specificity of the ERC-ESICM-recommended EEG patterns for predicting poor outcome after CA exceeds 90% but is lower than in previous studies, suggesting that large-scale implementation may reduce their accuracy. Combining HMEP with an unreactive EEG background significantly improved specificity. As in other prognostication studies, a self-fulfilling prophecy bias may have contributed to observed results

Prediction of neurological outcome after cardiac arrest and targeted temperature management

Background: Prediction of neurological outcome in unconscious patients after cardiac arrest (CA) forms the basis for decisions on further level-of-care based on results from clinical neurological examinations, neuroimaging (CT or MRI), neurophysiology (EEG or SSEP) and blood biomarkers of brain injury. Methods must be highly specific to avoid misclassifying patients with possibilities of a good outcome. In 2015, the European Resuscitation Council (ERC) and the European Society of Intensive Care Medicine (ESICM) published an algorithm to identify poor outcome patients after CA. Novel methods to analyse biomarkers of brain injury have become available and may prove superior to the recommended marker Neuron-specific enolase (NSE). Purpose: I) To describe findings on head computed tomography (CT) after CA, and evaluate the prognostic accuracy of generalised oedema. II & III) To explore the prognostic accuracies of 3 novel blood biomarkers after CA: the axonal marker serum Neurofilament light (NFL), the astrocytic Glial fibrillary acidic protein (GFAP) and the neuronal marker Ubiquitin C-terminal hydrolase (UCH-L1). IV) To assess the predictive performance of the ERC/ESICM algorithm and modifications thereof. To describe prognostic accuracies of single and combined prognostic methods as recommended by the ERC/ESICM.Methods: All patients participated in the Target Temperature after Out-of-hospital cardiac arrest (TTM) trial, a prospective international multicentre trial randomising adult patients with CA of presumed cardiac origin to targeted temperature managements of 33°C or 36°C for 24 hours. Papers I and IV are retrospective studies utilizing information from the TTM database. Serum samples studied in Papers II and III were collected prospectively at 24, 48 and 72 hours post-arrest, and stored in a biobank for batch analysis after trial completion. Primary outcome was poor neurological outcome, defined as Cerebral Performance Category Scale 3-5 (severe cerebral disability, vegetative state or death) at 6 months follow-up.Results: I) Early CT examinations ≤24h were usually normal. Subacutely, generalised oedema was the most common finding, and strongly associated with poor outcome. II) Already at 24 hours post-arrest, serum NFL analysed with an ultrasensitive assay (Simoa) predicted poor neurological outcome with higher prognostic accuracy than any prognostic method currently recommended in the ERC/ESICM algorithm. NFL also differentiatied between various levels of brain injury. II) GFAP and UCH-L1 may be useful as early markers 24h after CA, yet at 48 and 72 hours their prognostic accuracies were not superior to neuron specific enolase. GFAP and UCH-L1 were not elevated in hemolysis, which may prove an advantage compared to NSE. IV) The ERC/ESICM algorithm predicted poor outcome without false positive predictions (100% specificity) and identified approximately fourty percent of patients with poor outcome. Any two pathological findings according to the ERC/ESICM criteria predicted poor outcome without false positive predictions, regardless of level of unconsciousness. Withdrawal of life-sustaining-therapy (WLST) was common in the TTM trial and may have influenced our results.Conclusions: Prognostication after CA should always be multimodal. The current ERC/ESICM algorithm safely predicted poor outcome, but could benefit from minor modifications. Serum NFL has the potential to guide treatment decisions, both to predict poor outcome and to identify patients with a presumed good neurological prognosis where further treatment is life-saving

Hypothermia versus normothermia after out-of-hospital cardiac arrest; the effect on post-intervention serum concentrations of sedatives and analgesics and time to awakening

Background: This study investigated the association of two levels of targeted temperature management (TTM) after out-of-hospital cardiac arrest (OHCA) with administered doses of sedative and analgesic drugs, serum concentrations, and the effect on time to awakening. Methods: This substudy of the TTM2-trial was conducted at three centers in Sweden, with patients randomized to either hypothermia or normothermia. Deep sedation was mandatory during the 40-hour intervention. Blood samples were collected at the end of TTM and end of protocolized fever prevention (72 hours). Samples were analysed for concentrations of propofol, midazolam, clonidine, dexmedetomidine, morphine, oxycodone, ketamine and esketamine. Cumulative doses of administered sedative and analgesic drugs were recorded. Results: Seventy-one patients were alive at 40 hours and had received the TTM-intervention according to protocol. 33 patients were treated at hypothermia and 38 at normothermia. There were no differences between cumulative doses and concentration and of sedatives/analgesics between the intervention groups at any timepoint. Time until awakening was 53 hours in the hypothermia group compared to 46 hours in the normothermia group (p = 0.09). Conclusion: This study of OHCA patients treated at normothermia versus hypothermia found no significant differences in dosing or concentration of sedatives or analgesic drugs in blood samples drawn at the end of the TTM intervention, or at end of protocolized fever prevention, nor the time to awakening