Hypothermia vs Normothermia in Patients With Cardiac Arrest and Nonshockable Rhythm: A Meta-Analysis.

Importance: International guidelines recommend body temperature control below 37.8 °C in unconscious patients with out-of-hospital cardiac arrest (OHCA); however, a target temperature of 33 °C might lead to better outcomes when the initial rhythm is nonshockable. Objective: To assess whether hypothermia at 33 °C increases survival and improves function when compared with controlled normothermia in unconscious adults resuscitated from OHCA with initial nonshockable rhythm. Data Sources: Individual patient data meta-analysis of 2 multicenter, randomized clinical trials (Targeted Normothermia after Out-of-Hospital Cardiac Arrest [TTM2; NCT02908308] and HYPERION [NCT01994772]) with blinded outcome assessors. Unconscious patients with OHCA and an initial nonshockable rhythm were eligible for the final analysis. Study Selection: The study cohorts had similar inclusion and exclusion criteria. Patients were randomized to hypothermia (target temperature 33 °C) or normothermia (target temperature 36.5 to 37.7 °C), according to different study protocols, for at least 24 hours. Additional analyses of mortality and unfavorable functional outcome were performed according to age, sex, initial rhythm, presence or absence of shock on admission, time to return of spontaneous circulation, lactate levels on admission, and the cardiac arrest hospital prognosis score. Data Extraction and Synthesis: Only patients who experienced OHCA and had a nonshockable rhythm with all causes of cardiac arrest were included. Variables from the 2 studies were available from the original data sets and pooled into a unique database and analyzed. Clinical outcomes were harmonized into a single file, which was checked for accuracy of numbers, distributions, and categories. The last day of follow-up from arrest was recorded for each patient. Adjustment for primary outcome and functional outcome was performed using age, gender, time to return of spontaneous circulation, and bystander cardiopulmonary resuscitation. Main Outcomes and Measures: The primary outcome was mortality at 3 months; secondary outcomes included unfavorable functional outcome at 3 to 6 months, defined as a Cerebral Performance Category score of 3 to 5. Results: A total of 912 patients were included, 490 from the TTM2 trial and 422 from the HYPERION trial. Of those, 442 had been assigned to hypothermia (48.4%; mean age, 65.5 years; 287 males [64.9%]) and 470 to normothermia (51.6%; mean age, 65.6 years; 327 males [69.6%]); 571 patients had a first monitored rhythm of asystole (62.6%) and 503 a presumed noncardiac cause of arrest (55.2%). At 3 months, 354 of 442 patients in the hypothermia group (80.1%) and 386 of 470 patients in the normothermia group (82.1%) had died (relative risk [RR] with hypothermia, 1.04; 95% CI, 0.89-1.20; P = .63). On the last day of follow-up, 386 of 429 in the hypothermia group (90.0%) and 413 of 463 in the normothermia group (89.2%) had an unfavorable functional outcome (RR with hypothermia, 0.99; 95% CI, 0.87-1.15; P = .97). The association of hypothermia with death and functional outcome was consistent across the prespecified subgroups. Conclusions and Relevance: In this individual patient data meta-analysis, including unconscious survivors from OHCA with an initial nonshockable rhythm, hypothermia at 33 °C did not significantly improve survival or functional outcome.

Effects of Hypothermia vs Normothermia on Societal Participation and Cognitive Function at 6 Months in Survivors After Out-of-Hospital Cardiac Arrest: A Predefined Analysis of the TTM2 Randomized Clinical Trial.

Importance: The 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. Objectives: To 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 Participants: This 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. Interventions: Randomization 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 measures: Functional 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. Results: At 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%). Conclusions: In 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 Registration: ClinicalTrials.gov Identifier: NCT02908308.

Speed of cooling after cardiac arrest in relation to the intervention effect: a sub-study from the TTM2-trial.

BACKGROUND: Targeted temperature management (TTM) is recommended following cardiac arrest; however, time to target temperature varies in clinical practice. We hypothesised the effects of a target temperature of 33 °C when compared to normothermia would differ based on average time to hypothermia and those patients achieving hypothermia fastest would have more favorable outcomes. METHODS: In this post-hoc analysis of the TTM-2 trial, patients after out of hospital cardiac arrest were randomized to targeted hypothermia (33 °C), followed by controlled re-warming, or normothermia with early treatment of fever (body temperature, ≥ 37.8 °C). The average temperature at 4 h (240 min) after return of spontaneous circulation (ROSC) was calculated for participating sites. Primary outcome was death from any cause at 6 months. Secondary outcome was poor functional outcome at 6 months (score of 4-6 on modified Rankin scale). RESULTS: A total of 1592 participants were evaluated for the primary outcome. We found no evidence of heterogeneity of intervention effect based on the average time to target temperature on mortality (p = 0.17). Of patients allocated to hypothermia at the fastest sites, 71 of 145 (49%) had died compared to 68 of 148 (46%) of the normothermia group (relative risk with hypothermia, 1.07; 95% confidence interval 0.84-1.36). Poor functional outcome was reported in 74/144 (51%) patients in the hypothermia group, and 75/147 (51%) patients in the normothermia group (relative risk with hypothermia 1.01 (95% CI 0.80-1.26). CONCLUSIONS: Using a hospital's average time to hypothermia did not significantly alter the effect of TTM of 33 °C compared to normothermia and early treatment of fever.

Hypothermic versus Normothermic Temperature Control after Cardiac Arrest.

Hypothermia versus Normothermia after Cardiac ArrestHolgersson et al. perform an individual patient data meta-analysis of the TTM and TTM2 trials of hypothermia after cardiac arrest and find no difference in 6-month mortality with hypothermia to 33°C versus normothermia.

Hypothermia versus Normothermia after Out-of-Hospital Cardiac Arrest.

BACKGROUND: Targeted temperature management is recommended for patients after cardiac arrest, but the supporting evidence is of low certainty. METHODS: In an open-label trial with blinded assessment of outcomes, we randomly assigned 1900 adults with coma who had had an out-of-hospital cardiac arrest of presumed cardiac or unknown cause to undergo targeted hypothermia at 33°C, followed by controlled rewarming, or targeted normothermia with early treatment of fever (body temperature, ≥37.8°C). The primary outcome was death from any cause at 6 months. Secondary outcomes included functional outcome at 6 months as assessed with the modified Rankin scale. Prespecified subgroups were defined according to sex, age, initial cardiac rhythm, time to return of spontaneous circulation, and presence or absence of shock on admission. Prespecified adverse events were pneumonia, sepsis, bleeding, arrhythmia resulting in hemodynamic compromise, and skin complications related to the temperature management device. RESULTS: A total of 1850 patients were evaluated for the primary outcome. At 6 months, 465 of 925 patients (50%) in the hypothermia group had died, as compared with 446 of 925 (48%) in the normothermia group (relative risk with hypothermia, 1.04; 95% confidence interval [CI], 0.94 to 1.14; P = 0.37). Of the 1747 patients in whom the functional outcome was assessed, 488 of 881 (55%) in the hypothermia group had moderately severe disability or worse (modified Rankin scale score ≥4), as compared with 479 of 866 (55%) in the normothermia group (relative risk with hypothermia, 1.00; 95% CI, 0.92 to 1.09). Outcomes were consistent in the prespecified subgroups. Arrhythmia resulting in hemodynamic compromise was more common in the hypothermia group than in the normothermia group (24% vs. 17%, P<0.001). The incidence of other adverse events did not differ significantly between the two groups. CONCLUSIONS: In patients with coma after out-of-hospital cardiac arrest, targeted hypothermia did not lead to a lower incidence of death by 6 months than targeted normothermia. (Funded by the Swedish Research Council and others; TTM2 ClinicalTrials.gov number, NCT02908308.).

Targeted hypothermia versus targeted normothermia after out-of-hospital cardiac arrest: a statistical analysis plan.

BACKGROUND: To date, targeted temperature management (TTM) is the only neuroprotective intervention after resuscitation from cardiac arrest that is recommended by guidelines. The evidence on the effects of TTM is unclear. METHODS/DESIGN: The Targeted Hypothermia Versus Targeted Normothermia After Out-of-hospital Cardiac Arrest (TTM2) trial is an international, multicentre, parallel group, investigator-initiated, randomised, superiority trial in which TTM with a target temperature of 33 °C after cardiac arrest will be compared with a strategy to maintain normothermia and active treatment of fever (≥ 37.8 °C). Prognosticators, outcome assessors, the steering group, the trial coordinating team, and trial statisticians will be blinded to treatment allocation. The primary outcome will be all-cause mortality at 180 days after randomisation. We estimate a 55% mortality in the targeted normothermia group. To detect an absolute risk reduction of 7.5% with an alpha of 0.05 and 90% power, 1900 participants will be enrolled. The secondary neurological outcome will be poor functional outcome (modified Rankin scale 4-6) at 180 days after cardiac arrest. In this paper, a detailed statistical analysis plan is presented, including a comprehensive description of the statistical analyses, handling of missing data, and assessments of underlying statistical assumptions. Final analyses will be conducted independently by two qualified statisticians following the present plan. DISCUSSION: This SAP, which was prepared before completion of enrolment, should increase the validity of the TTM trial by mitigation of analysis-bias.

Protocol for outcome reporting and follow-up in the Targeted Hypothermia versus Targeted Normothermia after Out-of-Hospital Cardiac Arrest trial (TTM2).

AIMS: The TTM2-trial is a multi-centre randomised clinical trial where targeted temperature management (TTM) at 33 °C will be compared with normothermia and early treatment of fever (≥37.8 °C) after Out-of-Hospital Cardiac Arrest (OHCA). This paper presents the design and rationale of the TTM2-trial follow-up, where information on secondary and exploratory outcomes will be collected. We also present the explorative outcome analyses which will focus on neurocognitive function and societal participation in OHCA-survivors. METHODS: Blinded outcome-assessors will perform follow-up at 30-days after the OHCA with a telephone interview, including the modified Rankin Scale (mRS) and the Glasgow Outcome Scale Extended (GOSE). Face-to-face meetings will be performed at 6 and 24-months, and include reports on outcome from several sources of information: clinician-reported: mRS, GOSE; patient-reported: EuroQol-5 Dimensions-5 Level responses version (EQ-5D-5L), Life satisfaction, Two Simple Questions; observer-reported: Informant Questionnaire on Cognitive Decline in the Elderly-Cardiac Arrest version (IQCODE-CA) and neurocognitive performance measures: Montreal Cognitive Assessment, (MoCA), Symbol Digit Modalities Test (SDMT). Exploratory analyses will be performed with an emphasis on brain injury in the survivors, where the two intervention groups will be compared for potential differences in neuro-cognitive function (MoCA, SDMT) and societal participation (GOSE). Strategies to increase inter-rater reliability and decrease missing data are described. DISCUSSION: The TTM2-trial follow-up is a pragmatic yet detailed pre-planned and standardised assessment of patient's outcome designed to ensure data-quality, decrease missing data and provide optimal conditions to investigate clinically relevant effects of TTM, including OHCA-survivors' neurocognitive function and societal participation.

Targeted hypothermia versus targeted Normothermia after out-of-hospital cardiac arrest (TTM2): A randomized clinical trial-Rationale and design.

BACKGROUND: Less than 500 participants have been included in randomized trials comparing hypothermia with regular care for out-of-hospital cardiac arrest patients, and many of these trials were small and at a high risk of bias. Consequently, the accrued data on this potentially beneficial intervention resembles that of a drug following small phase II trials. A large confirmatory trial is therefore warranted. METHODS: The TTM2-trial is an international, multicenter, parallel group, investigator-initiated, randomized, superiority trial in which a target temperature of 33°C after cardiac arrest will be compared with a strategy to maintain normothermia and early treatment of fever (≥37.8°C). Participants will be randomized within 3 hours of return of spontaneous circulation with the intervention period lasting 40 hours in both groups. Sedation will be mandatory for all patients throughout the intervention period. The clinical team involved with direct patient care will not be blinded to allocation group due to the inherent difficulty in blinding the intervention. Prognosticators, outcome-assessors, the steering group, the trial coordinating team, and trial statistician will be blinded. The primary outcome will be all-cause mortality at 180 days after randomization. We estimate a 55% mortality in the control group. To detect an absolute risk reduction of 7.5% with an alpha of 0.05 and 90% power, 1900 participants will be enrolled. The main secondary neurological outcome will be poor functional outcome (modified Rankin Scale 4-6) at 180 days after arrest. DISCUSSION: The TTM2-trial will compare hypothermia to 33°C with normothermia and early treatment of fever (≥37.8°C) after out-of-hospital cardiac arrest.

Time to awakening after cardiac arrest and the association with target temperature management.

AIM: Target temperature management (TTM) at 32-36 °C is recommended in unconscious survivors of cardiac arrest. This study reports awakening in the TTM-trial. Our predefined hypotheses were that time until awakening correlates with long-term neurological outcome and is not affected by level of TTM. METHODS: Post-hoc analysis of time until awakening after cardiac arrest, its association with long-term (180-days) neurological outcome and predictors of late awakening (day 5 or later). The trial randomized 939 comatose survivors to TTM at 33 °C or 36 °C with strict criteria for withdrawal of life-sustaining therapies. Administered sedation in the treatment groups was compared. Awakening was defined as a Glasgow Coma Scale motor score 6. RESULTS: 496 patients had registered day of awakening in the ICU, another 43 awoke after ICU discharge. Good neurological outcome was more common in early (275/308, 89%) vs late awakening (142/188, 76%), p < 0.001. Awakening occurred later in TTM33 than in TTM36 (p = 0.002) with no difference in neurological outcome, or cumulative doses of sedative drugs at 12, 24 or 48 h. TTM33 (p = 0.006), clinical seizures (p = 0.004), and lower GCS-M on admission (p = 0.03) were independent predictors of late awakening. CONCLUSION: Late awakening is common and often has a good neurological outcome. Time to awakening was longer in TTM33 than in TTM36, this difference could not be attributed to differences in sedative drugs administered during the first 48 h.

Protein S100 as outcome predictor after out-of-hospital cardiac arrest and targeted temperature management at 33 °C and 36 °C.

BACKGROUND: We aimed to investigate the diagnostic performance of S100 as an outcome predictor after out-of-hospital cardiac arrest (OHCA) and the potential influence of two target temperatures (33 °C and 36 °C) on serum levels of S100. METHODS: This is a substudy of the Target Temperature Management after Out-of-Hospital Cardiac Arrest (TTM) trial. Serum levels of S100 were measured a posteriori in a core laboratory in samples collected at 24, 48, and 72 h after OHCA. Outcome at 6 months was assessed using the Cerebral Performance Categories Scale (CPC 1-2 = good outcome, CPC 3-5 = poor outcome). RESULTS: We included 687 patients from 29 sites in Europe. Median S100 values were higher in patients with a poor outcome at 24, 48, and 72 h: 0.19 (IQR 0.10-0.49) versus 0.08 (IQR 0.06-0.11) µg/ml, 0.16 (IQR 0.10-0.44) versus 0.07 (IQR 0.06-0.11) µg/L, and 0.13 (IQR 0.08-0.26) versus 0.06 (IQR 0.05-0.09) µg/L (p < 0.001), respectively. The ability to predict outcome was best at 24 h with an AUC of 0.80 (95% CI 0.77-0.83). S100 values were higher at 24 and 72 h in the 33 °C group than in the 36 °C group (0.12 [0.07-0.22] versus 0.10 [0.07-0.21] µg/L and 0.09 [0.06-0.17] versus 0.08 [0.05-0.10], respectively) (p < 0.02). In multivariable analyses including baseline variables and the allocated target temperature, the addition of S100 improved the AUC from 0.80 to 0.84 (95% CI 0.81-0.87) (p < 0.001), but S100 was not an independent outcome predictor. Adding S100 to the same model including neuron-specific enolase (NSE) did not further improve the AUC. CONCLUSIONS: The allocated target temperature did not affect S100 to a clinically relevant degree. High S100 values are predictive of poor outcome but do not add value to present prognostication models with or without NSE. S100 measured at 24 h and afterward is of limited value in clinical outcome prediction after OHCA. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT01020916 . Registered on 25 November 2009.

Single versus Serial Measurements of Neuron-Specific Enolase and Prediction of Poor Neurological Outcome in Persistently Unconscious Patients after Out-Of-Hospital Cardiac Arrest - A TTM-Trial Substudy.

BACKGROUND: Prediction of neurological outcome is a crucial part of post cardiac arrest care and prediction in patients remaining unconscious and/or sedated after rewarming from targeted temperature management (TTM) remains difficult. Current guidelines suggest the use of serial measurements of the biomarker neuron-specific enolase (NSE) in combination with other predictors of outcome in patients admitted after out-of-hospital cardiac arrest (OHCA). This study sought to investigate the ability of NSE to predict poor outcome in patients remaining unconscious at day three after OHCA. In addition, this study sought to investigate if serial NSE measurements add incremental prognostic information compared to a single NSE measurement at 48 hours in this population. METHODS: This study is a post-hoc sub-study of the TTM trial, randomizing OHCA patients to a course of TTM at either 33°C or 36°C. Patients were included from sites participating in the TTM-trial biobank sub study. NSE was measured at 24, 48 and 72 hours after ROSC and follow-up was concluded after 180 days. The primary end point was poor neurological function or death defined by a cerebral performance category score (CPC-score) of 3 to 5. RESULTS: A total of 685 (73%) patients participated in the study. At day three after OHCA 63 (9%) patients had died and 473 (69%) patients were not awake. In these patients, a single NSE measurement at 48 hours predicted poor outcome with an area under the receiver operating characteristics curve (AUC) of 0.83. A combination of all three NSE measurements yielded the highest discovered AUC (0.88, p = .0002). Easily applicable combinations of serial NSE measurements did not significantly improve prediction over a single measurement at 48 hours (AUC 0.58-0.84 versus 0.83). CONCLUSION: NSE is a strong predictor of poor outcome after OHCA in persistently unconscious patients undergoing TTM, and NSE is a promising surrogate marker of outcome in clinical trials. While combinations of serial NSE measurements may provide an increase in overall prognostic information, it is unclear whether actual clinical prognostication with low false-positive rates is improved by application of serial measurements in persistently unconscious patients. The findings of this study should be confirmed in another prospective cohort. TRIAL REGISTRATION: NCT01020916.

Usefulness of Serum B-Type Natriuretic Peptide Levels in Comatose Patients Resuscitated from Out-of-Hospital Cardiac Arrest to Predict Outcome.

N-terminal pro-B-type natriuretic (NT-proBNP) is expressed in the heart and brain, and serum levels are elevated in acute heart and brain diseases. We aimed to assess the possible association between serum levels and neurological outcome and death in comatose patients resuscitated from out-of-hospital cardiac arrest (OHCA). Of the 939 comatose OHCA patients enrolled and randomized in the Targeted Temperature Management (TTM) trial to TTM at 33°C or 36°C for 24 hours, 700 were included in the biomarker substudy. Of these, 647 (92%) had serum levels of NT-proBNP measured 24, 48, and 72 hours after return of spontaneous circulation (ROSC). Neurological outcome was evaluated by the Cerebral Performance Category (CPC) score and modified Rankin Scale (mRS) at 6 months. Six hundred thirty-eight patients (99%) had serum NT-proBNP levels ≥125 pg/ml. Patients with TTM at 33°C had significantly lower NT-proBNP serum levels (median 1,472 pg/ml) than those in the 36°C group (1,914 pg/ml) at 24 hours after ROSC, p <0.01 but not at 48 and 72 hours. At 24 hours, an increase in NT-proBNP quartile was associated with death (Plogrank <0.0001). In addition, NT-proBNP serum levels > median were independently associated with poor neurological outcome (odds ratio, ORCPC 2.02, CI 1.34 to 3.05, p <0.001; ORmRS 2.28, CI 1.50 to 3.46, p <0.001) adjusted for potential confounders. The association was diminished at 48 and 72 hours after ROSC. In conclusion, NT-proBNP serum levels are increased in comatose OHCA patients. Furthermore, serum NT-proBNP levels are affected by level of TTM and are associated with death and poor neurological outcome.

A low body temperature on arrival at hospital following out-of-hospital-cardiac-arrest is associated with increased mortality in the TTM-study.

AIM: To investigate the association of temperature on arrival to hospital after out-of-hospital-cardiac arrest (OHCA) with the primary outcome of mortality, in the targeted temperature management (TTM) trial. METHODS: The TTM trial randomized 939 patients to TTM at 33 or 36°C for 24h. Patients were categorized according to their recorded body temperature on arrival and also categorized to groups of patients being actively cooled or passively rewarmed. RESULTS: OHCA patients having a temperature ≤34.0°C on arrival at hospital had a significantly higher mortality compared to the OHCA patients with a higher temperature on arrival. A low body temperature on arrival was associated with a longer time to return of spontaneous circulation (ROSC) and duration of transport time to hospital. Patients who were actively cooled or passively rewarmed during the first 4h had similar mortality. In a multivariate logistic regression model mortality was significantly related to time from OHCA to ROSC, time from OHCA to advanced life support (ALS), age, sex and first registered rhythm. None of the temperature related variables (included the TTM-groups) were significantly related to mortality. CONCLUSION: OHCA patients with a temperature ≤34.0°C on arrival have a higher mortality than patients with a temperature ≥34.1°C on arrival. A low temperature on arrival is associated with a long time to ROSC. Temperature changes and TTM-groups were not associated with mortality in a regression model.

Atrial Fibrillation Following Out-of-Hospital Cardiac Arrest and Targeted Temperature Management-Are We Giving It the Attention it Deserves?

OBJECTIVES: Atrial fibrillation has been associated with increased mortality in the general population and mixed populations of critical ill. Atrial fibrillation can also affect patients during post-cardiac arrest care. We sought to assess the prognostic implications of atrial fibrillation following out-of-hospital cardiac arrest, including relation to the level of targeted temperature management. DESIGN: A post hoc analysis of a prospective randomized trial. SETTING: Thirty-six ICUs. PATIENTS: We included 897 (96%) of the 939 comatose out-of-hospital cardiac arrest survivors from the targeted temperature management trial (year, 2010-2013) with data on heart rhythm on day 2. INTERVENTIONS: Targeted temperature management at 33°C or 36°C. MEASUREMENTS AND MAIN RESULTS: Endpoints included cumulative proportion of atrial fibrillation following out-of-hospital cardiac arrest and 180-day all-cause mortality and specific death causes stratified by atrial fibrillation. Atrial fibrillation on day 2 was used as primary endpoint analyses to exclude effects of short-term atrial fibrillation related to resuscitation and initial management. The cumulative proportions of atrial fibrillation were 15% and 11% on days 1 and 2, respectively. Forty-three percent of patients with initial atrial fibrillation the first day were reported with sinus rhythm on day 2. No difference was found between the groups treated with targeted temperature management at 33°C and 36°C. Patients affected by atrial fibrillation had significantly higher 180-day mortality (atrial fibrillation: 66% vs no-atrial fibrillation: 43%; plogrank < 0.0001 and unadjusted hazard ratio, 1.75 [1.35-2.30]; p < 0.0001). The association between atrial fibrillation and higher mortality remained significant (adjusted hazard ratio, 1.34 [1.01-1.79]; p < 0.05) adjusted for potential confounders. Atrial fibrillation was independently associated with increased risk of cardiovascular death and multiple-organ failure (adjusted hazard ratio, 2.07 [1.39-3.09]; p < 0.001), whereas no association with higher risk of death from cerebral causes was found. CONCLUSIONS: Atrial fibrillation was independently associated with higher mortality, primarily driven by cardiovascular causes and multiple-organ failure, and may thus identify a vulnerable subpopulation. Whether treatment to prevent atrial fibrillation is associated with an improved prognosis remains to be established.

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.

Time to start of cardiopulmonary resuscitation and the effect of target temperature management at 33°C and 36°C.

INTRODUCTION: The optimal temperature during targeted temperature management (TTM) for comatose patients resuscitated from out-of-hospital cardiac arrest is unknown. It has been hypothesized that patients with long no-flow times, for example those without bystander CPR would have the most to gain from temperature management at lower temperatures. METHODS: We analysed data from an international clinical trial randomizing cardiac arrest patients to targeted temperature management at 33°C and 36°C for an interaction between no-flow time and intervention group, with neurological function at six months after cardiac arrest as the primary outcome. A cerebral performance category (CPC) score of 1 or 2 was considered a good outcome. RESULTS: No-flow time (min) was associated with poor neurological outcome (OR 1.13, 95% confidence interval 1.06-1.20, p<0.001). There was no statistically significant interaction between no flow-time and intervention group (p=0.11), which may imply that the non-superior effect of 33°C was consistent for all no-flow times. Bystander CPR was not independently associated with neurological function. CONCLUSIONS: TTM at 33°C compared to 36°C was not associated with an increased probability of a good neurological function for patients with longer no-flow times.

Predictive value of interleukin-6 in post-cardiac arrest patients treated with targeted temperature management at 33 °C or 36 °C.

AIM: Post-cardiac arrest syndrome (PCAS) is characterized by systemic inflammation, however data on the prognostic value of inflammatory markers is sparse. We sought to investigate the importance of systemic inflammation, assessed by interleukin-6 (IL-6) in comatose survivors of out-of-hospital cardiac arrest. METHODS: A total of 682 patients enrolled in the Target Temperature Management (TTM) trial, surviving >24h with available IL-6 data were included. IL-6 was measured on days 1, 2 and 3 after return of spontaneous circulation. Severity of PCAS was assessed daily by the Sequential Organ Failure Assessment score. Survival status was recorded at 30 days. RESULTS: High levels of IL-6 at day 1-3 (all p<0.0001) were independently associated with severity of PCAS with no interaction of target temperature (all p=NS). IL-6 levels did not differ between temperature groups (p(interaction)=0.99). IL-6 levels at day 2 (p<0.0001) and day 3 (p<0.0001) were associated with crude mortality. Adjusted Cox proportional-hazards analysis showed that a two-fold increase of IL-6 levels at day 2 (HR=1.15 (95% CI: 1.07-1.23), p=0.0002) and day 3 (HR=1.18 (95% CI: 1.09-1.27), p<0.0001) were associated with mortality. IL-6 levels at day 3 had the highest discriminative value in predicting mortality (AUC=0.66). IL-6 did not significantly improve 30-day mortality prediction compared to traditional prognostic factors (p=0.08). CONCLUSIONS: In patients surviving >24h following cardiac arrest, IL-6 levels were significantly elevated and associated with severity of PCAS with no significant influence of target temperature. High IL-6 levels were associated with increased mortality. Measuring levels of IL-6 did not provide incremental prognostic value.

Impact of time to return of spontaneous circulation on neuroprotective effect of targeted temperature management at 33 or 36 degrees in comatose survivors of out-of hospital cardiac arrest.

AIM: Time to Return of Spontaneous Circulation (ROSC) has a plausible relation to severity of hypoxic injury before and during resuscitation in Out-of-Hospital Cardiac Arrest (OHCA), and has consistently been associated with adverse outcome. The effect of Targeted Temperature Management (TTM) may not be similar over the full spectrum of time to ROSC. This study investigated the possible beneficial effect of targeting 33°C over 36°C on the prognostic importance of time to ROSC. METHODS: In predefined sub-study of the TTM-trial (NEJM 2013) we investigated the relationship between time to ROSC, level of TTM and mortality and neurological outcome as assessed by the Cerebral Performance Category (CPC) scale and modified Rankin Scale (mRS) after 180 days. RESULTS: Prolonged time to ROSC was significantly associated with increased mortality with a hazard ratio (HR) of 1.02 per minute (95% CI 1.01-1.02). Level of TTM did not modify the association of time to ROSC and mortality, pinteraction=0.85. Prolonged time to ROSC was associated with reduced odds of surviving with a favorable neurological outcome for CPC (p=0.008 for CPC 1-2) and mRS (p=0.17, mRS 0-3) with no significant interaction with level of TTM. CONCLUSION: Time to ROSC remains a significant prognostic factor in comatose OHCA patients with regards to risk of death and risk of adverse neurological outcome. For any time to ROSC, targeting 33°C in TTM was not associated with benefit with regards to reducing mortality or risk of adverse neurological outcome compared to targeting 36°C.

No difference in mortality between men and women after out-of-hospital cardiac arrest.

AIM: Comparing the outcome after out-of-hospital cardiac arrest (OHCA) in men and women and to determine whether sex modifies the effect of targeted temperature management (TTM) at 33 or 36°C. METHODS: The TTM trial randomized 950 patients to TTM at 33 or 36°C for 24h. This predefined sub-study of the TTM trial assessed survival and neurological outcome defined as Cerebral Performance Category (CPC) and modified Rankin Scale (mRS) using female sex as main predictor of outcome, in relation to level of TTM and other confounding factors. RESULTS: Compared to men, women more often had OHCA at home, p=0.04 and less often had bystander defibrillation, p=0.01. No other differences in arrest circumstances were found. Coronary angiography (CAG) and percutaneous coronary intervention (PCI) <24h after ROSC was less often performed in women, both: p=0.02. Female sex was associated with higher mortality in univariate analysis, hazard ratio (HR)=1.29, CI=1.04-1.61, p=0.02 compared to men. Adjusting for demographic factors (age and comorbidity), arrest circumstances, pre-hospital findings, inclusion sites, treatments and status at admission reduced this: HR=1.11, CI=0. 87-1.41, p=0.42, and sex was no longer an independent risk factor for death. The effect of sex did not modify the effect of TTM at 33 and 36°C, pinteraction=0.73. CONCLUSION: Female sex seems associated with adverse outcome, but this association is largely explained by differences in arrest circumstances and in-hospital treatment. Our data shows no interaction between sex and the effect of targeting 33 vs. 36°C.