Targeted temperature management and cardiac arrest after the TTM-2 study

Target Temperature Management Effect on the Clinical Outcome of Patients with Out-of-Hospital Cardiac Arrest Treated with Extracorporeal Cardiopulmonary Resuscitation: A Nationwide Observational Study

This study aimed to investigate whether targeted temperature management (TTM) could enhance outcomes in patients with out-of-hospital cardiac arrest (OHCA) treated with extracorporeal cardiopulmonary resuscitation (ECPR) for refractory cardiac arrest. Using a nationwide OHCA registry, adult patients with witnessed OHCA of presumed cardiac origin who underwent ECPR at the emergency department between 2008 and 2021 were included. We examined the effect of ECPR with TTM on survival and neurological outcomes at hospital discharge using propensity score matching and multivariable logistic regression compared with patients treated with ECPR without TTM. Odds ratios and 95% confidence intervals were determined. A total of 399 ECPR cases were analyzed among 380,239 patients with OHCA. Of these, 330 underwent ECPR without TTM and 69 with TTM. After propensity score matching, 69 matched pairs of patients were included in the analysis. No significant differences in survival and good neurological outcomes between the two groups were observed. In the multivariable logistic regression, no significant differences were observed in survival and neurological outcomes between ECPR with and without TTM. Among the patients who underwent ECPR after OHCA, ECPR with TTM did not improve outcomes compared with ECPR without TTM.

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.

A Commentary on the Effect of Targeted Temperature Management in Patients Resuscitated from Cardiac Arrest

The members of the International Liaison Committee on Resuscitation (ILCOR) Advanced Life Support Task Force have written a comprehensive summary of trials of the effectiveness of induced hypothermia (IH) or targeted temperature management (TTM) in comatose patients after cardiac arrest (CA). However, in-depth analysis of these studies is incomplete, especially since there was no significant difference in primary outcome between hypothermia versus normothermia in the recently reported TTM2 trial. We critically appraise trials of IH/TTM versus normothermia to characterize reasons for the lack of treatment effect, based on a previously published framework for what to consider when the primary outcome fails. We found a strong biologic rationale and external clinical evidence that IH treatment is beneficial. Recent TTM trials mainly included unselected patients with a high rate of bystander cardiopulmonary resuscitation. The treatment was not applied as intended, which led to a large delay in achievement of target temperature. While receiving intensive care, sedative drugs were likely used that might have led to increased neurologic damage as were antiplatelet drugs that could be associated with increased acute stent thrombosis in hypothermic patients. It is reasonable to still use or evaluate IH treatment in patients who are comatose after CA as there are multiple plausible reasons why IH compared to normothermia did not significantly improve neurologic outcome in the TTM trials.

Temperature Control After Cardiac Arrest: A Narrative Review

Cardiac arrest (CA) is a critical public health issue affecting more than half a million Americans annually. The main determinant of outcome post-CA is hypoxic-ischemic brain injury (HIBI), and temperature control is currently the only evidence-based, guideline-recommended intervention targeting secondary brain injury. Temperature control is a key component of a post-CA care bundle; however, conflicting evidence challenges its wide implementation across the vastly heterogeneous population of CA survivors. Here, we critically appraise the available literature on temperature control in HIBI, detail how the evidence has been integrated into clinical practice, and highlight the complications associated with its use and the timing of neuroprognostication after CA. Future clinical trials evaluating different temperature targets, rates of rewarming, duration of cooling, and identifying which patient phenotype benefits from different temperature control methods are needed to address these prevailing knowledge gaps.

Management of comatose survivors of out-of-hospital cardiac arrest in Europe: current treatment practice and adherence to guidelines. A joint survey by the Association for Acute CardioVascular Care (ACVC) of the ESC, the European Resuscitation Council (ERC), the European Society for Emergency Medicine (EUSEM), and the European Society of Intensive Care Medicine (ESICM)

AIMS

International guidelines give recommendations for the management of comatose out-of-hospital cardiac arrest (OHCA) survivors. We aimed to investigate adherence to guidelines and disparities in the treatment of OHCA in hospitals in Europe.

METHODS AND RESULTS

A web-based, multi-institutional, multinational survey in Europe was conducted using an electronic platform with a predefined questionnaire developed by experts in post-resuscitation care. The survey was disseminated to all members of the societies via email, social media, websites, and newsletters in June 2021. Of 252 answers received, 237 responses from different units were included and 166 (70%) were from cardiac arrest centres. First-line vasopressor used was noradrenaline in 195 (83%) and the first-line inotrope was dobutamine in 148 (64%) of the responses. Echocardiography is available 24/7 in 204 (87%) institutions. Targeted temperature management was used in 160 (75%) institutions for adult comatose survivors of OHCA with an initial shockable rhythm. Invasive or external cooling methods with feedback were used in 72 cardiac arrest centres (44%) and 17 (24%) non-cardiac arrest centres (P < 0.0003). A target temperature between 32 and 34°C was preferred by 46 centres (21%); a target between 34 and 36°C by 103 centres (52%); and <37.5°C by 35 (16%). Multimodal neuroprognostication was poorly implemented and a follow-up at 3 months after discharge was done in 71 (30%) institutions.

CONCLUSION

Post-resuscitation care is not well established and varies among centres in European hospitals. Cardiac arrest centres have a higher coherence with guidelines compared with respondents from non-cardiac arrest centres. The overall inconsistency in approaches and deviation from recommendations could be a focus for improvement.

Hypothermic versus Normothermic Temperature Control after Cardiac Arrest

BACKGROUND: The evidence for temperature control for comatose survivors of cardiac arrest is inconclusive. Controversy exists as to whether the effects of hypothermia differ per the circumstances of the cardiac arrest or patient characteristics. METHODS: An individual patient data meta-analysis of the Targeted Temperature Management at 33°C versus 36°C after Cardiac Arrest (TTM) and Hypothermia versus Normothermia after Out-of-Hospital Cardiac Arrest (TTM2) trials was conducted. The intervention was hypothermia at 33°C and the comparator was normothermia. The primary outcome was all-cause mortality at 6 months. Secondary outcomes included poor functional outcome (modified Rankin scale score of 4 to 6) at 6 months. Predefined subgroups based on the design variables in the original trials were tested for interaction with the intervention as follows: age (older or younger than the median), sex (female or male), initial cardiac rhythm (shockable or nonshockable), time to return of spontaneous circulation (above or below the median), and circulatory shock on admission (presence or absence). RESULTS: The primary analyses included 2800 patients, with 1403 assigned to hypothermia and 1397 to normothermia. Death occurred for 691 of 1398 participants (49.4%) in the hypothermia group and 666 of 1391 participants (47.9%) in the normothermia group (relative risk with hypothermia, 1.03; 95% confidence interval [CI], 0.96 to 1.11; P=0.41). A poor functional outcome occurred for 733 of 1350 participants (54.3%) in the hypothermia group and 718 of 1330 participants (54.0%) in the normothermia group (relative risk with hypothermia, 1.01; 95% CI, 0.94 to 1.08; P=0.88). Outcomes were consistent in the predefined subgroups. CONCLUSIONS: Hypothermia at 33°C did not decrease 6-month mortality compared with normothermia after out-of-hospital cardiac arrest. (Funded by Vetenskapsrådet; ClinicalTrials.gov numbers NCT02908308 and NCT01020916.)

Therapeutic hypothermia for stroke: Unique challenges at the bedside

Therapeutic hypothermia has shown promise as a means to improving neurological outcomes at several neurological conditions. At the clinical level, it has been shown to improve outcomes in comatose survivors of cardiac arrest and in neonatal hypoxic ischemic encephalopathy, but has yet to be convincingly demonstrated in stroke. While numerous preclinical studies have shown benefit in stroke models, translating this to the clinical level has proven challenging. Major obstacles include cooling patients with typical stroke who are awake and breathing spontaneously but often have significant comorbidities. Solutions around these problems include selective brain cooling and cooling to lesser depths or avoiding hyperthermia. This review will cover the mechanisms of protection by therapeutic hypothermia, as well as recent progress made in selective brain cooling and the neuroprotective effects of only slightly lowering brain temperature. Therapeutic hypothermia for stroke has been shown to be feasible, but has yet to be definitively proven effective. There is clearly much work to be undertaken in this area.

Through the Looking Glass: The Paradoxical Evolution of Targeted Temperature Management for Comatose Survivors of Cardiac Arrest

For the past two decades, targeted temperature management (TTM) has been a staple in the care of comatose survivors following cardiac arrest. However, recent clinical trials have failed to replicate the benefit seen in earlier studies, bringing into question the very existence of such clinical practice. In this review, we explore clinical scenarios within critical care that appeared to share a similar fate, but in actuality changed the landscape of practice in a modern world. Accordingly, clinicians may apply these lessons to the utilization of TTM among comatose survivors following cardiac arrest, potentially paving way for a re-framing of clinical care amidst an environment where current data appears upside down in comparison to past successes.

Targeted Temperature Management After In-Hospital Cardiac Arrest: An Ancillary Analysis of Targeted Temperature Management for Cardiac Arrest With Nonshockable Rhythm Trial Data

BACKGROUND

Targeted temperature management (TTM) currently is the only treatment with demonstrated efficacy in attenuating the harmful effects on the brain of ischemia-reperfusion injury after cardiac arrest. However, whether TTM is beneficial in the subset of patients with in-hospital cardiac arrest (IHCA) remains unclear.

RESEARCH QUESTION

Is TTM at 33 °C associated with better neurological outcomes after IHCA in a nonshockable rhythm compared with targeted normothermia (TN; 37 °C)?

STUDY DESIGN AND METHODS

We performed a post hoc analysis of data from the published Targeted Temperature Management for Cardiac Arrest with Nonshockable Rhythm randomized controlled trial in 584 patients. We included the 159 patients with IHCA; 73 were randomized to 33 °C treatment and 86 were randomized to 37 °C treatment. The primary outcome was survival with a good neurologic outcome (cerebral performance category [CPC] score of 1 or 2) on day 90. Mixed multivariate adjusted logistic regression analysis was performed to determine whether survival with CPC score of 1 or 2 on day 90 was associated with type of temperature management after adjustment on baseline characteristics not balanced by randomization.

RESULTS

Compared with TN for 48 h, hypothermia at 33 °C for 24 h was associated with a higher percentage of patients who were alive with good neurologic outcomes on day 90 (16.4% vs 5.8%; P = .03). Day 90 mortality was not significantly different between the two groups (68.5% vs 76.7%; P = .24). By mixed multivariate analysis adjusted by Cardiac Arrest Hospital Prognosis score and circulatory shock status, hypothermia was associated significantly with good day 90 neurologic outcomes (OR, 2.40 [95% CI, 1.17-13.03]; P = .03).

INTERPRETATION

Hypothermia at 33 °C was associated with better day 90 neurologic outcomes after IHCA in a nonshockable rhythm compared with TN. However, the limited sample size resulted in wide CIs. Further studies of patients after cardiac arrest resulting from any cause, including IHCA, are needed.

Impact of rewarming rate on interleukin-6 levels in patients with shockable cardiac arrest receiving targeted temperature management at 33 °C: the ISOCRATE pilot randomized controlled trial

Purpose

While targeted temperature management (TTM) has been recommended in patients with shockable cardiac arrest (CA) and suggested in patients with non-shockable rhythms, few data exist regarding the impact of the rewarming rate on systemic inflammation. We compared serum levels of the proinflammatory cytokine interleukin-6 (IL6) measured with two rewarming rates after TTM at 33 °C in patients with shockable out-of-hospital cardiac arrest (OHCA).

Methods

ISOCRATE was a single-center randomized controlled trial comparing rewarming at 0.50 °C/h versus 0.25 °C/h in patients coma after shockable OHCA in 2016–2020. The primary outcome was serum IL6 level 24–48 h after reaching 33 °C. Secondary outcomes included the day-90 Cerebral Performance Category (CPC) and the 48-h serum neurofilament light-chain (NF-L) level.

Results

We randomized 50 patients. The median IL6 area-under-the-curve was similar between the two groups (12,389 [7256–37,200] vs. 8859 [6825–18,088] pg/mL h; P = 0.55). No significant difference was noted in proportions of patients with favorable day-90 CPC scores (13/25 patients at 0.25 °C/h (52.0%; 95% CI 31.3–72.2%) and 13/25 patients at 0.50 °C/h (52.0%; 95% CI 31.3–72.2%; P = 0.99)). Median NF-L levels were not significantly different between the 0.25 °C/h and 0.50 °C/h groups (76.0 pg mL, [25.5–3074.0] vs. 192 pg mL, [33.6–4199.0]; P = 0.43; respectively).

Conclusion

In our RCT, rewarming from 33 °C at 0.25 °C/h, compared to 0.50 °C/h, did not decrease the serum IL6 level after shockable CA. Further RCTs are needed to better define the optimal TTM strategy for patients with CA.

Trial registration ClinicalTrials.gov, NCT02555254. Registered September 14, 2015.

Take-Home Message: Rewarming at a rate of 0.25 °C/h, compared to 0.50 °C, did not result in lower serum IL6 levels after achievement of hypothermia at 33 °C in patients who remained comatose after shockable cardiac arrest. No associations were found between the slower rewarming rate and day-90 functional outcomes or mortality.

140-character Tweet: Rewarming at 0.25 °C versus 0.50 °C did not decrease serum IL6 levels after hypothermia at 33 °C in patients comatose after shockable cardiac arrest.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03842-9.

Predictors of poor outcome after extra-corporeal membrane oxygenation for refractory cardiac arrest (ECPR): A post hoc analysis of a multicenter database

BACKGROUND

The objective was to assess predictors for unfavorable neurological outcome (UO) in out-of-hospital (OHCA) and in-hospital (IHCA) cardiac arrest patients treated with Extracorporeal cardiopulmonary resuscitation (ECPR).

METHODS

A post hoc analysis of retrospective data from five European ECPR centers (January 2012-December 2016) was performed. The primary composite endpoint was 3-month UO defined as survival with a cerebral performance category (CPC) of 3-4 or death (CPC 5).

RESULTS

A total of 413 patients treated with ECPR were included (median age was 57 [48-65] years, male gender 78%): 61% of patients (n = 250) suffered OHCA. The median time from collapse to ECMO placement was 63 [45-82] minutes. Overall, 81% patients (n = 333) showed unfavorable UO, which was higher in OHCA patients (90% vs 66%), as compared to IHCA. In OHCA, prolonged time from collapse to ECMO initiation (OR 1.02, p < 0.01) and higher ECMO blood flow (OR 1.99, p = 0.01) were associated with UO while initial shockable rhythm (OR 0.04, p < 0.01), previous heart disease (OR 0.20, p < 0.01) and pre-hospital hypothermia (OR 0.08, p < 0.01) had a protective role. In IHCA, prolonged time from arrest to ECMO implantation (OR 1.02, p = 0.03), high lactate level on admission (OR 1.15, p < 0.01) and higher body weight (OR 1.03, p < 0.01) were independently associated with UO.

CONCLUSIONS

IHCA and OHCA patients receiving ECPR have different predictors of UO at presentation, suggesting that selection criteria for ECPR should be decided according to the location of CA. After ECMO initiation, ECMO blood flow management and mean arterial pressure targets might also impact neurological recovery.

Targeted Temperature Management after Cardiac Arrest: A Systematic Review and Meta-Analysis with Trial Sequential Analysis

Target temperature management (TTM) in cardiac arrest (CA) survivors is recommended after hospital admission for its possible beneficial effects on survival and neurological outcome. Whether a lower target temperature (i.e., 32–34 °C) improves outcomes is unclear. We conducted a systematic review and meta-analysis on Pubmed and EMBASE to evaluate the effects on mortality and neurologic outcome of TTM at 32–34 °C as compared to controls (patients cared with “actively controlled” or “uncontrolled” normothermia). Results were analyzed via risk ratios (RR) and 95% confidence intervals (CI). Eight randomized controlled trials (RCTs) were included. TTM at 32–34 °C was compared to “actively controlled” normothermia in three RCTs and to “uncontrolled” normothermia in five RCTs. TTM at 32–34 °C does not improve survival as compared to normothermia (RR:1.06 (95%CI 0.94, 1.20), p = 0.36; I² = 39%). In the subgroup analyses, TTM at 32–34 °C is associated with better survival when compared to “uncontrolled” normothermia (RR: 1.31 (95%CI 1.07, 1.59), p = 0.008) but shows no beneficial effects when compared to “actively controlled” normothermia (RR: 0.97 (95%CI 0.90, 1.04), p = 0.41). TTM at 32–34 °C does not improve neurological outcome as compared to normothermia (RR: 1.17 (95%CI 0.97, 1.41), p = 0.10; I² = 60%). TTM at 32–34 °C increases the risk of arrhythmias (RR: 1.35 (95%CI 1.16, 1.57), p = 0.0001, I² = 0%). TTM at 32–34 °C does not improve survival nor neurological outcome after CA and increases the risk of arrhythmias.