No benefit to prehospital initiation of therapeutic hypothermia in out-of-hospital cardiac arrest: a systematic review and meta-analysis

Therapeutic Hypothermia Combined with Hydrogen Sulfide Treatment Attenuated Early Blood-Brain Barrier Disruption and Brain Edema Induced by Cardiac Arrest and Resuscitation in Rat Model

Brain injury remains a major problem in patients suffering cardiac arrest (CA). Disruption of the blood-brain barrier (BBB) is an important factor leading to brain injury. Therapeutic hypothermia is widely accepted to limit neurological impairment. However, the efficacy is incomplete. Hydrogen sulfide (H2S), a signaling gas molecule, has protective effects after cerebral ischemia reperfusion injury. This study showed that combination of hypothermia and H2S after resuscitation was more beneficial for attenuated BBB disruption and brain edema than that of hypothermia or H2S treatment alone. CA was induced by ventricular fibrillation for 4 min. Hypothermia was performed by applying alcohol and ice bags to the body surface under anesthesia. We used sodium hydrosulphide (NaHS) as the H2S donor. We found that global brain ischemia induced by CA and cardiopulmonary resuscitation (CPR) resulted in brain edema and BBB disruption; Hypothermia or H2S treatment diminished brain edema, decreased the permeability and preserved the structure of BBB during the early period of CA and resuscitation, and more importantly, improved the neurologic function, increased the 7-day survival rate after resuscitation; the combination of hypothermia and H2S treatment was more beneficial than that of hypothermia or H2S treatment alone. The beneficial effects were associated with the inhibition of matrix metalloproteinase-9 expression, attenuated the degradation of the tight junction protein occludin, and subsequently protected the structure of BBB. These findings suggest that combined use of therapeutic hypothermia and hydrogen sulfide treatment during resuscitation of CA patients could be a potential strategy to improve clinical outcomes and survival rate.

Impact of therapeutic hypothermia during cardiopulmonary resuscitation on neurologic outcome: A systematic review and meta-analysis

BACKGROUND

Therapeutic cooling initiated during cardiopulmonary resuscitation (intra arrest therapeutic hypothermia, IATH) provided diverging effect on neurological outcome of out-of-hospital cardiac arrest (OHCA) patients depending on the initial cardiac rhythm and the cooling methods used.

METHODS

We performed a systematic search of PubMed, EMBASE and the CENTRAL databases using established Medical Subject Headings (MeSH) terms for IATH and OHCA. Only studies comparing IATH to standard in-hospital targeted temperature management (TTM) were selected. We used the revised Cochrane RoB-2 and the Newcastle-Ottawa scale tool to assess risk of bias of each study. Primary outcome was favorable neurological outcome (FO); secondary outcomes included return of spontaneous circulation (ROSC) rate and survival to hospital discharge.

RESULTS

Out of 20,950 studies, 8 studies (n = 3493 patients, including 4 randomized trials, RCTs) were included in the final analysis. Compared to controls, the use of IATH was not associated with improved FO (OR 0.96 [95% CIs 0.68-1.37]; p = 0.84), increased ROSC rate (OR 1.11 [95% CIs 0.83-1.49]; p = 0.46) or survival (OR 0.91 [95% CIs 0.73-1.14]; p = 0.43). Significant heterogeneity among studies was observed for the analysis of ROSC rate (I² = 69%). Trans-nasal evaporative cooling and cold fluids were explored in two RCTs each and no differences were observed on FO, event when only patients with an initial shockable rhythm were analyzed (OR 1.62 [95% CI 1.00-2.64]; p = 0.05].

CONCLUSIONS

In this meta-analysis, IATH was not associated with improved neurological outcome when compared to standard in-hospital TTM, based on very low certainty of evidence.

CLINICAL TRIAL REGISTRATION

PROSPERO (CRD42019130322).

Targeted Temperature Management After Cardiac Arrest: Systematic Review and Meta-analyses

BACKGROUND

Targeted temperature management (TTM) with therapeutic hypothermia is an integral component of postarrest care for survivors. However, recent randomized controlled trials (RCTs) have failed to demonstrate the benefit of TTM on clinical outcomes. We sought to determine if the pooled data from available RCTs support the use of prehospital and/or in-hospital TTM after cardiac arrest.

METHODS

A comprehensive search of SCOPUS, Elsevier's abstract and citation database of peer-reviewed literature, from 1966 to November 2016 was performed using predefined criteria. Therapeutic hypothermia was defined as any strategy that aimed to cool post-cardiac arrest survivors to a temperature ≤34°C. Normothermia was temperature of ≥36°C. We compared mortality and neurologic outcomes in patients by categorizing the studies into 2 groups: (1) hypothermia versus normothermia and (2) prehospital hypothermia versus in-hospital hypothermia using standard meta-analytic methods. A random effects modeling was utilized to estimate comparative risk ratios (RR) and 95% confidence intervals (CIs).

RESULTS

The hypothermia and normothermia strategies were compared in 5 RCTs with 1389 patients, whereas prehospital hypothermia and in-hospital hypothermia were compared in 6 RCTs with 3393 patients. We observed no difference in mortality (RR, 0.88; 95% CI, 0.73-1.05) or neurologic outcomes (RR, 1.26; 95% CI, 0.92-1.72) between the hypothermia and normothermia strategies. Similarly, no difference was observed in mortality (RR, 1.00; 95% CI, 0.97-1.03) or neurologic outcome (RR, 0.96; 95% CI, 0.85-1.08) between the prehospital hypothermia versus in-hospital hypothermia strategies.

CONCLUSIONS

Our results suggest that TTM with therapeutic hypothermia may not improve mortality or neurologic outcomes in postarrest survivors. Using therapeutic hypothermia as a standard of care strategy of postarrest care in survivors may need to be reevaluated.

The efficacy and safety of pre-hospital cooling after out-of-hospital cardiac arrest: a systematic review and meta-analysis

Background

Mild therapeutic hypothermia (TH), or targeted temperature management, improves survival and neurological outcomes in patients after out-of-hospital cardiac arrest (OHCA). International guidelines strongly support initiating TH for all eligible individuals presenting with OHCA; however, the timing of cooling initiation remains uncertain. This systematic review and meta-analysis was conducted with all available randomised controlled trials (RCTs) included to explore the efficacy and safety of initiating pre-hospital TH in patients with OHCA.

Methods

The MEDLINE and Cochrane databases were searched from inception to October 2017. Inclusion criteria for full-text review included RCTs comparing pre-hospital TH with no pre-hospital TH after cardiac arrest, patients > 14 years of age with documented cardiac arrest from any rhythm, and outcome data that included survival to hospital discharge and temperature at hospital arrival. Results of retrieved studies were compared through meta-analysis using random effects modelling.

Results

A total of 10 trials comprising 4220 patients were included. There were no significant differences between the two arms for the primary outcome of neurological recovery (risk ratio [RR] 1.04, 95% CI 0.93–1.15) or the secondary outcome of survival to hospital discharge (RR 1.01, 95% CI 0.92–1.11). However, there was a significantly lower temperature at hospital arrival in patients receiving pre-hospital TH (mean difference − 0.83, 95% CI − 1.03 to − 0.63). Pre-hospital TH significantly increased the risk of re-arrest (RR 1.19, 95% CI 1.00 to 1.41). No survival differences were observed among subgroups of patients who received intra-arrest TH vs post-arrest TH or who had shockable vs non-shockable rhythms.

Conclusions

Pre-hospital TH after OHCA effectively decreases body temperature at the time of hospital arrival. However, it does not improve rates of survival with good neurological outcome or overall survival and is associated with increased rates of re-arrest.

Electronic supplementary material

The online version of this article (10.1186/s13054-018-1984-2) contains supplementary material, which is available to authorized users.

Evaluation of Evidence of Statistical Support and Corroboration of Subgroup Claims in Randomized Clinical Trials

Importance

Many published randomized clinical trials (RCTs) make claims for subgroup differences.

Objective

To evaluate how often subgroup claims reported in the abstracts of RCTs are actually supported by statistical evidence (P < .05 from an interaction test) and corroborated by subsequent RCTs and meta-analyses.

Data Sources

This meta-epidemiological survey examines data sets of trials with at least 1 subgroup claim, including Subgroup Analysis of Trials Is Rarely Easy (SATIRE) articles and Discontinuation of Randomized Trials (DISCO) articles. We used Scopus (updated July 2016) to search for English-language articles citing each of the eligible index articles with at least 1 subgroup finding in the abstract.

Study Selection

Articles with a subgroup claim in the abstract with or without evidence of statistical heterogeneity (P < .05 from an interaction test) in the text and articles attempting to corroborate the subgroup findings.

Data Extraction and Synthesis

Study characteristics of trials with at least 1 subgroup claim in the abstract were recorded. Two reviewers extracted the data necessary to calculate subgroup-level effect sizes, standard errors, and the P values for interaction. For individual RCTs and meta-analyses that attempted to corroborate the subgroup findings from the index articles, trial characteristics were extracted. Cochran Q test was used to reevaluate heterogeneity with the data from all available trials.

Main Outcomes and Measures

The number of subgroup claims in the abstracts of RCTs, the number of subgroup claims in the abstracts of RCTs with statistical support (subgroup findings), and the number of subgroup findings corroborated by subsequent RCTs and meta-analyses.

Results

Sixty-four eligible RCTs made a total of 117 subgroup claims in their abstracts. Of these 117 claims, only 46 (39.3%) in 33 articles had evidence of statistically significant heterogeneity from a test for interaction. In addition, out of these 46 subgroup findings, only 16 (34.8%) ensured balance between randomization groups within the subgroups (eg, through stratified randomization), 13 (28.3%) entailed a prespecified subgroup analysis, and 1 (2.2%) was adjusted for multiple testing. Only 5 (10.9%) of the 46 subgroup findings had at least 1 subsequent pure corroboration attempt by a meta-analysis or an RCT. In all 5 cases, the corroboration attempts found no evidence of a statistically significant subgroup effect. In addition, all effect sizes from meta-analyses were attenuated toward the null.

Conclusions and Relevance

A minority of subgroup claims made in the abstracts of RCTs are supported by their own data (ie, a significant interaction effect). For those that have statistical support (P < .05 from an interaction test), most fail to meet other best practices for subgroup tests, including prespecification, stratified randomization, and adjustment for multiple testing. Attempts to corroborate statistically significant subgroup differences are rare; when done, the initially observed subgroup differences are not reproduced.

Mild therapeutic hypothermia in patients resuscitated from out-of-hospital cardiac arrest: A meta-analysis of randomized controlled trials

AIMS

Guidelines recommend mild therapeutic hypothermia (MTH) for survivors of out-of-hospital cardiac arrest (OHCA). However, there is little literature demonstrating a survival benefit. We performed a meta-analysis of randomized controlled trials (RCTs) assessing the efficacy of MTH in patients successfully resuscitated from OHCA.

MATERIALS AND METHODS

Electronic databases were searched for RCT involving MTH in survivors of OHCA, and the results were put through a meta-analysis. The primary endpoint was all-cause mortality, and the secondary endpoint was favorable neurological function. Odds ratios (ORs) and 95% confidence intervals (CIs) were computed using the Mantel-Haenszel method. A fixed-effect model was used and, if heterogeneity (I2 ) was >40, effects were analyzed using a random model.

RESULTS

Six RCT (n = 1400 patients) were included. Overall survival was 50.7%, and favorable neurological recovery was 45.5%. Pooled data demonstrated no significant all-cause mortality (OR, 0.81; 95% CI 0.55-1.21) or neurological recovery (OR, 0.77; 95% CI 0.47-1.24). No evidence of publication bias was observed.

CONCLUSION

This meta-analysis demonstrated that MTH did not confer benefit on overall survival rate and neurological recovery in patients resuscitated from OHCA.

Receiving Hospital Characteristics Associated With Survival in Patients Transported by Emergency Medical Services After Out-of-hospital Cardiac Arrest

OBJECTIVE

To test whether primary emergency medical services (EMS) transport to hospitals with certain characteristics (24/7 percutaneous coronary intervention [PCI] availability, trauma center status, large [>24 bed] intensive care unit [ICU]) versus hospitals without those characteristics is associated with improved hospital survival after out-of-hospital cardiac arrest (OHCA).

METHODS

This is an analysis of a prospectively collected EMS database, which archives patients with OHCA treated by a single large metropolitan EMS system. The database contains Utstein data, EMS transport data, and survival to hospital discharge. EMS providers uniformly apply advanced cardiac life support protocols to OHCA patients in the field. Patients with return of spontaneous circulation (ROSC) are transported to one of 10 hospitals in the area. If ROSC is not achieved within 30 minutes, efforts are terminated and the patient is not transported. We used multivariate logistic regression to test if receiving hospital characteristics were independently associated with survival among those transported after ROSC. We excluded patients not transported to a hospital and patients with incomplete outcome data.

RESULTS

Between January 2011 and December 2014, a total of 1,188 OHCA patients were resuscitated in the field and transported to an area hospital. After patients with missing data were excluded, 1,024 patients were included in the analysis. The mean (±SD) age was 61.1 (±17.0) years, and 57.7% were male. Of transported patients, 76% were taken to 24/7 PCI centers, 46% were taken to trauma centers, and 37% were taken to hospitals with large ICUs. There was considerable overlap in these hospital characteristics. A multivariate logistic regression model including age, sex, shockable rhythm, EMS time to scene, and dispatch complaint of cardiac arrest found that none of the hospital characteristics were independently associated with increased survival to discharge. The odds ratios (95% confidence intervals) for survival were as follows: PCI center, 1.28 (0.80 to 2.04); trauma center, 1.44 (0.73 to 2.85); and large ICU, 1.39 (0.69 to 2.80).

CONCLUSIONS

After adjusting for patient demographic data, we found no significant independent association between receiving hospital characteristics and survival to discharge among OHCA patients transported after ROSC by a single EMS agency.

Targeted temperature management for adult out-of-hospital cardiac arrest: current concepts and clinical applications

Targeted temperature management (TTM) (primarily therapeutic hypothermia (TH)) after out-of-hospital cardiac arrest (OHCA) has been considered effective, especially for adult-witnessed OHCA with a shockable initial rhythm, based on pathophysiology and on several clinical studies (especially two randomized controlled trials (RCTs) published in 2002). However, a recently published large RCT comparing TTM at 33 °C (TH) and TTM at 36 °C (normothermia) showed no advantage of 33 °C over 36 °C. Thus, this RCT has complicated the decision to perform TH after cardiac arrest. The results of this RCT are sometimes interpreted fever control alone is sufficient to improve outcomes after cardiac arrest because fever control was not strictly performed in the control groups of the previous two RCTs that showed an advantage for TH. Although this may be possible, another interpretation that the optimal target temperature for TH is much lower than 33 °C may be also possible. Additionally, there are many points other than target temperature that are unknown, such as the optimal timing to initiate TTM, the period between OHCA and initiating TTM, the period between OHCA and achieving the target temperature, the duration of maintaining the target temperature, the TTM technique, the rewarming method, and the management protocol after rewarming. RCTs are currently underway to shed light on several of these underexplored issues. In the present review, we examine how best to perform TTM after cardiac arrest based on the available evidence.

Targeted temperature management in emergency medicine: current perspectives

Landmark trials in 2002 showed that therapeutic hypothermia (TH) after out-of-hospital cardiac arrest due to ventricular tachycardia or ventricular fibrillation resulted in improved likelihood of good neurologic recovery compared to standard care without TH. Since that time, TH has been frequently instituted in a wide range of cardiac arrest patients regardless of initial heart rhythm. Recent evidence has evaluated how, when, and to what degree TH should be instituted in cardiac arrest victims. We outline early evidence, as well as recent trials, regarding the use of TH or targeted temperature management in these patients. We also provide evidence-based suggestions for the institution of targeted temperature management/TH in a variety of emergency medicine settings.

The efficacy and safety of prehospital therapeutic hypothermia in patients with out-of-hospital cardiac arrest: A systematic review and meta-analysis

BACKGROUND

The benefit of therapeutic hypothermia (TH) to patients suffering out-of-hospital cardiac arrest (OHCA) has been well established. However, the effect of prehospital cooling remains unclear. We aimed to investigate the efficacy and safety of prehospital TH for OHCA patients by conducting a systematic review of randomised controlled trials (RCTs).

METHODS

The MEDLINE, EMbase and CENTRAL databases were searched for publications from inception to April 2015. RCTs that compared cooling with no cooling in a prehospital setting among adults with OHCA were eligible for inclusion. Random- and fixed-effect models were used depending on inter-study heterogeneity.

RESULTS

Eight trials that recruited 2379 participants met the inclusion criteria. Prehospital TH was significantly associated with a lower temperature at admission (mean difference (MD) -0.94; 95% confidence interval (CI) -1.06 to -0.82). However, survival upon admission (Risk ratio (RR) 1.01, 95%CI 0.98-1.04), survival at discharge (RR 1.02, 95%CI 0.91-1.14), in-hospital survival (RR 1.05, 95%CI 0.92-1.19) and good neurological function recovery (RR 1.06, 95% CI 0.91-1.23) did not differ between the TH-treated and non-treated groups. Prehospital cooling increased the incidence of recurrent arrest (RR 1.23, 95%CI 1.02-1.48) and decreased the PH at admission (MD -0.04, 95%CI -0.07 to -0.02). Pulmonary oedema did not differ between the arms (RR 1.02, 95%CI 0.67-1.57). None of the potentially controversial issues (cooling methods, time of inducing TH, the proportion of continuing cooling in hospital, actual prehospital infusion volume and primary cardiac rhythms) affected the efficacy.

CONCLUSION

Evidence does not support the administration of prehospital TH to patients with OHCA.