Mild hypothermia induced by a helmet device: a clinical feasibility study

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.

Recovery and Survival of Patients After Out-of-Hospital Cardiac Arrest: A Literature Review Showcasing the Big Picture of Intensive Care Unit-Related Factors

As an important public health issue, out-of-hospital cardiac arrest (OHCA) requires several stages of high quality medical care, both on-field and after hospital admission. Post-cardiac arrest shock can lead to severe neurological injury, resulting in poor recovery outcome and increased risk of death. These characteristics make this condition one of the most important issues to deal with in post-OHCA patients hospitalized in intensive care units (ICUs). Also, the majority of initial post-resuscitation survivors have underlying coronary diseases making revascularization procedure another crucial step in early management of these patients. Besides keeping myocardial blood flow at a satisfactory level, other tissues must not be neglected as well, and maintaining mean arterial pressure within optimal range is also preferable. All these procedures can be simplified to a certain level along with using targeted temperature management methods in order to decrease metabolic demands in ICU-hospitalized post-OHCA patients. Additionally, withdrawal of life-sustaining therapy as a controversial ethical topic is under constant re-evaluation due to its possible influence on overall mortality rates in patients initially surviving OHCA. Focusing on all of these important points in process of managing ICU patients is an imperative towards better survival and complete recovery rates.

Temperature control after adult cardiac arrest: An updated systematic review and meta-analysis

AIM

To perform an updated systematic review and meta-analysis on temperature control in adult patients with cardiac arrest.

METHODS

The review is an update of a previous systematic review published in 2021. An updated search including PubMed, Embase, and the Cochrane Central Register of Controlled Trials was performed on May 31, 2023. Controlled trials in humans were included. The population included adult patients with cardiac arrest. The review included all aspects of temperature control including timing, temperature, duration, method of induction and maintenance, and rewarming. Two investigators reviewed trials for relevance, extracted data, and assessed risk of bias. Data were pooled using random-effects models. Certainty of evidence was evaluated using GRADE.

RESULTS

The updated systematic search identified six new trials. Risk of bias in the trials was assessed as intermediate for most of the outcomes. For temperature control with a target of 32-34 °C vs. normothermia or 36 °C, two new trials were identified, with seven trials included in an updated meta-analysis. Temperature control with a target of 32-34 °C did not result in an improvement in survival (risk ratio: 1.06 [95%CI: 0.91, 1.23]) or favorable neurological outcome (risk ratio: 1.27 [95%CI: 0.89, 1.81]) at 90-180 days after the cardiac arrest (low certainty evidence). Subgroup analysis according to location of cardiac arrest (in-hospital vs. out-of-hospital) found similar results. A sensitivity analysis of nine trials comparing temperature control at 32-34 °C to normothermia or 36 °C for favorable neurological outcome at any time point also did not show an improvement in outcomes (risk ratio: 1.14 [95%CI 0.98, 1.34]). New individual trials comparing a target of 31-34 °C, temperature control for 12-24 hours to 36 hours, a rewarming rate of 0.25-0.5 °C/hour, and the effect of temperature control with fever prevention found no differences in outcomes.

CONCLUSIONS

This updated systematic review showed no benefit of temperature control at 32-34 °C compared to normothermia or 36 °C, although the 95% confidence intervals cannot rule out a potential beneficial effect. Important knowledge gaps exist for topics such as hypothermic temperature targets, rewarming rate, and fever control.

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.

Targeted Temperature Management After Cardiac Arrest in COVID-19 Patients

There is a paucity of evidence regarding the utility of targeted temperature management (TTM) in COVID-19 patients who suffer cardiac arrest. This systematic review and meta-analysis aimed to use the available data of how temperature predicts outcomes in COVID-19 patients and the association between active cooling and outcomes in non-COVID-19 cardiac arrest patients to give recommendations for the utility of TTM in COVID-19 survivors of cardiac arrest. The PubMed, Embase, and Web of Science databases were queried in August 2022 for two separate searches: (1) temperature as a predictor of clinical outcomes in COVID-19 and (2) active cooling after return of spontaneous circulation (ROSC) in non-COVID-19. Forest plots were generated to summarize the results. Of the 4209 abstracts screened, none assessed the target population of TTM in COVID-19 victims of cardiac arrest. One retrospective cohort study evaluated hyperthermia in critically ill COVID-19 patients, two retrospective cohort studies evaluated hypothermia in septic COVID-19 patients, and 20 randomized controlled trials evaluated active cooling in non-COVID-19 patients after ROSC. Risk of death was higher in COVID-19 patients who presented with hyperthermia (risk ratio [RR] = 1.87) or hypothermia (RR = 1.77; p < 0.001). In non-COVID-19 victims of cardiac arrest, there was no significant difference in mortality (RR = 0.94; p = 0.098) or favorable neurological outcome (RR = 1.05; p = 0.41) with active cooling after ROSC. Further studies are needed to evaluate TTM in COVID-19 victims of cardiac arrest. However, given the available evidence that hyperthermia or hypothermia in COVID-19 patients is associated with increased mortality as well as our findings suggesting limited utility for active cooling in non-COVID-19 cardiac arrest patients, we posit that TTM to normothermia (core body temperature ∼37°C) would most likely be optimal for the best outcomes in COVID-19 survivors of cardiac arrest.

Therapeutic hypothermia in patients after cardiac arrest: A systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

Targeted temperature management (TTM) with therapeutic hypothermia (TH) has been used to improve neurological outcomes in patients after cardiac arrest; however, several trials have reported conflicting results regarding its effectiveness. This systematic review and meta-analysis assessed whether TH was associated with better survival and neurological outcomes after cardiac arrest.

METHOD

We searched online databases for relevant studies published before May 2023. Randomized controlled trials (RCTs) comparing TH and normothermia in post-cardiac-arrest patients were selected. Neurological outcomes and all-cause mortality were assessed as the primary and secondary outcomes, respectively. A subgroup analysis according to initial electrocardiography (ECG) rhythm was performed.

RESULT

Nine RCTs (4058 patients) were included. The neurological prognosis was significantly better in patients with an initial shockable rhythm after cardiac arrest (RR = 0.87, 95% confidence interval [CI] = 0.76-0.99, P = 0.04), especially in those with earlier TH initiation (<120 min) and prolonged TH duration (≥24 h). However, the mortality rate after TH was not lower than that after normothermia (RR = 0.91, 95% CI = 0.79-1.05). In patients with an initial nonshockable rhythm, TH did not provide significantly more neurological or survival benefits (RR = 0.98, 95% CI = 0.93-1.03 and RR = 1.00, 95% CI = 0.95-1.05, respectively).

CONCLUSION

Current evidence with a moderate level of certainty suggests that TH has potential neurological benefits for patients with an initial shockable rhythm after cardiac arrest, especially in those with faster TH initiation and longer TH maintenance.

Meta-Analysis Comparing Hypothermia Versus Normothermia in Patients After a Cardiac Arrest

The current American Heart Association 2022 guidelines recommend actively preventing fever by targeting a temperature ≤37.5°C for comatose patients after cardiac arrest. Contemporary randomized controlled trials (RCTs) show conflicting results regarding the benefit of targeted hypothermia (TH). We performed this updated meta-analysis of RCTs to evaluate the role of hypothermia in patients after a cardiac arrest. We searched Cochrane, MEDLINE, and EMBASE from inception to December 2022. Trials with patients randomly allocated for targeted temperature monitoring and reported neurologic and mortality outcomes were included. Statistical analysis was performed using Cochrane Review Manager using the random-effects model and calculated the pooled risk ratios of outcomes using the Mantel-Haenszel method. A total of 12 RCTs and 4,262 patients were included in the review. Compared with normothermia, the TH group had significantly improved neurologic outcomes (risk ratio 0.90, 95% confidence interval 0.83 to 0.98). However, no significant difference in mortality was observed (risk ratio 0.97, 95% confidence interval 0.90 to 1.06) between the groups. This meta-analysis supports the role of TH in patients after a cardiac arrest, especially secondary to improvement in neurologic outcomes.

Hypothermia for neuroprotection in adults after cardiac arrest

BACKGROUND

Good neurological outcome after cardiac arrest is difficult to achieve. Interventions during the resuscitation phase and treatment within the first hours after the event are critical for a favourable prognosis. Experimental evidence suggests that therapeutic hypothermia is beneficial, and several clinical studies on this topic have been published. This review was originally published in 2009; updated versions were published in 2012 and 2016.

OBJECTIVES

To evaluate the benefits and harms of therapeutic hypothermia after cardiac arrest in adults compared to standard treatment.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date was 30 September 2022.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs in adults comparing therapeutic hypothermia after cardiac arrest with standard treatment (control). We included studies with adults cooled by any method, applied within six hours of cardiac arrest, to target body temperatures of 32 °C to 34 °C. Good neurological outcome was defined as no or only minor brain damage allowing people to live an independent life.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcome was 1. neurological recovery. Our secondary outcomes were 2. survival to hospital discharge, 3. quality of life, 4. cost-effectiveness and 5.

ADVERSE EVENTS

We used GRADE to assess certainty.

MAIN RESULTS

We found 12 studies with 3956 participants reporting the effects of therapeutic hypothermia on neurological outcome or survival. There were some concerns about the quality of all the studies, and two studies had high risk of bias overall. When we compared conventional cooling methods versus any type of standard treatment (including a body temperature of 36 °C), we found that participants in the therapeutic hypothermia group were more likely to reach a favourable neurological outcome (risk ratio (RR) 1.41, 95% confidence interval (CI) 1.12 to 1.76; 11 studies, 3914 participants). The certainty of the evidence was low. When we compared therapeutic hypothermia with fever prevention or no cooling, we found that participants in the therapeutic hypothermia group were more likely to reach a favourable neurological outcome (RR 1.60, 95% CI 1.15 to 2.23; 8 studies, 2870 participants). The certainty of the evidence was low. When we compared therapeutic hypothermia methods with temperature management at 36 °C, there was no evidence of a difference between groups (RR 1.78, 95% CI 0.70 to 4.53; 3 studies; 1044 participants). The certainty of the evidence was low. Across all studies, the incidence of pneumonia, hypokalaemia and severe arrhythmia was increased amongst participants receiving therapeutic hypothermia (pneumonia: RR 1.09, 95% CI 1.00 to 1.18; 4 trials, 3634 participants; hypokalaemia: RR 1.38, 95% CI 1.03 to 1.84; 2 trials, 975 participants; severe arrhythmia: RR 1.40, 95% CI 1.19 to 1.64; 3 trials, 2163 participants). The certainty of the evidence was low (pneumonia, severe arrhythmia) to very low (hypokalaemia). There were no differences in other reported adverse events between groups.

AUTHORS' CONCLUSIONS

Current evidence suggests that conventional cooling methods to induce therapeutic hypothermia may improve neurological outcomes after cardiac arrest. We obtained available evidence from studies in which the target temperature was 32 °C to 34 °C.

Therapeutic Hypothermia Following Cardiopulmonary Arrest: A Systematic Review and Meta-Analysis with Trial Sequential Analysis

Introduction

The risk-benefit profile of therapeutic hypothermia is controversial with several randomized controlled trials providing conflicting results.

Aim of Study

The purpose of this systematic review and meta-analysis was to determine if therapeutic hypothermia provides beneficial neurologic outcomes relative to adverse effects.

Material and Methods

MEDLINE and EMBASE databases were searched for randomized controlled trials of post-cardiac arrest patients comparing therapeutic hypothermia (~33 degrees Celsius) to normothermia or the standard of care (36 - 38 degrees Celsius). Data were collected using the Covidence systematic review software. Statistical analysis was performed by Review Manager software. Risk of bias, sensitivity, and heterogeneity were analyzed using the Cochran's Collaboration tool, trial sequential analysis (TSA) software, and I2 statistic respectively.

Results

A total of 1825 studies were screened and 5 studies (n=3614) were included. No significant differences existed between the hypothermia group and normothermia for favorable neurologic outcome (risk ratio [RR] 1.17, 95% confidence interval [CI] 0.97 to 1.41) or all-cause mortality (RR 0.97, 95% CI 0.89 to 1.05). When compared to normothermia, the hypothermia group had greater risk of adverse effects (RR 1.16, 95% CI 1.04 to 1.28), which was driven by the onset of arrhythmias. Subgroup analyses revealed that therapeutic hypothermia provided greater neurologic benefit in trials with a higher percentage of subjects with shockable rhythms (RR 0.73, 95% CI 0.6 to 0.88). Trial sequential analysis revealed statistical futility for therapeutic hypothermia and favorable neurologic outcome, mortality, and adverse effects.

Conclusions

Therapeutic hypothermia does not provide consistent benefit in neurologic outcome or mortality in the general cardiac arrest population. Patients with shockable rhythms may show favorable neurologic outcome with therapeutic hypothermia and further investigation in this population is warranted. Any potential benefit associated with therapeutic hypothermia must be weighed against the increased risk of adverse effects, particularly the onset of arrhythmias.

Mild therapeutic hypothermia protects against inflammatory and proapoptotic processes in the rat model of cochlear implant trauma

OBJECTIVE

Mild therapeutic hypothermia (MTH) has been demonstrated to prevent residual hearing loss from surgical trauma associated with cochlear implant (CI) insertion. Here, we aimed to characterize the mechanisms of MTH-induced hearing preservation in CI in a well-established preclinical rodent model.

APPROACH

Rats were divided into four experimental conditions: MTH-treated and implanted cochleae, cochleae implanted under normothermic conditions, MTH only cochleae and un-operated cochleae (controls). Auditory brainstem responses (ABRs) were recorded at different time points (up to 84 days) to confirm long-term protection and safety of MTH locally applied to the cochlea for 20 min before and after implantation. Transcriptome sequencing profiling was performed on cochleae harvested 24 h post CI and MTH treatment to investigate the potential beneficial effects and underlying active gene expression pathways targeted by the temperature management.

RESULTS

MTH treatment preserved residual hearing up to 3 months following CI when compared to the normothermic CI group. In addition, MTH applied locally to the cochleae using our surgical approach was safe and did not affect hearing in the long-term. Results of RNA sequencing analysis highlight positive modulation of signaling pathways and gene expression associated with an activation of cellular inflammatory and immune responses against the mechanical damage caused by electrode insertion.

SIGNIFICANCE

These data suggest that multiple and possibly independent molecular pathways play a role in the protection of residual hearing provided by MTH against the trauma of cochlear implantation.

Recent developments and controversies in therapeutic hypothermia after cardiopulmonary resuscitation

Therapeutic hypothermia was recommended as the only neuroprotective treatment in comatose patients after return of spontaneous circulation (ROSC). With new evidence suggesting a similar neuroprotective effect of 36 °C and 33 °C, the term "therapeutic hypothermia" was substituted by "targeted temperature management" in 2011, which in turn was replaced by the term "temperature control" in 2022 because of new evidence of the similar effects of target normothermia and 33 °C. However, there is no clear consensus on the efficacy of therapeutic hypothermia. In this article, we provide an overview of the recent evidence from basic and clinical research related to therapeutic hypothermia and re-evaluate its application as a post-ROSC neuroprotective intervention in clinical settings.

Active conductive head cooling of normal and infarcted brain: A magnetic resonance spectroscopy imaging study

Active conductive head cooling is a simple and non-invasive intervention that may slow infarct growth in ischemic stroke. We investigated the effect of active conductive head cooling on brain temperature using whole brain echo-planar spectroscopic imaging. A cooling cap (WElkins Temperature Regulation System, 2nd Gen) was used to administer cooling for 80 minutes to healthy volunteers and chronic stroke patients. Whole brain echo-planar spectroscopic imaging scans were obtained before and after cooling. Brain temperature was estimated using the Metabolite Imaging and Data Analysis System software package, which allows voxel-level temperature calculations using the chemical shift difference between metabolite (N-acetylaspartate, creatine, choline) and water resonances. Eleven participants (six healthy volunteers, five post-stroke) underwent 80 ± 5 minutes of cooling. The average temperature of the coolant was 1.3 ± 0.5°C below zero. Significant reductions in brain temperature (ΔT = -0.9 ± 0.7°C, P = 0.002), and to a lesser extent, rectal temperature (ΔT = -0.3 ± 0.1°C, P = 0.03) were observed. Exploratory analysis showed that the occipital lobes had the greatest reduction in temperature (ΔT = -1.5 ± 1.2°C, P = 0.002). Regions of infarction had similar temperature reductions to the contralateral normal brain. Future research could investigate the feasibility of head cooling as a potential neuroprotective strategy in patients being considered for acute stroke therapies.

Targeted Temperature Management for Cardiac Arrest Due to Non-shockable Rhythm: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background

Targeted temperature management (TTM) is recommended in adult patients following cardiac arrest (CA) with any rhythm. However, as to non-shockable (NSR) CA, high-quality evidence of TTM supporting its practices remains uncertain. Thus, we aimed to conduct a systematic review and meta-analysis with randomized controlled trials (RCTs) to explore the efficacy and safety of TTM in this population.

Methods

We searched PubMed, Embase, and Cochrane library databases for potential trials from inception through Aug 25, 2021. RCTs evaluating TTM for CA adults due to NSR were included, regardless of the timing of cooling initiation. Outcome measurements were mortality and good neurological function. We used the Cochrane bias tools to evaluate the quality of the included studies. Heterogeneity, subgroup analyses, and sensitivity analysis were investigated to test the robustness of the primary outcomes.

Results

A total of 14 RCTs with 4,009 adults were eligible for the final analysis. All trials had a low to moderate risk of bias. Of the included trials, six compared NSR patients with or without TTM, while eight compared pre-hospital to in-hospital TTM. Pooled data showed that TTM was not associated with improved mortality (Risk ratio [RR] 1.00; 95% CI, 0.944–1.05; P = 0.89, I² = 0%) and good neurological outcome (RR 1.18; 95% CI 0.90–1.55; P = 0.22, I² = 8%). Similarly, use of pre-hospital TTM resulted in neither an improved mortality (RR 0.99, 95% CI 0.97–1.03; I² = 0%, P = 0.32) nor favorable neurological outcome (RR 1.13, 95% CI 0.93–1.38; I² = 0%, P = 0.22). These results were further confirmed in the sensitivity analyses and subgroup analyses.

Conclusions

Our results showed that using the TTM strategy did not significantly affect the mortality and neurologic outcomes in CA survival presenting initial NSR.

Targeted Hypothermia vs Targeted Normothermia in Survivors of Cardiac Arrest: A Systematic Review and Meta-Analysis of Randomized Trials

BACKGROUND

The role of targeted hypothermia in patients with coma after cardiac arrest has been challenged in a recent randomized clinical trial.

METHODS

We performed a computerized search of MEDLINE, EMBASE, and Cochrane databases through July 2021 for randomized trials evaluating the outcomes of targeted hypothermia vs normothermia in patients with coma after cardiac arrest with shockable or non-shockable rhythm. The main study outcome was mortality at the longest reported follow-up.

RESULTS

The final analysis included 8 randomized studies with a total of 2927 patients, with a weighted follow-up period of 4.9 months. The average targeted temperature in the hypothermia arm in the included trials varied from 31.7°C to 34°C. There was no difference in long-term mortality between the hypothermia and normothermia groups (56.2% vs 56.9%, risk ratio [RR] 0.96; 95% confidence interval [CI], 0.87-1.06). There was no significant difference between hypothermia and normothermia groups in rates of favorable neurological outcome (37.9% vs 34.2%, RR 1.31; 95% CI, 0.99-1.73), in-hospital mortality (RR 0.88; 95% CI, 0.77-1.01), bleeding, sepsis, or pneumonia. Ventricular arrhythmias were more common among the hypothermia vs normothermia groups (RR 1.36; 95% CI, 1.17-1.58; P = .42). Sensitivity analysis, excluding the Targeted Hypothermia vs Targeted Normothermia after Out-of-Hospital Cardiac Arrest (TTM2) trial, showed favorable neurological outcome with hypothermia vs normothermia (RR 1.45; 95% CI, 1.17-1.79).

CONCLUSION

Targeted temperature management was not associated with improved survival or neurological outcomes compared with normothermia in comatose patients after cardiac arrest. Further studies are warranted to further clarify the value of targeted hypothermia compared with targeted normothermia.

Targeted Temperature Management in Unconscious Survivors of Postcardiac Arrest: A Systematic Review and Meta-analysis of Randomized Controlled Trials

Background

Targeted temperature management (TTM) is a vital element of postresuscitation management after cardiac arrest. Though international guidelines recommend TTM, the supporting evidence is of low certainty.

Aims and objectives

To estimate the effect of TTM strategy on mortality and neurological outcomes in postcardiac arrest survivors.

Materials and methods

Randomized controlled trials (RCTs) published in English evaluating the use of TTM in adult comatose survivors of cardiac arrest were included. Studies were categorized into two groups, based on hypothermia vs normothermia. The main outcome was death due to any origin. The secondary outcome measures evaluated neurological outcome and complications associated with TTM. Outcomes were analyzed by calculating Odds Ratio (OR) of a worse outcome. ORs with 95% CIs in a forest plot were used to show the results of random-effects meta-analyses.

Results

On pooled analysis of 11 RCTs, no difference was observed in death due to any origin rates in the hypothermia compared to the normothermia group (OR; 0.88, 95% CI: 0.39–1.16). Overall, no difference in poor neurological outcome was observed between the two groups (OR; 0.86, 95% CI: 0.66–1.12). Trial sequencing analysis for mortality and poor neurological outcome showed that number to achieve power to predict futility has been achieved in both the parameters.

Conclusions

This meta-analysis showed that hypothermia compared to normothermia TTM strategies does not improve survival or neurologic outcomes.

How to cite this article

Mishra SB, Patnaik R, Rath A, Samal S, Dash A, Nayak B. Targeted Temperature Management in Unconscious Survivors of Postcardiac Arrest: A Systematic Review and Meta-analysis of Randomized Controlled Trials. Indian J Crit Care Med 2022;26(4):506–513.

Therapeutic Hypothermia Is Associated With a Decrease in All-cause Mortality in Cardiac Arrest Due to Shockable Rhythm

BACKGROUND

The benefits of therapeutic hypothermia (TH) in comatose patients postcardiac arrest remain uncertain. While some studies have shown benefit, others have shown equivocal results. We pooled data from randomized controlled trials to better study the outcomes of TH.

METHODS

Electronic research databases were queried up till September 21, 2021. Randomized controlled trials comparing TH (32-34 °C) with control (normothermia or temperature ≥36 °C) in comatose postcardiac arrest patients were included.

RESULTS

The study included 10 randomized controlled trials with 3988 subjects (1999 in the TH arm and 1989 in the control arm). There was no difference in all-cause mortality between TH and control (odds ratio [OR], 0.83; 95% confidence interval [CI], 0.66-1.05; P = 0.08; I2 = 41%). There was no difference in the odds of poor neurological outcomes (OR, 0.78; 95% CI, 0.61-1.01; P = 0.07; I2 = 43%). Subgroup analysis showed a decrease in all-cause mortality and poor neurological outcomes with TH in shockable rhythms (OR, 0.55; 95% CI, 0.37-0.80; P = 1.00; I2 = 0% and OR, 0.48; 95% CI, 0.32-0.72; P = 0.92; I2 = 0%, respectively).

CONCLUSIONS

TH may be beneficial in reducing mortality and poor neurological outcomes in comatose postcardiac arrest patients with shockable rhythms.

[Targeted temperature management after cardiac arrest : What is new?]

The current guidelines of the European Resuscitation Council recommend targeted temperature management to improve functional neurological outcome in comatose survivors after cardiac arrest. With the pathophysiological background of hypothermia-induced neuroprotection for prevention of hypoxic-ischemic encephalopathy, targeted temperature management is a key measure and represents a central aspect in postresuscitation care.In the 2021 guidelines the application of targeted temperature management in postresuscitation care has been recommended for all rhythms and irrespective of the location of cardiac arrest. Targeted temperature management is advocated for adult patients who remain unresponsive following return of spontaneous circulation (ROSC) after either out-of-hospital cardiac arrest or in-hospital cardiac arrest. The body temperature should be maintained at a constant value between 32 °C and 36 °C for at least 24 h. To avoid rebound hyperthermia, fever following targeted temperature management, defined as a temperature above 37.7 °C, should be prevented and treated for at least 72 h after ROSC in persistently comatose patients. The routine use of prehospital cooling by rapid infusion of large volumes of cold i.v. fluid immediately after ROSC is not recommended.Based on a systematic review of the current literature, this article summarizes the results of randomized trials and new findings on targeted temperature management in comatose adult patients after cardiac arrest. The review has a particular focus on the most recent evidence regarding the optimum range of target temperatures. Furthermore, recent data on preclinical management, different patient populations, the duration of targeted temperature management, cooling methods and rebound hyperthermia are discussed.The impact of targeted temperature management on neurological outcome after cardiac arrest has been a matter of controversy. Despite contradictory results and heterogeneity of study designs, the current evidence supports the relevance and the necessity of strict temperature control in postresuscitation care for neuroprotection and improvement in functional neurological outcomes.

Targeted temperature management in adult cardiac arrest: Systematic review and meta-analysis

AIM

To perform a systematic review and meta-analysis on targeted temperature management in adult cardiac arrest patients.

METHODS

PubMed, Embase, and the Cochrane Central Register of Controlled Trials were searched on June 17, 2021 for clinical trials. The population included adult patients with cardiac arrest. The review included all aspects of targeted temperature management including timing, temperature, duration, method of induction and maintenance, and rewarming. Two investigators reviewed trials for relevance, extracted data, and assessed risk of bias. Data were pooled using random-effects models. Certainty of evidence was evaluated using GRADE.

RESULTS

The systematic search identified 32 trials. Risk of bias was assessed as intermediate for most of the outcomes. For targeted temperature management with a target of 32-34 °C vs. normothermia (which often required active cooling), 9 trials were identified, with six trials included in meta-analyses. Targeted temperature management with a target of 32-34 °C did not result in an improvement in survival (risk ratio: 1.08 [95%CI: 0.89, 1.30]) or favorable neurologic outcome (risk ratio: 1.21 [95%CI: 0.91, 1.61]) at 90 to 180 days after the cardiac arrest (low certainty of evidence). Three trials assessed different hypothermic temperature targets and found no difference in outcomes (low certainty of evidence). Ten trials were identified comparing prehospital cooling vs. no prehospital cooling with no improvement in survival (risk ratio: 1.01 [95%CI: 0.92, 1.11]) or favorable neurologic outcome (risk ratio: 1.00 [95%CI: 0.90, 1.11]) at hospital discharge (moderate certainty of evidence).

CONCLUSIONS

Among adult patients with cardiac arrest, the use of targeted temperature management at 32-34 °C, when compared to normothermia, did not result in improved outcomes in this meta-analysis. There was no effect of initiating targeted temperature management prior to hospital arrival. These findings warrant an update of international cardiac arrest guidelines.

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.

Targeted temperature management following out-of-hospital cardiac arrest: a systematic review and network meta-analysis of temperature targets

PURPOSE

Targeted temperature management (TTM) may improve survival and functional outcome in comatose survivors of out-of-hospital cardiac arrest (OHCA), though the optimal target temperature remains unknown. We conducted a systematic review and network meta-analysis to investigate the efficacy and safety of deep hypothermia (31-32 °C), moderate hypothermia (33-34 °C), mild hypothermia (35-36 °C), and normothermia (37-37.8 °C) during TTM.

METHODS

We searched six databases from inception to June 2021 for randomized controlled trials (RCTs) evaluating TTM in comatose OHCA survivors. Two reviewers performed screening, full text review, and extraction independently. The primary outcome of interest was survival with good functional outcome. We used GRADE to rate our certainty in estimates.

RESULTS

We included 10 RCTs (4218 patients). Compared with normothermia, deep hypothermia (odds ratio [OR] 1.30, 95% confidence interval [CI] 0.73-2.30), moderate hypothermia (OR 1.34, 95% CI 0.92-1.94) and mild hypothermia (OR 1.44, 95% CI 0.74-2.80) may have no effect on survival with good functional outcome (all low certainty). Deep hypothermia may not improve survival with good functional outcome, as compared to moderate hypothermia (OR 0.97, 95% CI 0.61-1.54, low certainty). Moderate hypothermia (OR 1.23, 95% CI 0.86-1.77) and deep hypothermia (OR 1.27, 95% CI 0.70-2.32) may have no effect on survival, as compared to normothermia. Finally, incidence of arrhythmia was higher with moderate hypothermia (OR 1.45, 95% CI 1.08-1.94) and deep hypothermia (OR 3.58, 95% CI 1.77-7.26), compared to normothermia (both high certainty).

CONCLUSIONS

Mild, moderate, or deep hypothermia may not improve survival or functional outcome after OHCA, as compared to normothermia. Moderate and deep hypothermia were associated with higher incidence of arrhythmia. Routine use of moderate or deep hypothermia in comatose survivors of OHCA may potentially be associated with more harm than benefit.

Insight into the use of tympanic temperature during target temperature management in emergency and critical care: a scoping review

BACKGROUND

Target temperature management (TTM) is suggested to reduce brain damage in the presence of global or local ischemia. Prompt TTM application may help to improve outcomes, but it is often hindered by technical problems, mainly related to the portability of cooling devices and temperature monitoring systems. Tympanic temperature (T_Ty) measurement may represent a practical, non-invasive approach for core temperature monitoring in emergency settings, but its accuracy under different TTM protocols is poorly characterized. The present scoping review aimed to collect the available evidence about T_Ty monitoring in TTM to describe the technique diffusion in various TTM contexts and its accuracy in comparison with other body sites under different cooling protocols and clinical conditions.

METHODS

The scoping review was conducted following the guidelines of the Preferred Reporting Items for Systematic Review and Meta-Analysis extension for scoping reviews (PRISMA-ScR). PubMed, Scopus, and Web of Science electronic databases were systematically searched to identify studies conducted in the last 20 years, where T_Ty was measured in TTM context with specific focus on pre-hospital or in-hospital emergency settings.

RESULTS

The systematic search identified 35 studies, 12 performing T_Ty measurements during TTM in healthy subjects, 17 in patients with acute cardiovascular events, and 6 in patients with acute neurological diseases. The studies showed that T_Ty was able to track temperature changes induced by either local or whole-body cooling approaches in both pre-hospital and in-hospital settings. Direct comparisons to other core temperature measurements from other body sites were available in 22 studies, which showed a faster and larger change of T_Ty upon TTM compared to other core temperature measurements. Direct brain temperature measurements were available only in 3 studies and showed a good correlation between T_Ty and brain temperature, although T_Ty displayed a tendency to overestimate cooling effects compared to brain temperature.

CONCLUSIONS

T_Ty was capable to track temperature changes under a variety of TTM protocols and clinical conditions in both pre-hospital and in-hospital settings. Due to the heterogeneity and paucity of comparative temperature data, future studies are needed to fully elucidate the advantages of T_Ty in emergency settings and its capability to track brain temperature.

Targeted temperature management after cardiac arrest. A systematic review and meta-analysis of animal studies

AIM

Animal studies are an important knowledge base when information from clinical trials is missing or conflicting. The goal of this systematic review and meta-analysis was to investigate the effect of conventional targeted temperature management (TTM) between 32-36 °C in animal cardiac arrest models, and to estimate the influence of effect modifiers on the pooled effect of TTM.

DATA SOURCES

We searched Medline and Scopus from inception to May 2020 for randomised controlled animal trials assessing the effect of conventional TTM versus normothermia on neurologic outcome after cardiac arrest. We extracted data on study characteristics, study quality data, neurologic outcome, mortality, and potential effect modifiers.

RESULTS

We retrieved 1635 studies, 45 studies comprising data of 981 animals met the inclusion criteria. Risk of bias was high in 17 studies and moderate in 28 studies. We undertook random-effects meta-analyses and meta-regression analyses to calculate the pooled effect and the influence of effect modifiers. There was a strong beneficial effect of TTM as compared to normothermia on neurologic outcome (standardised mean difference of 1.4 [95% CI -1.7 to -1.1; I² = 75%]). Faster cooling rates, lower target temperature of TTM within the range of 32-36 °C, and shorter duration of cooling were independently associated with an increasing effect size of TTM.

CONCLUSIONS

This systematic review of animal cardiac arrest studies showed a consistent favourable effect of postresuscitation TTM as compared to normothermia on neurologic outcome that increased with lower target temperatures.

Selective Brain Hypothermia in Acute Ischemic Stroke: Reperfusion Without Reperfusion Injury

In acute ischemic stroke, early recanalization of the occluded artery is crucial for best outcome to be achieved. Recanalization aims at restoring blood flow to the ischemic tissue (reperfusion) and is achieved with pharmacological thrombolytic drugs, endovascular thrombectomy (EVT) devices, or both. The introduction of modern endovascular devices has led to tremendous anatomical and clinical success with rates of substantial reperfusion exceeding 80% and proven clinical benefit in patients with anterior circulation large vessel occlusions (LVOs). However, not every successful reperfusion procedure leads to the desired clinical outcome. In fact, the rate of non-disabled outcome at 3 months with current EVT treatment is ~1 out of 4. A constraint upon better outcomes is that reperfusion, though resolving ischemic stress, may not restore the anatomic structures and metabolic functions of ischemic tissue to their baseline states. In fact, ischemia triggers a complex cascade of destructive mechanisms that can sometimes be exacerbated rather than alleviated by reperfusion therapy. Such reperfusion injury may cause infarct progression, intracranial hemorrhage, and unfavorable outcome. Therapeutic hypothermia has been shown to have a favorable impact on the molecular elaboration of ischemic injury, but systemic hypothermia is limited by slow speed of attaining target temperatures and clinical complications. A novel approach is endovascular delivery of hypothermia to cool the affected brain tissue selectively and rapidly with tight local temperature control, features not available with systemic hypothermia devices. In this perspective article, we discuss the possible benefits of adjunctive selective endovascular brain hypothermia during interventional stroke treatment.

Meta-Analysis of the Usefulness of Therapeutic Hypothermia After Cardiac Arrest

Despite current guidelines recommending therapeutic hypothermia (TH) for post cardiac arrest comatose patient, its use remains limited. Randomized controlled trials (RCTs) have also reported conflicting results on the efficacy of TH. Therefore, we conducted an updated meta-analysis to evaluate the effect of TH in post cardiac arrest patients. We searched electronic databases for RCTs comparing TH (32°C to 34°C) with controls (normothermia or temperature ≥36°C) in comatose patients who sustained cardiac arrest. Mortality and neurological outcomes were the outcomes of interest. We used random effect meta-analysis to estimate risk ratio (RR) with 95% confidence interval (CI). Eight RCTs with a total of 2,026 patients (TH n = 1,025 and control n = 1,001) were included. Irrespective of initial rhythm, TH was associated with significant reduction in poor neurological outcomes (RR 0.87, 95% CI 0.77 to 0.98; p = 0.02) without any difference in mortality (RR 0.94, 95% CI 0.85 to 1.03; p = 0.17). In patients with initial shockable rhythm compared with control, TH reduced mortality (RR 0.85, 95% CI 0.73 to 0.99; p = 0.04) and poor neurological outcomes (RR 0.81, 95% CI 0.67 to 0.99; p = 0.04). Whereas, in patients with initial nonshockable rhythm, TH was associated with decreased poor neurological outcomes after excluding one trial (RR 0.95 95% CI 0.91 to 1.00; p = 0.05). In conclusion, TH is associated with improved neurological outcomes in all patients sustaining cardiac arrest and with decreased mortality in patients with initial shockable rhythm.

Targeted Temperature Management in Cardiac Arrest Patients With an Initial Non-Shockable Rhythm: A Systematic Review and Meta-Analysis

BACKGROUND

Targeted temperature management (TTM) is now recommended for patients presenting with an out-of-hospital cardiac arrest. However, there are limited data that support its use in patients with an initial non-shockable rhythm (NSR).

METHODS

A literature search of PubMed/MEDLINE, Cochrane Library, and Embase was conducted by two independent authors for studies that compared TTM along with standard care versus standard care alone in treating cardiac arrest with initial NSR. Outcomes were short-term and long-term survival, and a Cerebral Performance Category (CPC) score of 1 to 2 at the longest follow-up period. The Mantel-Haenszel random-effects model was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs). Trial sequential analysis (TSA) was performed on the randomized controlled trials (RCTs).

RESULTS

Thirty studies were included in the final analysis: 25 observational and five RCTs, totalling 10,703 patients, 4,023 of whom received TTM and 6,680 received standard care alone. Compared with standard care, patients who presented with an initial NSR cardiac arrest and received TTM (target of 32°C -34°C) had a significantly higher short-term survival (OR 1.44 95% CI 1.15-1.81; P = 0.002), long-term survival (OR 1.52 95% CI 1.03-2.26; P = 0.04), and CPC score of 1 to 2 (OR 1.63 95% CI 1.22-2.17; P = 0.0010). Sensitivity analyses by including only RCTs showed a trend, although not significant, toward better short-term survival (OR 1.25 95% CI 0.82-1.89; P = 0.30), long-term survival (OR 1.15 95% CI 0.80-1.66; P = 0.46), and neurologic outcomes (OR 1.51 95% CI 0.81-2.80; P = 0.19). However, TSA performed on the RCTs revealed that the results were inconclusive.

CONCLUSION

Among patients who survived cardiac arrest with an initial NSR, TTM is associated with a higher rate of survival and favorable neurological outcomes compared with no TTM. However, analyses from the included RCTs did not support this conclusion.

Effects of endovascular and surface cooling on resuscitation in patients with cardiac arrest and a comparison of effectiveness, stability, and safety: a systematic review and meta-analysis

Objectives

This study conducted a meta-analysis to assess the effectiveness, stability, and safety of mild therapeutic hypothermia (TH) induced by endovascular cooling (EC) and surface cooling (SC) and its effect on ICU, survival rate, and neurological function integrity in adult CA patients.

Methods

We developed inclusion criteria, intervention protocols, results, and data collection. The results included outcomes during target temperature management as well as ICU stay, survival rate, and neurological functional integrity. The characteristics of the included population and each study were analyzed.

Results

Four thousand nine hundred thirteen participants met the inclusion criteria. Those receiving EC had a better cooling efficiency (cooling rates MD = 0.31[0.13, 0.50], p < 0.01; induced cooling times MD = − 90.45[− 167.57, − 13.33], p = 0.02; patients achieving the target temperature RR = 1.60[1.19, 2.15], p < 0.01) and thermal stability during the maintenance phase (maintenance time MD = 2.35[1.22, 3.48], p < 0.01; temperature fluctuation MD = − 0.68[− 1.03, − 0.33], p < 0.01; overcooling RR = 0.33[0.23, 0.49], p < 0.01). There were no differences in ICU survival rate (RR = 1.22[0.98, 1.52], p = 0.07, I² = 0%) and hospital survival rate (RR = 1.02 [0.96, 1.09], p = 0.46, I² = 0%), but EC reduced the length of stay in ICU (MD = − 1.83[− 3.45, − 0.21], p = 0.03, I² = 49%) and improved outcome of favorable neurological function at discharge (RR = 1.15[1.04, 1.28], p < 0.01, I² = 0%). EC may delay the hypothermia initiation time, and there was no significant difference between the two cooling methods in the time from the start of patients’ cardiac arrest to achieve the target temperature (MD = − 46.64[− 175.86, 82.58]). EC was superior to non-ArcticSun in terms of cooling efficiency. Although there was no statistical difference in ICU survival rate, ICU length of stay, and hospitalization survival rate, in comparison to non-ArcticSun, EC improved rates of neurologically intact survival (RR = 1.16 [1.01, 1.35], p = 0.04, I² = 0%).

Conclusions

Among adult patients receiving cardiopulmonary resuscitation, although there is no significant difference between the two cooling methods in the time from the start of cardiac arrest to achieve the target temperature, the faster cooling rate and more stable cooling process in EC shorten patients’ ICU hospitalization time and help more patients obtain good neurological prognosis compared with patients receiving SC. Meanwhile, although EC has no significant difference in patient outcomes compared with ArcticSun, EC has improved rates of neurologically intact survival.

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.

Targeted temperature management after cardiac arrest: Updated meta-analysis of all-cause mortality and neurological outcomes

BACKGROUND

Cardiac arrest carries high mortality and morbidity burden. Different studies showed conflicting data regarding outcomes of targeted temperature management (TTM) for cardiac arrest. The purpose of this meta-analysis is to systematically determine the effect of TTM on all-cause mortality and neurological outcomes after cardiac arrest.

METHODS

We conducted a systematic search for randomized controlled trials in Pubmed, Cochrane & ScienceDirect. Primary outcomes were neurological outcome and all-cause mortality.

RESULTS

Nine randomized controlled trials utilizing data for in-hospital and out-of-hospital cardiac arrest were selected for meta-analysis. Total number of patients included was 1592. Mortality was lower in targeted temperature management group (OR 0.637, 95% CI 0.436-0.93, p-value 0.019, I² = 44.78%, n = 1592). Therapeutic hypothermia group also demonstrated reduction in poor neurological outcomes (OR 0.582, 95% CI 0.363-931, p-value 0.024, I² = 56.79%, n = 1567). Subgroup analysis was conducted, after excluding in-hospital cardiac arrest patients, and demonstrated reduction in poor neurological outcome (OR 0.562, 95% CI 0.331-0.955, p-value 0.033, I² = 61.78%, n = 1480) and mortality in out-of-hospital cardiac arrest patients (OR 0.674, 95% CI 0.454-999, p-value 0.049, I² = 43.8%, n = 1505).

CONCLUSION

Targeted temperature management after cardiac arrest may be associated with improvement in all-cause mortality and reduction in poor neurological outcome.

Therapeutic hypothermia in acute traumatic spinal cord injury

Therapeutic hypothermia is already widely acknowledged as an effective neuroprotective intervention, especially within the acute care setting in relation to conditions such as cardiac arrest and neonatal encephalopathy. Its multifactorial mechanisms of action, including lowering metabolic rate and reducing acute inflammatory cellular processes, ultimately provide protection for central nervous tissue from continuing injury following ischaemic or traumatic insult. Its clinical application within acute traumatic spinal cord injury would therefore seem very plausible, it having the potential to combat the pathophysiological secondary injury processes that can develop in the proceeding hours to days following the initial injury. As such it could offer invaluable assistance to lessen subsequent sensory, motor and autonomic dysfunction for an individual affected by this devastating condition. Yet research surrounding this intervention's applicability in this field is somewhat lacking, the majority being experimental. Despite a recent resurgence of interest, which in turn has produced encouraging results, there is a real possibility that this potentially transformational intervention for treating traumatic spinal cord injury could remain an experimental therapy and never reach clinical implementation.

Targeted temperature management in the ICU: Guidelines from a French expert panel

Over the recent period, the use of induced hypothermia has gained an increasing interest for critically ill patients, in particular in brain-injured patients. The term "targeted temperature management" (TTM) has now emerged as the most appropriate when referring to interventions used to reach and maintain a specific level temperature for each individual. TTM may be used to prevent fever, to maintain normothermia, or to lower core temperature. This treatment is widely used in intensive care units, mostly as a primary neuroprotective method. Indications are, however, associated with variable levels of evidence based on inhomogeneous or even contradictory literature. Our aim was to conduct a systematic analysis of the published data in order to provide guidelines. We present herein recommendations for the use of TTM in adult and paediatric critically ill patients developed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) method. These guidelines were conducted by a group of experts from the French Intensive Care Society (Société de réanimation de langue française [SRLF]) and the French Society of Anesthesia and Intensive Care Medicine (Société francaise d'anesthésie réanimation [SFAR]) with the participation of the French Emergency Medicine Association (Société française de médecine d'urgence [SFMU]), the French Group for Pediatric Intensive Care and Emergencies (Groupe francophone de réanimation et urgences pédiatriques [GFRUP]), the French National Association of Neuro-Anesthesiology and Critical Care (Association nationale de neuro-anesthésie réanimation française [ANARLF]), and the French Neurovascular Society (Société française neurovasculaire [SFNV]). Fifteen experts and two coordinators agreed to consider questions concerning TTM and its practical implementation in five clinical situations: cardiac arrest, traumatic brain injury, stroke, other brain injuries, and shock. This resulted in 30 recommendations: 3 recommendations were strong (Grade 1), 13 were weak (Grade 2), and 14 were experts' opinions. After two rounds of rating and various amendments, a strong agreement from voting participants was obtained for all 30 (100%) recommendations, which are exposed in the present article.

Targeted temperature management in the ICU: guidelines from a French expert panel

Over the recent period, the use of induced hypothermia has gained an increasing interest for critically ill patients, in particular in brain-injured patients. The term “targeted temperature management” (TTM) has now emerged as the most appropriate when referring to interventions used to reach and maintain a specific level temperature for each individual. TTM may be used to prevent fever, to maintain normothermia, or to lower core temperature. This treatment is widely used in intensive care units, mostly as a primary neuroprotective method. Indications are, however, associated with variable levels of evidence based on inhomogeneous or even contradictory literature. Our aim was to conduct a systematic analysis of the published data in order to provide guidelines. We present herein recommendations for the use of TTM in adult and paediatric critically ill patients developed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) method. These guidelines were conducted by a group of experts from the French Intensive Care Society (Société de Réanimation de Langue Française [SRLF]) and the French Society of Anesthesia and Intensive Care Medicine (Société Francaise d’Anesthésie Réanimation [SFAR]) with the participation of the French Emergency Medicine Association (Société Française de Médecine d’Urgence [SFMU]), the French Group for Pediatric Intensive Care and Emergencies (Groupe Francophone de Réanimation et Urgences Pédiatriques [GFRUP]), the French National Association of Neuro-Anesthesiology and Critical Care (Association Nationale de Neuro-Anesthésie Réanimation Française [ANARLF]), and the French Neurovascular Society (Société Française Neurovasculaire [SFNV]). Fifteen experts and two coordinators agreed to consider questions concerning TTM and its practical implementation in five clinical situations: cardiac arrest, traumatic brain injury, stroke, other brain injuries, and shock. This resulted in 30 recommendations: 3 recommendations were strong (Grade 1), 13 were weak (Grade 2), and 14 were experts’ opinions. After two rounds of rating and various amendments, a strong agreement from voting participants was obtained for all 30 (100%) recommendations, which are exposed in the present article.

A survey on general and temperature management of post cardiac arrest patients in large teaching and university hospitals in 14 European countries-The SPAME trial results

INTRODUCTION

International guidelines recommend a bundle of care, including targeted temperature management (TTM), in post cardiac arrest survivors. Aside from a few small surveys in different European countries, adherence to the European Resuscitation Council (ERC) and European Society of Intensive Care Medicine (ESICM) recommendations are unknown.

METHODS

This international European telephone survey was conducted to provide an overview of current clinical practice of post cardiac arrest management with a main focus on TTM. We targeted large teaching and university hospitals within Europe as leading facilities and key opinion leaders in the field of post cardiac arrest care. Selected national principal investigators conducted the survey, which was based on a predefined questionnaire, between December 2014 and March 2015, before the publication of the ERC Guidelines 2015.

RESULTS

The return rate was 94% from 268 participating intensive care units (ICU). The majority had a predefined standard operating procedure (SOP) protocol for post cardiac arrest patients. Altogether, 68% of the ICUs provided TTM at a target temperature of 32-34°C for 24h, and 33% had changed the target temperature to 36°C. The minority provided a written SOP for neurological prognostication, which was generally initiated 72h after return of spontaneous circulation (ROSC). Electroencephalography and somatosensory evoked potentials were used by most ICUs for early prognostication. Treating more than fifty patients a year was significantly associated with providing written SOPs for TTM and prognostication (p<0.01), as well as the use of a computer feedback device (p=0.03) for TTM.

CONCLUSION

This international European telephone survey revealed a high rate of implementation of TTM in post cardiac arrest patients in university and teaching hospitals. Most participants also provided a SOP, but only a minority had a SOP for neurological prognostication.

Neurology of cardiopulmonary resuscitation

This chapter aims to provide an up-to-date review of the science and clinical practice pertaining to neurologic injury after successful cardiopulmonary resuscitation. The past two decades have seen a major shift in the science and practice of cardiopulmonary resuscitation, with a major emphasis on postresuscitation neurologic care. This chapter provides a nuanced and thoughtful historic and bench-to-bedside overview of the neurologic aspects of cardiopulmonary resuscitation. A particular emphasis is made on the anatomy and pathophysiology of hypoxic-ischemic encephalopathy, up-to-date management of survivors of cardiopulmonary resuscitation, and a careful discussion on neurologic outcome prediction. Guidance to practice evidence-based clinical care when able and thoughtful, pragmatic suggestions for care where evidence is lacking are also provided. This chapter serves as both a useful clinical guide and an updated, thorough, and state-of-the-art reference on the topic for advanced students and experienced practitioners in the field.

Therapeutic Hypothermia After Resuscitation From a Non-Shockable Rhythm Improves Outcomes in a Regionalized System of Cardiac Arrest Care

OBJECTIVE

Therapeutic hypothermia (TH) improves neurologic outcome in patients resuscitated from ventricular fibrillation. The purpose of this study was to evaluate TH effects on neurologic outcome in patients resuscitated from a non-shockable out-of-hospital cardiac arrest rhythm.

DESIGN AND SETTING

This is a retrospective cohort study of data reported to a registry in an emergency medical system in a large metropolitan region. Patients achieving field return of spontaneous circulation are transported to designated hospitals with TH protocols.

PATIENTS

Patients with an initial non-shockable rhythm were identified. Patients were excluded if awake in the Emergency Department or if TH was withheld due to preexisting coma or death prior to initiation. The decision to initiate TH was determined by the treating physician.

MEASUREMENTS

The primary outcome was survival with good neurologic outcome defined by a cerebral performance category of 1 or 2.

MAIN RESULTS

Of the 2772 patients treated for cardiac arrest during the study period, there were 1713 patients resuscitated from cardiac arrest with an initial non-shockable rhythm and 1432 patients met inclusion criteria. The median age was 69 years [IQR 59-82]; 802 (56%) male. TH was induced in 596 (42%) patients. Survival with good neurologic outcome was 14% in the group receiving TH, compared with 5% in those not treated with TH (risk difference = 8%, 95% CI 5-12%). The adjusted OR for a CPC 1 or 2 with TH was 2.9 (95% CI 1.9-4.4).

CONCLUSION

Analyzing the data collected from the registry of the standard practice in a large metropolitan region, TH is associated with improved neurologic outcome in patients resuscitated from initial non-shockable rhythms in a regionalized system for post-resuscitation care.

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.

History and current use of mild therapeutic hypothermia after cardiac arrest

In spite of many years of development and implementation of pre-hospital advanced life support programmes, the survival rate of out-of-hospital cardiac arrest (OHCA) used to be very poor. Neurologic injury from cerebral hypoxia is the most common cause of death in patients with OHCA. In the past two decades, post-resuscitation care has developed many new concepts aimed at improving the neurological outcome and survival rate of patients after cardiac arrest. Systematic post-cardiac arrest care after the return of spontaneous circulation, including induced mild therapeutic hypothermia (TH) in selected patients, is aimed at significantly improving rates of long-term neurologically intact survival. This review summarises the history and current knowledge in the field of mild TH after OHCA.

Application of a novel rectal cooling device in hypothermia therapy after cerebral hypoxia-ischemia in rats

BACKGROUND

A new rectal cooling device for therapeutic hypothermia (TH) therapy is designed and is applied in TH treatment of SD rats with ischemic-hypoxic brain damage.

METHODS

Healthy adult SD rats (n = 45) were randomly assigned into four groups: the healthy control group (n = 5), the ischemia and hypoxia group (n = 10), the rectal TH cooling group (n = 18), and the ice blanket TH cooling group (n = 11). The rats in the rectal cooling and ice blanket TH groups received 12 h treatment after hypoxic-ischemic brain damage had been established, while those in the ischemia and hypoxia group did not. Taking the start of TH as the zero point, rats were sacrificed after 24 h and the brain and rectum tissues were sampled for histological analysis.

RESULTS

The TH induction time (37.3 ± 14.7 min) in the rectal cooling group was significantly shorter (F = 4.937, P < 0.05) than that in the ice blanket cooling group (75.6 ± 27.2 min). The HE and NISSL staining results showed that rats in the rectal TH cooling group had significantly decreased (P < 0.01) positive neurons cell count compared to those in ischemia and hypoxia group. In addition, TUNEL staining indicated that the number of apoptotic cells (3.9 ± 1.8 cells / × 400 field) and the apoptosis index (4.4 % ± 1.5) were significantly lower in rectal TH cooling group (P < 0.05) than in ischemia and hypoxia group (23.2 ± 12.1 cells / × 400 field, 26.6 % ± 12.1). Also, no rectal frostbite or inflammatory infiltration was observed in rats in the rectal TH treatment groups.

CONCLUSION

Our new cooling device realized rapid TH induction in SD rats with ischemic-hypoxic brain damage, inhibited the apoptosis of cells in the hippocampal CAl region, and did not cause histological damage to the rectal tissues.

Emergency Neurological Life Support: Resuscitation Following Cardiac Arrest

Cardiac arrest is the most common cause of death in North America. Neurocritical care interventions, including targeted temperature management (TTM), have significantly improved neurological outcomes in patients successfully resuscitated from cardiac arrest. Therefore, resuscitation following cardiac arrest was chosen as an emergency neurological life support protocol. Patients remaining comatose following resuscitation from cardiac arrest should be considered for TTM. This protocol will review induction, maintenance, and re-warming phases of TTM, along with management of TTM side effects. Aggressive shivering suppression is necessary with this treatment to ensure the maintenance of a target temperature. Ancillary testing, including electrocardiography, computed tomography and/or magnetic resonance imaging of the brain, continuous electroencephalography monitoring, and correction of electrolyte, blood gas, and hematocrit changes, are also necessary to optimize outcomes.

Controversies in the temperature management of critically ill patients

Although body temperature is a classic primary vital sign, its value has received little attention compared with the others (blood pressure, heart rate, and respiratory rate). This may result from the fact that unlike the other primary vital signs, aging and diseases rarely affect the thermoregulatory system. Despite this, when humans are exposed to various anesthetics and analgesics and acute etiologies of non-infectious and infectious diseases in perioperative and intensive care settings, abnormalities may occur that shift body temperature up and down. A recent upsurge in clinical evidence in the perioperative and critical care field resulted in many clinical trials in temperature management. The results of these clinical trials suggest that aggressive body temperature modifications in comatose survivors after resuscitation from shockable rhythm, and permissive fever in critically ill patients, are carried out in critical care settings to improve patient outcomes; however, its efficacy remains to be elucidated. A recent, large multicenter randomized controlled trial demonstrated contradictory results, which may disrupt the trends in clinical practice. Thus, updated information concerning thermoregulatory interventions is essential for anesthesiologists and intensivists. Here, recent controversies in therapeutic hypothermia and fever management are summarized, and their relevance to the physiology of human thermoregulation is discussed.

Use of Targeted Temperature Management After Out-of-hospital Cardiac Arrest: A Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Individual randomized trials have yielded variable results regarding the benefits of targeted temperature management in patients encountering out-of-hospital cardiac arrest. This study aimed to systemically determine if targeted temperature management initiated after an out-of-hospital cardiac arrest was associated with improved outcomes.

METHODS

Electronic databases were searched for published randomized trials that compared targeted temperature management (core body temperature 32-34°C) vs control (core body temperature ≥36°C) after an out-of-hospital cardiac arrest. The main outcomes assessed were all-cause mortality and poor neurological outcome.

RESULTS

Six trials with 1391 patients were included in the analysis. Compared with the control group, targeted temperature management was associated with a nonsignificant reduction in all-cause mortality (relative risk [RR] 0.90; 95% confidence interval [CI], 0.77-1.04; P = .15, I(2) = 34%), which was similar among those with a shockable rhythm (RR 0.89; 95% CI, 0.74-1.08, P = .25, I(2) = 46%). All-cause mortality was significantly reduced with targeted temperature management after exclusion of one trial that allowed for mild hypothermia in the control arm (RR 0.83; 95% CI, 0.71-0.96; P = .01, I(2) = 0%). There was a nonsignificant reduction in poor neurological outcome with targeted temperature management compared with control (RR 0.87; 95% CI, 0.74-1.03, P = .10, I(2) = 54%), which was similar among those with a shockable rhythm (RR 0.87; 95% CI, 0.70-1.07, P = .19, I(2) = 63%). Poor neurological outcome was significantly reduced with targeted temperature management after exclusion of one trial that allowed for mild hypothermia in the control arm (RR 0.82; 95% CI, 0.70-0.95; P = .01, I(2) = 19%).

CONCLUSION

Targeted temperature management initiated after successful resuscitation in patients who encountered an out-of-hospital cardiac arrest was associated with a nonsignificant reduction in mortality and poor neurological outcome. Lack of benefit was strongly influenced by inclusion of one study that used mild hypothermia in the control arm. These results indicate that only mild hypothermia may be needed to improve outcomes among patients presenting with an out-of-hospital cardiac arrest.