Regional cerebral oxygen saturation in cardiac arrest survivors undergoing targeted temperature management 36℃ versus 33℃: A randomized clinical trial

Predictive Performance of Neuron-Specific Enolase (NSE) for Survival after Resuscitation from Cardiac Arrest: A Systematic Review and Meta-Analysis

The prediction of outcomes following cardiac arrest continues to provide significant difficulties. A preferred strategy involves adopting a multimodal approach, which encompasses the careful evaluation of the biomarker neuron-specific enolase (NSE). This systematic review and meta-analysis aimed to gather and summarize new and existing evidence on the prediction effect of neuron-specific enolase for survival to hospital discharge among adult patients with cardiac arrest. We searched PubMed Central, Scopus, EMBASE databases, and the Cochrane Library without language restrictions from their inceptions until 30 October 2023 and checked the reference lists of the included studies. Pooled results were reported as standardized mean differences (SMDs) and were presented with corresponding 95% confidence intervals (CIs). The primary outcome was survival to hospital discharge (SHD). Eighty-six articles with 10,845 participants were included. NSE showed a notable degree of specificity in its ability to predict mortality as well as neurological status among individuals who experienced cardiac arrest (p < 0.05). This study demonstrates the ability to predict fatality rates and neurological outcomes, both during the time of admission and at various time intervals after cardiac arrest. The use of NSE in a multimodal neuroprognostication algorithm has promise in improving the accuracy of prognoses for persons who have undergone cardiac arrest.

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.

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.

Effect of cooling methods and target temperature on outcomes in comatose patients resuscitated from cardiac arrest: Systematic review and network meta-analysis of randomized trials

BACKGROUND

Targeted temperature management (TTM) has been recommended after cardiac arrest (CA), however the specific temperature targets and cooling methods (intravascular cooling (IVC) versus surface cooling (SC)) remain uncertain.

METHODS

PUBMED and EMBASE were searched until October 8, 2022 for randomized clinical trials (RCTs) investigating the efficacy of TTM after CA. The randomized treatment arms were categorized into the following 6 groups: 31..C to 33..C IVC, 31..C to 33..C SC, 34..C to 36..C IVC, 34..C to 36..C SC, strict normothermia or fever prevention (Strict NT or FP), and standard of care without TTM (No-TTM). The primary outcome was neurological recovery. P-score was used to rank the treatments, where a larger value indicates better performance.

RESULTS

We identified 15 RCTs, involving 5,218 patients with CA. Compared to No-TTM as the reference, the other therapeutic options significantly improved neurological outcomes (vs No-TTM; 31..C to 33..

C IVC

RR = 0.67, 95% CI 0.54 to 0.83; 31..C to 33..C SC RR = 0.73, 95% CI 0.61 to 0.87; 34..C to 36..

C IVC

RR = 0.66, 95% CI 0.51 to 0.86; 34..C to 36..C SC: RR = 0.73, 0.59 to 0.90; Strict NT or FP: RR = 0.75, 95% CI 0.62 to 0.90). Overall, 31-33..C IVC had the highest probability to be the best therapeutic option to improve outcomes (the ranking P-score of 0.836). As a subgroup analysis, the ranking P-score showed that IVC might be a better cooling method compared to SC (IVC vs SC P-score: 0.960 vs 0.670).

CONCLUSIONS

Hypothermia (31..C to 36..C IVC and SC) and active normothermia (Strict-NT and Strict-FP) were associated with better neurological outcomes compared to No-TTM, with IVC having a greater probability of being the better cooling method than SC.