Brain injury after cardiac arrest

Identification of predictors for neurological outcome after cardiac arrest in peripheral blood mononuclear cells through integrated bioinformatics analysis and machine learning

Neurological prognostication after cardiac arrest (CA) is important to avoid pursuing futile treatments for poor outcome and inappropriate withdrawal of life-sustaining treatment for good outcome. To predict neurological outcome after CA through biomarkers in peripheral blood mononuclear cells, four datasets were downloaded from the Gene Expression Omnibus database. GSE29546 and GSE74198 were used as training datasets, while GSE92696 and GSE34643 were used as verification datasets. The intersection of differentially expressed genes and hub genes from multiscale embedded gene co-expression network analysis (MEGENA) was utilized in the machine learning screening. Key genes were identified using support vector machine recursive feature elimination (SVM-RFE), least absolute shrinkage and selection operator (LASSO) logistic regression, and random forests (RF). The results were validated using receiver operating characteristic curve analysis. An mRNA-miRNA network was constructed. The distribution of immune cells was evaluated using cell-type identification by estimating relative subsets of RNA transcripts (CIBERSORT). Five biomarkers were identified as predictors for neurological outcome after CA, with an area under the curve (AUC) greater than 0.7: CASP8 and FADD-like apoptosis regulator (CFLAR), human protein kinase X (PRKX), miR-483-5p, let-7a-5p, and let-7c-5p. Interestingly, the combination of CFLAR minus PRKX showed an even higher AUC of 0.814. The mRNA-miRNA network consisted of 30 nodes and 76 edges. Statistical differences were found in immune cell distribution, including neutrophils, NK cells active, NK cells resting, T cells CD4 memory activated, T cells CD4 memory resting, T cells CD8, B cells memory, and mast cells resting between individuals with good and poor neurological outcome after CA. In conclusion, our study identified novel predictors for neurological outcome after CA. Further clinical and laboratory studies are needed to validate our findings.

Refractory out-of-hospital cardiac arrest and extracorporeal cardiopulmonary resuscitation: A meta-analysis of randomized trials

BACKGROUND

In adults with refractory out-of-hospital cardiac arrest, when conventional cardiopulmonary resuscitation (CPR) alone does not achieve return of spontaneous circulation, extracorporeal CPR is attempted to restore perfusion and improve outcomes. Considering the contrasting findings of recent studies, we conducted a meta-analysis of randomized controlled trials to ascertain the effect of extracorporeal CPR on survival and neurological outcome.

METHODS

Pubmed via MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials were searched up to February 3, 2023, for randomized controlled trials comparing extracorporeal CPR versus conventional CPR in adults with refractory out-of-hospital cardiac arrest. Survival with a favorable neurological outcome at the longest follow-up available was the primary outcome.

RESULTS

Among four randomized controlled trials included, extracorporeal CPR compared with conventional CPR increased survival with favorable neurological outcome at the longest follow-up available for all rhythms (59/220 [27%] vs. 39/213 [18%]; OR = 1.72; 95% CI, 1.09-2.70; p = 0.02; I²  = 26%; number needed to treat of 9), for initial shockable rhythms only (55/164 [34%] vs. 38/165 [23%]; OR = 1.90; 95% CI, 1.16-3.13; p = 0.01; I²  = 23%; number needed to treat of 7), and at hospital discharge or 30 days (55/220 [25%] vs. 34/212 [16%]; OR = 1.82; 95% CI, 1.13-2.92; p = 0.01; I²  = 0.0%). Overall survival at the longest follow-up available was similar (61/220 [25%] vs. 34/212 [16%]; OR = 1.82; 95% CI, 1.13-2.92; p = 0.59; I²  = 58%).

CONCLUSIONS

Extracorporeal CPR compared with conventional CPR increased survival with favorable neurological outcome in adults with refractory out-of-hospital cardiac arrest, especially when the initial rhythm was shockable.

REVIEW REGISTRATION

PROSPERO CRD42023396482.

The Effect of Early Application of Synthetic Peptides 19-2.5 and 19-4LF to Improve Survival and Neurological Outcome in a Mouse Model of Cardiac Arrest and Resuscitation

The synthetic antimicrobial peptides (sAMPs) Pep19-2.5 and Pep19-4LF have been shown in vitro and in vivo to reduce the release of pro-inflammatory cytokines, leading to the suppression of inflammation and immunomodulation. We hypothesized that intervention with Pep19-2.5 and Pep19-4LF immediately after cardiac arrest and resuscitation (CA-CPR) might attenuate immediate systemic inflammation, survival, and long-term outcomes in a standardized mouse model of CA-CPR. Long-term outcomes up to 28 days were assessed between a control group (saline) and two peptide intervention groups. Primarily, survival as well as neurological and cognitive parameters were assessed. In addition, systemic inflammatory molecules and specific biomarkers were analyzed in plasma as well as in brain tissue. Treatment with sAMPs did not provide any short- or long-term benefits for either survival or neurological outcomes, and no significant benefit on inflammation in the CA-CPR animal model. While no difference was found in the plasma analysis of early cytokines between the intervention groups four hours after resuscitation, a significant increase in UCH-L1, a biomarker of neuronal damage and blood–brain barrier rupture, was measured in the Pep19-4LF-treated group. The theoretical benefit of both sAMPs tested here for the treatment of post-cardiac arrest syndrome could not be proven.

Improving vasopressor use in cardiac arrest

The Chain of Survival highlights the effectiveness of early recognition of cardiac arrest and call for help, early cardiopulmonary resuscitation and early defibrillation. Most patients, however, remain in cardiac arrest despite these interventions. Drug treatments, particularly the use of vasopressors, have been included in resuscitation algorithms since their inception. This narrative review describes the current evidence base for vasopressors and reports that adrenaline (1 mg) is highly effective at achieving return of spontaneous circulation (number needed to treat 4) but is less effective on long-term outcomes (survival to 30 days, number needed to treat 111) with uncertain effects on survival with a favourable neurological outcome. Randomised trials evaluating vasopressin, either as an alternative to or in addition to adrenaline, and high-dose adrenaline have failed to find evidence of improved long-term outcomes. There is a need for future trials to evaluate the interaction between steroids and vasopressin. Evidence for other vasopressors (e.g. noradrenaline, phenylephedrine) is insufficient to support or refute their use. The use of intravenous calcium chloride as a routine intervention in out of hospital cardiac arrest is not associated with benefit and may cause harm. The optimal route for vascular access between peripheral intravenous versus intraosseous routes is currently the subject of two large randomised trials. Intracardiac, endobronchial, and intramuscular routes are not recommended. Central venous administration should be limited to patients where an existing central venous catheter is in situ and patent.

BAICALEIN RELIEVES BRAIN INJURY VIA INHIBITING FERROPTOSIS AND ENDOPLASMIC RETICULUM STRESS IN A RAT MODEL OF CARDIAC ARREST

ABSTRACT

Background: Cardiac arrest (CA) is one of the leading causes of death worldwide. Endoplasmic reticulum (ER) stress and ferroptosis are proven pathological mechanisms implicated in neuronal damage. Baicalein, a ferroptosis Inhibitor, improved outcomes after traumatic brain injury. We aimed to explore the effects of baicalein on brain injury via ferroptosis and ER stress in a rat model of CA.Methods: Cardiac arrest models were established in Sprague-Dawley (SD) rats. The sham group (n = 6) was untreated with inducing ventricular fibrillation to cardiac arrest and cardiopulmonary resuscitation (CPR). Survival rats were randomly divided into five groups (n = 6). Ferroptosis inhibitor and ER stress agonist were administered separately and together in three groups. There was no drug intervention in the remaining group. The neurological deficit scores were recorded. Characteristics of ferroptosis were observed. And the associated protein of ferroptosis and ER stress were determined by Western blot. Cerebral ROS production was measured by using 2',7'-dichlorofluorescein diacetate as the oxidative fluorescent probe. Results: Baicalein treatment improved neurological outcomes and decreased neurocyte injuries compared with CPR group. The changes of ferroptosis, more specifically, iron content, glutathione peroxidase 4 (GPX4), reactive oxygen species (ROS), arachidonate 15-lipoxygenase (ALOX15) and mitochondrial characteristics, were observed in brain tissue after ROSC. ALOX15 was lower in baicalein group than in CPR group. The morphology and structure of mitochondria in baicalein group were better than in CPR group. The ER stress markers, glucose-regulated protein 78, activating Transcription Factor 4 and C/EBP homologous protein was lower in baicalein group compared with CPR group. ROS in tunicamycin group was higher than in CPR group. And ROS in baicalein +tunicamycin group was lower than in tunicamycin group. Conclusion: Ferroptosis and ER stress are both involved in brain injury after ROSC. Baicalein alleviates brain injury via suppressing the ferroptosis and ER stress, and reduces ROS partly through inhibiting ER stress. Baicalein is a potential drug to relieve brain injury after ROSC.

Efficacy of acupuncture for cardiopulmonary cerebral resuscitation: A systematic review and meta-analysis

Background

Cerebral resuscitation is one of the main therapeutic aims in the treatment of cardiac arrest (CA) patients who experience a return of spontaneous circulation (ROSC). However, the therapeutic effects of current treatments are not ideal. The purpose of this study was to evaluate the efficacy of neurological function of acupuncture combined with conventional cardiopulmonary cerebral resuscitationthe (CPCR) for patients after ROSC.

Methods

Seven electronic databases and other related websites were searched to identify studies on acupuncture combined with conventional CPCR for patients after ROSC. R software was used to conduct a meta-analysis, and the outcomes that could not be pooled were analyzed using a descriptive analysis.

Results

Seven RCTs involving 411 participants who had experienced ROSC were eligible for inclusion. The main acupoints were Neiguan (PC6), Shuigou (DU26), Baihui (DU20), Yongquan (KI1), and Sanyinjiao (SP6). Compared to conventional CPCR, acupuncture combined with conventional CPCR led to significantly higher Glasgow Coma Scale (GCS) scores on day 3 (mean difference (MD)=0.89, 95% CI: 0.43, 1.35, I² = 0%), day 5 (MD = 1.21, 95% CI: 0.27, 2.15; I² = 0%), and day 7 (MD = 1.92, 95% CI: 1.35, 2.50; I² = 0%).

Conclusion

Acupuncture-assisted conventional CPCR may have a potential role in improving neurological function in CA patients after ROSC, but the certainty of evidence is very low and more high-quality studies are required.

Protocol registration

This review was registered at the International Prospective Registry of Systematic Reviews (PROSPERO): CRD42021262262.

A Nanotherapy of Octanoic Acid Ameliorates Cardiac Arrest/Cardiopulmonary Resuscitation-Induced Brain Injury via RVG29- and Neutrophil Membrane-Mediated Injury Relay Targeting

Treatment of cardiac arrest/cardiopulmonary resuscitation (CA/CPR)-induced brain injury remains a challenging issue without viable therapeutic options. Octanoic acid (OA), a lipid oil that is mainly metabolized in the astrocytes of the brain, is a promising treatment for this type of injury owing to its potential functions against oxidative stress, apoptosis, inflammation, and ability to stabilize mitochondria. However, the application of OA is strictly limited by its short half-life and low available concentration in the target organ. Herein, based on our previous research, an OA-based nanotherapy coated with a neutrophil membrane highly expressing RVG29, RVG29-H-NP_OA, was successfully constructed by computer simulation-guided supramolecular assembly of polyethylenimine and OA. The in vitro and in vivo experiments showed that RVG29-H-NP_OA could target and be distributed in the injured brain focus via the relay-targeted delivery mediated by RVG29-induced blood-brain barrier (BBB) penetration and neutrophil membrane protein-induced BBB binding and injury targeting. This results in enhancements of the antioxidant, antiapoptotic, mitochondrial stability-promoting and anti-inflammatory effects of OA and exhibited systematic alleviation of astrocyte injury, neuronal damage, and inflammatory response in the brain. Due to their systematic intervention in multiple pathological processes, RVG29-H-NP_OA significantly increased the 24 h survival rate of CA/CPR model rats from 40% to 100% and significantly improved their neurological functions. Thus, RVG29-H-NP_OA are expected to be a promising therapeutic for the treatment of CA/CPR-induced brain injury.

Bio-physiological susceptibility of the brain, heart, and lungs to systemic ischemia reperfusion and hyperoxia-induced injury in post-cardiac arrest rats

Cardiac arrest (CA) patients suffer from systemic ischemia-reperfusion (IR) injury leading to multiple organ failure; however, few studies have focused on tissue-specific pathophysiological responses to IR-induced oxidative stress. Herein, we investigated biological and physiological parameters of the brain and heart, and we particularly focused on the lung dysfunction that has not been well studied to date. We aimed to understand tissue-specific susceptibility to oxidative stress and tested how oxygen concentrations in the post-resuscitation setting would affect outcomes. Rats were resuscitated from 10 min of asphyxia CA. Mechanical ventilation was initiated at the beginning of cardiopulmonary resuscitation. We examined animals with or without CA, and those were further divided into the animals exposed to 100% oxygen (CA_Hypero) or those with 30% oxygen (CA_Normo) for 2 h after resuscitation. Biological and physiological parameters of the brain, heart, and lungs were assessed. The brain and lung functions were decreased after CA and resuscitation indicated by worse modified neurological score as compared to baseline (222 ± 33 vs. 500 ± 0, P < 0.05), and decreased PaO2 (20 min after resuscitation: 113 ± 9 vs. baseline: 128 ± 9 mmHg, P < 0.05) and increased airway pressure (2 h: 10.3 ± 0.3 vs. baseline: 8.1 ± 0.2 mmHg, P < 0.001), whereas the heart function measured by echocardiography did not show significant differences compared before and after CA (ejection fraction, 24 h: 77.9 ± 3.3% vs. baseline: 82.2 ± 1.9%, P = 0.2886; fractional shortening, 24 h: 42.9 ± 3.1% vs. baseline: 45.7 ± 1.9%, P = 0.4658). Likewise, increases of superoxide production in the brain and lungs were remarkable, while those in the heart were moderate. mRNA gene expression analysis revealed that CA_Hypero group had increases in Il1b as compared to CA_Normo group significantly in the brain (P < 0.01) and lungs (P < 0.001) but not the heart (P = 0.4848). Similarly, hyperoxia-induced increases in other inflammatory and apoptotic mRNA gene expression were observed in the brain, whereas no differences were found in the heart. Upon systemic IR injury initiated by asphyxia CA, hyperoxia-induced injury exacerbated inflammation/apoptosis signals in the brain and lungs but might not affect the heart. Hyperoxia following asphyxia CA is more damaging to the brain and lungs but not the heart.

A randomized, double-blind trial comparing the effect of two blood pressure targets on global brain metabolism after out-of-hospital cardiac arrest

PURPOSE

This study aimed to assess the effect of different blood pressure levels on global cerebral metabolism in comatose patients resuscitated from out-of-hospital cardiac arrest (OHCA).

METHODS

In a double-blinded trial, we randomly assigned 60 comatose patients following OHCA to low (63 mmHg) or high (77 mmHg) mean arterial blood pressure (MAP). The trial was a sub-study in the Blood Pressure and Oxygenation Targets after Out-of-Hospital Cardiac Arrest-trial (BOX). Global cerebral metabolism utilizing jugular bulb microdialysis (JBM) and cerebral oxygenation (rSO₂) was monitored continuously for 96 h. The lactate-to-pyruvate (LP) ratio is a marker of cellular redox status and increases during deficient oxygen delivery (ischemia, hypoxia) and mitochondrial dysfunction. The primary outcome was to compare time-averaged means of cerebral energy metabolites between MAP groups during post-resuscitation care. Secondary outcomes included metabolic patterns of cerebral ischemia, rSO₂, plasma neuron-specific enolase level at 48 h and neurological outcome at hospital discharge (cerebral performance category).

RESULTS

We found a clear separation in MAP between the groups (15 mmHg, p < 0.001). Cerebral biochemical variables were not significantly different between MAP groups (LPR low MAP 19 (16-31) vs. high MAP 23 (16-33), p = 0.64). However, the LP ratio remained high (> 16) in both groups during the first 30 h. During the first 24 h, cerebral lactate > 2.5 mM, pyruvate levels > 110 µM, LP ratio > 30, and glycerol > 260 µM were highly predictive for poor neurological outcome and death with AUC 0.80. The median (IQR) rSO₂ during the first 48 h was 69.5% (62.0-75.0%) in the low MAP group and 69.0% (61.3-75.5%) in the high MAP group, p = 0.16.

CONCLUSIONS

Among comatose patients resuscitated from OHCA, targeting a higher MAP 180 min after ROSC did not significantly improve cerebral energy metabolism within 96 h of post-resuscitation care. Patients with a poor clinical outcome exhibited significantly worse biochemical patterns, probably illustrating that insufficient tissue oxygenation and recirculation during the initial hours after ROSC were essential factors determining neurological outcome.

Very early environmental enrichment protects against apoptosis and improves functional recovery from hypoxic-ischemic brain injury

Appropriate rehabilitation of stroke patients at a very early phase results in favorable outcomes. However, the optimal strategy for very early rehabilitation is at present unclear due to the limited knowledge on the effects of very early initiation of rehabilitation based on voluntary exercise (VE). Environmental enrichment (EE) is a therapeutic paradigm for laboratory animals that involves complex combinations of physical, cognitive, and social stimuli, as well as VE. Few studies delineated the effect of EE on apoptosis in very early stroke in an experimental model. Although a minimal benefit of early rehabilitation in stroke models has been claimed in previous studies, these were based on a forced exercise paradigm. The aim of this study is to determine whether very early exposure to EE can effectively regulate Fas/FasL-mediated apoptosis following hypoxic-ischemic (HI) brain injury and improve neurobehavioral function. C57Bl/6 mice were housed for 2 weeks in either cages with EE or standard cages (SC) 3 h or 72 h after HI brain injury. Very early exposure to EE was associated with greater improvement in motor function and cognitive ability, reduced volume of the infarcted area, decreased mitochondria-mediated apoptosis, and decreased oxidative stress. Very early exposure to EE significantly downregulated Fas/FasL-mediated apoptosis, decreased expression of Fas, Fas-associated death domain, cleaved caspase-8/caspase-8, cleaved caspase-3/caspase-3, as well as Bax and Bcl-2, in the cerebral cortex and the hippocampus. Delayed exposure to EE, on the other hand, failed to inhibit the extrinsic pathway of apoptosis. This study demonstrates that very early exposure to EE is a potentially useful therapeutic translation for stroke rehabilitation through effective inhibition of the extrinsic and intrinsic apoptotic pathways.

Auditory stimulation and deep learning predict awakening from coma after cardiac arrest

Assessing the integrity of neural functions in coma after cardiac arrest remains an open challenge. Prognostication of coma outcome relies mainly on visual expert scoring of physiological signals, which is prone to subjectivity and leaves a considerable number of patients in a 'grey zone', with uncertain prognosis. Quantitative analysis of EEG responses to auditory stimuli can provide a window into neural functions in coma and information about patients' chances of awakening. However, responses to standardized auditory stimulation are far from being used in a clinical routine due to heterogeneous and cumbersome protocols. Here, we hypothesize that convolutional neural networks can assist in extracting interpretable patterns of EEG responses to auditory stimuli during the first day of coma that are predictive of patients' chances of awakening and survival at 3 months. We used convolutional neural networks (CNNs) to model single-trial EEG responses to auditory stimuli in the first day of coma, under standardized sedation and targeted temperature management, in a multicentre and multiprotocol patient cohort and predict outcome at 3 months. The use of CNNs resulted in a positive predictive power for predicting awakening of 0.83 ± 0.04 and 0.81 ± 0.06 and an area under the curve in predicting outcome of 0.69 ± 0.05 and 0.70 ± 0.05, for patients undergoing therapeutic hypothermia and normothermia, respectively. These results also persisted in a subset of patients that were in a clinical 'grey zone'. The network's confidence in predicting outcome was based on interpretable features: it strongly correlated to the neural synchrony and complexity of EEG responses and was modulated by independent clinical evaluations, such as the EEG reactivity, background burst-suppression or motor responses. Our results highlight the strong potential of interpretable deep learning algorithms in combination with auditory stimulation to improve prognostication of coma outcome.

Mechanical ventilation during cardiopulmonary resuscitation: influence of positive end-expiratory pressure and head-torso elevation

BACKGROUND

Efficient ventilation is important during cardiopulmonary resuscitation (CPR). Nevertheless, there is insufficient knowledge on how the patient's position affects ventilatory parameters during mechanically assisted CPR. We studied ventilatory parameters at different positive end-expiratory pressure (PEEP) levels and when using an inspiratory impedance valve (ITD) during horizontal and head-up CPR (HUP-CPR).

METHODS

In this human cadaver experimental study, we measured tidal volume (V_T) and pressure during CPR at different randomized PEEP levels (0, 5 or 10 cmH₂O) or with an ITD. CPR was performed, in the following order: horizontal (FLAT), at 18° and then at 35° head-thorax elevation. During the inspiratory phase we measured the net tidal volume (V_T) adjusted to predicted body weight (V_TPBW), reversed airflow (RAF), and maximum and minimum airway pressure (P_max and P_min).

RESULTS

Using ten thawed fresh-frozen cadavers we analyzed the inspiratory phase of 1843 respiratory cycles, 229 without CPR and 1614 with CPR. In a mixed linear model, thoracic position and PEEP significantly impacted V_TPBW (p < 0.001 for each), and the insufflation time, thoracic position and PEEP significantly affected the RAF (p < 0.001 for each) and P_max (p < 0.001). For P_min, only PEEP was significant (p < 0.001). In subgroup analysis, at 35° V_TPBW and P_max were significantly reduced compared with the flat or 18° position.

CONCLUSION

When using mechanical ventilation during CPR, it seems that the PEEP level and patient position are important determinants of respiratory parameters. Moreover, tidal volume seems to be lower when the thorax is positioned at 35°.

Targeted Temperature Management After Out-of-Hospital Cardiac Arrest: Integrating Evidence Into Real World Practice

Targeted temperature management (TTM) after out-of-hospital cardiac arrest (OHCA) has been a focus of debate in an attempt to improve post-arrest outcomes. Contemporary trials examining the role of TTM after cardiac arrest suggest that targeting normothermia should be the standard of care for initially comatose survivors of cardiac arrest. Differences in patient populations have been demonstrated across trials, and important subgroups may be under-represented in clinical trials compared with real-world registries. In this review, we aimed to describe the populations represented in international OHCA registries and to propose a pathway to integrate clinical trial evidence into practice. The patient case mix among registries including survivors to hospital admission was similar to the pivotal trials (shockable rhythm, witnessed arrest), suggesting reasonable external validity. Therefore, for the majority of OHCA, targeted normothermia should be the strategy of choice. There remains conflicting evidence for patients with a nonshockable rhythm, with no clear evidence-based justification for mild hypothermia over targeted normothermia.

Outcomes of Patients With in- and out-of-hospital Cardiac Arrest on Extracorporeal Cardiopulmonary Resuscitation: A Single-center Retrospective Cohort Study

Extracorporeal membrane oxygenation (ECMO) support has been suggested to improve the survival rate in patients with refractory in- and out-of-hospital cardiac arrest (IHCA and OHCA). Several factors predict outcome in these patients, including initial heart rhythm and low-flow time. Literature shows variable survival rates among patients who received extracorporeal cardiopulmonary resuscitation (EPCR). The objective of this study is to analyze the outcomes (survival rate as well as neurological and disability outcomes) of patients treated with ECPR following refractory OHCA and IHCA. This single-center, retrospective cohort study was conducted on patients with refractory cardiac arrest treated with ECPR between February 2016 and March 2020. The primary outcomes were 24-hour, hospital discharge and 1-year survival after CA and the secondary endpoints were neurological and disability outcomes. Forty-eight patients were included in the analysis. 11/48 patients are In Hospital Cardiac Arrest (IHCA) and 37/48 patients are Out of Hospital Cardiac Arrest (OHCA). Time from collapse to CPR for 79.2% of the patients was less than 5 minutes. The median CPR duration and collapse to ECMO were 40 and 45 minutes, respectively. The rate of survival was significantly higher in patient who presented with initial shockable rhythm (P = 0.006) and to whom targeted temperature management (TTM) post cardiac arrest was applied (P = 0.048). This first descriptive study about ECPR in the middle east region shows that 20.8% of ECPR patients survived until hospital discharge. Our analysis revealed that initial shockable rhythm and TTM are most important prognostic factors that predicts favorable neurological survival.

Post-Cardiac Arrest: Mechanisms, Management, and Future Perspectives

Cardiac arrest is an important public health issue, with a survival rate of approximately 15 to 22%. A great proportion of these deaths occur after resuscitation due to post-cardiac arrest syndrome, which is characterized by the ischemia-reperfusion injury that affects the role body. Understanding physiopathology is mandatory to discover new treatment strategies and obtain better results. Besides improvements in cardiopulmonary resuscitation maneuvers, the great increase in survival rates observed in recent decades is due to new approaches to post-cardiac arrest care. In this review, we will discuss physiopathology, etiologies, and post-resuscitation care, emphasizing targeted temperature management, early coronary angiography, and rehabilitation.

Prognostication after cardiac arrest: how EEG and evoked potentials may improve the challenge

About 80% of patients resuscitated from CA are comatose at ICU admission and nearly 50% of survivors are still unawake at 72 h. Predicting neurological outcome of these patients is important to provide correct information to patient's relatives, avoid disproportionate care in patients with irreversible hypoxic-ischemic brain injury (HIBI) and inappropriate withdrawal of care in patients with a possible favorable neurological recovery. ERC/ESICM 2021 algorithm allows a classification as "poor outcome likely" in 32%, the outcome remaining "indeterminate" in 68%. The crucial question is to know how we could improve the assessment of both unfavorable but also favorable outcome prediction. Neurophysiological tests, i.e., electroencephalography (EEG) and evoked-potentials (EPs) are a non-invasive bedside investigations. The EEG is the record of brain electrical fields, characterized by a high temporal resolution but a low spatial resolution. EEG is largely available, and represented the most widely tool use in recent survey examining current neuro-prognostication practices. The severity of HIBI is correlated with the predominant frequency and background continuity of EEG leading to "highly malignant" patterns as suppression or burst suppression in the most severe HIBI. EPs differ from EEG signals as they are stimulus induced and represent the summated activities of large populations of neurons firing in synchrony, requiring the average of numerous stimulations. Different EPs (i.e., somato sensory EPs (SSEPs), brainstem auditory EPs (BAEPs), middle latency auditory EPs (MLAEPs) and long latency event-related potentials (ERPs) with mismatch negativity (MMN) and P300 responses) can be assessed in ICU, with different brain generators and prognostic values. In the present review, we summarize EEG and EPs signal generators, recording modalities, interpretation and prognostic values of these different neurophysiological tools. Finally, we assess the perspective for futures neurophysiological investigations, aiming to reduce prognostic uncertainty in comatose and disorders of consciousness (DoC) patients after CA.

Association Between Quantitative Diffusion-Weighted Magnetic Resonance Neuroimaging and Outcome After Pediatric Cardiac Arrest

BACKGROUND AND OBJECTIVES

Diffusion MRI can quantify the extent of hypoxic-ischemic brain injury after cardiac arrest. Our objective was to determine the association between the adult-derived threshold of apparent diffusion coefficient (ADC) <650 × 10-6 mm2/s in >10% of brain tissue and an unfavorable outcome after pediatric cardiac arrest. Since ADC decreases exponentially as a function of increasing age, we determined the association between (1) having >10% of brain tissue below a novel age-dependent ADC threshold, and (2) age-normalized whole-brain mean ADC and unfavorable outcome.

METHODS

This was a retrospective study of patients aged ≤18 years who had cardiac arrest and a clinically obtained brain MRI within 7 days. The primary outcome was unfavorable neurologic status at hospital discharge based on the Pediatric Cerebral Performance Category score. ADC images were extracted from 3-direction diffusion imaging. We determined whether each patient had >10% of voxels with an ADC below prespecified thresholds. We computed the whole-brain mean ADC for each patient.

RESULTS

One hundred thirty-four patients were analyzed. Patients with ADC <650 × 10-6 mm2/s in >10% of voxels had 15 times higher odds (95% CI 5-65) of an unfavorable outcome compared with patients with ADC <650 × 10-6 mm2/s (area under the receiver operating characteristic curve [AUROC] 0.72 [95% CI 0.63-0.80]). These ADC criteria had a sensitivity and specificity of 0.49 and 0.94, respectively, and positive and negative predictive values of 0.93 and 0.52, respectively, for an unfavorable outcome. The age-dependent ADC threshold that yielded optimal sensitivity and specificity for unfavorable outcomes was <300 × 10-6 mm2/s below each patient's predicted whole-brain mean ADC. The sensitivity, specificity, and positive and negative predictive values for this ADC threshold were 0.53, 0.96, 0.96, and 0.54, respectively (odds ratio [OR] 26.4 [95% CI 7.5-168.3]; AUROC 0.74 [95% CI 0.66-0.83]). Lower age-normalized whole-brain mean ADC was also associated with an unfavorable outcome (OR 0.42 [0.24-0.64], AUROC 0.76 [95% CI 0.66-0.82]).

DISCUSSION

Quantitative diffusion thresholds on MRI within 7 days after cardiac arrest were associated with an unfavorable outcome in children. The age-independent ADC threshold was highly specific for predicting an unfavorable outcome. However, the specificity and sensitivity increased when using age-dependent ADC thresholds. Age-dependent ADC thresholds may improve prognostic accuracy and require further investigation in larger cohorts.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that quantitative diffusion-weighted imaging within 7 days postarrest can predict an unfavorable clinical outcome in children.

Temperature control after cardiac arrest

Most of the patients who die after cardiac arrest do so because of hypoxic-ischemic brain injury (HIBI). Experimental evidence shows that temperature control targeted at hypothermia mitigates HIBI. In 2002, one randomized trial and one quasi-randomized trial showed that temperature control targeted at 32-34 °C improved neurological outcome and mortality in patients who are comatose after cardiac arrest. However, following the publication of these trials, other studies have questioned the neuroprotective effects of hypothermia. In 2021, the largest study conducted so far on temperature control (the TTM-2 trial) including 1900 adults comatose after resuscitation showed no effect of temperature control targeted at 33 °C compared with normothermia or fever control. A systematic review of 32 trials published between 2001 and 2021 concluded that temperature control with a target of 32-34 °C compared with fever prevention did not result in an improvement in survival (RR 1.08; 95% CI 0.89-1.30) or favorable functional outcome (RR 1.21; 95% CI 0.91-1.61) at 90-180 days after resuscitation. There was substantial heterogeneity across the trials, and the certainty of the evidence was low. Based on these results, the International Liaison Committee on Resuscitation currently recommends monitoring core temperature and actively preventing fever (37.7 °C) for at least 72 h in patients who are comatose after resuscitation from cardiac arrest. Future studies are needed to identify potential patient subgroups who may benefit from temperature control aimed at hypothermia. There are no trials comparing normothermia or fever control with no temperature control after cardiac arrest.

AA147 ameliorates post-cardiac arrest cerebral ischemia/reperfusion injury through the co-regulation of the ATF6 and Nrf2 signaling pathways

Ischemia/reperfusion caused by cardiac arrest (CA) disturbs endoplasmic reticulum (ER) homeostasis and redox balance in neurons. AA147, originally developed as a pharmacologic activator of the activating transcription factor 6 (ATF6), can protect multiple tissues from ischemia/reperfusion injury (IRI) by decreasing reactive oxygen species (ROS) and restoring ER function. However, it is unclear whether pharmacologic treatment of AA147 could ameliorate post-CA cerebral IRI and whether it is associated with proteostasis regulation and anti-oxidative stress mechanism. In the present study, mice were subjected to 9 min-CA surgery followed by cardiopulmonary resuscitation (CPR). AA147 or vehicle was administered 1 day before the operation and 15 min after the return of spontaneous circulation. We found that AA147 restored neurological function and reduced dead neurons in mice suffering from CA. Moreover, AA147 inhibited CA/CPR-caused neuronal apoptosis and ER stress, indicated by reduced TUNEL-positive neurons, surged expression of Bcl-2/Bax, and down expression of cleaved caspase-3, caspase-12, C/EBP homologous protein (CHOP). The expression of ATF6 and its regulated gene glucose-regulated protein 78 (GRP78) increased significantly after the administration of AA147, suggesting the activation of the ATF6 pathway. In addition, AA147 also alleviated the upsurge of the ROS generation and MDA levels as well as increased SOD activity, accompanied by enhancement of the nuclear factor E2-related factor 2 (Nrf2) and its modulated heme-oxygenase-1 (HO-1) expressions. Cotreatment of AA147 with inhibitors of the ATF6 or Nrf2 significantly suppressed AA147-dependent reductions in ROS scavenging and neuronal death after CA/CPR. The results suggested that AA147 could confer neuroprotection against post-CA cerebral IRI through inhibition of oxidative stress along with ER stress-associated apoptosis, which is attributed to the coregulation of both ATF6 and Nrf2 signaling pathways activity. Our findings support the potential for AA147 as a therapeutic approach to improve post-CA brain injury.

The 2022 Lady Estelle Wolfson lectureship on neurofilaments

Neurofilament proteins (Nf) have been validated and established as a reliable body fluid biomarker for neurodegenerative pathology. This review covers seven Nf isoforms, Nf light (NfL), two splicing variants of Nf medium (NfM), two splicing variants of Nf heavy (NfH), α -internexin (INA) and peripherin (PRPH). The genetic and epigenetic aspects of Nf are discussed as relevant for neurodegenerative diseases and oncology. The comprehensive list of mutations for all Nf isoforms covers Amyotrophic Lateral Sclerosis, Charcot-Marie Tooth disease, Spinal muscular atrophy, Parkinson Disease and Lewy Body Dementia. Next, emphasis is given to the expanding field of post-translational modifications (PTM) of the Nf amino acid residues. Protein structural aspects are reviewed alongside PTMs causing neurodegenerative pathology and human autoimmunity. Molecular visualisations of NF PTMs, assembly and stoichiometry make use of Alphafold2 modelling. The implications for Nf function on the cellular level and axonal transport are discussed. Neurofilament aggregate formation and proteolytic breakdown are reviewed as relevant for biomarker tests and disease. Likewise, Nf stoichiometry is reviewed with regard to in vitro experiments and as a compensatory mechanism in neurodegeneration. The review of Nf across a spectrum of 87 diseases from all parts of medicine is followed by a critical appraisal of 33 meta-analyses on Nf body fluid levels. The review concludes with considerations for clinical trial design and an outlook for future research.

Self-reported limitations in physical function are common 6 months after out-of-hospital cardiac arrest

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Limitations in physical function are common in cardiac arrest survivors.

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Age and gender are associated with limitations in physical function.

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Cognitive impairment is a predictive variable for physical limitations.

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Anxiety and depression symptoms are associated with physical limitations.

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Physical function should be addressed at follow-up after cardiac arrest.

Title

Self-reported limitations in physical function are common 6 months after out-of-hospital cardiac arrest.

Background

Out-of-hospital cardiac arrest (OHCA) survivors generally report good health-related quality of life, but physical aspects of health seem more affected than other domains. Limitations in physical function after surviving OHCA have received little attention.

Aims

To describe physical function 6 months after OHCA and compare it with a group of ST elevation myocardial infarction (STEMI) controls, matched for country, age, sex and time of the cardiac event. A second aim was to explore variables potentially associated with self-reported limitations in physical function in OHCA survivors.

Methods

A cross-sectional sub-study of the Targeted Temperature Management at 33 °C versus 36 °C (TTM) trial with a follow-up 6 months post-event. Physical function was the main outcome assessed with the self-reported Physical Functioning-10 items scale (PF-10). PF-10 is presented as T-scores (0–100), where 50 represents the norm mean. Scores <47 at a group level, or <45 at an individual level indicate limitations in physical function.

Results

287 OHCA survivors and 119 STEMI controls participated. Self-reported physical function by PF-10 was significantly lower for OHCA survivors compared to STEMI controls (mean 46.0, SD 11.2 vs. 48.8, SD 9.0, p = 0.025). 38% of OHCA survivors compared to 26% of STEMI controls reported limitations in physical function at an individual level (p = 0.022). The most predictive variables for self-reported limitations in physical function in OHCA survivors were older age, female sex, cognitive impairment, and symptoms of anxiety and depression after 6 months.

Conclusion

Self-reported limitations in physical function are more common in OHCA survivors compared to STEMI controls.

Trial registration

ClinicalTrials.gov Identifier: NCT01946932.

An international collaborative study to co-produce a patient-reported outcome measure of cardiac arrest survivorship and health-related quality of life (CASHQoL): A protocol for developing the long-form measure

Background

Current measures of health-related quality of life are neither sufficiently sensitive or specific to capture the complex and heterogenous nature of the recovery and survivorship associated with cardiac arrest. To address this critical practice gap, we plan a mixed-methods study to co-produce and evaluate a new cardiac arrest-specific patient/survivor-reported outcome measure (PROM).

Methods

International guidelines have informed a two-stage, iterative, and interactive process.

Stage one will establish what is important to measure following cardiac arrest. A meta-ethnography of published qualitative research and a qualitative exploration of the experiences of survivors and their key supporters will inform the development of a measurement framework. This will be supplemented by existing, extensive reviews describing concepts that have previously been measured in this population. Focus groups with survivors, key supporters, and healthcare professionals, followed by further interviews with survivors and key supporters, will inform the iterative refinement of the framework, candidate items, and PROM structure.

Stage two will involve a psychometric evaluation following completion by a large cohort of survivors. Measurement theory will inform: the identification of items that best measure important outcomes; item reduction; and provide robust evidence of measurement and practical properties.

Discussion

An international, collaborative approach to PROM development will engage survivors, key supporters, researchers, and health professionals from study commencement. Successful co-production of the cardiac arrest survivorship and health-related quality of life (CASHQoL) measure will provide a robust, relevant, and internationally applicable measure, suitable for completion by adult survivors, and integration into research, registries, and routine care settings.

Ethical approval: University of Warwick Biomedical & Scientific Research Ethics Committee (BSREC 22/20-21 granted 10/11/20).

Manganese Porphyrin Promotes Post Cardiac Arrest Recovery in Mice and Rats

Introduction Cardiac arrest (CA) and resuscitation induces global cerebral ischemia and reperfusion, causing neurologic deficits or death. Manganese porphyrins, superoxide dismutase mimics, are reportedly able to effectively reduce ischemic injury in brain, kidney, and other tissues. This study evaluates the efficacy of a third generation lipophilic Mn porphyrin, MnTnBuOE-2-PyP5+, Mn(III) ortho meso-tetrakis (N-n-butoxyethylpyridinium-2-yl)porphyrin (MnBuOE, BMX-001), in both mouse and rat models of CA. Methods Forty-eight animals were subjected to 8 min of CA and resuscitated subsequently by chest compression and epinephrine infusion. Vehicle or MnBuOE was given immediately after resuscitation followed by daily subcutaneous injections. Body weight, spontaneous activity, neurologic deficits, rotarod performance, and neuronal death were assessed. Kidney tubular injury was assessed in CA mice. Data were collected by the investigators who were blinded to the treatment groups. Results Vehicle mice had a mortality of 20%, which was reduced by 50% by MnBuOE. All CA mice had body weight loss, spontaneous activity decline, neurologic deficits, and decreased rotarod performance that were significantly improved at three days post MnBuOE daily treatment. MnBuOE treatment reduced cortical neuronal death and kidney tubular injury in mice (p < 0.05) but not hippocampus neuronal death (23% MnBuOE vs. 34% vehicle group, p = 0.49). In rats, they had a better body-weight recovery and increased rotarod latency after MnBuOE treatment when compared to vehicle group (p < 0.01 vs. vehicle). MnBuOE-treated rats had a low percentage of hippocampus neuronal death (39% MnBuOE vs. 49% vehicle group, p = 0.21) and less tubular injury (p < 0.05) relative to vehicle group. Conclusions We demonstrated the ability of MnBuOE to improve post-CA survival, as well as functional outcomes in both mice and rats, which jointly account for the improvement not only of brain function but also of the overall wellbeing of the animals. While MnBuOE bears therapeutic potential for treating CA patients, the females and the animals with comorbidities must be further evaluated before advancing toward clinical trials.

Targeted temperature management after out of hospital cardiac arrest: quo vadis?

Targeted temperature management (TTM) has become a cornerstone in the treatment of comatose post-cardiac arrest patients over the last two decades. Belief in the efficacy of this intervention for improving neurologically intact survival was based on two trials from 2002, one truly randomized-controlled and one small quasi-randomized trial, without clear confirmation of that finding. Subsequent large randomized trials reported no difference in outcomes between TTM at 33 vs. 36°C and no benefit of TTM at 33°C as compared with fever control alone. Given that these results may help shape post-cardiac arrest patient care, we sought to review the history and rationale as well as trial evidence for TTM, critically review the TTM2 trial, and highlight gaps in knowledge and research needs for the future. Finally, we provide contemporary guidance for the use of TTM in daily clinical practice.

Temperature control after cardiac arrest: friend or foe

PURPOSE OF REVIEW

Most patients who are successfully resuscitated after cardiac arrest are initially comatose and require mechanical ventilation and other organ support in an ICU. Best practice has been to cool these patients and control their temperature at a constant value in the range of 32-36 oC for at least 24 h. But the certainty of the evidence for this practice is increasingly being challenged. This review will summarize the evidence on key aspects of temperature control in comatose postcardiac arrest patients.

RECENT FINDINGS

The Targeted Temperature Management 2 (TTM-2) trial documented no difference in 6-month mortality among comatose postcardiac arrest patients managed at 33 oC vs. targeted normothermia. A systematic review and meta-analysis completed by the Advanced Life Support (ALS) Task Force of the International Liaison Committee on Resuscitation (ILCOR) concluded that temperature control with a target of 32-34 °C did not improve survival or favourable functional outcome after cardiac arrest. Two observational studies have documented an association between predicted moderate hypoxic-ischaemic brain injury and better outcome with temperature control at 33-34 oC compared with 35-36 oC.

SUMMARY

We suggest actively preventing fever by targeting a temperature 37.5 oC or less for those patients who remain comatose following return of spontaneous circulation (ROSC) after cardiac arrest.

Cardiac arrest centres: what, who, when, and where?

PURPOSE OF REVIEW

Cardiac arrest centres (CACs) may play a key role in providing postresuscitation care, thereby improving outcomes in out-of-hospital cardiac arrest (OHCA). There is no consensus on CAC definitions or the optimal CAC transport strategy despite advances in research. This review provides an updated overview of CACs, highlighting evidence gaps and future research directions.

RECENT FINDINGS

CAC definitions vary worldwide but often feature 24/7 percutaneous coronary intervention capability, targeted temperature management, neuroprognostication, intensive care, education, and research within a centralized, high-volume hospital. Significant evidence exists for benefits of CACs related to regionalization. A recent meta-analysis demonstrated clearly improved survival with favourable neurological outcome and survival among patients transported to CACs with conclusions robust to sensitivity analyses. However, scarce data exists regarding 'who', 'when', and 'where' for CAC transport strategies. Evidence for OHCA patients without ST elevation postresuscitation to be transported to CACs remains unclear. Preliminary evidence demonstrated greater benefit from CACs among patients with shockable rhythms. Randomized controlled trials should evaluate specific strategies, such as bypassing nearest hospitals and interhospital transfer.

SUMMARY

Real-world study designs evaluating CAC transport strategies are needed. OHCA patients with underlying culprit lesions, such as those with ST-elevation myocardial infarction (STEMI) or initial shockable rhythms, will likely benefit the most from CACs.

Protocol for an individual patient data meta-analysis on blood pressure targets after cardiac arrest

Background

Hypotension is common after cardiac arrest (CA), and current guidelines recommend using vasopressors to target mean arterial blood pressure (MAP) higher than 65 mmHg. Pilot trials have compared higher and lower MAP targets. We will review the evidence on whether higher MAP improves outcome after cardiac arrest.

Methods

This systematic review and meta‐analysis will be conducted based on a systematic search of relevant major medical databases from their inception onwards, including MEDLINE, Embase and the Cochrane Central Register of Controlled Trials (CENTRAL), as well as clinical trial registries.

We will identify randomised controlled trials published in the English language that compare targeting a MAP higher than 65–70 mmHg in CA patients using vasopressors, inotropes and intravenous fluids. The data extraction will be performed separately by two authors (a third author will be involved in case of disagreement), followed by a bias assessment with the Cochrane Risk of Bias tool using an eight‐step procedure for assessing if thresholds for clinical significance are crossed. The outcomes will be all‐cause mortality, functional long‐term outcomes and serious adverse events. We will contact the authors of the identified trials to request individual anonymised patient data to enable individual patient data meta‐analysis, aggregate data meta‐analyses, trial sequential analyses and multivariable regression, controlling for baseline characteristics. The certainty of the evidence will be assessed by the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system. We will register this systematic review with Prospero and aim to redo it when larger trials are published in the near future.

Conclusions

This protocol defines the performance of a systematic review on whether a higher MAP after cardiac arrest improves patient outcome. Repeating this systematic review including more data likely will allow for more certainty regarding the effect of the intervention and possible sub‐groups differences.

Vagus Nerve Stimulation Improves Mitochondrial Dysfunction in Post–cardiac Arrest Syndrome in the Asphyxial Cardiac Arrest Model in Rats

Cerebral mitochondrial dysfunction during post–cardiac arrest syndrome (PCAS) remains unclear, resulting in a lack of therapeutic options that protect against cerebral ischemia–reperfusion injury. We aimed to assess mitochondrial dysfunction in the hippocampus after cardiac arrest and whether vagus nerve stimulation (VNS) can improve mitochondrial dysfunction and neurological outcomes. In an asphyxial cardiac arrest model, male Sprague–Dawley rats were assigned to the vagus nerve isolation (CA) or VNS (CA + VNS) group. Cardiopulmonary resuscitation was performed 450 s after pulseless electrical activity. After the return of spontaneous circulation (ROSC), left cervical VNS was performed for 3 h in the CA + VNS group. Mitochondrial respiratory function was evaluated using high-resolution respirometry of the hippocampal tissue. The neurologic deficit score (NDS) and overall performance category (OPC) were assessed at 24, 48, and 72 h after resuscitation. The leak respiration and oxidative phosphorylation capacity of complex I (OXPHOS CI) at 6 h after ROSC were significantly higher in the CA + VNS group than in the CA group (p = 0.0308 and 0.0401, respectively). Compared with the trends of NDS and OPC in the CA group, the trends of those in the CA + VNS group were significantly different, thus suggesting a favorable neurological outcome in the CA + VNS group (p = 0.0087 and 0.0064 between times × groups interaction, respectively). VNS ameliorated mitochondrial dysfunction after ROSC and improved neurological outcomes in an asphyxial cardiac arrest rat model.

Prevalence of intracranial hemorrhage amongst patients presenting with out-of-hospital cardiac arrest: A systematic review and meta-analysis

INTRODUCTION

An unknown proportion of out-of-hospital cardiac arrest (OHCA) is caused by intracranial hemorrhage (ICH). There is uncertainty over the role of early head computed tomography (CT) in non-traumatic OHCA due to uncertain diagnostic yield and ways to identify high-risk patients. This study aimed to identify the prevalence of ICH in non-traumatic OHCA and possible predictors.

METHODS

PubMed, EMBASE, and the Cochrane library were searched from inception to January 2022. Data extraction and quality assessment were independently reviewed by two authors. Meta-analyses estimated the prevalence of ICH amongst OHCA patients and pre-specified subgroups and geographical settings. Subgroup analysis were used to explore potential clinical predictors.

RESULTS

23 studies involving 54,349 patients were included. The pooled ICH prevalence was 4.28% (95%CI: 3.31-5.24). Asia had a significantly larger risk ratio (RR= 3.93, P value < 0.0001) than Europe. The ICH subgroup was significantly more likely to be female (OR: 2.16; 95%CI: 1.10-4.26), and less likely to experience shockable rhythms compared with non-shockable rhythms (OR: 0.22; 95% CI: 0.04-1.22), achieve ROSC prior to arrival (OR: 0.27; 95%CI: 0.10-0.77), and survive to discharge compared to those without ICH (OR: 0.26; 95%CI: 0.11-0.59).

CONCLUSIONS

One in twenty OHCA have ICH at the time of presentation. An early head CT scan should be strongly considered after return of spontaneous circulation (ROSC), especially in patients who are female, with non-shockable rhythm and did not attain ROSC prior to arrival. These finding should influence clinical protocols to favor routine scans especially in Asia where prevalence is higher.

Association of High-Volume Centers With Survival Outcomes Among Patients With Nontraumatic Out-of-Hospital Cardiac Arrest: A Systematic Review and Meta-Analysis

Importance

Although high volume of cases of out-of-hospital cardiac arrest (OHCA) is a key feature of cardiac arrest centers, which have proven survival benefit, the role of center volume as an independent variable associated with improved outcomes is unclear.

Objective

To assess the association of high-volume centers with survival and neurological outcomes in nontraumatic OHCA.

Data Sources

Medline, Embase, and the Cochrane Central Register of Controlled Trials were searched from inception to October 11, 2021, for studies including adult patients with nontraumatic OHCA who were treated at high-volume vs non-high-volume centers.

Study Selection

Randomized clinical trials, nonrandomized studies of interventions, prospective cohort studies, and retrospective cohort studies were selected that met the following criteria: (1) adult patients with OHCA of nontraumatic etiology, (2) comparison of high-volume with low-volume centers, (3) report of a volume-outcome association, and (4) report of outcomes of interest. At least 2 authors independently reviewed each article, blinded to each other's decision.

Data Extraction and Synthesis

Data abstraction and quality assessment were independently conducted by 2 authors. Meta-analyses were performed for adjusted odds ratios (aORs) and crude ORs using a random-effects model. This study followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline.

Main Outcomes and Measures

Survival and good neurological outcomes according to the Cerebral Performance Categories Scale at hospital discharge or 30 days.

Results

A total of 16 studies involving 82 769 patients were included. Five studies defined high volume as 40 or more cases of OHCA per year; 3 studies defined high volume as greater than 100 cases of OHCA per year. All other studies differed in definitions. Survival to discharge or 30 days improved with treatment at high-volume centers, regardless of whether aORs (1.28 [95% CI, 1.00-1.64]) or crude ORs (1.43 [95% CI, 1.09-1.87]) were pooled. There was no association between center volume and good neurological outcomes at 30 days or hospital discharge in patients with OHCA (aOR, 0.96 [95% CI, 0.77-1.20]).

Conclusions and Relevance

In this meta-analysis and systematic review, care at high-volume centers was associated with improved survival outcomes, even after adjustment for potential confounders, but was not associated with improved neurological outcomes for patients with nontraumatic OHCA. More studies evaluating the relative importance of center volume compared with other variables (eg, the availability of treatment modalities) associated with survival outcomes in patients with OHCA are required.

Advanced Life Support Update

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2022. Other selected articles can be found online at https://www.biomedcentral.com/collections/annualupdate2022 . Further information about the Annual Update in Intensive Care and Emergency Medicine is available from https://link.springer.com/bookseries/8901 .

Target temperature management following cardiac arrest: a systematic review and Bayesian meta-analysis

Background

Temperature control with target temperature management (TTM) after cardiac arrest has been endorsed by expert societies and adopted in international clinical practice guidelines but recent evidence challenges the use of hypothermic TTM.

Methods

Systematic review and Bayesian meta-analysis of clinical trials on adult survivors from cardiac arrest undergoing TTM for at least 12 h comparing TTM versus no TTM or with a separation > 2 °C between intervention and control groups using the PubMed/MEDLINE, EMBASE, CENTRAL databases from inception to 1 September 2021 (PROSPERO CRD42021248140). All randomised and quasi-randomised controlled trials were considered. The risk ratio and 95% confidence interval for death (primary outcome) and unfavourable neurological recovery (secondary outcome) were captured using the original study definitions censored up to 180 days after cardiac arrest. Bias was assessed using the updated Cochrane risk-of-bias for randomised trials tool and certainty of evidence assessed using the Grading of Recommendation Assessment, Development and Evaluation methodology. A hierarchical robust Bayesian model-averaged meta-analysis was performed using both minimally informative and data-driven priors and reported by mean risk ratio (RR) and its 95% credible interval (95% CrI).

Results

In seven studies (three low bias, three intermediate bias, one high bias, very low to low certainty) recruiting 3792 patients the RR by TTM 32–34 °C was 0.95 [95% CrI 0.78—1.09] for death and RR 0.93 [95% CrI 0.84—1.02] for unfavourable neurological outcome. The posterior probability for no benefit (RR ≥ 1) by TTM 32–34 °C was 24% for death and 12% for unfavourable neurological outcome. The posterior probabilities for favourable treatment effects of TTM 32–34 °C were the highest for an absolute risk reduction of 2–4% for death (28–53% chance) and unfavourable neurological outcome (63–78% chance). Excluding four studies without active avoidance of fever in the control arm reduced the probability to achieve an absolute risk reduction > 2% for death or unfavourable neurological outcome to ≤ 50%.

Conclusions

The posterior probability distributions did not support the use of TTM at 32–34 °C compared to 36 °C also including active control of fever to reduce the risk of death and unfavourable neurological outcome at 90–180 days. Any likely benefit of hypothermic TTM is smaller than targeted in RCTs to date.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-03935-z.

Extracorporeal cardiopulmonary resuscitation for out-of-hospital cardiac arrest: A systematic review and meta-analysis of randomized and propensity score-matched studies

BACKGROUND

In selected patients with refractory out-of-hospital cardiac arrest, extracorporeal cardiopulmonary resuscitation represents a promising approach when conventional cardiopulmonary resuscitation fails to achieve return of spontaneous circulation. This systematic review and meta-analysis aimed to compare extracorporeal cardiopulmonary resuscitation to conventional cardiopulmonary resuscitation.

METHODS

We searched PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials up to November 28, 2021, for randomized trials and observational studies reporting propensity score-matched data and comparing adults with out-of-hospital cardiac arrest treated with extracorporeal cardiopulmonary resuscitation with those treated with conventional cardiopulmonary resuscitation. The primary outcome was survival with favorable neurological outcome at the longest follow-up available. Secondary outcomes were survival at the longest follow-up available and survival at hospital discharge/30 days.

RESULTS

We included six studies, two randomized and four propensity score-matched studies. Patients treated with extracorporeal cardiopulmonary resuscitation had higher rates of survival with favorable neurological outcome (81/584 [14%] vs. 46/593 [7.8%]; OR = 2.11; 95% CI, 1.41-3.15; p < 0.001, number needed to treat 16) and of survival (131/584 [22%] vs. 102/593 [17%]; OR = 1.40; 95% CI, 1.05-1.87; p = 0.02) at the longest follow-up available compared with conventional cardiopulmonary resuscitation. Survival at hospital discharge/30 days was similar between the two groups (142/584 [24%] vs. 122/593 [21%]; OR = 1.26; 95% CI, 0.95-1.66; p = 0.10).

CONCLUSIONS

Evidence from randomized trials and propensity score-matched studies suggests increased survival and favorable neurological outcome in patients with refractory out-of-hospital cardiac arrest treated with extracorporeal cardiopulmonary resuscitation. Large, multicentre randomized studies are still ongoing to confirm these findings.