Targeting mitochondria for resuscitation from cardiac arrest

Markers of Mitochondrial Injury and Neurological Outcomes of Comatose Patients after Cardiac Arrest

Background and Objectives: Most patients who are successfully resuscitated from cardiac arrest remain comatose, and only half regain consciousness 72 h after the arrest. Neuroprognostication methods can be complex and even inconclusive. As mitochondrial components have been identified as markers of post-cardiac-arrest injury and associated with survival, we aimed to investigate cytochrome c and mtDNA in comatose patients after cardiac arrest to compare neurological outcomes and to evaluate the markers' neuroprognostic value. Materials and Methods: This prospective observational study included 86 comatose post-cardiac-arrest patients and 10 healthy controls. Cytochrome c and mtDNA were determined at admission. Neuron-specific enolase (NSE) was measured after 72 h. Additional neuroprognostication methods were performed when patients remained unconscious. Cerebral performance category (CPC) was determined. Results: Cytochrome c was elevated in patients compared to healthy controls (2.029 [0.85-4.97] ng/mL vs. 0 [0.0-0.16], p < 0.001) but not mtDNA (95,228 [52,566-194,060] vs. 41,466 [28,199-104,708] copies/μL, p = 0.074). Compared to patients with CPC 1-2, patients with CPC 3-5 had higher cytochrome c (1.735 [0.717-3.40] vs. 4.109 [1.149-8.457] ng/mL, p = 0.011), with no differences in mtDNA (87,855 [47,598-172,464] vs. 126,452 [69,447-260,334] copies/μL, p = 0.208). Patients with CPC 1-2 and CPC 3-5 differed in all neuroprognostication methods. In patients with good vs. poor neurological outcome, ROC AUC was 0.664 (p = 0.011) for cytochrome c, 0.582 (p = 0.208) for mtDNA, and 0.860 (p < 0.001) for NSE. The correlation between NSE and cytochrome c was moderate, with a coefficient of 0.576 (p < 0.001). Conclusions: Cytochrome c was higher in comatose patients after cardiac arrest compared to healthy controls and higher in post-cardiac-arrest patients with poor neurological outcomes. Although cytochrome c correlated with NSE, its neuroprognostic value was poor. We found no differences in mtDNA.

Organ-Specific Mitochondrial Alterations Following Ischemia-Reperfusion Injury in Post-Cardiac Arrest Syndrome: A Comprehensive Review

BACKGROUND

Mitochondrial dysfunction, which is triggered by systemic ischemia-reperfusion (IR) injury and affects various organs, is a key factor in the development of post-cardiac arrest syndrome (PCAS). Current research on PCAS primarily addresses generalized mitochondrial responses, resulting in a knowledge gap regarding organ-specific mitochondrial dynamics. This review focuses on the organ-specific mitochondrial responses to IR injury, particularly examining the brain, heart, and kidneys, to highlight potential therapeutic strategies targeting mitochondrial dysfunction to enhance outcomes post-IR injury.

METHODS AND RESULTS

We conducted a narrative review examining recent advancements in mitochondrial research related to IR injury. Mitochondrial responses to IR injury exhibit considerable variation across different organ systems, influenced by unique mitochondrial structures, bioenergetics, and antioxidative capacities. Each organ demonstrates distinct mitochondrial behaviors that have evolved to fulfill specific metabolic and functional needs. For example, cerebral mitochondria display dynamic responses that can be both protective and detrimental to neuronal activity and function during ischemic events. Cardiac mitochondria show vulnerability to IR-induced oxidative stress, while renal mitochondria exhibit a unique pattern of fission and fusion, closely linked to their susceptibility to acute kidney injury. This organ-specific heterogeneity in mitochondrial responses requires the development of tailored interventions. Progress in mitochondrial medicine, especially in the realms of genomics and metabolomics, is paving the way for innovative strategies to combat mitochondrial dysfunction. Emerging techniques such as mitochondrial transplantation hold the potential to revolutionize the management of IR injury in resuscitation science.

CONCLUSIONS

The investigation into organ-specific mitochondrial responses to IR injury is pivotal in the realm of resuscitation research, particularly within the context of PCAS. This nuanced understanding holds the promise of revolutionizing PCAS management, addressing the unique mitochondrial dysfunctions observed in critical organs affected by IR injury.

Effect of adjuvant thiamine and ascorbic acid administration on the neurologic outcomes of out-of-hospital cardiac arrest patients: A before-and-after study

AIM

This study aimed to evaluate the impact of early thiamine and ascorbic acid administration on the neurologic outcome in out-of-hospital cardiac arrest (OHCA) patients treated with targeted temperature management (TTM).

METHODS

This before-and-after cohort study used data extracted from two hospitals of the Korean Hypothermia Network prospective registry. The treatment group incorporated patients enrolled from December 2019 to May 2021, that received intravenous thiamine (200 mg) and ascorbic acid (3 g) at 12-hour intervals for a total of six doses. The control group incorporated those enrolled from May 2018 to November 2019. The one-month good neurologic outcome, defined as a Cerebral Performance Category score ≤ 2, between the groups was evaluated using inverse probability of treatment weighting (IPTW).

RESULTS

Among the 234 OHCA survivors with TTM, 102 were included in the treatment group and 132 were included in the control group. The one-month (31.4 % vs. 29.5 %, respectively; P = 0.76) good neurologic outcome rates did not differ between the treatment and control groups. After adjusting using the IPTW, vitamin supplementation was not associated with good neurologic outcome (odds ratio [OR], 1.134; 95 % confidence interval [CI], 0.644-1.999; P = 0.66). In subgroup analysis, vitamin administration was significantly associated with a good neurologic outcome in older (≥65 years) patients (adjusted OR, 5.53; 95 % CI, 1.21-25.23; P = 0.03).

CONCLUSION

Adjuvant thiamine and ascorbic acid administration in OHCA survivors with TTM did not improve their neurologic outcome after one month. Further clinical trials are warranted.

Association between prothrombin time-international normalized ratio and prognosis of post-cardiac arrest patients: A retrospective cohort study

Background

Cardiac arrest (CA) can activate blood coagulation. This study aimed to explore the potential prognostic value of prothrombin time-international normalized ratio (INR) in post-CA patients.

Methods

The clinical data of eligible subjects diagnosed with CA was extracted from the MIMIC-IV database as the training cohort. Restricted cubic spline (RCS), Kaplan-Meier (K-M) survival curve, and Cox regression analyses were conducted to elucidate the association between the INR and all-cause mortality of post-CA patients. Subgroup analysis, propensity score matching (PSM), and inverse probability of treatment (IPTW) were also conducted to improve stability and reliability. Data of the validation cohort were collected from the eICU database, and logistic-regression analyses were performed to verify the findings of the training cohort.

Results

A total of 1,324 subjects were included in the training cohort. A linear correlation existed between INR and the risk of all-cause death of post-CA patients, as shown in RCS analysis, with a hazard ratio (HR) >1 when INR exceeded 1.2. K-M survival curve preliminarily indicated that subjects with INR ≥ 1.2 presented lower survival rate and shorter survival time, and the high level of INR was independently associated with 30-day, 90-day, 1-year, and in-hospital mortalities, with multivariate-adjusted HR of 1.44 (1.20, 1.73), 1.46 (1.23, 1.74), 1.44 (1.23, 1.69), and 1.37 (1.14, 1.64), respectively. These findings were consistent and robust across the subgroup analysis, PSM and IPTW analyses, and validation cohort.

Conclusions

We systematically and comprehensively demonstrated that elevated INR was associated with increased short- and long-term all-cause mortality of post-CA patients. Therefore, elevated INR may be a promising biomarker with prognosis significance.

Targeted plasma metabolomics in resuscitated comatose out-of-hospital cardiac arrest patients

BACKGROUND

Out-of-hospital cardiac arrest (OHCA) is a leading cause of death. Even if successfully resuscitated, mortality remains high due to ischemic and reperfusion injury (I/R). The oxygen deprivation leads to a metabolic derangement amplified upon reperfusion resulting in an uncontrolled generation of reactive oxygen species in the mitochondria triggering cell death mechanisms. The understanding of I/R injury in humans following OHCA remains sparse, with no existing treatment to attenuate the reperfusion injury.

AIM

To describe metabolic derangement in patients following resuscitated OHCA.

METHODS

Plasma from consecutive resuscitated unconscious OHCA patients drawn at hospital admission were analyzed using ultra-performance-liquid-mass-spectrometry. Sixty-one metabolites were prespecified for quantification and studied.

RESULTS

In total, 163 patients were included, of which 143 (88%) were men, and the median age was 62 years (53-68). All measured metabolites from the tricarboxylic acid (TCA) cycle were significantly higher in non-survivors vs. survivors (180-days survival). Hierarchical clustering identified four clusters (A-D) of patients with distinct metabolic profiles. Cluster A and B had higher levels of TCA metabolites, amino acids and acylcarnitine species compared to C and D. The mortality was significantly higher in cluster A and B (A:62% and B:59% vs. C:21 % and D:24%, p < 0.001). Cluster A and B had longer time to return of spontaneous circulation (A:33 min (21-43), B:27 min (24-35), C:18 min (13-28), and D:18 min (12-25), p < 0.001).

CONCLUSION

Circulating levels of metabolites from the TCA cycle best described the variance between survivors and non-survivors. Four different metabolic phenotypes with significantly different mortality were identified.

Sodium-Glucose Co-Transporter 2 Inhibition With Empagliflozin Improves Cardiac Function After Cardiac Arrest in Rats by Enhancing Mitochondrial Energy Metabolism

Empagliflozin is a newly developed antidiabetic drug to reduce hyperglycaemia by highly selective inhibition of sodium–glucose co-transporter 2. Hyperglycaemia is commonly seen in patients after cardiac arrest (CA) and is associated with worse outcomes. In this study, we examined the effects of empagliflozin on cardiac function in rats with myocardial dysfunction after CA. Non-diabetic male Sprague–Dawley rats underwent ventricular fibrillation to induce CA, or sham surgery. Rats received 10 mg/kg of empagliflozin or vehicle at 10 min after return of spontaneous circulation by intraperitoneal injection. Cardiac function was assessed by echocardiography, histological analysis, molecular markers of myocardial injury, oxidative stress, mitochondrial ultrastructural integrity and metabolism. We found that empagliflozin did not influence heart rate and blood pressure, but left ventricular function and survival time were significantly higher in the empagliflozin treated group compared to the group treated with vehicle. Empagliflozin also reduced myocardial fibrosis, serum cardiac troponin I levels and myocardial oxidative stress after CA. Moreover, empagliflozin maintained the structural integrity of myocardial mitochondria and increased mitochondrial activity after CA. In addition, empagliflozin increased circulating and myocardial ketone levels as well as heart β-hydroxy butyrate dehydrogenase 1 protein expression. Together, these metabolic changes were associated with an increase in cardiac energy metabolism. Therefore, empagliflozin favorably affected cardiac function in non-diabetic rats with acute myocardial dysfunction after CA, associated with reducing glucose levels and increasing ketone body oxidized metabolism. Our data suggest that empagliflozin might benefit patients with myocardial dysfunction after CA.

Exogenous Nicotinamide Adenine Dinucleotide Attenuates Postresuscitation Myocardial and Neurologic Dysfunction in a Rat Model of Cardiac Arrest

OBJECTIVES

To investigate the therapeutic potential and underlying mechanisms of exogenous nicotinamide adenine dinucleotide+ on postresuscitation myocardial and neurologic dysfunction in a rat model of cardiac arrest.

DESIGN

Thirty-eight rats were randomized into three groups: 1) Sham, 2) Control, and 3) NAD. Except for the sham group, untreated ventricular fibrillation for 6 minutes followed by cardiopulmonary resuscitation was performed in the control and NAD groups. Nicotinamide adenine dinucleotide+ (20 mg/kg) was IV administered at the onset of return of spontaneous circulation.

SETTING

University-affiliated research laboratory.

SUBJECTS

Sprague-Dawley rats.

INTERVENTIONS

Nicotinamide adenine dinucleotide+.

MEASUREMENTS AND MAIN RESULTS

Hemodynamic and myocardial function were measured at baseline and within 4 hours following return of spontaneous circulation. Survival analysis and Neurologic Deficit Score were performed up to 72 hours after return of spontaneous circulation. Adenosine triphosphate (adenosine triphosphate) level was measured in both brain and heart tissue. Mitochondrial respiratory chain function, acetylation level, and expression of Sirtuin3 and NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 9 (NDUFA9) in isolated mitochondrial protein from both brain and heart tissue were evaluated at 4 hours following return of spontaneous circulation. The results demonstrated that nicotinamide adenine dinucleotide+ treatment improved mean arterial pressure (at 1 hr following return of spontaneous circulation, 94.69 ± 4.25 mm Hg vs 89.57 ± 7.71 mm Hg; p < 0.05), ejection fraction (at 1 hr following return of spontaneous circulation, 62.67% ± 6.71% vs 52.96% ± 9.37%; p < 0.05), Neurologic Deficit Score (at 24 hr following return of spontaneous circulation, 449.50 ± 82.58 vs 339.50 ± 90.66; p < 0.05), and survival rate compared with that of the control group. The adenosine triphosphate level and complex I respiratory were significantly restored in the NAD group compared with those of the control group. In addition, nicotinamide adenine dinucleotide+ treatment activated the Sirtuin3 pathway, down-regulating acetylated-NDUFA9 in the isolated mitochondria protein.

CONCLUSIONS

Exogenous nicotinamide adenine dinucleotide+ treatment attenuated postresuscitation myocardial and neurologic dysfunction. The responsible mechanisms may involve the preservation of mitochondrial complex I respiratory capacity and adenosine triphosphate production, which involves the Sirtuin3-NDUFA9 deacetylation.

Cerebral and myocardial mitochondrial injury differ in a rat model of cardiac arrest and cardiopulmonary resuscitation

Brain mitochondria are more sensitive to global ischemia compared to heart mitochondria. Complex I in the electron transport chain (ETC) is sensitive to ischemic injury and is a major control point of the rate of ADP stimulated oxygen consumption. The purpose of this study was to explore whether changes in cerebral and myocardial mitochondria differ after cardiac arrest. Animals were randomized into 4 groups (n = 6): 1) Sham 2) VF 3) VF+CPR 4) ROSC 1hr. Ventricular Fibrillation (VF) was induced through a guide wire advanced from the right jugular vein into the ventricle and untreated for 8 min. Resuscitation was attempted with a 4J defibrillation after 8 min of cardiopulmonary resuscitation (CPR). Brain mitochondria and cardiac mitochondrial subpopulations were isolated. Calcium retention capacity was measured to assess susceptibility to mitochondrial permeability transition pore opening. ADP stimulated oxygen consumption and ETC activity assays were performed. Brain mitochondria are far more sensitive to injury during cardiac arrest and resuscitation compared to cardiac mitochondria. Complex I is highly sensitive to injury in brain mitochondria. With markedly decreased calcium retention capacity, mitochondria contribute to cerebral reperfusion injury. Therapeutic preservation of cerebral mitochondrial activity and mitochondrial function during cardiac arrest may improve post-resuscitation neurologic function.

Increased cerebral mitochondrial dysfunction and reactive oxygen species with cardiopulmonary bypass

OBJECTIVES

Neurodevelopmental injury after cardiac surgery using cardiopulmonary bypass (CPB) for congenital heart defects is common, but the mechanism behind this injury is unclear. This study examines the impact of CPB on cerebral mitochondrial reactive oxygen species (ROS) generation and mitochondrial bioenergetics.

METHODS

Twenty-three piglets (mean weight 4.2 ± 0.5 kg) were placed on CPB for either 1, 2, 3 or 4 h (n = 5 per group) or underwent anaesthesia without CPB (sham, n = 3). Microdialysis was used to measure metabolic markers of ischaemia. At the conclusion of CPB or 4 h of sham, brain tissue was harvested. Utilizing high-resolution respirometry, with simultaneous fluorometric analysis, mitochondrial respiration and ROS were measured.

RESULTS

There were no significant differences in markers of ischaemia between sham and experimental groups. Sham animals had significantly higher mitochondrial respiration than experimental animals, including maximal oxidative phosphorylation capacity of complex I (OXPHOSCI) (3.25 ± 0.18 vs 4-h CPB: 1.68 ± 0.10, P < 0.001) and maximal phosphorylating respiration capacity via convergent input through complexes I and II (OXPHOSCI+CII) (7.40 ± 0.24 vs 4-h CPB: 3.91 ± 0.20, P < 0.0001). At 4-h, experimental animals had significantly higher ROS related to non-phosphorylating respiration through complexes I and II (ETSCI+CII) than shams (1.08 ± 0.13 vs 0.64 ± 0.04, P = 0.026).

CONCLUSIONS

Even in the absence of local markers of ischaemia, CPB is associated with decreased mitochondrial respiration relative to shams irrespective of duration. Exposure to 4 h of CPB resulted in a significant increase in cerebral mitochondrial ROS formation compared to shorter durations. Further study is needed to improve the understanding of cerebral mitochondrial health and its effects on the pathophysiology of neurological injury following exposure to CPB.

Haemodynamic-directed cardiopulmonary resuscitation promotes mitochondrial fusion and preservation of mitochondrial mass after successful resuscitation in a pediatric porcine model

Objective

Cerebral mitochondrial dysfunction is a key mediator of neurologic injury following cardiac arrest (CA) and is regulated by the balance of fusion and fission (mitochondrial dynamics). Under stress, fission can decrease mitochondrial mass and signal apoptosis, while fusion promotes oxidative phosphorylation efficiency. This study evaluates mitochondrial dynamics and content in brain tissue 24 h after CA between two cardiopulmonary resuscitation (CPR) strategies.

Interventions

Piglets (1 month), previously randomized to three groups: (1) Std-CPR (n = 5); (2) HD-CPR (n = 5; goal systolic blood pressure 90 mmHg, goal coronary perfusion pressure 20 mmHg); (3) Shams (n = 7). Std-CPR and HD-CPR groups underwent 7 min of asphyxia, 10 min of CPR, and standardized post-resuscitation care. Primary outcomes: (1) cerebral cortical mitochondrial protein expression for fusion (OPA1, OPA1 long to short chain ratio, MFN2) and fission (DRP1, FIS1), and (2) mitochondrial mass by citrate synthase activity. Secondary outcomes: (1) intra-arrest haemodynamics and (2) cerebral performance category (CPC) at 24 h.

Results

HD-CPR subjects had higher total OPA1 expression compared to Std-CPR (1.52; IQR 1.02-1.69 vs 0.67; IQR 0.54-0.88, p = 0.001) and higher OPA1 long to short chain ratio than both Std-CPR (0.63; IQR 0.46-0.92 vs 0.26; IQR 0.26-0.31, p = 0.016) and shams. Citrate synthase activity was lower in Std-CPR than sham (11.0; IQR 10.15-12.29 vs 13.4; IQR 12.28-15.66, p = 0.047), but preserved in HD-CPR. HD-CPR subjects had improved intra-arrest haemodynamics and CPC scores at 24 h compared to Std-CPR.

Conclusions

Following asphyxia-associated CA, HD-CPR exhibits increased pro-mitochondrial fusion protein expression, preservation of mitochondrial mass, improved haemodynamics and superior neurologic scoring compared to Std-CPR.

Institutional protocol number

IAC 16-001023.

Mitochondrial dysfunction in fatal ventricular arrhythmias

Ventricular fibrillation (VF) and sudden cardiac arrest (SCA) remain some of the most important public health concerns worldwide. For the past 50 years, the recommendation in the Advanced Cardiac Life Support (ACLS) guidelines has been that defibrillation is the only option for shockable cardiac arrest. There is growing evidence to demonstrate that mitochondria play a vital role in the outcome of postresuscitation cardiac function. Although targeting mitochondria to improve resuscitation outcome following cardiac arrest has been proposed for many years, understanding concerning the changes in mitochondria during cardiac arrest, especially in the case of VF, is still limited. In addition, despite new research initiatives and improved medical technology, the overall survival rates of patients with SCA still remain the same. Understanding cardiac mitochondrial alterations during fatal arrhythmias may help to enable the formulation of strategies to improve the outcomes of resuscitation. The attenuation of cardiac mitochondrial dysfunction during VF through pharmacological intervention as well as ischaemic postconditioning could also be a promising target for intervention and inform a new paradigm of treatments. In this review, the existing evidence available from in vitro, ex vivo and in vivo studies regarding the roles of mitochondrial dysfunction during VF is comprehensively summarized and discussed. In addition, the effects of interventions targeting cardiac mitochondria during fatal ventricular arrhythmias are presented. Since there are no clinical reports from studies targeting mitochondria to improve resuscitation outcome available, this review will provide important information to encourage further investigations in a clinical setting.

Effects of Post-Resuscitation Normoxic Therapy on Oxygen-Sensitive Oxidative Stress in a Rat Model of Cardiac Arrest

Background

Cardiac arrest (CA) can induce oxidative stress after resuscitation, which causes cellular and organ damage. We hypothesized that post‐resuscitation normoxic therapy would protect organs against oxidative stress and improve oxygen metabolism and survival. We tested the oxygen‐sensitive reactive oxygen species from mitochondria to determine the association with hyperoxia‐induced oxidative stress.

Methods and Results

Sprague–Dawley rats were subjected to 10‐minute asphyxia‐induced CA with a fraction of inspired O₂ of 0.3 or 1.0 (normoxia versus hyperoxia, respectively) after resuscitation. The survival rate at 48 hours was higher in the normoxia group than in the hyperoxia group (77% versus 28%, P<0.01), and normoxia gave a lower neurological deficit score (359±140 versus 452±85, P<0.05) and wet to dry weight ratio (4.6±0.4 versus 5.6±0.5, P<0.01). Oxidative stress was correlated with increased oxygen levels: normoxia resulted in a significant decrease in oxidative stress across multiple organs and lower oxygen consumption resulting in normalized respiratory quotient (0.81±0.05 versus 0.58±0.03, P<0.01). After CA, mitochondrial reactive oxygen species increased by ≈2‐fold under hyperoxia. Heme oxygenase expression was also oxygen‐sensitive, but it was paradoxically low in the lung after CA. In contrast, the HMGB‐1 (high mobility group box‐1) protein was not oxygen‐sensitive and was induced by CA.

Conclusions

Post‐resuscitation normoxic therapy attenuated the oxidative stress in multiple organs and improved post‐CA organ injury, oxygen metabolism, and survival. Additionally, post‐CA hyperoxia increased the mitochondrial reactive oxygen species and activated the antioxidation system.

Neuroprotective Treatment of Postanoxic Encephalopathy: A Review of Clinical Evidence

Postanoxic encephalopathy is the key determinant of death or disability after successful cardiopulmonary resuscitation. Animal studies have provided proof-of-principle evidence of efficacy of divergent classes of neuroprotective treatments to promote brain recovery. However, apart from targeted temperature management (TTM), neuroprotective treatments are not included in current care of patients with postanoxic encephalopathy after cardiac arrest. We aimed to review the clinical evidence of efficacy of neuroprotective strategies to improve recovery of comatose patients after cardiac arrest and to propose future directions. We performed a systematic search of the literature to identify prospective, comparative clinical trials on interventions to improve neurological outcome of comatose patients after cardiac arrest. We included 53 studies on 21 interventions. None showed unequivocal benefit. TTM at 33 or 36°C and adrenaline (epinephrine) are studied most, followed by xenon, erythropoietin, and calcium antagonists. Lack of efficacy is associated with heterogeneity of patient groups and limited specificity of outcome measures. Ongoing and future trials will benefit from systematic collection of measures of baseline encephalopathy and sufficiently powered predefined subgroup analyses. Outcome measurement should include comprehensive neuropsychological follow-up, to show treatment effects that are not detectable by gross measures of functional recovery. To enhance translation from animal models to patients, studies under experimental conditions should adhere to strict methodological and publication guidelines.

Baicalin Improves Cardiac Outcome and Survival by Suppressing Drp1-Mediated Mitochondrial Fission after Cardiac Arrest-Induced Myocardial Damage

Myocardial injury after cardiac arrest (CA) often results in severe myocardial dysfunction and death involving mitochondrial dysfunction. Here, we sought to investigate whether baicalin, a natural flavonoid compound, exerts cardioprotection against CA-induced injury via regulating mitochondrial dysfunction. We subjected the rats to asphyxia CA after a daily baicalin treatment for 4 weeks. After the return of spontaneous circulation, baicalin treatment significantly improved cardiac function performance, elevated survival rate from 35% to 75%, prevented necrosis and apoptosis in the myocardium, which was accompanied by reduced phosphorylation of Drp1 at serine 616, inhibited Drp1 translocation to the mitochondria and mitochondrial fission, and improved mitochondrial function. In H9c2 cells subjected to simulated ischemia/reperfusion, increased phosphorylation of Drp1 at serine 616 and subsequently enhanced mitochondrial Drp1 translocation as well as mitochondrial fission, augmented cardiomyocyte death, increased reactive oxygen species production, released cytochrome c from mitochondria and injured mitochondrial respiration were efficiently improved by baicalin and Drp1 specific inhibitor with Mdivi-1. Furthermore, overexpression of Drp1 augmented excessive mitochondrial fission and abolished baicalin-afforded cardioprotection, indicating that the protective impacts of baicalin are linked to the inhibition of Drp1. Altogether, our findings disclose for the first time that baicalin offers cardioprotection against ischemic myocardial injury after CA by inhibiting Drp1-mediated mitochondrial fission. Baicalin might be a prospective therapy for the treatment of post-CA myocardial injury.

Inhaled Gases as Therapies for Post-Cardiac Arrest Syndrome: A Narrative Review of Recent Developments

Despite recent advances in the management of post-cardiac arrest syndrome (PCAS), the survival rate, without neurologic sequelae after resuscitation, remains very low. Whole-body ischemia, followed by reperfusion after cardiac arrest (CA), contributes to PCAS, for which established pharmaceutical interventions are still lacking. It has been shown that a number of different processes can ultimately lead to neuronal injury and cell death in the pathology of PCAS, including vasoconstriction, protein modification, impaired mitochondrial respiration, cell death signaling, inflammation, and excessive oxidative stress. Recently, the pathophysiological effects of inhaled gases including nitric oxide (NO), molecular hydrogen (H₂), and xenon (Xe) have attracted much attention. Herein, we summarize recent literature on the application of NO, H₂, and Xe for treating PCAS. Recent basic and clinical research has shown that these gases have cytoprotective effects against PCAS. Nevertheless, there are likely differences in the mechanisms by which these gases modulate reperfusion injury after CA. Further preclinical and clinical studies examining the combinations of standard post-CA care and inhaled gas treatment to prevent ischemia-reperfusion injury are warranted to improve outcomes in patients who are being failed by our current therapies.

Plasma metabolomics supports the use of long-duration cardiac arrest rodent model to study human disease by demonstrating similar metabolic alterations

Cardiac arrest (CA) is a leading cause of death and there is a necessity for animal models that accurately represent human injury severity. We evaluated a rat model of severe CA injury by comparing plasma metabolic alterations to human patients. Plasma was obtained from adult human control and CA patients post-resuscitation, and from male Sprague–Dawley rats at baseline and after 20 min CA followed by 30 min cardiopulmonary bypass resuscitation. An untargeted metabolomics evaluation using UPLC-QTOF-MS/MS was performed for plasma metabolome comparison. Here we show the metabolic commonality between humans and our severe injury rat model, highlighting significant metabolic dysfunction as seen by similar alterations in (1) TCA cycle metabolites, (2) tryptophan and kynurenic acid metabolites, and (3) acylcarnitine, fatty acid, and phospholipid metabolites. With substantial interspecies metabolic similarity in post-resuscitation plasma, our long duration CA rat model metabolically replicates human disease and is a suitable model for translational CA research.

Cardiac function after cardiac arrest: what do we know?

Postcardiac arrest myocardial dysfunction (PCAMD) is a frequent complication faced during post-resuscitation care that adversely impacts survival and neurological outcome. Both mechanical and electrical factors contribute to the occurrence of PCAMD. Prearrest ventricular function, the cause of cardiac arrest, global ischemia, resuscitation factors, ischemia/reperfusion injury and post-resuscitation treatments contribute to the severity of PCMAD. The pathophysiology of PCAMD is complex and include myocytes energy failure, impaired contractility, cardiac edema, mitochondrial damage, activation of inflammatory pathways and the coagulation cascade, persistent ischemic injury and myocardial stiffness. Hypotension and low cardiac output with vasopressor/inotropes need are frequent after resuscitation. However, clinical, hemodynamic and laboratory signs of shock are frequently altered by cardiac arrest pathophysiology and post-resuscitation treatment, potentially being misleading and not fully reflecting the severity of postcardiac arrest syndrome. Even if validated criteria are lacking, an extensive hemodynamic evaluation is useful to define a "benign" and a "malign" form of myocardial dysfunction and circulatory shock, potentially having treatment and prognostic implications. Cardiac output is frequently decreased after cardiac arrest, particularly in patients treated with target temperature management (TTM); however, it is not independently associated with outcome. Sinus bradycardia during TTM seems independently associated with survival and good neurological outcome, representing a promising prognostic indicator. Higher mean arterial pressure (MAP) seems to be associated with improved survival and cerebral function after cardiac arrest; however, two recent randomized clinical trials failed to replicate these results. Recommendations on hemodynamic optimization are relatively poor and are largely based on general principle of intensive care medicine.

Efficacy of Thiamine in the Treatment of Postcardiac Arrest Patients: A Randomized Controlled Study

Background

Thiamine administration has been shown to improve survival in a postcardiac arrest animal study. We aimed to evaluate the efficacy of thiamine in comatose out-of-hospital cardiac arrest (OHCA) patients following return of spontaneous circulation.

Methods

A randomized, double-blinded, placebo-controlled study was conducted. Thirty-seven OHCA patients were randomly assigned to receive either thiamine 100 mg every 8 hours or a placebo. The primary outcome was 28-day all-cause mortality.

Results

Over the course of 2 years, 37 patients were randomized to either receive thiamine (n = 20) or a placebo (n = 17). The primary outcome was not different between the groups: 10/20 (50%) in the thiamine group vs. 8/17 (47.1%) in the placebo group (P=0.93 by the log-rank test). There were no significant differences in secondary outcomes between the groups (good neurological outcome, lactate level, and S100B level).

Conclusions

In this study, there were no significant differences in survival outcome. Further studies with a larger population are necessary to confirm these results.

PD98059 Protects Cerebral Cortex Mitochondrial Structure and Function at 48 h Post-Resuscitation in a Rat Model of Cardiac Arrest

Background

Mitochondria play a critical role as effectors and targets of brain injury in the post-resuscitation period. Although we found previously that the extracellular signal-regulated kinase (ERK)1/2 inhibitor PD98059 (PD) protects the brain against mitochondrial-mediated cell death at 24 h post-resuscitation in rats subjected to cardiac arrest/cardiopulmonary resuscitation (CA/CPR), it is not clear whether PD also exerts mitochondrial protective effect for a lasting time. Therefore, we examined the effect of PD on brain mitochondria at 48 h post-resuscitation to evaluate the time-effect of PD in the current study.

Methods

Experimental rats were divided randomly into 5 groups: Sham, CA, dimethylsulfoxide (DMSO), 0.15mg/kg PD and 0.3mg/kg PD. Rats except for sham group were subjected to CA for 6 min followed by CPR. We detected survival rates and neurologic deficit scores, cerebral cortex mitochondrial function by evaluating adenosine triphosphate (ATP) levels, mitochondrial permeability transition pore (MPTP) opening, and the expression of mitofusin2 (Mfn2) and observing the ultrastructure by electron microscopy at 48 h post-resuscitation in a 6-min CA rat model.

Results

PD improved survival rates and neurologic deficit scores, alleviated cerebral cortex mitochondrial damage by reducing MPTP opening and increasing Mfn2 production at 48 h post-resuscitation in a 6-min CA rat model.

Conclusion

A single dose of PD improved 48 h post-resuscitation outcome and mitochondrial function, indicating the potential of the use of ERK inhibitors for the treatment of brain injury resulting from CA in the future.

CTL-Derived Granzyme B Participates in Hippocampal Neuronal Apoptosis Induced by Cardiac Arrest and Resuscitation in Rats

Hippocampal neuronal apoptosis is a devastating consequence of cardiac arrest (CA) and subsequent cardiopulmonary resuscitation (CPR). In this study, we assessed the contribution of cytotoxic T lymphocyte (CTL)-derived toxic mediator granzyme B (Gra-b) to the hippocampal neuronal apoptosis following CA/CPR in rats. Rats that experienced CA/CPA presented with cytosomal shrinkage, dense cytoplasm, and intensive eosinophilic staining in the CA1 region of dorsal hippocampus. CA/CPR rats also exhibited inability in spatial navigation and a local infiltration of peripheral CD8+ T cells into the hippocampus. The protein levels of Gra-b, cleaved Caspase-3, and cleaved PARP1 were significantly elevated in rats undergoing CA/CPR. Pretreatment with Gra-b inhibitor suppressed Gra-b release, attenuated hippocampal neuronal apoptosis, as well as improved cognitive impairment. Together, this study indicates that CTL-derived Gra-b is involved in the CA/CPR-induced neuronal apoptosis, and pharmacological manipulation of Gra-b may represent a novel avenue for the treatment of brain injury following CA/CPR.

Increased Heat Generation in Postcardiac Arrest Patients During Targeted Temperature Management Is Associated With Better Outcomes

OBJECTIVES

Assess if amount of heat generated by postcardiac arrest patients to reach target temperature (Ttarget) during targeted temperature management is associated with outcomes by serving as a proxy for thermoregulatory ability, and whether it modifies the relationship between time to Ttarget and outcomes.

DESIGN

Retrospective cohort study.

SETTING

Urban tertiary-care hospital.

PATIENTS

Successfully resuscitated targeted temperature management-treated adult postarrest patients between 2008 and 2015 with serial temperature data and Ttarget less than or equal to 34°C.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Time to Ttarget was defined as time from targeted temperature management initiation to first recorded patient temperature less than or equal to 34°C. Patient heat generation ("heat units") was calculated as inverse of average water temperature × hours between initiation and Ttarget × 100. Primary outcome was neurologic status measured by Cerebral Performance Category score; secondary outcome was survival, both at hospital discharge. Univariate analyses were performed using Wilcoxon rank-sum tests; multivariate analyses used logistic regression. Of 203 patients included, those with Cerebral Performance Category score 3-5 generated less heat before reaching Ttarget (median, 8.1 heat units [interquartile range, 3.6-21.6 heat units] vs median, 20.0 heat units [interquartile range, 9.0-33.5 heat units]; p = 0.001) and reached Ttarget quicker (median, 2.3 hr [interquartile range, 1.5-4.0 hr] vs median, 3.6 hr [interquartile range, 2.0-5.0 hr]; p = 0.01) than patients with Cerebral Performance Category score 1-2. Nonsurvivors generated less heat than survivors (median, 8.1 heat units [interquartile range, 3.6-20.8 heat units] vs median, 19.0 heat units [interquartile range, 6.5-33.5 heat units]; p = 0.001) and reached Ttarget quicker (median, 2.2 hr [interquartile range, 1.5-3.8 hr] vs median, 3.6 hr [interquartile range, 2.0-5.0 hr]; p = 0.01). Controlling for average water temperature between initiation and Ttarget, the relationship between outcomes and time to Ttarget was no longer significant. Controlling for location, witnessed arrest, age, initial rhythm, and neuromuscular blockade use, increased heat generation was associated with better neurologic (adjusted odds ratio, 1.01 [95% CI, 1.00-1.03]; p = 0.039) and survival (adjusted odds ratio, 1.01 [95% CI, 1.00-1.03]; p = 0.045) outcomes.

CONCLUSIONS

Increased heat generation during targeted temperature management initiation is associated with better outcomes at hospital discharge and may affect the relationship between time to Ttarget and outcomes.

Pre-arrest hypothermia improved cardiac function of rats by ameliorating the myocardial mitochondrial injury after cardiac arrest

This study investigated the effects of hypothermia induced before cardiac arrest or after return of spontaneous circulation (ROSC) on cardiac function and myocardial mitochondrial injury after ROSC in a rat cardiac arrest model. Sixty healthy, male Wistar rats were randomly divided into the Normothermia group, pre-arrest hypothermia (Pre-HT) group, and post-resuscitation hypothermia (Post-HT) group. The rats underwent 8 min of untreated ventricular fibrillation followed by cardiopulmonary resuscitation. Twelve rats in each group were used to evaluate the left ventricular ejection fraction before ventricular fibrillation and 4 h after ROSC. Survival was determined at 24 h after ROSC. The remaining eight rats in each group were used to detect for heart malondialdehyde, reduced glutathione, adenosine triphosphate levels and mitochondrial histology. Oxygen consumption rate and mitochondrial membrane potential were evaluated 4 h after ROSC; 10 of 12 rats in Pre-HT group, 5 of 12 in Post-HT group, and 6 of 12 in normothermia group were successfully resuscitated. The survival rate of each group was 66.7%, 33.3%, and 25%, respectively. Rats in the Pre-HT group showed less alteration of the mitochondrial ultrastructure and oxidative stress injury, better maintenance of adenine nucleotides, and more preservation of the mitochondrial membrane potential and respiratory function when compared with rats in the Post-HT and normothermia groups. Transient hypothermia is an effective preconditioning stimulus to induce ischemic tolerance in a cardiac arrest model and worthy of further evaluation for potential clinical use.

Impact statement

In this paper, we investigated the effects of hypothermia induced before ischemia or after ROSC on cardiac function, oxidative stress damage, and myocardial mitochondrial ischemia–reperfusion injury after cardiac arrest in a rat model with VF. We demonstrated that pre-arrest hypothermia conferred greater cardio-protective benefits than delayed post-resuscitation hypothermia, reduced the number of defibrillations required and dosages of epinephrine during CPR, decreased oxidative stress, ameliorated mitochondrial dysfunction, and subsequently improved survival rate.

Predicting Outcome After Out-of-Hospital Cardiac Arrest: Lactate, Need for Vasopressors, and Cytochrome c

BACKGROUND

Outcome prediction after out-of-hospital cardiac arrest (OHCA) is difficult. We hypothesized that lactate and need for vasopressors would predict outcome, and that addition of a mitochondrial biomarker would enhance performance of the tool.

METHODS

Prospective observational study of OHCA patients presenting to an academic medical center September 2008 to April 2016. We conducted univariate and multivariate logistic regressions.

RESULTS

Patients were divided based on 2 variables: vasopressor status and initial lactate (<5 mmol/L, 5-10, ≥10). Three hundred fifty-two patients were evaluated; 249 had a lactate within 3 hours and were included. Patients on vasopressors had higher mortality (74% vs 40%; P < .001). A stepwise increase in mortality is associated with increasing lactate (45% lactate <5, 66% 5-10, and 83% ≥10; P < 001). Multivariable models with lactate group and vasopressors as predictors demonstrated excellent discrimination (area under the receiver operating curve [AUC]: 0.73 [95% confidence interval, CI: 0.66-0.79]; adjusted for additional covariates: AUC: 0.81 [95% CI: 0.75-0.86]). Thirty-six patients had cytochrome c levels available; among these 36, when comparing models with and without cytochrome c, there was no difference (AUC: 0.88 [95% CI: 0.76-1.00] vs AUC: 0.85 [95% CI: 0.73-0.98], respectively; P = .30).

CONCLUSION

In this prospective validation, the combination of lactate and vasopressors in the immediate postarrest period is predictive of mortality. Cytochrome c offered minimal additional predictive power.

Protective effects of ghrelin on brain mitochondria after cardiac arrest and resuscitation

Mitochondrial dysfunction plays a critical role in brain injury after cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). Our recent study demonstrated that ghrelin protected against post-resuscitation brain injury with an elevated expression of mitochondrial uncoupling protein 2 (UCP2). However, the effects of ghrelin on mitochondrial dysfunction after CA are not clear. In the present study, the protective role of ghrelin was evaluated on mitochondrial dysfunction and the subsequent damage induced by CA in rats. In addition, mitochondrial unfolded protein response (UPRmt), an intrinsic cytoprotective pathway, was observed at the same time. Either vehicle (saline) or ghrelin (80 μg/kg) was injected blindly immediately after 6 min of CA and successful resuscitation. Neurological deficit was evaluated 6 h after CA and then cortex was collected for assessments. As a result, we found that ghrelin significantly improved the neurological deficit score in rats after CA. The functional analysis of isolated mitochondria revealed that ghrelin improved the mitochondrial ATP synthesis capacity and significantly reduced the reactive oxygen species (ROS) leakage after 6 h of CA. Concomitantly, we observed an increased ATP level and an attenuated oxidative stress in ghrelin treated animals. Moreover, ghrelin markedly improved the mitochondrial morphology compared with the vehicle animals. Further research revealed that ghrelin treatment significantly activated the UPRmt as demonstrated by the increased expression of heat shock protein 60 (HSP60), heat shock protein 10 (HSP10), caseinolytic protease 1 (CLPP1), and high-temperature requirement protein A2 (HTRA2). Our results suggest that ghrelin protected against cerebral mitochondria dysfunction after CA and the mechanism may involve a UPRmt pathway.

Endovascular hypothermia improves post-resuscitation myocardial dysfunction by increasing mitochondrial biogenesis in a pig model of cardiac arrest

The aim of the study was to investigate the effects of endovascular hypothermia on mitochondrial biogenesis in a pig model of prolonged cardiac arrest (CA). Ventricular fibrillation was electrically induced, and animals were left untreated for 10 min; then after 6min of cardiopulmonary resuscitation (CPR), defibrillation was attempted. 25 animals that were successfully resuscitated were randomized into three groups: Sham group (SG, 5, no CA), normal temperature group (NTG, 5 for 12 h observation and 5 for 24 h observation), and endovascular hypothermia group (EHG, 5 for 12 h observation and 5 for 24 h observation). The core temperatures (T_c) in the EHG were maintained at 34 ± 0.5 °C for 6 h by an endovascular hypothermia device (Coolgard 3000), then actively increased at the speed of 0.5 °C per hour during the next 6 h to achieve a normal body temperature, while T_c were maintained at 37.5 ± 0.5 °C in the NTG. Cardiac and mitochondrial functions, the quantification of myocardial mitochondrial DNA (mtDNA), peroxisome proliferator-activated receptor coactivator-1α (PGC-1α), nuclear respiratory factor (NRF)-1, and NRF-2 were examined. Results showed that myocardial and mitochondrial injury and dysfunction increased significantly at 12 h and 24 h after CA. Endovascular hypothermia offered a method to rapidly achieve the target temperature and provide stable target temperature management (TTM). Cardiac outcomes were improved and myocardial injuries were alleviated with endovascular hypothermia. Compared with NTG, endovascular hypothermia significantly increased mitochondrial activity and biogenesis by amplifying mitochondrial biogenesis factors' expressions, including PGC-1α, NRF-1, and NRF-2. In conclusions, endovascular hypothermia after CA alleviated myocardial and mitochondrial dysfunction, and was associated with increasing mitochondrial biogenesis.

Cardiopulmonary resuscitation ameliorates myocardial mitochondrial dysfunction in a cardiac arrest rat model

PURPOSE

Previous studies implicate that the mitochondrial injury may play an important role in the development of post-resuscitation myocardial dysfunction, however few of them are available regarding the ultrastructural alterations of myocardial mitochondria, mitochondrial energy producing and utilization ability in the stage of arrest time (no-low) and resuscitation time (low-flow). This study aimed to observe the dynamic changes of myocardial mitochondrial function and metabolic disorders during cardiac arrest (CA) and following cardiopulmonary resuscitation (CPR).

METHODS

A total of 30 healthy male Sprague-Dawley rats were randomized into three groups: 1) VF/CPR: Ventricular fibrillation (VF) was electrically induced, and 5 min of CPR was performed after 10 min of untreated VF; 2) Untreated VF: VF was induced and untreated for 15 min; and 3) Sham: Rats were identically prepared without VF/CPR. Amplitude spectrum area (AMSA) at VF 5, 10 and 15 min were calculated from ECG signals. The rats' hearts were quickly removed at the predetermined time of 15 min after beginning the procedure to gather measurements of myocardial mitochondrial function, high-energy phosphate stores, lactate, mitochondrial ultrastructure, and myocardial glycogen.

RESULTS

The mitochondrial respiratory control ratios significantly decreased after CA compared to sham group. CPR significantly increased respiratory control ratios compared with untreated VF animals. A significant decrease of myocardial glycogen was observed after CA, and a more rapid depletion of myocardial glycogen was observed in CPR animals. CPR significantly reduced the tissue lactate. The mitochondrial ultrastructure abnormalities in CPR animals were less severe than untreated VF animals. AMSA decayed during untreated VF; however, it was significantly greater in CPR group than the untreated VF group. In addition, AMSA was clearly positively correlated with ATP, but negatively correlated with myocardial glycogen.

CONCLUSION

Impairment of myocardial mitochondrial function and the incapability of utilizing glycogen were observed after CA. Furthermore, optimal CPR might, in part, preserved mitochondrial function and enhanced utilization of myocardial glycogen.

Mitochondrial dysfunction in adults after out-of-hospital cardiac arrest

BACKGROUND

While preclinical studies suggest that mitochondria play a pivotal role in ischaemia-reperfusion injury, the knowledge of mitochondrial function in human out-of-hospital cardiac arrest remains scarce. The present study sought to compare oxidative phosphorylation capacity in skeletal muscle biopsies from out-of-hospital cardiac arrest patients to healthy controls.

METHODS

This was a substudy of a randomised trial comparing targeted temperature management at 33°C versus 36°C for out-of-hospital cardiac arrest patients. Skeletal muscle biopsies were obtained from adult resuscitated comatose out-of-hospital cardiac arrest patients 28 hours after initiation of targeted temperature management, i.e. at target temperature prior to rewarming, and from age-matched healthy controls. Mitochondrial function was analysed by high-resolution respirometry. Maximal sustained respiration through complex I, maximal coupled respiration through complex I and complex II and maximal electron transport system capacity was compared.

RESULTS

A total of 20 out-of-hospital cardiac arrest patients and 21 controls were included in the analysis. We found no difference in mitochondrial function between temperature allocations. We found no difference in complex I sustained respiration between out-of-hospital cardiac arrest and controls (23 (18-26) vs. 22 (19-26) pmol O₂/mg/s, P=0.76), whereas coupled complex I and complex II respiration was significantly lower in out-of-hospital cardiac arrest patients versus controls (53 (42-59) vs. 64 (54-68) pmol O₂/mg/s, P=0.01). Furthermore, electron transport system capacity was lower in out-of-hospital cardiac arrest versus controls (63 (51-69) vs. 73 (66-78) pmol O₂/mg/s, P=0.005).

CONCLUSIONS

Mitochondrial oxidative phosphorylation capacity in skeletal muscle biopsies was reduced in out-of-hospital cardiac arrest patients undergoing targeted temperature management compared to age-matched, healthy controls. The role of mitochondria as risk markers and potential targets for post-resuscitation care remains unknown.

Hemodynamic-Directed Cardiopulmonary Resuscitation Improves Neurologic Outcomes and Mitochondrial Function in the Heart and Brain

OBJECTIVES

Less than half of the thousands of children who suffer in-hospital cardiac arrests annually survive, and neurologic injury is common among survivors. Hemodynamic-directed cardiopulmonary resuscitation improves short-term survival, but its impact on longer term survival and mitochondrial respiration-a potential neurotherapeutic target-remains unknown. The primary objectives of this study were to compare rates of 24-hour survival with favorable neurologic outcome after cardiac arrest treated with hemodynamic-directed cardiopulmonary resuscitation versus standard depth-guided cardiopulmonary resuscitation and to compare brain and heart mitochondrial respiration between groups 24 hours after resuscitation.

DESIGN

Randomized preclinical large animal trial.

SETTING

A large animal resuscitation laboratory at a large academic children's hospital.

SUBJECTS

Twenty-eight 4-week-old female piglets (8-11 kg).

INTERVENTIONS

Twenty-two swine underwent 7 minutes of asphyxia followed by ventricular fibrillation and randomized treatment with either hemodynamic-directed cardiopulmonary resuscitation (n = 10; compression depth titrated to aortic systolic pressure of 90 mm Hg, vasopressors titrated to coronary perfusion pressure ≥ 20 mm Hg) or depth-guided cardiopulmonary resuscitation (n = 12; depth 1/3 chest diameter, epinephrine every 4 min). Six animals (sham group) underwent anesthesia and instrumentation without cardiac arrest. The primary outcomes were favorable neurologic outcome (swine Cerebral Performance Category ≤ 2) and mitochondrial maximal oxidative phosphorylation utilizing substrate for complex I and complex II (OXPHOSCI+CII) in the cerebral cortex and hippocampus.

MEASUREMENTS AND MAIN RESULTS

Favorable neurologic outcome was more likely with hemodynamic-directed cardiopulmonary resuscitation (7/10) than depth-guided cardiopulmonary resuscitation (1/12; p = 0.006). Hemodynamic-directed cardiopulmonary resuscitation resulted in higher intra-arrest coronary perfusion pressure, aortic pressures, and brain tissue oxygenation. Hemodynamic-directed cardiopulmonary resuscitation resulted in higher OXPHOSCI+CII (pmol oxygen/s × mg/citrate synthase) in the cortex (6.00 ± 0.28 vs 3.88 ± 0.43; p < 0.05) and hippocampus (6.26 ± 0.67 vs 3.55 ± 0.65; p < 0.05) and higher complex I respiration (pmol oxygen/s × mg) in the right (20.62 ± 1.06 vs 15.88 ± 0.81; p < 0.05) and left ventricles (20.14 ± 1.40 vs 14.17 ± 1.53; p < 0.05).

CONCLUSIONS

In a model of asphyxia-associated pediatric cardiac arrest, hemodynamic-directed cardiopulmonary resuscitation increases rates of 24-hour survival with favorable neurologic outcome, intra-arrest hemodynamics, and cerebral and myocardial mitochondrial respiration.

Cerebral mitochondrial dysfunction associated with deep hypothermic circulatory arrest in neonatal swine

OBJECTIVES

Controversy remains regarding the use of deep hypothermic circulatory arrest (DHCA) in neonatal cardiac surgery. Alterations in cerebral mitochondrial bioenergetics are thought to contribute to ischaemia-reperfusion injury in DHCA. The purpose of this study was to compare cerebral mitochondrial bioenergetics for DHCA with deep hypothermic continuous perfusion using a neonatal swine model.

METHODS

Twenty-four piglets (mean weight 3.8 kg) were placed on cardiopulmonary bypass (CPB): 10 underwent 40-min DHCA, following cooling to 18°C, 10 underwent 40 min DHCA and 10 remained at deep hypothermia for 40 min; animals were subsequently rewarmed to normothermia. 4 remained on normothermic CPB throughout. Fresh brain tissue was harvested while on CPB and assessed for mitochondrial respiration and reactive oxygen species generation. Cerebral microdialysis samples were collected throughout the analysis.

RESULTS

DHCA animals had significantly decreased mitochondrial complex I respiration, maximal oxidative phosphorylation, respiratory control ratio and significantly increased mitochondrial reactive oxygen species (P < 0.05 for all). DHCA animals also had significantly increased cerebral microdialysis indicators of cerebral ischaemia (lactate/pyruvate ratio) and neuronal death (glycerol) during and after rewarming.

CONCLUSIONS

DHCA is associated with disruption of mitochondrial bioenergetics compared with deep hypothermic continuous perfusion. Preserving mitochondrial health may mitigate brain injury in cardiac surgical patients. Further studies are needed to better understand the mechanisms of neurological injury in neonatal cardiac surgery and correlate mitochondrial dysfunction with neurological outcomes.

Preliminary observations in systemic oxygen consumption during targeted temperature management after cardiac arrest

AIM

Limited data suggests low oxygen consumption (VO₂), driven by mitochondrial injury, is associated with mortality after cardiac arrest. Due to the challenges of measurement in the critically ill, post-arrest metabolism remains poorly characterized. We monitored VO₂, carbon dioxide production (VCO₂) and the respiratory quotient (RQ) in post-arrest patients and explored associations with outcome.

METHODS

Using a gas exchange monitor, we measured continuous VO₂ and VCO₂ in post- arrest patients treated with targeted temperature management. We used area under the curve and medians over time to evaluate the association between VO₂, VCO₂, RQ and the VO₂:lactate ratio with survival.

RESULTS

In 17 patients, VO₂ in the first 12 h after return of spontaneous circulation (ROSC) was associated with survival (median in survivors 3.35 mL/kg/min [2.98,3.88] vs. non-survivors 2.61 mL/kg/min [2.21,2.94], p = .039). This did not persist over 24 h. The VO₂:lactate ratio was associated with survival (median in survivors 1.4 [IQR: 1.1,1.7] vs. non-survivors 0.8 [IQR: 0.6,1.2] p < 0.001). Median RQ was 0.66 (IQR 0.63,0.70) and 71% of RQ measurements were <0.7. Patients with initial RQ < 0.7 had 17% survival versus 64% with initial RQ > 0.7 (p = .131). VCO₂ was not associated with survival.

CONCLUSIONS

There was a significant association between VO₂ and mortality in the first 12 h after ROSC, but not over 24 h. Lower VO_2: lactate ratio was associated with mortality. A large percentage of patients had RQs below physiologic norms. Further research is needed to explore whether these parameters could have true prognostic value or be a potential treatment target.

Characterization of mitochondrial injury after cardiac arrest (COMICA)

INTRODUCTION

Mitochondrial injury post-cardiac arrest has been described in pre-clinical settings but the extent to which this injury occurs in humans remains largely unknown. We hypothesized that increased levels of mitochondrial biomarkers would be associated with mortality and neurological morbidity in post-cardiac arrest subjects.

METHODS

We performed a prospective multicenter study of post-cardiac arrest subjects. Inclusion criteria were comatose adults who suffered an out-of-hospital cardiac arrest. Mitochondrial biomarkers were measured at 0, 12, 24, 36 and 48h after return of spontaneous circulation as well as in healthy controls.

RESULTS

Out of 111 subjects enrolled, 102 had evaluable samples at 0h. Cardiac arrest subjects had higher baseline cytochrome c levels compared to controls (2.18ng/mL [0.74, 7.74] vs. 0.16ng/mL [0.03, 0.91], p<0.001), and subjects who died had higher 0h cytochrome c levels compared to survivors (3.66ng/mL [1.40, 14.9] vs. 1.27ng/mL [0.16, 2.37], p<0.001). There were significantly higher Ribonuclease P (RNaseP) (3.3 [1.2, 5.7] vs. 1.2 [0.8, 1.2], p<0.001) and Beta-2microglobulin (B2M) (12.0 [1.0, 22.9], vs. 0.6 [0.6, 1.3], p<0.001) levels in cardiac arrest subjects at baseline compared to the control subjects. There were no differences between survivors and non-survivors for mitochondrial DNA, nuclear DNA, or cell free DNA.

CONCLUSIONS

Cytochrome c was increased in post- cardiac arrest subjects compared to controls, and in post-cardiac arrest non-survivors compared to survivors. Nuclear DNA and cell free DNA was increased in plasma of post-cardiac arrest subjects. There were no differences in mitochondrial DNA, nuclear DNA, or cell free DNA between survivors and non-survivors. Mitochondrial injury markers showed mixed results in the post-cardiac arrest period. Future research needs to investigate these differences.

Cytochrome C in Patients with Septic Shock

PURPOSE

Cytochrome c is an essential component of the electron transport chain, and circulating cytochrome c might be an indicator of mitochondrial injury. The objective of this study was to determine whether cytochrome c levels are elevated in septic patients, whether there is an association between cytochrome c levels and lactate/inflammatory markers, and whether elevated levels of cytochrome c are associated with poor outcomes.

METHODS

This was a single-center, prospective, observational, pilot study within a randomized, placebo-controlled trial. We enrolled adult patients in septic shock and with an elevated lactate (>3 mmol/L). Blood was collected at enrollment and at 12 and 24  h thereafter. Cytochrome c was measured in plasma using an electrochemiluminescence immunoassay.

RESULTS

We included 77 patients. Plasma cytochrome c levels were significantly higher in septic patients than in healthy controls (0.70  ng/mL [quartiles: 0.06, 1.99] vs. 0.19  ng/mL [quartiles: 0.03, 1.32], P = 0.008). Cytochrome c levels at enrollment were positively correlated with lactate levels (r(s) = 0.40, P < 0.001) but not with inflammatory markers. Patients who died before hospital discharge had significantly higher cytochrome c levels than survivors (0.99  ng/mL [quartiles: 0.36, 4.09] vs. 0.58  ng/mL [quartiles: 0.03, 1.64], P = 0.01). When analyzed over time, the difference between survivors and nonsurvivors remained significant (P < 0.001).

CONCLUSIONS

Cytochrome c levels are higher in septic patients than in controls. In unadjusted analysis, septic nonsurvivors had higher cytochrome c levels than survivors.

Carbon Monoxide Improves Neurologic Outcomes by Mitochondrial Biogenesis after Global Cerebral Ischemia Induced by Cardiac Arrest in Rats

Mitochondrial dysfunction contributes to brain injury following global cerebral ischemia after cardiac arrest. Carbon monoxide treatment has shown potent cytoprotective effects in ischemia/reperfusion injury. This study aimed to investigate the effects of carbon monoxide-releasing molecules on brain mitochondrial dysfunction and brain injury following resuscitation after cardiac arrest in rats. A rat model of cardiac arrest was established by asphyxia. The animals were randomly divided into the following 3 groups: cardiac arrest and resuscitation group, cardiac arrest and resuscitation plus carbon monoxide intervention group, and sham control group (no cardiac arrest). After the return of spontaneous circulation, neurologic deficit scores (NDS) and S-100B levels were significantly decreased at 24, 48, and 72 h, but carbon monoxide treatment improved the NDS and S-100B levels at 24 h and the 3-day survival rates of the rats. This treatment also decreased the number of damaged neurons in the hippocampus CA1 area and increased the brain mitochondrial activity. In addition, it increased mitochondrial biogenesis by increasing the expression of biogenesis factors including peroxisome proliferator-activated receptor-γ coactivator-1α, nuclear respiratory factor-1, nuclear respiratory factor-2 and mitochondrial transcription factor A. Thus, this study showed that carbon monoxide treatment alleviated brain injury after cardiac arrest in rats by increased brain mitochondrial biogenesis.

Thiamine as a neuroprotective agent after cardiac arrest

AIMS

Reduction of pyruvate dehydrogenase (PDH) activity in the brain is associated with neurological deficits in animals resuscitated from cardiac arrest. Thiamine is an essential co-factor of PDH. The objective of this study was to examine whether administration of thiamine improves outcomes after cardiac arrest in mice. Secondarily, we aimed to characterize the impact of cardiac arrest on PDH activity in mice and humans.

METHODS

Animal study: Adult mice were subjected to cardiac arrest whereupon cardiopulmonary resuscitation was performed. Thiamine or vehicle was administered 2min before resuscitation and daily thereafter. Mortality, neurological outcome, and metabolic markers were evaluated. Human study: In a convenience sample of post-cardiac arrest patients, we measured serial PDH activity from peripheral blood mononuclear cells and compared them to healthy controls.

RESULTS

Animal study: Mice treated with thiamine had increased 10-day survival (48% versus 17%, P<0.01) and improved neurological function when compared to vehicle-treated mice. In addition, thiamine markedly improved histological brain injury compared to vehicle. The beneficial effects of thiamine were accompanied by improved oxygen consumption in mitochondria, restored thiamine pyrophosphate levels, and increased PDH activity in the brain at 10 days. Human study: Post-cardiac arrest patients had lower PDH activity in mononuclear cells than did healthy volunteers (estimated difference: -5.8O.D./min/mg protein, P<0.001).

CONCLUSIONS

The provision of thiamine after cardiac arrest improved neurological outcome and 10-day survival in mice. PDH activity was markedly depressed in post-cardiac arrest patients suggesting that this pathway may represent a therapeutic target.

Identifying the role of cytochrome c in post-resuscitation pathophysiology

Cytochrome c, an electron carrier that normally resides in the mitochondrial intermembrane space, may translocate to the cytosol under ischemic and hypoxic conditions and contribute to mitochondrial permeability transition pore opening. In addition, reperfusion of brain tissue following ischemia initiates a cell death cascade that includes cytochrome c-mediated induction of apoptosis. Further studies are needed to determine the contribution of cytochrome c in the regulation of cell death, as well as its value as an in vivo prognostic marker after cardiac arrest and resuscitation.

The science of reperfusion injury post cardiac arrest--Implications for emergency nurses

Survival following cardiac arrest in the developed world remains below 10%. In those who survive the initial cardiac arrest, prognosis remains poor due to the onset of multi-organ failure with both significant cardiac and neurological dysfunction. Nurses have demonstrated good understanding of cardiac arrest/post arrest guidelines and have good technical skills but deficits remain in their understanding of pathophysiological processes involved in post cardiac arrest syndromes. This article aims to provide an overview of these pathophysiological processes involved in the post cardiac arrest phase, potential treatment options and the nursing interventions that may be required within the emergency department setting. This article will focus emergency nurses to become more involved in patient management at this critical phase of treatment and highlight potential early signs of deterioration. Although return of spontaneous circulation (ROSC) is crucial in the process of recovery from cardiac arrest, it is only the first of many complex stages. Given the complexity of post cardiac arrest syndrome and its impact on the patient, healthcare professionals need to understand the cellular changes associated with reperfusion injuries in order to improve outcomes. It is only through effective nursing care and medical management that improved outcomes will become more common in the future.

Persistently Altered Brain Mitochondrial Bioenergetics After Apparently Successful Resuscitation From Cardiac Arrest

BACKGROUND

Although advances in cardiopulmonary resuscitation have improved survival from cardiac arrest (CA), neurologic injury persists and impaired mitochondrial bioenergetics may be critical for targeted neuroresuscitation. The authors sought to determine if excellent cardiopulmonary resuscitation and postresuscitation care and good traditional survival rates result in persistently disordered cerebral mitochondrial bioenergetics in a porcine pediatric model of asphyxia-associated ventricular fibrillation CA.

METHODS AND RESULTS

After 7 minutes of asphyxia, followed by ventricular fibrillation, 5 female 1-month-old swine (4 sham) received blood pressure-targeted care: titration of compression depth to systolic blood pressure of 90 mm Hg and vasopressor administration to a coronary perfusion pressure >20 mm Hg. All animals received protocol-based vasopressor support after return of spontaneous circulation for 4 hours before they were killed. The primary outcome was integrated mitochondrial electron transport system (ETS) function. CA animals displayed significantly decreased maximal, coupled oxidative phosphorylating respiration (OXPHOSCI + CII) in cortex (P<0.02) and hippocampus (P<0.02), as well as decreased phosphorylation and coupling efficiency (cortex, P<0.05; hippocampus, P<0.05). Complex I- and complex II-driven respiration were both significantly decreased after CA (cortex: OXPHOSCI P<0.01, ETSCII P<0.05; hippocampus: OXPHOSCI P<0.03, ETSCII P<0.01). In the hippocampus, there was a significant decrease in maximal uncoupled, nonphosphorylating respiration (ETSCI + CII), as well as a 30% reduction in citrate synthase activity (P<0.04).

CONCLUSIONS

Mitochondria in both the cortex and hippocampus displayed significant alterations in respiratory function after CA despite excellent cardiopulmonary resuscitation and postresuscitation care in asphyxia-associated ventricular fibrillation CA. Analysis of integrated ETS function identifies mitochondrial bioenergetic failure as a target for goal-directed neuroresuscitation after CA. IACUC Protocol: IAC 13-001023.

Minor Changes in Core Temperature Prior to Cardiac Arrest Influence Outcomes: An Experimental Study

AIM

To investigate whether slight variations in core temperature prior to cardiac arrest (CA) influence short-term outcomes and mitochondrial functions.

METHODS AND MATERIALS

Three groups of New Zealand White rabbits (n = 12/group) were submitted to 15 minutes of CA at 38°C (T-38 group), 39°C (T-39), or 40°C (T 40) and 120 minutes of reperfusion. A Sham-operated group (n = 6) underwent only surgery. Restoration of spontaneous circulation (ROSC), survival, hemodynamics, and pupillary reactivity were recorded. Animals surviving to the end of the observation period were euthanized to assess fresh brain and heart mitochondrial functions (permeability transition and oxidative phosphorylation). Markers of brain and heart damages were also measured.

RESULTS

The duration of asphyxia required to induce CA was significantly lower in the T-40 group when compared to the T-38 group (P < .05). The rate of ROSC was >80% in all groups (P = nonsignificant [ns]). Survival significantly differed among the T-38, T-39, and T-40 groups: 10 (83%) of 12, 7 (58%) of 12, and 4 (33%) of 12, respectively (log-rank test, P = .027). At the end of the protocol, none of the animals in the T-40 group had pupillary reflexes compared to 8 (67%) of 12 in the T-38 group (P < .05). Troponin and protein S100B were significantly higher in the T-40 versus T-38 group (P < .05). Cardiac arrest significantly impaired both inner mitochondrial membrane integrity and oxidative phosphorylation in all groups. Brain mitochondria disorders were significantly more severe in the T-40 group compared to the T-38 group (P < .05).

CONCLUSION

Small changes in body temperature prior to asphyxial CA significantly influence brain mitochondrial functions and short-term outcomes in rabbits.

Protective effect of shen-fu injection on neuronal mitochondrial function in a porcine model of prolonged cardiac arrest

Background. Shen-Fu injection (SFI) following cardiac arrest exhibits neurological effects, but its effect on neurological dysfunction is unclear. This study sought to investigate the protective effect of SFI on nerve cells in a porcine model of cardiac arrest. Methods. After eight minutes of untreated ventricular fibrillation (VF) and 2 minutes of basic life support, 24 pigs were randomized and divided into three cardiopulmonary resuscitation groups, which received central venous injection of either Shen-Fu (SFI group; 1.0 ml/kg), epinephrine (EP group; 0.02 mg/kg), or saline (SA group). Surviving pigs were sacrificed at 24 h after ROSC and brains were removed for analysis for morphologic changes of mitochondria by electron microscopy, for mitochondrial transmembrane potential (MTP) by flow cytometry, and for opening of the mitochondrial permeability transition pore (MPTP) by mitochondrial light scattering. Results. Compared with the EP and SA groups, SFI treatment reduced opening of MPTP, showing higher MMP. In addition, animals treated with SFI showed slight cerebral ultrastructure damage under the electron microscopy. Conclusion. Shen-Fu injection alleviated brain injury, improved neurological ultrastructure, stabilized membrane potential, and inhibited opening of MPTP. Therefore, SFI could significantly attenuate postresuscitation cerebral ischemia and reperfusion injury by modulating mitochondrial dysfunction of nerve cells.

Ubiquitous protective effects of cyclosporine A in preventing cardiac arrest-induced multiple organ failure

Opening of the mitochondrial permeability transition pore (mPTP) appears to be a pivotal event in myocardial ischemia-reperfusion (I/R) injury. Resuscitated cardiac arrest (CA) leads to the post-CA syndrome that encompasses, not only myocardial dysfunction, but also brain injury, failure of other organs (kidney, liver, or lung), and systemic response to I/R. We aimed to determine whether cyclosporine A (CsA) might prevent multiple organ failure following CA through a ubiquitous mPTP inhibition in each distant vital organ. Anesthetized New Zealand White rabbits were subjected to 15 min of CA and 120 min of reperfusion. At the onset of resuscitation, the rabbits received CsA, its non-immunosuppressive derivative NIM811, or vehicle (controls). Survival, hemodynamics, brain damage, organ injuries, and systemic I/R response were analyzed. Fresh mitochondria were isolated from the brain, heart, kidney, liver, and lung to assess both oxidative phosphorylation and permeability transition. CsA analogs significantly improved short-term survival and prevented multiple organ failure, including brain damage and myocardial dysfunction (P < 0.05 vs. controls). Susceptibility of mPTP opening was significantly increased in heart, brain, kidney, and liver mitochondria isolated from controls, while mitochondrial respiration was impaired (P < 0.05 vs. sham). CsA analogs prevented these mitochondrial dysfunctions (P < 0.05 vs. controls). These results suggest that CsA and NIM811 can prevent the post-CA syndrome through a ubiquitous mitochondrial protective effect at the level of each major distant organ.

A systematic review of neuroprotective strategies after cardiac arrest: from bench to bedside (Part I - Protection via specific pathways)

Neurocognitive deficits are a major source of morbidity in survivors of cardiac arrest. Treatment options that could be implemented either during cardiopulmonary resuscitation or after return of spontaneous circulation to improve these neurological deficits are limited. We conducted a literature review of treatment protocols designed to evaluate neurologic outcome and survival following cardiac arrest with associated global cerebral ischemia. The search was limited to investigational therapies that were utilized to treat global cerebral ischemia associated with cardiac arrest. In this review we discuss potential mechanisms of neurologic protection following cardiac arrest including actions of several medical gases such as xenon, argon, and nitric oxide. The 3 included mechanisms are: 1. Modulation of neuronal cell death; 2. Alteration of oxygen free radicals; and 3. Improving cerebral hemodynamics. Only a few approaches have been evaluated in limited fashion in cardiac arrest patients and results show inconclusive neuroprotective effects. Future research focusing on combined neuroprotective strategies that target multiple pathways are compelling in the setting of global brain ischemia resulting from cardiac arrest.

Impaired cerebral mitochondrial oxidative phosphorylation function in a rat model of ventricular fibrillation and cardiopulmonary resuscitation

Postcardiac arrest brain injury significantly contributes to mortality and morbidity in patients suffering from cardiac arrest (CA). Evidence that shows that mitochondrial dysfunction appears to be a key factor in tissue damage after ischemia/reperfusion is accumulating. However, limited data are available regarding the cerebral mitochondrial dysfunction during CA and cardiopulmonary resuscitation (CPR) and its relationship to the alterations of high-energy phosphate. Here, we sought to identify alterations of mitochondrial morphology and oxidative phosphorylation function as well as high-energy phosphates during CA and CPR in a rat model of ventricular fibrillation (VF). We found that impairment of mitochondrial respiration and partial depletion of adenosine triphosphate (ATP) and phosphocreatine (PCr) developed in the cerebral cortex and hippocampus following a prolonged cardiac arrest. Optimal CPR might ameliorate the deranged phosphorus metabolism and preserve mitochondrial function. No obvious ultrastructural abnormalities of mitochondria have been found during CA. We conclude that CA causes cerebral mitochondrial dysfunction along with decay of high-energy phosphates, which would be mitigated with CPR. This study may broaden our understanding of the pathogenic processes underlying global cerebral ischemic injury and provide a potential therapeutic strategy that aimed at preserving cerebral mitochondrial function during CA.