Animal Model Of Cardiac Arrest Research Articles

Abstract 141: Automated Head-Up Cardiopulmonary Resuscitation Increased End Tidal Co2 in Patients With Out-of-Hospital Cardiac Arrest Compared With Conventional CPR: A Prospective Before-After Interventional Study

Background: Little is known in humans about the physiological effects of the combination of automated Head-Up cardiopulmonary resuscitation CPR, active compression-decompression CPR and an impedance threshold device (ITD). This new approach, termed AHUP-CPR, improves perfusion of vital organs and lowers intracranial pressure compared with conventional (C)CPR in animal models of cardiac arrest. This study tested the hypothesis that AHUP-CPR treatment would increase end tidal CO2 (ETCO2), a circulation surrogate, more than C-CPR in out-of-hospital cardiac arrest (OHCA) patients. Method: Prospective before-after interventional study of witnessed OHCA patients. C-CPR and AHUP-CPR were performed by firefighters who measured ETCO2. AHUP-CPR was delivered using a LUCAS AD (5 cm of compression and 3 cm active decompression) (Stryker Medical, USA), an EleGARD Patient Positioning System (AdvancedCPR Solutions, USA), and an ITD (ResQPOD-16, Zoll, USA). The study was performed in the greater Grenoble France region in four different fire stations. The primary endpoint was the measurement of maximum EtCO2 during CPR. Results are presented as mean ± standard deviation. Results: Baseline characteristics (age, sex, arrest location, initial rhythm, bystander CPR, witnessed) were not statistically different between groups.EtCO2 was higher for patients treated with AHUP-CPR (n=63) compared to the C-CPR (n=59) (41±18 vs. 30.2 mmHg, p<0.001). This difference was significant for shockable (45±13 vs. 34±12 mmHg, p=0.03) and non-shockable (40±19 vs. 28±13 mmHg, p=0.004) rhythms, respectively. The calculated difference between the maximum and first recorded ETCO2 values was 6.3 ± 20.4 in the C-CPR arm versus 21.1 ± 20.6 in the AHUP-CPR group (P<0.001). A total of 29% (n=18) of the AHUP patients vs. 22 % (n=13) were admitted alive to the hospital (P=0.34). Conclusion: Results from this first prospective clinical trial on AHUP-CPR demonstrated that ETCO2 values were significantly higher after AHUP-CPR versus C-CPR, regardless of the presenting rhythm. Using ETCO2 as a surrogate for circulation, these findings confirm animal studies showing AHUP-CPR provides significantly more vital organ blood flow to patients in OHCA compared with C-CPR.

Surge of neurophysiological coupling and connectivity of gamma oscillations in the dying human brain

The brain is assumed to be hypoactive during cardiac arrest. However, animal models of cardiac and respiratory arrest demonstrate a surge of gamma oscillations and functional connectivity. To investigate whether these preclinical findings translate to humans, we analyzed electroencephalogram and electrocardiogram signals in four comatose dying patients before and after the withdrawal of ventilatory support. Two of the four patients exhibited a rapid and marked surge of gamma power, surge of cross-frequency coupling of gamma waves with slower oscillations, and increased interhemispheric functional and directed connectivity in gamma bands. High-frequency oscillations paralleled the activation of beta/gamma cross-frequency coupling within the somatosensory cortices. Importantly, both patients displayed surges of functional and directed connectivity at multiple frequency bands within the posterior cortical "hot zone," a region postulated to be critical for conscious processing. This gamma activity was stimulated by global hypoxia and surged further as cardiac conditions deteriorated in the dying patients. These data demonstrate that the surge of gamma power and connectivity observed in animal models of cardiac arrest can be observed in select patients during the process of dying.

Efficacy of inhaled hydrogen on neurological outcome following brain ischaemia during post-cardiac arrest care (HYBRID II): a multi-centre, randomised, double-blind, placebo-controlled trial

Inhaled molecular hydrogen gas (H2) has been shown to improve outcomes in animal models of cardiac arrest (CA). H2 inhalation is safe and feasible in patients after CA. We investigated whether inhaled H2 would improve outcomes after out-of-hospital CA (OHCA). HYBRID II is a prospective, multicentre, randomised, double-blind, placebo-controlled trial performed at 15 hospitals in Japan, between February 1, 2017, and September 30, 2021. Patients aged 20-80 years with coma following cardiogenic OHCA were randomly assigned (1:1) using blinded gas cylinders to receive supplementary oxygen with 2% H2 or oxygen (control) for 18h. The primary outcome was the proportion of patients with a 90-day Cerebral Performance Category (CPC) of 1 or 2 assessed in a full-analysis set. Secondary outcomes included the 90-day score on a modified Rankin scale (mRS) and survival. HYBRID II was registered with the University Hospital Medical Information Network (registration number: UMIN000019820) and re-registered with the Japan Registry for Clinical Trials (registration number: jRCTs031180352). The trial was terminated prematurely because of the restrictions imposed on enrolment during the COVID-19 pandemic. Between February 1, 2017, and September 30, 2021, 429 patients were screened for eligibility, of whom 73 were randomly assigned to H2 (n=39) or control (n=34) groups. The primary outcome, i.e., a CPC of 1 or 2at 90 days, was achieved in 22 (56%) and 13 (39%) patients in the H2 and control groups (relative risk compared with the control group, 0.72; 95% CI, 0.46-1.13; P=0.15), respectively. Regarding the secondary outcomes, median mRS was 1 (IQR: 0-5) and 5 (1-6) in the H2 and control groups, respectively (P=0.01). An mRS score of 0 was achieved in 18 (46%) and 7 (21%) patients in the H2 and control groups, respectively (P=0.03). The 90-day survival rate was 85% (33/39) and 61% (20/33) in the H2 and control groups, respectively (P=0.02). The increase in participants with good neurological outcomes following post-OHCA H2 inhalation in a selected population of patients was not statistically significant. However, the secondary outcomes suggest that H2 inhalation may increase 90-day survival without neurological deficits. Taiyo Nippon Sanso Corporation. For the Japanese translation of the abstract see Supplementary Materials section.

Protection Against Post-resuscitation Acute Kidney Injury by N-Acetylcysteine via Activation of the Nrf2/HO-1 Pathway.

Background and ObjectiveAcute kidney injury (AKI), the common complication after cardiopulmonary resuscitation (CPR), seriously affects the prognosis of cardiac arrest (CA) patients. However, there are limited studies on post-resuscitation AKI. In addition, it has been demonstrated that N-acetylcysteine (N-AC) as an ROS scavenger, has multiorgan-protective effects on systemic and regional ischaemia-reperfusion injuries. However, no studies have reported its protective effects against post-resuscitation AKI and potential mechanisms. This study aimed to clarify the protective effects of N-AC on post-resuscitation AKI and investigate whether its potential mechanism was mediated by activating Nrf-2/HO-1 pathway in the kidney.MethodsWe established cardiac arrest models in rats. All animals were divided into four groups: the sham, control, N-AC, and ZnPP groups. Animals in each group except for the ZnPP group were assigned into two subgroups based on the survival time: 6 and 48 h. The rats in the control, N-AC, and ZnPP groups underwent induction of ventricular fibrillation (VF), 8 min untreated VF and cardiopulmonary resuscitation. Renal function indicators, were detected using commercial kits. Renal pathologic changes were assessed by haematoxylin–eosin (HE) staining. Oxidative stress and inflammatory responses were measured using the corresponding indicators. Apoptosis was evaluated using terminal uridine nick-end labeling (TUNEL) staining, and expression of proteins associated with apoptosis and the Nrf-2/HO-1 pathway was measured by western blotting.ResultsN-AC inhibited post-resuscitation AKI. We observed that N-AC reduced the levels of biomarkers of renal function derangement; improved renal pathological changes; and suppressed apoptosis, oxidative stress, and inflammatory response. Additionally, the production of ROS in the kidneys markedly decreased by N-AC. More importantly, compared with the control group, N-AC further upregulated the expression of nuclear Nrf2 and endogenous HO-1 in N-AC group. However, N-AC-determined protective effects on post-resuscitation AKI were markedly reversed after pretreatment of the HO-1 inhibitor zinc protoporphyrin (ZnPP).ConclusionsN-AC alleviated renal dysfunction and prolonged survival in animal models of CA. N-AC partially exerts beneficial renal protection via activation of the Nrf-2/HO-1 pathway. Altogether, all these findings indicated that N-AC as a common clinical agent, may have the potentially clinical utility to improve patients the outcomes in cardiac arrest.

A comprehensive neuromonitoring approach in a large animal model of cardiac arrest.

BackgroundAnoxic brain injuries represent the main determinant of poor outcome after cardiac arrest (CA). Large animal models have been described to investigate new treatments during CA and post‐resuscitation phase, but a detailed model that includes extensive neuromonitoring is lacking.MethodBefore an electrically‐induced 10‐minute CA and resuscitation, 46 adult pigs underwent neurosurgery for placement of a multifunctional probe (intracranial pressure or ICP, tissue oxygen tension or PbtO2 and cerebral temperature) and a bolt‐based technique for the placement and securing of a regional blood flow probe and two sEEG electrodes; two modified cerebral microdialysis (CMD) probes were also inserted in the frontal lobes and accidental misplacement was prevented using a perforated head support.Result42 animals underwent the CA procedure and 41 achieved the return of spontaneous circulation (ROSC). In 4 cases (8.6%) an adverse event took place during preparation, but only in two cases (4.3%) this was related to the neurosurgery. In 6 animals (13.3%) the minor complications that occurred resolved after probe repositioning.ConclusionHerein we provide a detailed comprehensive neuromonitoring approach in a large animal model of CA that might help future research.

Hemodynamic efficacy of a motor-driven automatic device performing simultaneous sternothoracic cardiopulmonary resuscitation compared to standard cardiopulmonary resuscitation in an animal model of cardiac arrest

The aim of this study was to investigate hemodynamic effects and resuscitation outcomes of simultaneous sternothoracic cardiopulmonary resuscitation (SST-CPR) with a prototype of a motor-driven automatic device, comparing to manual standard CPR (S-CPR), in an animal model of ventricular fibrillation (VF). 20 male pigs were randomized to receive standard CPR (S-CPR group) or CPR with an automatic SST-CPR device (A-CPR group) after 5 minutes of VF. Five minutes of basic life support CPR was performed, followed by 10 minutes of advanced life support CPR. Hemodynamic variables including systolic blood pressure (SBP), diastolic blood pressure (DBP), coronary perfusion pressure (CPP), and end-tidal carbon dioxide tension (ETCO2), and resuscitation outcomes including rate of restoration of spontaneous circulation (ROSC) and 2-hour survival were compared between two groups. Ten animals among the A-CPR group and 8 animals among the S-CPR group were included in the final analysis. SBP was higher in the A-CPR group than in the S-CPR group during CPR (p = 0.046). The DBP, CPP and ETCO2 were not different between two groups (p = 0.412, 0.585, and 0.243, respectively). ROSC rate was 38% in the S-CPR group and 10% in the A-CPR group (p = 0.275). The 2-hour survival rate was 25% in the S-CPR group and 0% in the A-CPR group (p = 0.183). In a swine model of cardiac arrest, CPR with a prototype of a motor-driven automatic SST-CPR device, compared with standard CPR, produced higher systolic blood pressure, but there was no difference in diastolic pressure, coronary perfusion pressure, ROSC rate and 2-hour survival rate.

Evaluation of a Novel Left Ventricular Assist Device for Resuscitation in an Animal Model of Ventricular Fibrillation Cardiac Arrest.

We evaluated an independently developed novel percutaneous implantable left ventricular assist device for resuscitation in a pig model of ventricular fibrillation cardiac arrest. The model was established in 10 domestic pigs by blocking the anterior descending coronary artery with a balloon after anesthesia. With ventilator-assisted ventilation, the independently developed percutaneous implantable left ventricular assist device was inserted via the femoral artery to assist circulation. According to whether effective circulatory support was achieved, the pigs were randomly divided into an experimental group and a control group. The experimental group was subjected to insertion of the assist device and received continuous circulatory support. The control group underwent insertion of the assist device; however, it did not start it within 15 minutes. For all animals, if successful rescue was achieved (sinus rhythm restoration within 15 minutes and maintenance for over 5 minutes), circulatory support was stopped, and the arterial blockage was removed. If sinus rhythm was not restored within 15 minutes, electric defibrillation, adrenaline injection, and removal of the arterial blockage were performed, and circulatory support was provided until sinus rhythm recovered. A determination of failed rescue was made when sinus rhythm was not restored after 1 hour. All successfully rescued animals were fed for 1 week. There were no significant differences in baseline data between the groups. All animals underwent successful novel left ventricular assist device implantation through the femoral artery. The rescue rate was significantly higher in the experimental group than in the control group (80% vs. 0%, n}{}P = 0.01n). All successfully rescued animals survived after 1 week of feeding, and no eating or movement abnormalities were observed. We conclude that this independently developed percutaneous implantable left ventricular assist device can be conveniently and rapidly implanted through the femoral artery and can maintain basic circulatory perfusion during resuscitation in an animal model of cardiac arrest.

Early Thalamic Injury After Resuscitation From Severe Asphyxial Cardiac Arrest in Developing Rats.

Children who survive cardiac arrest often develop debilitating sensorimotor and cognitive deficits. In animal models of cardiac arrest, delayed neuronal death in the hippocampal CA1 region has served as a fruitful paradigm for investigating mechanisms of injury and neuroprotection. Cardiac arrest in humans, however, is more prolonged than in most experimental models. Consequently, neurologic deficits in cardiac arrest survivors arise from injury not solely to CA1 but to multiple vulnerable brain structures. Here, we develop a rat model of prolonged pediatric asphyxial cardiac arrest and resuscitation, which better approximates arrest characteristics and injury severity in children. Using this model, we characterize features of microglial activation and neuronal degeneration in the thalamus 24 h after resuscitation from 11 and 12 min long cardiac arrest. In addition, we test the effect of mild hypothermia to 34°C for 8 h after 12.5 min of arrest. Microglial activation and neuronal degeneration are most prominent in the thalamic Reticular Nucleus (nRT). The severity of injury increases with increasing arrest duration, leading to frank loss of nRT neurons at longer arrest times. Hypothermia does not prevent nRT injury. Interestingly, injury occurs selectively in intermediate and posterior nRT segments while sparing the anterior segment. Since all nRT segments consist exclusively of GABA-ergic neurons, we asked if GABA-ergic neurons in general are more susceptible to hypoxic-ischemic injury. Surprisingly, cortical GABA-ergic neurons, like their counterparts in the anterior nRT segment, do not degenerate in this model. Hence, we propose that GABA-ergic identity alone is not sufficient to explain selective vulnerability of intermediate and posterior nRT neurons to hypoxic-ischemic injury after cardiac arrest and resuscitation. Our current findings align the animal model of pediatric cardiac arrest with human data and suggest novel mechanisms of selective vulnerability to hypoxic-ischemic injury among thalamic GABA-ergic neurons.

Changes of fibrinolytic system in thrombolytic resuscitation of pulmonary thromboembolism-induced cardiac arrest model.

The objective of this study is to explore the changes in the coagulation and fibrinolysis system in an animal model with pulmonary embolism after cardiopulmonary bypass and to provide a theoretical basis for clinical practice. An animal model of cardiac arrest due to pulmonary embolism was established for venous thrombus (10‐15 mL) in the left external jugular vein of 21 pigs. Computed tomography (CT) pulmonary arteriography was performed after the recovery of the underlying state, cardiac arrest state and spontaneous circulation, and then thrombolysis and cardiopulmonary resuscitation (recombinant tissue plasminogen activator [t‐PA] 50 mg) were performed immediately. The changes of tissue factor (TF), tissue factor pathway inhibitor (TFPI), t‐PA and plasminogen activator inhibitor‐1 (PAI‐1) in the blood were detected by ELISA. The blood samples were collected immediately, 1, 2, 4 and 6 hours after the recovery of spontaneous circulation. Data from animals that were successfully resuscitated at different time points were compared using a repeated measures one‐way analysis of variance. Seventeen pigs had cardiac arrest after 10 to 15 mL of thrombus injection, and the other four had cardiac arrest after 5 to 8 mL of additional thrombus. Nine pigs survived 6 hours of cardiopulmonary resuscitation. CT pulmonary angiogram showed pulmonary artery obstruction. TF levels were increased compared with basal status, but there was no statistical difference (P > .05). TFPI levels were higher at 1, 2, 4 and 6 hours after recovery of spontaneous circulation compared with basal state (P < .05); t‐PA levels were higher at cardiac arrest, and immediately after recovery of spontaneous circulation compared with basal state. There was a statistical difference in PAI‐1 level at 1, 2, 4 and 6 hours after recovery of spontaneous circulation (P < .05). There was no statistical difference in PAI‐1 level at each stage compared with basal state (P > .05). TFPI has a certain influence on the coagulation and thrombosis regulation of the body, and the increase in fibrinolytic activity has a positive promoting effect on the thrombolysis. It provided the theoretical basis of clinical treatment of thrombotic diseases.

Inhaled gases as novel neuroprotective therapies in the postcardiac arrest period.

The purpose of this review is to summarize recent advances about inhaled gases as novel neuroprotective agents in the postcardiac arrest period. Inhaled gases, as nitric oxide (NO) and molecular hydrogen (H2), and noble gases as xenon (Xe) and argon (Ar) have shown neuroprotective properties after resuscitation. In experimental settings, the protective effect of these gases has been demonstrated in both in-vitro studies and animal models of cardiac arrest. They attenuate neuronal degeneration and improve neurological function after resuscitation acting on different pathophysiological pathways. Safety of both Xe and H2 after cardiac arrest has been reported in phase 1 clinical trials. A randomized phase 2 clinical trial showed the neuroprotective effects of Xe, combined with targeted temperature management. Xe inhalation for 24 h after resuscitation preserves white matter integrity as measured by fractional anisotropy of diffusion tensor MRI. Inhaled gases, as Xe, Ar, NO, and H2 have consistently shown neuroprotective effects in experimental studies. Ventilation with these gases appears to be well tolerated in pigs and in preliminary human trials. Results from phase 2 and 3 clinical trials are needed to assess their efficacy in the treatment of postcardiac arrest brain injury.

Effect of Out-of-Hospital Sodium Nitrite on Survival to Hospital Admission After Cardiac Arrest

Therapeutic delivery of sodium nitrite during resuscitation improved survival in animal models of cardiac arrest, but efficacy has not been evaluated in clinical trials in humans. To determine whether parenteral administration of sodium nitrite given by paramedics during resuscitation for out-of-hospital cardiac arrest improved survival to hospital admission. Double-blind, placebo-controlled, phase 2 randomized clinical trial including 1502 adults in King County, Washington, with out-of-hospital cardiac arrest from ventricular fibrillation or nonventricular fibrillation. Patients underwent resuscitation by paramedics and were enrolled between February 8, 2018, and August 19, 2019; follow-up and data abstraction were completed by December 31, 2019. Eligible patients with out-of-hospital cardiac arrest were randomized (1:1:1) to receive 45 mg of sodium nitrite (n = 500), 60 mg of sodium nitrite (n = 498), or placebo (n = 499), which was given via bolus injection by the paramedics as soon as possible during active resuscitation. The primary outcome was survival to hospital admission and was evaluated with 1-sided hypothesis testing. The secondary outcomes included out-of-hospital variables (rate of return of spontaneous circulation, rate of rearrest, and use of norepinephrine to support blood pressure) and in-hospital variables (survival to hospital discharge; neurological outcomes at hospital discharge; cumulative survival to 24 hours, 48 hours, and 72 hours; and number of days in the intensive care unit). Among 1502 patients with out-of-hospital cardiac arrest who were randomized (mean age, 64 years [SD, 17 years]; 34% were women), 99% completed the trial. Overall, 205 patients (41%) in the 45 mg of sodium nitrite group and 212 patients (43%) in the 60 mg of sodium nitrite group compared with 218 patients (44%) in the placebo group survived to hospital admission; the mean difference for the 45-mg dose vs placebo was -2.9% (1-sided 95% CI, -8.0% to ∞; P = .82) and the mean difference for the 60-mg dose vs placebo was -1.3% (1-sided 95% CI, -6.5% to ∞; P = .66). None of the 7 prespecified secondary outcomes were significantly different, including survival to hospital discharge for 66 patients (13.2%) in the 45 mg of sodium nitrite group and 72 patients (14.5%) in the 60 mg of sodium nitrite group compared with 74 patients (14.9%) in the placebo group; the mean difference for the 45-mg dose vs placebo was -1.7% (2-sided 95% CI, -6.0% to 2.6%; P = .44) and the mean difference for the 60-mg dose vs placebo was -0.4% (2-sided 95% CI, -4.9% to 4.0%; P = .85). Among patients with out-of-hospital cardiac arrest, administration of sodium nitrite, compared with placebo, did not significantly improve survival to hospital admission. These findings do not support the use of sodium nitrite during resuscitation from out-of-hospital cardiac arrest. ClinicalTrials.gov Identifier: NCT03452917.

Remote Ischemic Postconditioning Inhibited Mitophagy to Achieve Neuroprotective Effects in the Rat Model of Cardiac Arrest.

Remote ischemic postconditioning (RI-postC) is an effective measure to improve nerve function after cardiac arrest. However, the brain protective mechanism of RI-postC has not been fully elucidated, and whether it is related to mitophagy is unclear. In this study, we used the rat model of cardiac arrest to study the effect of RI-postC on mitophagy and explore its possible signaling pathways. Rats were randomly divided into Sham group, CA/CPR group, Mdivi-1 group and RI-postC group. The animal model of cardiac arrest was established by asphyxia. RI-postC was performed by clamping and loosening the left femoral artery. Mdivi-1 was treated with a single intravenous injection. Levels of TOMM20, TIM23, Mfn1, PINK1 and parkin were detected by western blots. Mitochondrial membrane potential was measured by flow cytometry. Real-time PCR was used to detect relative mitochondrial DNA levels. The apoptosis of hippocampal neurons was detected by flow and TUNEL. In addition, Histopathological tests were performed. The results showed that RI-postC was similar to the mitophagy inhibitor Mdivi-1, which could inhibit the decrease of mitophagy-related protein level, improve mitochondrial membrane potential and up-regulate the ratio of mt-Atp6/Rpl13 after cardiopulmonary resuscitation (CPR). Furthermore, RI-postC could also reduce the rate of hippocampal nerve apoptosis and the damage of hippocampal neurons after CPR. Moreover, RI-postC and Mdivi-1 could reduce the protein levels of PINK1 and parkin in mitochondria after CPR, while increasing PINK1 levels in the cytoplasm. These findings suggested that RI-postC could inhibit the overactivation mitophagy through the PINK1/parkin signaling pathway, thus providing neuroprotective effects.

Neuronal Death in the CNS Autonomic Control Center Comes Very Early after Cardiac Arrest and Is Not Significantly Attenuated by Prompt Hypothermic Treatment in Rats.

Autonomic dysfunction in the central nervous system (CNS) can cause death after recovery from a cardiac arrest (CA). However, few studies on histopathological changes in animal models of CA have been reported. In this study, we investigated the prevalence of neuronal death and damage in various brain regions and the spinal cord at early times after asphyxial CA and we studied the relationship between the mortality rate and neuronal damage following hypothermic treatment after CA. Rats were subjected to 7–8 min of asphyxial CA, followed by resuscitation and prompt hypothermic treatment. Eight regions related to autonomic control (the cingulate cortex, hippocampus, thalamus, hypothalamus, myelencephalon, and spinal cord) were examined using cresyl violet (a marker for Nissl substance) and Fluoro-Jade B (a marker for neuronal death). The survival rate was 44.5% 1 day post-CA, 18.2% 2 days post-CA and 0% 5 days post-CA. Neuronal death started 12 h post-CA in the gigantocellular reticular nucleus and caudoventrolateral reticular nucleus in the myelencephalon and lamina VII in the cervical, thoracic, lumbar, and sacral spinal cord, of which neurons are related to autonomic lower motor neurons. In these regions, Iba-1 immunoreactivity indicating microglial activation (microgliosis) was gradually increased with time after CA. Prompt hypothermic treatment increased the survival rate at 5 days after CA with an attenuation of neuronal damages and death in the damaged regions. However, the survival rate was 0% at 12 days after CA. Taken together, our study suggests that the early damage and death of neurons related to autonomic lower motor neurons was significantly related to the high mortality rate after CA and that prompt hypothermic therapy could increase the survival rate temporarily after CA, but could not ultimately save the animal.

Ultrafast Hypothermia Selectively Mitigates the Early Humoral Response After Cardiac Arrest.

BackgroundTotal liquid ventilation (TLV) has been shown to prevent neurological damage though ultrafast cooling in animal models of cardiac arrest. We investigated whether its neuroprotective effect could be explained by mitigation of early inflammatory events.Methods and ResultsRabbits were submitted to 10 minutes of ventricular fibrillation. After resuscitation, they underwent normothermic follow‐up (control) or ultrafast cooling by TLV and hypothermia maintenance for 3 hours (TLV). Immune response, survival, and neurological dysfunction were assessed for 3 days. TLV improved neurological recovery and reduced cerebral lesions and leukocyte infiltration as compared with control (eg, neurological dysfunction score=34±6 versus 66±6% at day 1, respectively). TLV also significantly reduced interleukin‐6 blood levels during the hypothermic episode (298±303 versus 991±471 pg/mL in TLV versus control at 3 hours after resuscitation, respectively), but not after rewarming (752±563 versus 741±219 pg/mL in TLV versus control at 6 hours after resuscitation, respectively). In vitro assays confirmed the high temperature sensitivity of interleukin‐6 secretion. Conversely, TLV did not modify circulating high‐mobility group box 1 levels or immune cell recruitment into the peripheral circulation. The link between interleukin‐6 early transcripts (<8 hours) and neurological outcome in a subpopulation of the previously described Epo‐ACR‐02 (High Dose of Erythropoietin Analogue After Cardiac Arrest) trial confirmed the importance of this cytokine at the early stages as compared with delayed stages (>8 hours).ConclusionsThe neuroprotective effect of hypothermic TLV was associated with a mitigation of humoral interleukin‐6 response. A temperature‐dependent attenuation of immune cell reactivity during the early phase of the post–cardiac arrest syndrome could explain the potent effect of rapid hypothermia.RegistrationURL: https://www.clinicaltrials.gov; Unique identifier: NCT00999583.

Effect of ventilation rate on recovery after cardiac arrest in a pediatric animal model.

AimsTo assess the impact of two different respiratory rates in hemodynamic, perfusion and ventilation parameters in a pediatric animal model of cardiac arrest (CA).MethodsAn experimental randomized controlled trial was carried out in 50 piglets under asphyxial CA. After ROSC, they were randomized into two groups: 20 and 30 respirations per minute (rpm). Hemodynamic, perfusion and ventilation parameters were measured 10 minutes after asphyxia, just before ROSC and at 5, 15, 30 and 60 minutes after ROSC. Independent medians test, Kruskal-Wallis test and χ2 test, were used to compare continuous and categorical variables, respectively. Spearman’s Rho was used to assess correlation between continuous variables. A p-value <0.05 was considered significant.ResultsArterial partial pressure of carbon dioxide (PaCO2) was significantly lower in the 30 rpm group after 15 minutes (41 vs. 54.5 mmHg, p <0.01), 30 minutes (39.5 vs. 51 mmHg, p < 0.01) and 60 minutes (36.5 vs. 48 mmHg, p = 0.02) of ROSC. The percentage of normoventilated subjects (PaCO2 30–50 mmHg) was significantly higher in the 30 rpm group throughout the experiment. pH normalization occurred faster in the 30 rpm group with significant differences at 60 minutes (7.40 vs. 7.34, p = 0.02). Lactic acid levels were high immediately after ROSC in both groups, but were significantly lower in the 20 rpm group at 30 (3.7 vs. 4.7 p = 0.04) and 60 minutes (2.6 vs. 3.6 p = 0.03).ConclusionsThis animal model of asphyxial CA shows that a respiratory rate of 30 rpm is more effective to reach normoventilation than 20 rpm in piglets after ROSC. This ventilation strategy seems to be safe, as it does not cause hyperventilation and does not affect hemodynamics or cerebral tissue perfusion.

Meta-analysis of targeted temperature management in animal models of cardiac arrest

BackgroundTargeted temperature management (TTM) of 32 to 34 °C has been the standard treatment for out-of-hospital cardiac arrest since clinical trials in 2002 indicated benefit on survival and neurological outcome. In 2013, a clinical trial showed no difference in outcome between TTM of 33 °C and TTM of 36 °C. In this meta-analysis, we investigate the evidence for TTM in animal models of cardiac arrest.MethodsWe searched PubMed and EMBASE for adult animal studies using TTM as a treatment in different models of cardiac arrest or global brain ischemia which reported neurobehavioural outcome, brain histology or mortality. We used a random effects model to calculate estimates of efficacy and assessed risk of bias using an adapted eight-item version of the Collaborative Approach to Meta-Analysis and Review of Animal Data from Experimental Studies (CAMARADES) quality checklist. We also used a scoring system based on the recommendations of the Stroke Treatment Academic Industry Roundtable (STAIR), to assess the scope of testing in the field. Included studies which investigated a post-ischemic induction of TTM had their treatment regimens characterized with regard to depth, duration and time to treatment and scored against the modified STAIR criteria.ResultsThe initial and updated search generated 17809 studies after duplicate removal. One hundred eighty-one studies met the inclusion criteria, including data from 1,787, 6,495 and 2,945 animals for neurobehavioural, histological and mortality outcomes, respectively. TTM was favoured compared to control for all outcomes. TTM was beneficial using short and prolonged cooling, deep and moderate temperature reduction, and early and delayed time to treatment. Median [IQR] study quality was 4 [3 to 6]. Eighteen studies checked seven or more of the eight CAMARADES quality items. There was no clear correlation between study quality and efficacy for any outcome. STAIR analysis identified 102 studies investigating post-ischemic induction of TTM, comprising 147 different treatment regimens of TTM. Only 2 and 8 out of 147 regimens investigated comorbid and gyrencephalic animals, respectively.ConclusionsTTM is beneficial under most experimental conditions in animal models of cardiac arrest or global brain ischemia. However, research on gyrencephalic species and especially comorbid animals is uncommon and a possible translational gap. Also, low study quality suggests risk of bias within studies. Future animal research should focus on mimicking the clinical scenario and employ similar rigour in trial design to that of modern clinical trials.

Hydrogen gas inhalation alleviates oxidative stress in patients with post-cardiac arrest syndrome.

Oxidative stress plays a key role in the pathophysiology of post-cardiac arrest syndrome. Molecular hydrogen reduces oxidative stress and exerts anti-inflammatory effects in an animal model of cardiac arrest. However, its effect on human post-cardiac arrest syndrome is unclear. We consecutively enrolled five comatose post-cardiac arrest patients (three males; mean age, 65 ± 15 years; four cardiogenic, one septic cardiac arrest) and evaluated temporal changes in oxidative stress markers and cytokines with inhaled hydrogen. All patients were treated with target temperature management. Hydrogen gas inhalation (2% hydrogen with titrated oxygen) was initiated upon admission for 18 h. Blood hydrogen concentrations, plasma and urine oxidative stress markers (derivatives of reactive oxygen metabolites, biological antioxidant potential, 8-hydroxy-2'-deoxyguanosine, Nɛ-hexanoyl-lysine, lipid hydroperoxide), and cytokines (interleukin-6 and tumor necrosis factor-α) were measured before and 3, 9, 18, and 24 h after hydrogen gas inhalation. Arterial hydrogen concentration was measurable and it was equilibrated with inhaled hydrogen. Oxidative stress was reduced and cytokine levels were unchanged in cardiogenic patients, whereas oxidative stress was unchanged and cytokine levels were diminished in the septic patient. The effect of inhaled hydrogen on oxidative stress and cytokines in comatose post-cardiac arrest patients remains indefinite because of methodological weaknesses.

Abstract 13: Adenosine Receptor Activation During Extracorporeal Cardiopulmonary Resuscitation Improves Survival After Cardiac Arrest in Swine

Introduction: Despite advances in resuscitation protocols, including the addition of Extracorporeal Cardiopulmonary Resuscitation (ECPR), survival after cardiac arrest remains less than 40% and novel methods are needed to attenuate global injury and improve outcomes. ATL1223, an adenosine 2A receptor (A2AR) agonist has been shown to attenuate organ specific reperfusion injury by modulating the interaction of inflammatory cells. Hypothesis: A2AR activation during ECPR will improve survival and decrease the burden of injury in a large animal model of cardiac arrest. Methods: Adult swine underwent 20 minutes of circulatory arrest followed by defibrillation and 6 hours of ECPR. Animals were randomized to receive saline control (n=5) or the A2AR agonist Regadenoson (0.144 and 14.4mcg/kg/hr, n=5/group). Animals were subsequently weaned from ECPR and monitored for 24 hours. Clinical and biochemical endpoints were compared between groups. Results: The administration of Regadenoson increased survival after cardiac arrest compared to saline controls (10/10, 100% vs 2/5, 40%, p=0.02, Figure 1). Anesthetic administration (p=0.41), fluid resuscitation (p=0.54), and epinephrine required to maintain target arterial pressure (p=0.08) were similar for all subjects. Biochemical markers of organ damage, including creatinine (p=0.87), aspartate aminotransferase (p=0.89), and troponin I (p=0.38), were similar among groups (Figure 2). Conclusions: In a clinically relevant model of cardiac arrest treated with ECPR, selective A2AR agonism increased survival from 40% to 100% at 24 hours. These results suggest A2AR activation is a promising therapeutic target after cardiac arrest.

Abstract 19: Ultra-Fast Cooling Induced by Total Liquid Ventilation Provides Neuroprotection Through a Delay in the Acute Systemic Inflammatory Response After Cardiac Arrest in Rabbits

Introduction: Ultra-fast cooling with total liquid ventilation (TLV) is potently protective in animal models of cardiac arrest. Hypothesis: Here, we hypothesized that this protection involves a mitigation of the acute phase of the inflammatory syndrome after cardiac arrest. Methods: Rabbits were anesthetized and submitted to 10 min of ventricular fibrillation. After resuscitation, animals underwent normothermic follow-up (Control, n=6) or ultra-fast cooling by TLV started after resuscitation (TLV, n=6). TLV was used for induction of cooling during 20 min and hypothermia was further maintained during 3 h using external techniques before rewarming. A third group was submitted to a Sham procedure (n=5). Survival and neurological dysfunction were assessed during 3 days. Results: TLV improved the clinical neurological recovery as compared to Control group after cardiac arrest. It was corroborated by histological examination showing an attenuation of neuronal degeneration in parasagittal cortex and hippocampus in TLV vs Control groups. After resuscitation, TLV delayed the elevation of interleukin-6 blood levels as compared to Control after cardiac arrest (e.g., 298±63 vs 991±471 pg/ml at 180 min after cardiac arrest in TLV vs Control, respectively). Blood cytometry analyses showed a massive recruitment of neutrophils and leukocytes (including T4, T8 and B-lymphocytes) in both groups. The early lymphocytosis was attenuated in TLV vs Control groups, despite not achieving statistical significance. Blood levels of high-mobility group box 1 increased rapidly and similarly in both groups after cardiac arrest. This suggests that TLV does not mitigate the early release of danger-associated molecular patterns after resuscitation, which is closely related to the immediate cell death after resuscitation. Altogether, these results show an attenuation of the early inflammatory response during hypothermia, suggesting a role of early but not delayed inflammation in the mechanism of ultra-fast cooling after cardiac arrest. Conclusion: Beneficial effect of hypothermic TLV could be explained by a delay in immune peripheral cells activation and cytokine release, rather than sustained inhibition of inflammation after cardiac arrest.

Abstract 172: Ultra-Fast Cooling Through Total Liquid Ventilation is Safe and Feasible in Non-Human Primates

Introduction: Total liquid ventilation (TLV) with temperature-controlled perfluorocarbons (PFC) provides ultra-rapid and protective cooling in animal models of cardiac arrest. However, the ideal ventilatory parameters still need to be determined for a perfectly safe translation of the procedure in humans, especially regarding expiratory residual volume (RV) and tidal volume of PFC (TV) during TLV. Hypothesis: We hypothetised that TLV with low RV and TV of PFC is safe and efficient for ultra-fast cooling induction in non-human primates. Method: We enrolled two 13-years monkeys ( Macaca Fascicularis ) weighting 10.6 and 11.7 kg, respectively. Lung functional residual capacity (FRC) was measured by CT-scan and 3D-reconstruction of the lung. Two weeks later, animals were anesthetised and submitted to 20 min of TLV with end-expiratory volume of ≈50% of the FRC and TV = 8 ml/kg. The respiratory rate was set to 8/min and the target temperature was 33°C. After the TLV procedure, animals were weaned by prolonged exhalation followed by 6 hours under conventional mechanical ventilation (PEEP = 5 mmHg) before awakening. Three weeks later, they were ansthestized again for blood gases measurement and CT-scan examination for evaluation of the lung parenchyma integrity. Result: The initial CT-scan revealed a FRC of 26 and 32 ml/kg in the two animals, respectively. RV was then set at 15 ml/kg for TLV in both animals. During TLV, gas exchanges were normal (arterial partial pressure of CO 2 was 34 and 43 mmHg, respectively). Pulse oxymetry also remained above 97% throughout TLV. The target temperature of 33°C was achieved in the entire body within 15 min for both animals. Additionally, lung static compliance was not altered during or after TLV. After animal weaning, no any sign of respiratory discomfort was evidenced despite careful clinical monitoring. After three weeks, CT-scan examination revealed no structural abnormality of the lung parenchym and arterial partial pressure of CO 2 was normal (35 and 46 mmHg). Based on their excellent health status, animals were transferred to a rehabilitation center. Conclusion: Total liquid ventilation below FRC is feasible and safe, without any impairement of the cooling performance in a clinically relevant non-human primate model.