Asphyxial Cardiac Arrest Research Articles

Abstract 296: Early Mitochondrial Gene Regulation in Pediatric Cardiac Arrest

Introduction: Cerebral mitochondrial dysfunction is thought to play a role in the post-cardiac arrest syndrome, propagating secondary morbidity and mortality after return of spontaneous circulation (ROSC). Hypothesis: Based on our previous studies showing a persistent decrease in oxidative phosphorylation (particularly Complex I) and increased mitochondrial fission in a swine model of in-hospital cardiac arrest, we hypothesized that nuclear and mitochondrial genes related to respiratory function would be downregulated and genes promoting mitochondrial fission would be upregulated four hours post-ROSC. Methods: One-month old piglets were subjected to sham anesthesia (n=5) or asphyxial cardiac arrest (n=6; 7 minutes of asphyxia followed by induction of ventricular fibrillation) and treated with 10-20 minutes of AHA guideline-based CPR followed by four hours of standardized post-arrest management and humane euthanasia. RNA was extracted from flash-frozen sections of cerebral cortex using a QIAsymphony robot and sequenced on an Illumina HiSeq. Reads were aligned to the reference (SusScrofa11.1 and NC_012095) using STAR and quantified using subreads. Normalization and differential expression analysis were performed using DESeq2 with RNA quality, intra-arrest and post-ROSC physiologic variables as covariates. All p values were adjusted for multiple comparisons (Benjamini-Hochberg) with a significance cutoff of 0.05. Results: Compared to sham, cardiac arrest animals demonstrated reduced expression of multiple components of the respiratory chain, including NDUFA5 (2.4-fold, p<0.001) and NDUFC1 (2.0-fold, p=0.02), key components of Complex I. Components of Complex III (UQCRB, UQCRH) and Complex IV (COX1, COX7C, COX7A2, COX7B) were also downregulated. Dynamin-2 (DNM2), which increases mitochondrial fission, was upregulated (2.3-fold, p=0.005). There was also differential expression of inner membrane solute channel expression (SLC44A1, SLC25A48 and SLC25A16). Conclusions: Multiple components of the mitochondrial respiratory chain are downregulated 4 hours post-ROSC in the brain, including key components of Complex I with concurrent upregulation of the mitochondrial fission protein dynamin-2.

Abstract 102: Inhaled Nitric Oxide Mitigates Pulmonary Hypertension and Improves Cerebral Hemodynamics During Prolonged Cardiopulmonary Pesuscitation in a Swine Model of Pediatric Cardiac Arrest

Introduction: Pulmonary hypertension may play a role in preventing ROSC during prolonged CPR. Targeted pulmonary vasodilation with inhaled nitric oxide (iNO) during CPR may improve pulmonary blood flow and improve outcomes. The purpose of this study was to study the effects of iNO in a randomized, blinded, placebo controlled, pediatric swine model of asphyxial cardiac arrest. Hypothesis: Animals treated with iNO will have lower pulmonary artery pressure, improved systemic hemodynamics, and increased cerebral blood flow during prolonged CPR compared to control. Methods: Four-week-old piglets (n=10) that underwent seven minutes of asphyxia, induction of VF, and 10 minutes of CPR were randomized to either iNO (20 ppm) or placebo in a blinded fashion starting one min into CPR and needed more than 1 defibrillation attempt. Defibrillation was attempted after 10 minutes of CPR. Animals that did not achieve ROSC by 20 minutes were euthanized. Invasive pulmonary and systemic hemodynamics, and both invasive and noninvasive cerebral hemodynamics were continuously measured. Data described as mean ± SD and compared using a generalized estimating equation regression model. Results: All 5 iNO-treated animals and 2/5 placebo-treated animals achieved ROSC. Those treated with iNO had lower mean pulmonary artery pressures (29.5 ± 9.1 vs. 48.3 ± 5.6 mmHg, p=0.04); higher mean aortic pressures (51.9 ± 6.4 vs. 35.5 ± 4.4 mmHg, p=0.01); higher cerebral blood flow (invasive: 230.4 ± 57.4 vs. 28.7 ± 42.1 % baseline, p<0.001; noninvasive: 58.4 ± 10.9 vs. 32.4 ± 8.1 % baseline, p=0.02); and higher cerebral tissue oxygenation (invasive: 33.1 ± 13.0 vs. 1.2 ± 9.8 mmHg, p=0.01; noninvasive: 38.0 ± 4.2 vs. 26.2 ± 3.1%, p=0.005) compared with placebo. Conclusions: Treatment with iNO during prolonged CPR results in lower pulmonary artery pressure, improved systemic hemodynamics, and increased cerebral blood flow and oxygenation. Pulmonary vasodilation may have an important role during prolonged CPR for asphyxial cardiac arrests.

Abstract 328: Hemodynamic Comparison of Zucker Diabetic Fatty Rats to Their Lean Littermates After Asphyxial Cardiac Arrest

Patients with metabolic syndrome are at higher risk for cardiac arrest (CA), and also have worse neurologic outcome after CA related to their comorbidities (e.g., Type 2 Diabetes Mellitus [T2DM]). Using Zucker Diabetic Fatty (ZDF) rats as a new and relevant model with common comorbidities for CA and cardiopulmonary resuscitation (CPR), we hypothesized that T2DM is associated with a lower chance for return of spontaneous circulation (ROSC) and/or a worse outcome regarding heart function after asphyxial CA compared to their lean littermates. Two groups of rats (8 ZDF, 7 lean) were monitored for 37±2 weeks. The rats were anesthetized and intubated; heart rate was monitored by subcutaneous ECG needles. Femoral artery and vein were cannulated for continuous blood pressure measurement and delivery of fluids and medications, respectively. Before ventilation was stopped to initiate asphyxial CA, rocuronium was given. After 8 minutes of CA, ventilation was re-initiated with FiO 2 1.0, epinephrine and sodium-bicarbonate were administered, and pneumatic chest compression were started with 200 compressions per minute. Chest compressions were stopped when a systolic blood pressure of 120 mmHg was achieved. During 4 hours of observation, vital parameters were closely monitored, blood gases were measured, and ejection fraction (EF %) was assessed with ultrasound. Data are mean ± SD. Statistics: Unpaired student’s t-test (two-tailed), α.05. At baseline, ZDF rats showed significantly higher blood glucose levels (504±52 vs 174±14 mg/dl) compared to their lean littermates. All ZDF and lean rats achieved ROSC, and measurements taken directly after ROSC and after the first hour showed no relevant differences. After four hours, there was no difference in heart rate between ZDF and lean rats. However, diabetic rats had a significantly higher mean arterial blood pressure (142±24vs. 107±19 mmHg) and ejection fraction (42±16%vs 20±8%) compared to their lean littermates. The hypothesis that ROSC-rate in diabetic rats would be lower could not be proven. Conversely, the ZDF rats showed a significantly higher blood pressure related to an increased EF%. Further analysis in this study will focus on the impact of T2DM on cardiac and neurological ischemia-reperfusion injury.

Abstract 222: Role of Pathologic Calpain Activity in Post-Cardiac Arrest Hypothermic Targeted Temperature Management

Objective: Optimization of post-cardiac arrest hypothermic-targeted temperature management (HTTM) is limited by an inadequate understanding of the fundamental mechanisms of action. This study tested the hypothesis that post-cardiac arrest HTTM reduces delayed secondary neuronal cytosolic Ca 2+ overload that causes pathologic calpain activity and neuronal death after cardiac arrest (CA) Methods: Male Long Evens rats were subjected to 8-minute asphyxial CA (ACA) followed by CPR. Rats that achieved return of spontaneous circulation (ROSC) were block randomized to normothermic- targeted temperature management (NTTM; n=13), hypothermic-TTM at 36 o C (HTTM-36;n=13) or 33 o C (HTTM-33;n=10). HTTM was initiated 1h after ROSC and maintained for 24h. Neurologic function score was assessed daily. Rats were euthanized at 48h post-ROSC. Regional brain homogenates were generated in a subset of animals for Western blot analysis of calpain-cleaved alpha-spectrin as a measure of pathologic calpain activity (n=6/group). Sham rats were used as uninjured controls (n=9) Results: Survival at 48h post-ROSC was 69%, 69%, and 90% in the NTTM, HTTM-36 and HTTM-33 groups respectively (p>0.05: chi-squared). Survival with good neurologic function (GNF: defined as NFS > 450 out of 500) was 0%, 15%, and 60% in the NTTM, HTTM-36 and HTTM-33 groups respectively (p<0.05 for HTTM-33 vs. HTTM-36 and NTTM: chi-squared). Compared to NTTM, pathologic calpain activity in the hippocampus, cortex, caudoputamen, and cerebellum was decreased by 23±20%, 38±56%, 40±55%, 62±20% in the HTTM-36 groups and 33±13%, 55±72%, 66±89%, 69±17% in the HTTM-33 group respectively (p <0.05 for HTTM-33 and HTTM-36 cerebellum, p> 0.05 for all other regions: ANOVA, Tukey’s post-hoc) Conclusion: In this rat model of asphyxial cardiac arrest, HTTM with a target temperature of 33°C improved 48-hour survival with GNF compared to HTTM with a target temperature of 36°C and NTTM. Post-cardiac arrest regional brain calpain activity was significantly reduced with HTTM at 33°C and 36°C compared to NTTM in the cerebellum, but not other brain regions. Further work is needed to explore the potential causal link between the reduction of pathologic calpain activity and the neuroprotective effect of post-cardiac arrest HTTM

Abstract 10: Transcriptional Profiling of the Neuroprotective Mechanisms of Inhaled Nitric Oxide in a Swine Model of Pediatric Cardiac Arrest

Introduction: Neurologic morbidity is common after pediatric cardiac arrest and inhaled nitric oxide (iNO) may be protective. RNA sequencing may have a role in identifying differences in gene expression related to neurologic injury following cardiac arrest and the neuroprotective mechanism of iNO. Hypothesis: We hypothesized that genes related to energetically intensive functions such as synaptic vesicle trafficking would be downregulated after cardiac arrest and that this finding would be less prominent with iNO therapy. Methods: One-month old piglets underwent sham anesthesia or 7 minutes of asphyxia, induction of VF, and randomized and blinded therapy with AHA guideline-based CPR with iNO (iNO + ) or without iNO (iNO - ). Four hours post-ROSC, animals were euthanized and RNA was extracted from cerebral cortical tissue and sequenced on an Illumina HiSeq instrument. STAR was used to align reads to the SusScrofa11.1 reference followed by quantification with sub-reads. Normalization and differential expression analyses were performed using DESeq2 with RIN, RNA concentration, shocks delivered, epinephrine doses, post-ROSC epinephrine use, cerebral blood flow, ETCO 2 , and blood gas values as covariates. Benjamini-Hochberg-adjusted p values <0.05 were considered statistically significant. Results: Sham animals (n=5) and cardiac arrest animals with ROSC (iNO+ n=9; iNO- n=6) were included in analyses. 817 genes were differentially expressed between cardiac arrest and sham. 798 genes were differentially expressed between iNO + and iNO - . 24 genes were differentially expressed in opposite directions in the two comparisons, making them candidates for protective mechanisms of iNO. These included genes related to synaptic vesicle function (RAB27B, PACSIN1, DOC2A) and maintenance of synaptic structure (SH2D5, CA10). Cardiac arrest induced downregulation of synaptic vesicle genes including SNAP25 and synaptophysin, while iNO induced upregulation of others in the same ontology, including synapsins and synaptogamins. Conclusions: Piglets subjected to asphyxial cardiac arrest exhibited downregulation of genes related to synaptic vesicle trafficking. This was partially prevented by treatment with iNO.

Abstract 103: Propofol Infusion in the Early Post-Cardiac Arrest Phase Improves Cerebral Perfusion and Confers Anti-Apoptotic Neuroprotection via Akt-eNOS-NO Signaling

Introduction: Neurological outcome after cardiac arrest (CA) and CPR is usually unsatisfactory even in this era of target temperature management (TTM). Propofol is not only a useful sedative drug for TTM but confers neuroprotective effect. We previously showed that propofol combined with TTM improves survival in patients resuscitated from CA. In this study we aimed to explore the underlying mechanism focusing on cerebrovascular circulation and anti-apoptosis signaling. Hypothesis: Infusion of propofol in the early post-CA phase improves cerebral perfusion and mitigates neuronal apoptosis via Akt-eNOS signaling. Methods: Using an established rat model of asphyxia cardiac arrest and CPR, propofol infusion (20 mg/kg/h) was instituted after return of spontaneous circulation (ROSC) and continued in the first 2 h. Hemodynamics were monitored and the cerebral perfusion was continuously recorded by OxyFLO probe. The arterial blood was regularly sampled for measurement of reactive oxygen species (ROS, chemiluminescence method) and NO (demonstrated by nitrate/nitrite). Two hours after ROSC, the brain was harvested for measurement of casepase-3, endothelial NO synthase (eNOS) and protein kinase B (Akt). Results: After CA and CPR, the cerebral perfusion was significantly reduced to ~0.5 folds that of baseline. With the infusion of propofol, the cerebral perfusion was significantly increased from the beginning after ROSC ( P < 0.01 vs. CPR control). The plasma NO indicated by nitrate/nitrite 2 h post-CPR was significantly increased ( P < 0.01) while ROS abrogated ( P < 0.05). The cleaved caspase-3/caspase-3 of the brain was markedly reduced ( P < 0.001), suggesting anti-apoptotic neuroprotection. When exploring the mechanism, the phosphorylated (p)-eNOS/eNOS and p-Akt/Akt were significantly increased (both P < 0.001), indicating activation of Akt-eNOS-NO signaling. Conclusions: Infusion of propofol in the early post-CA phase reduces oxidative stress, improves cerebral perfusion, and ameliorates neuronal apoptosis. The protection is, at least in part, mediated via activation of Akt-eNOS-NO signaling.

Abstract 16: Spatiotemporally-Controlled Ultrasound-Triggered Release of Nitric Oxide Using Nano Au-Polymersomes/S-Nitrosoglutathione Mitigates Post-Resuscitation Cerebral Vasoconstriction and Neuronal Apoptosis via Reciprocating Akt-eNOS-NO Signaling

Introduction: Cerebral vasoconstriction in the post-resuscitation phase worsens neurological outcome. Nitric oxide (NO) plays important roles mediating vasodilatation and anti-apoptotic protection. We therefore designed an Au-polymersomes/S-nitrosoglutathione (Au-PLGA/GSNO) nanoparticle that can be triggered by ultrasound (US) to release NO, and investigated its roles in mitigating cerebral vasoconstriction and neuronal apoptosis post-CPR. Hypothesis: Spatiotemporally controlled, US-triggered NO release by Au-PLGA/GSNO improves post-CPR cerebral perfusion and confers anti-apoptotic neuroprotection. Methods: Using an established rat model of asphyxia cardiac arrest and CPR, Au-PLGA/GSNO (7500 PPM, 0.4 ml) was infused with simultaneous US (1 MHz) stimulation at the brain 10 min after ROSC. Brain tissue perfusion was continuously recorded by OxyFLO probe and cerebral vasculature videoed by CytoCam. The blood was sampled 2 h post-CPR for measurement of nitrate/nitrite, and the brain harvested for measurement of casepase-3, endothelial NO synthase (eNOS) and protein kinase B (Akt). In a subgroup the brain was harvested at 24 h for TUNEL stain. Results: After CPR, marked cerebral vasoconstriction was noted on CytoCam while brain perfusion significantly reduced to ~0.5 folds that of baseline. After Au-PLGA/GSNO infusion and US stimulation, cerebral vasoconstriction was ameliorated and the brain perfusion significantly enhanced ( P < 0.05 vs. CPR control). The plasma NO indicated by nitrate/nitrite 2 h post-CPR was significantly increased ( P < 0.01) while cleaved caspase-3/caspase-3 of the brain markedly reduced ( P < 0.001). TUNEL stain of the hippocampus CA1 and CA3 regions were also remarkably abrogated, suggesting anti-apoptotic neuroprotection. Specifically, the phosphorylated (p)-eNOS/eNOS and p-Akt/Akt were also increased ( P < 0.01 and 0.001, respectively), indicating reciprocating activation of Akt-eNOS signaling upstream of NO. Conclusion: Spatiotemporally controlled US-triggered NO release by Au-PLGA/GSNO mitigates cerebral vasoconstriction, improves brain perfusion and confers anti-apoptotic neuroprotection post-CPR via reciprocating Akt-eNOS-NO signaling.

Abstract 255: Dendrimer-Based N-Acetyl-l-Cysteine Therapy Improves 7 Days Outcomes After Cardiac Arrest in a Rat Model

Cardiac arrest (CA) entails significant risks of coma resulting in poor neurological and behavioral outcomes after resuscitation. Morbidity and mortality in post-CA patients are due largely to the cerebral dysfunction that accompanies prolonged whole-body ischemia called as post-CA syndrome (PCAS). PCAS involves strong inflammatory responses including neuroinflammation. Currently, there are no proven neuroprotective therapies to improve post-CA outcomes apart from therapeutic hypothermia. Furthermore, there are no acceptable approaches which can target neuroinflammation and lead to good neurological outcome post-CA. Moreover, delivering drugs across the blood-brain barrier to the target injured cells for treating diffuse brain injury is a major challenge. We hypothesize that dendrimer-based N-acetyl-L-cysteine (D-NAC) therapy ameliorates Neuroinflammation by specifically targeting activated glial cells and leads to a marked improvement in post-CA neurological outcome. we used an asphyxial CA rat model to determine the effects of D-NAC treatment. D-NAC was administered 30-minute post return of spontaneous circulation after cardiopulmonary resuscitation (ROSC). The behavioral neurologic deficit score (NDS score) was evaluated at 4, 24 and 48 hrs post-CA. CA resulted in a 50% decrease in survival and a dramatic decrease in NDS score acutely. D-NAC improved survival to 75% and led to a more rapid improvement in NDS scores when compared to the saline group in the short term while free NAC was not effective. We also tested long term (7 days) behavioral outcomes (novel object and fear conditioning) post-CA. Administration of D-NAC significantly improved novel object recognition and decreases freezing behavior in a novel context suggesting an improvement in cognitive deficits following CA in this model. In summary, acute administration of D-NAC following CA results in physiological and behavioral improvements both acutely and long term.

Melatonin improves neurological outcomes and preserves hippocampal mitochondrial function in a rat model of cardiac arrest.

Cerebral injury after cardiac arrest (CA)/cardiopulmonary resuscitation (CPR) has been implicated in the poor prognosis of CA survivors. This study was designed to evaluate the impact of melatonin on postresuscitation neurological outcomes and to explore the underlying mechanism. Sprague-Dawley rats were randomly assigned to four groups: sham group, CPR group, melatonin pretreatment group (Pre-M) and posttreatment group (Post-M). For the last 2 groups, daily melatonin gavage was performed for 12 consecutive days before or 24 hours after rat survival from CA/CPR. No statistical differences were observed in heart rate (HR), mean arterial blood pressure (MAP), and end-tidal carbon dioxide (ETCO2) at baseline and after restoration of spontaneous circulation (ROSC) among groups. However, melatonin pretreatment or posttreatment significantly improved neurological deficit score and memory and spatial learning ability after CA/CPR. Further studies demonstrated that the complex I- and complex-II supported mitochondrial respiration were greatly increased under melatonin treatment. In addition, melatonin treatment preserved the mitochondrial-binding hexokinase II (HKII) and ATP levels and suppressed the upregulated protein lysine acetylation in hippocampus after CA/CPR. In conclusion, using a rat asphyxial CA model we have demonstrated that treatment with melatonin either before or after CA/CPR provides a promising neuroprotective effect, and this protection was mediated by increasing mitochondrial HKII expression, suppressing protein acetylation and improving mitochondrial function in hippocampus.

Abstract 252: Older Brains vs. Younger Brains: Effect of Cardiac Arrest on Hemodynamic Fluctuations and Neurologic Impairment in a Rodent Model

Introduction: The patient suffering from cardiac arrest (CA) is elderly. Numerous laboratory experimental studies of CA are based on the young rodent model. Post-CA patients are often hemodynamically unstable, hypotension is correlated with poor neurologic outcomes. To improve the clinical relevance of CA research in laboratory, we compared the effect of CA in retired breeder (RB) and young group (YG) rats. Hypothesis: The objective of this study was to investigate the effect of CA on systemic arterial blood pressure and neurologic impairment outcomes in RB and YG rats. We hypothesize that RB rats will demonstrate lower mean arterial pressure (MAP) and delayed restoration of electroencephalogram (EEG) associated with neurologic recovery. Methods: Male RB Wistar rats (10-12 months, n=7) and male YG Wistar rats (2-2.5 months, n=6) were subjected to 7 min of asphyxia CA. Multiple parameters including MAP, EEG were recorded. The neurological outcomes were evaluated via neurological deficit score (NDS). Results: There was no significant difference between the two groups’ pre-arrest baseline characteristics except for the body weights (RB vs YG as 581 ± 54 vs 395 ± 9 g). This includes baseline heart rate, MAP, EEG and time to CA. After CA, RB rats showed significantly longer time to achieve return of spontaneous circulation (ROSC) compared to the YG (123 ± 42 vs 81 ± 9 sec, p < 0.05). RB rats showed lower MAP post ROSC compared to YG (98.8 ± 19.0 vs 115.0 ± 16.2 mmHg, p < 0.05 during 0-30 min post ROSC). The recovery sequences of EEG post ROSC are as follows: non-detectable cortical activity (non-DCA); intermittent cortical activity (ICA); continuous cortical activity (CCA). Analysis of recovering EEG indicates a higher gamma fraction for the RB rats during CCA period (p<0.03). High gamma is a surrogate for better EEG recovery for complex cognitive function. NDS scores were no significant difference for both groups from 4 hours to 7 days post ROSC. Conclusion: It appears that older rats have slower hemodynamic recovery post ROSC compared to younger rats. The neurologic deficits are similar in both groups, but cognitive recovery by Gamma fraction seems better in RB. More study is needed to fully understand the effect of aging on the post ROSC brain.

Effect of Electrical Vagus Nerve Stimulation on Cerebral Blood Flow and Neurological Outcome in Asphyxial Cardiac Arrest Model of Rats.

Vagus nerve stimulation (VNS) during post-resuscitation may increase recovery of cerebral blood flow (CBF) and reduce neurological injury. This study was designed to investigate the effect of electrical VNS on neurological outcomes following cardiac arrest (CA). Male Sprague-Dawley rats (n = 48) were subjected to the asphyxial CA model and blindly allocated to the VN isolation (CA + VN isolation) or VNS group (CA + VNS group). Cardiopulmonary resuscitation was initiated 450s after pulseless electrical arrest, and the left cervical vagus nerve was electrically stimulated (0.05mA, 1Hz) for 3h in the CA + VNS group. The neurological deficit score (NDS) and overall performance category (OPC) were assessed at 24h after resuscitation, and histological injury of the hippocampus was evaluated. Independent experiments were performed to evaluate the effect of VNS on global cortical CBF after resuscitation using laser speckle Doppler imaging through a thinned skull window from pre-arrest to 6h after resuscitation. The baseline characteristics were not significantly different between the two groups. The NDS was significantly higher, and the OPC was substantially lower in the CA + VNS group (p = 0.022 and p = 0.049, respectively) supported by decrease in histological injury of the hippocampal CA1 region. CBF in the early period of post-return of spontaneous circulation (ROSC) was significantly higher in the CA + VNS group (p < 0.05 at post-ROSC 2h and 4h), and 4-hydroxynonenal was significantly lower in the CA + VNS group (p = 0.026). VNS improved cerebral perfusion and neurological outcomes at 24h after ROSC in an asphyxial CA model of rats.

The aquaporin-4 inhibitor AER-271 blocks acute cerebral edema and improves early outcome in a pediatric model of asphyxial cardiac arrest.

Background:Cerebral edema after cardiac arrest (CA) is associated with increased mortality and unfavorable outcome in children and adults. Aquaporin-4 mediates cerebral water movement and its absence in models of ischemia improves outcome. We investigated early and selective pharmacologic inhibition of aquaporin-4 in a clinically relevant asphyxial CA model in immature rats in a threshold CA insult that produces primarily cytotoxic edema in the absence of blood brain barrier permeability.Methods:Postnatal day 16–18 Sprague-Dawley rats were studied in our established 9-min asphyxial CA model. Rats were randomized to aquaporin-4 inhibitor (AER-271) vs vehicle treatment, initiated at return of spontaneous circulation. Cerebral edema (% brain water) was the primary outcome with secondary assessments of the neurologic deficit score (NDS), hippocampal neuronal death, and neuroinflammation.Results:Treatment with AER-271 ameliorated early cerebral edema measured at 3 h after CA vs. vehicle treated rats. This treatment also attenuated early NDS. In contrast to rats treated with vehicle after CA, rats treated with AER-271 did not develop significant neuronal death or neuroinflammation as compared to sham.Conclusion:Early post-resuscitation aquaporin-4 inhibition blocks the development of early cerebral edema, reduces early neurologic deficit, and blunts neuronal death and neuroinflammation post-CA.

Proteasome Biology Is Compromised in White Matter After Asphyxic Cardiac Arrest in Neonatal Piglets.

BackgroundNeurological deficits in hypoxic‐ischemic encephalopathy, even with therapeutic hypothermia, are partially attributed to white matter injury. We theorized that proteasome insufficiency contributes to white matter injury.Methods and ResultsNeonatal piglets received hypoxia‐ischemia (HI) or sham procedure with normothermia, hypothermia, or hypothermia+rewarming. Some received a proteasome activator drug (oleuropein) or white matter–targeted, virus‐mediated proteasome knockdown. We measured myelin oligodendrocyte glycoprotein, proteasome subunit 20S (P20S), proteasome activity, and carbonylated and ubiquitinated protein levels in white matter and cerebral cortex. HI reduced myelin oligodendrocyte glycoprotein levels regardless of temperature, and myelin oligodendrocyte glycoprotein loss was associated with increased ubiquitinated and carbonylated protein levels. Ubiquitinated and carbonyl‐damaged proteins increased in white matter 29 hours after HI during hypothermia to exceed levels at 6 to 20 hours. In cortex, ubiquitinated proteins decreased. Ubiquitinated and carbonylated protein accumulation coincided with lower P20S levels in white matter; P20S levels also decreased in cerebral cortex. However, proteasome activity in white matter lagged behind that in cortex 29 hours after HI during hypothermia. Systemic oleuropein enhanced white matter P20S and protected the myelin, whereas proteasome knockdown exacerbated myelin oligodendrocyte glycoprotein loss and ubiquitinated protein accumulation after HI. At the cellular level, temperature and HI interactively affected macroglial P20S enrichment in subcortical white matter. Rewarming alone increased macroglial P20S immunoreactivity, but this increase was blocked by HI.ConclusionsOxidized and ubiquitinated proteins accumulate with HI‐induced white matter injury. Proteasome insufficiency may drive this injury. Hypothermia did not prevent myelin damage, protect the proteasome, or preserve oxidized and ubiquitinated protein clearance after HI.

Pilot Study to Compare the Use of End‐Tidal Carbon Dioxide–Guided and Diastolic Blood Pressure–Guided Chest Compression Delivery in a Swine Model of Neonatal Asphyxial Cardiac Arrest

BackgroundThe American Heart Association recommends use of physiologic feedback when available to optimize chest compression delivery. We compared hemodynamic parameters during cardiopulmonary resuscitation in which either end‐tidal carbon dioxide (ETCO 2) or diastolic blood pressure (DBP) levels were used to guide chest compression delivery after asphyxial cardiac arrest.Methods and ResultsOne‐ to 2‐week‐old swine underwent a 17‐minute asphyxial‐fibrillatory cardiac arrest followed by alternating 2‐minute periods of ETCO 2‐guided and DBP‐guided chest compressions during 10 minutes of basic life support and 10 minutes of advanced life support. Ten animals underwent resuscitation. We found significant changes to ETCO 2 and DBP levels within 30 s of switching chest compression delivery methods. The overall mean ETCO 2 level was greater during ETCO 2‐guided cardiopulmonary resuscitation (26.4±5.6 versus 22.5±5.2 mm Hg; P=0.003), whereas the overall mean DBP was greater during DBP‐guided cardiopulmonary resuscitation (13.9±2.3 versus 9.4±2.6 mm Hg; P=0.003). ETCO 2‐guided chest compressions resulted in a faster compression rate (149±3 versus 120±5 compressions/min; P=0.0001) and a higher intracranial pressure (21.7±2.3 versus 16.0±1.1 mm Hg; P=0.002). DBP‐guided chest compressions were associated with a higher myocardial perfusion pressure (6.0±2.8 versus 2.4±3.2; P=0.02) and cerebral perfusion pressure (9.0±3.0 versus 5.5±4.3; P=0.047).ConclusionsUsing the ETCO 2 or DBP level to optimize chest compression delivery results in physiologic changes that are method‐specific and occur within 30 s. Additional studies are needed to develop protocols for the use of these potentially conflicting physiologic targets to improve outcomes of prolonged cardiopulmonary resuscitation.

Comparison of the constant flow insufflation of oxygen with a one-way valve and intermittent positive pressure ventilation during cardiopulmonary resuscitation in asphyxic cardiac arrest

Comparison of the constant flow insufflation of oxygen with a one-way valve and intermittent positive pressure ventilation during cardiopulmonary resuscitation in asphyxic cardiac arrest

Metformin Improves Neurologic Outcome Via AMP-Activated Protein Kinase-Mediated Autophagy Activation in a Rat Model of Cardiac Arrest and Resuscitation.

BackgroundSudden cardiac arrest (CA) often results in severe injury to the brain, and neuroprotection after CA has proved to be difficult to achieve. Herein, we sought to investigate the effects of metformin pretreatment on brain injury secondary to CA and cardiopulmonary resuscitation.Methods and ResultsRats were subjected to 9‐minute asphyxial CA after receiving daily metformin treatment for 2 weeks. Survival rate, neurologic deficit scores, neuronal loss, AMP‐activated protein kinase (AMPK), and autophagy activation were assessed at indicated time points within the first 7 days after return of spontaneous circulation. Our results showed that metformin pretreatment elevated the 7‐day survival rate from 55% to 85% and significantly reduced neurologic deficit scores. Moreover, metformin ameliorated CA‐induced neuronal degeneration and glial activation in the hippocampal CA1 region, which was accompanied by augmented AMPK phosphorylation and autophagy activation in affected neuronal tissue. Inhibition of AMPK or autophagy with pharmacological inhibitors abolished metformin‐afforded neuroprotection, and augmented autophagy induction by metformin treatment appeared downstream of AMPK activation.ConclusionsTaken together, our data demonstrate, for the first time, that metformin confers neuroprotection against ischemic brain injury after CA/cardiopulmonary resuscitation by augmenting AMPK‐dependent autophagy activation.

Phenotyping Cardiac Arrest: Bench and Bedside Characterization of Brain and Heart Injury Based on Etiology.

Cardiac arrest etiology may be an important source of between-patient heterogeneity, but the impact of etiology on organ injury is unknown. We tested the hypothesis that asphyxial cardiac arrest results in greater neurologic injury than cardiac etiology cardiac arrest (ventricular fibrillation cardiac arrest), whereas ventricular fibrillation cardiac arrest results in greater cardiovascular dysfunction after return of spontaneous circulation. Prospective observational human and randomized animal study. University laboratory and ICUs. Five-hundred forty-three cardiac arrest patients admitted to ICU. Seventy-five male Sprague-Dawley rats. We examined neurologic and cardiovascular injury in Isoflurane-anesthetized rat cardiac arrest models matched by ischemic time. Hemodynamic and neurologic outcomes were assessed after 5 minutes no flow asphyxial cardiac arrest or ventricular fibrillation cardiac arrest. Comparison was made to injury patterns observed after human asphyxial cardiac arrest or ventricular fibrillation cardiac arrest. In rats, cardiac output (20 ± 10 vs 45 ± 9 mL/min) and pH were lower and lactate higher (9.5 ± 1.0 vs 6.4 ± 1.3 mmol/L) after return of spontaneous circulation from ventricular fibrillation cardiac arrest versus asphyxial cardiac arrest (all p < 0.01). Asphyxial cardiac arrest resulted in greater early neurologic deficits, 7-day neuronal loss, and reduced freezing time (memory) after conditioned fear (all p < 0.05). Brain antioxidant reserves were more depleted following asphyxial cardiac arrest. In adjusted analyses, human ventricular fibrillation cardiac arrest was associated with greater cardiovascular injury based on peak troponin (7.8 ng/mL [0.8-57 ng/mL] vs 0.3 ng/mL [0.0-1.5 ng/mL]) and ejection fraction by echocardiography (20% vs 55%; all p < 0.0001), whereas asphyxial cardiac arrest was associated with worse early neurologic injury and poor functional outcome at hospital discharge (n = 46 [18%] vs 102 [44%]; p < 0.0001). Most ventricular fibrillation cardiac arrest deaths (54%) were the result of cardiovascular instability, whereas most asphyxial cardiac arrest deaths (75%) resulted from neurologic injury (p < 0.0001). In transcending rat and human studies, we find a consistent phenotype of heart and brain injury after cardiac arrest based on etiology: ventricular fibrillation cardiac arrest produces worse cardiovascular dysfunction, whereas asphyxial cardiac arrest produces worsened neurologic injury associated with greater oxidative stress.

Activation of Pyruvate Dehydrogenase Activity by Dichloroacetate Improves Survival and Neurologic Outcomes After Cardiac Arrest in Rats.

No pharmacological interventions are currently available to provide neuroprotection for patients suffering from cardiac arrest. Dichloroacetate (DCA) is a pyruvate dehydrogenase kinase inhibitor, which activates pyruvate dehydrogenase (PDH), and increases cell adenosine triphosphate (ATP) production by promoting influx of pyruvate into the Krebs cycle. In this study, we investigated the effects of DCA on post-resuscitation neurological injury in an asphyxial cardiac arrest rat model. Asphyxial cardiac arrest was established by endotracheal tube clamping. A total of 111 rats were randomized into three groups: Sham group, Control group, and DCA intervention group. Animals in DCA intervention group were intraperitoneally administered DCA with a loading dose of 80 mg/kg at 15 min after return of spontaneous circulation (ROSC), whereas rats in the Control group received equivalent volume of saline. DCA treatment increased 3-day survival time, and reduced neurologic deficit scores at 24, 48, and 72 h after ROSC. It also attenuated cellular apoptosis and neuronal damage in the hippocampal cornuammonis one region by hematoxylin-eosin staining and TdT-mediated dUTP nick-end labeling assay. In addition, DCA reduced the messenger RNA expression of tumor necrosis factor α and interleukin 1β in brain hippocampus and cortex after ROSC. Furthermore, DCA treatment significantly increased ATP production, PDH activity, and decreased blood glucose, lactate, and brain pyruvate levels after ROSC. Our results suggested that DCA has neuroprotective effects on brain injury after cardiac arrest, and its salutary effects were associated with an increase of mitochondrial energy metabolism in the brain through activation of PDH activity.

Abstract P-019: COMPARISON BETWEEN SYNCHRONIZED AND NON-SYNCHRONIZED VENTILATION AND BETWEEN GUIDED AND NON-GUIDED CHEST COMPRESSIONS DURING RESUSCITATION IN A PEDIATRIC ANIMAL MODEL AFTER ASPHYXIAL CARDIAC ARREST

Aims & Objectives: To compare between synchronized and non-synchronized bag-valve-mask ventilation (BVMV) with chest compression and between guided and non-guided chest compression (CC) with a real-time feedback-device in a pediatric animal model of asphyxial cardiac arrest (CA). Methods Experimental model of asphyxial CA in piglets. Piglets were randomized for cardiopulmonary resuscitation (CPR) into four groups according to BVMV (synchronized and non-synchronized with CC) and to CC feedback (with and without CC feedback accelerometer, ZOLL®): Group A, guided-CC and synchronized ventilation; B, guided-CC and non-synchronized ventilation; C, non-guided CC and synchronized ventilation; D, non-guided CC and non-synchronized ventilation. Systolic, diastolic and mean blood pressure (SBP, DBP and MBP), and return of spontaneous circulation (ROSC) were compared between all groups. Results 43 piglets (median weight 11.8 kg) were studied. Twenty (46.5%) achieved ROSC: group A 36.4%, group B 75%, group C 30% and group D 46.5% (p=0.13). Survival rates was higher in group B than in A+C+D (75% vs 35.5%, p=0.02). ROSC was higher with non-synchronized ventilation (B+D 59.1% vs A+C 33.3%, p=0.091) and with guided-CC (A+B 56.5% vs C+D 35%, p=0.16). BP after 3 minutes of resuscitation are shown in Table 1. Non-synchronized ventilation was associated with higher SBP and MBP. No significant differences were found regarding blood pressures between group B and the rest of groups.Conclusions In a pediatric animal model of CA, non-synchronized ventilation and guided CPR obtained significantly higher survival rates. Better SBP and MBP after 3 minutes of resuscitation were achieved with non-synchronized ventilation.

Abstract P-018: ANALYSIS OF CHEST COMPRESSIONS QUALITY DURING RESUSCITATION IN A PEDIATRIC ANIMAL MODEL AFTER ASPHYXIAL CARDIAC ARREST

Aims & Objectives: To analyze quality of chest compressions (CC) during resuscitation and its impact on the return of spontaneous circulation (ROSC) in a pediatric animal model of cardiac arrest (CA) using a real-time feedback-device. Methods Depth and rate of CC were measured with an accelerometer (ZOLL®) during resuscitation in an experimental model of asphyxial CA in piglets. Compression depth between 3.8 and 5 cm and a rate between 100 and 120 compressions per minute were considered optimal. Results CC quality was recorded in 19 piglets. Twelve of them (63.2%) achieved ROSC. Only 41.3% of CC were optimal regarding rate and depth. Compression depth was optimal in 48.9%, too deep in 43.2% and too shallow in 7.9%. CC rate was optimal in 80.3%, too fast in 4.6% and slow in 15.1%. Compressions were more shallow and faster in piglets who recovered spontaneous circulation than in those who didn´t (table 1). Optimal compressions (rate and depth) (52.7 ± 25% vs 21.7 ± 16.2% p=0.010) and optimal depth (61.9 ± 28.2% vs 26.5 ± 17% p=0.008) were associated with higher ROSC. Animals who suffered airway bleeding or thoracic injuries had received deeper CC after 3 minutes of CPR, p=0.006. There was a correlation between mean arterial pressure and quality of CC (table 2).Conclusions In this pediatric CA model, only 41.3% of chest compressions were optimal. Optimal quality of CPR was associated with higher survival. Excessive CC depth was associated with airway bleeding or thoracic injuries and increased mortality.