Global and regional differences in cerebral blood flow after asphyxial versus ventricular fibrillation cardiac arrest in rats using ASL-MRI

Relationships of Jugular Bulb Parameters with Cerebral Perfusion and Metabolism After Resuscitation from Cardiac Arrest: A Post-Hoc Analysis of Experimental Studies Using a Minipig Model

BACKGROUND

Cerebral blood flow (CBF) decreases in the first few hours or days following resuscitation from cardiac arrest, increasing the risk of secondary cerebral injury. Using data from experimental studies performed in minipigs, we investigated the relationships of parameters derived from arterial and jugular bulb blood gas analyses and lactate levels (jugular bulb parameters), which have been used as indicators of cerebral perfusion and metabolism, with CBF and the cerebral lactate to creatine ratio measured with dynamic susceptibility contrast magnetic resonance imaging and proton magnetic resonance spectroscopy, respectively.

METHODS

We retrospectively analyzed 36 sets of the following data obtained during the initial hours following resuscitation from cardiac arrest: percent of measured CBF relative to that at the prearrest baseline (%CBF), cerebral lactate to creatine ratio, and jugular bulb parameters, including jugular bulb oxygen saturation, jugular bulb lactate, arterial-jugular bulb oxygen content difference, cerebral extraction of oxygen, jugular bulb-arterial lactate content difference, lactate oxygen index, estimated respiratory quotient, and arterial-jugular bulb hydrogen ion content difference. Linear mixed-effects models were constructed to examine the effects of each jugular bulb parameter on the %CBF and cerebral lactate to creatine ratio.

RESULTS

The arterial-jugular bulb oxygen content difference (P = 0.047) and cerebral extraction of oxygen (P = 0.030) had a significant linear relationship with %CBF, but they explained only 12.0% (95% confidence interval [CI] 0.002-0.371) and 14.2% (95% CI 0.005-0.396) of the total %CBF variance, respectively. The arterial-jugular bulb hydrogen ion content difference had a significant linear relationship with cerebral lactate to creatine ratio (P = 0.037) but explained only 13.8% (95% CI 0.003-0.412) of the total variance in the cerebral lactate to creatine ratio. None of the other jugular bulb parameters were related to the %CBF or cerebral lactate to creatine ratio.

CONCLUSIONS

In conclusion, none of the jugular bulb parameters appeared to provide sufficient information on cerebral perfusion and metabolism in this setting.

Differences in Pathophysiology and Treatment Efficacy Based on Heterogeneous Out-of-Hospital Cardiac Arrest

Out-of-hospital cardiac arrest (OHCA) is heterogeneous in terms of etiology and severity. Owing to this heterogeneity, differences in outcome and treatment efficacy have been reported from case to case; however, few reviews have focused on the heterogeneity of OHCA. We conducted a literature review to identify differences in the prognosis and treatment efficacy in terms of CA-related waveforms (shockable or non-shockable), age (adult or pediatric), and post-CA syndrome severity and to determine the preferred treatment for patients with OHCA to improve outcomes.

Association between ASL MRI-derived cerebral blood flow and outcomes after pediatric cardiac arrest

AIM

Cerebral blood flow (CBF) is dysregulated after cardiac arrest. It is unknown if post-arrest CBF is associated with outcome. We aimed to determine the association of CBF derived from arterial spin labelling (ASL) MRI with outcome after pediatric cardiac arrest.

METHODS

Retrospective observational study of patients ≤18 years who had a clinically obtained brain MRI within 7 days of cardiac arrest between June 2005 and December 2019. Primary outcome was unfavorable neurologic status: change in Pediatric Cerebral Performance Category (PCPC) ≥1 from pre-arrest that resulted in hospital discharge PCPC 3-6. We measured CBF in whole brain and regions of interest (ROIs) including frontal, parietal, and temporal cortex, caudate, putamen, thalamus, and brainstem using pulsed ASL. We compared CBF between outcome groups using Wilcoxon Rank-Sum and performed logistic regression to associate each region's CBF with outcome, accounting for age, sex, and time between arrest and MRI.

RESULTS

Forty-eight patients were analyzed (median age 2.8 [IQR 0.95, 8.8] years, 65% male). Sixty-nine percent had unfavorable outcome. Time from arrest to MRI was 4 [3,5] days and similar between outcome groups (p = 0.39). Whole brain median CBF was greater for unfavorable compared to favorable groups (28.3 [20.9,33.0] vs. 19.6 [15.3,23.1] ml/100 g/min, p = 0.007), as was CBF in individual ROIs. Greater CBF in the whole brain and individual ROIs was associated with higher odds of unfavorable outcome after controlling for age, sex, and days from arrest to MRI (aOR for whole brain 19.08 [95% CI 1.94, 187.41]).

CONCLUSION

CBF measured 3-5 days after pediatric cardiac arrest by ASL MRI was independently associated with unfavorable outcome.

Differential Effects of Targeted Temperature Management on Sex-Dependent Outcomes After Experimental Asphyxial Cardiac Arrest

Asphyxial cardiac arrest (ACA) survivors face lasting neurological disability from hypoxic ischemic brain injury. Sex differences in long-term outcomes after cardiac arrest (CA) are grossly understudied and underreported. We used rigorous targeted temperature management (TTM) to understand its influence on survival and lasting sex-specific neurological and neuropathological outcomes in a rodent ACA model. Adult male and female rats underwent either sham or 5-minute no-flow ACA with 18 hours TTM at either ∼37°C (normothermia) or ∼36°C (mild hypothermia). Survival, temperature, and body weight (BW) were recorded over the 14-day study duration. All rats underwent neurological deficit score (NDS) assessment on days 1-3 and day 14. Hippocampal pathology was assessed for cell death, degenerating neurons, and microglia on day 14. Although ACA females were less likely to achieve return of spontaneous circulation (ROSC), post-ROSC physiology and biochemical profiles were similar between sexes. ACA females had significantly greater 14-day survival, NDS, and BW recovery than ACA males at normothermia (56% vs. 29%). TTM at 36°C versus 37°C improved 14-day survival in males, producing similar survival in male (63%) versus female (50%). There were no sex or temperature effects on CA1 histopathology. We conclude that at normothermic conditions, sex differences favoring females were observed after ACA in survival, NDS, and BW recovery. We achieved a clinically relevant ACA model using TTM at 36°C to improve long-term survival. This model can be used to more fully characterize sex differences in long-term outcomes and test novel acute and chronic therapies.

Optimal inhaled oxygen and carbon dioxide concentrations for post-cardiac arrest cerebral reoxygenation and neurological recovery

Prolonged cerebral hypoperfusion after the return of spontaneous circulation (ROSC) from cardiac arrest (CA) may lead to poor neurological recovery. In a 7-min asphyxia-induced CA rat model, four combinations of inhaled oxygen (iO2) and carbon dioxide (iCO2) were administered for 150 min post-ROSC and compared in a randomized animal trial. At the end of administration, the partial pressure of brain tissue oxygenation (PbtO2) monitored in the hippocampal CA1 region returned to the baseline for the 88% iO2 [ΔPbtO2, median: -0.39 (interquartile range: 5.6) mmHg] and 50% iO2 [ΔpbtO2, -2.25 (10.9) mmHg] groups; in contrast, PbtO2 increased substantially in the 88% iO2+12% iCO2 [ΔpbtO2, 35.05 (16.0) mmHg] and 50% iO2+12% iCO2 [ΔpbtO2, 42.03 (31.7) mmHg] groups. Pairwise comparisons (post hoc Dunn's test) indicated the significant role of 12% iCO2 in augmenting PbtO2 during the intervention and improving neurological recovery at 24 h post-ROSC. Facilitating brain reoxygenation may improve post-CA neurological outcomes.

Assessment of the Effects of Sodium Nitroprusside Administered Via Intracranial Subdural Catheters on the Cerebral Blood Flow and Lactate Using Dynamic Susceptibility Contrast Magnetic Resonance Imaging and Proton Magnetic Resonance Spectroscopy in a Pig Cardiac Arrest Model

Background Cerebral blood flow (CBF) is impaired in the early phase after return of spontaneous circulation. Sodium nitroprusside (SNP) administration via intracranial subdural catheters improves cerebral cortical microcirculation. We determined whether the SNP treatment improves CBF in the subcortical tissue and evaluated the effects of this treatment on cerebral lactate. Methods and Results Sixty minutes after return of spontaneous circulation following 14 minutes of untreated cardiac arrest, 14 minipigs randomly received 4 mg SNP or saline via intracranial subdural catheters. CBF was measured in regions of interest within the cerebrum and thalamus using dynamic susceptibility contrast-magnetic resonance imaging. After return of spontaneous circulation, CBF was expressed as a percentage of the baseline value. In the saline group, the %CBF in the regions of interest within the cerebrum remained at approximately 50% until 3.5 hours after return of spontaneous circulation, whereas %CBF in the thalamic regions of interest recovered to approximately 73% at this time point. The percentages of the baseline values in the cortical gray matter and subcortical white matter were higher in the SNP group (group effect P=0.026 and 0.025, respectively) but not in the thalamus. The cerebral lactate/creatine ratio measured using magnetic resonance spectroscopy increased over time in the saline group but not in the SNP group (group-time interaction P=0.035). The thalamic lactate/creatine ratio was similar in the 2 groups. Conclusions SNP administered via intracranial subdural catheters improved CBF not only in the cortical gray matter but also in the subcortical white matter. The CBF improvement by SNP was accompanied by a decrease in cerebral lactate.

Establishment of a Rat Model of Capillary Leakage Syndrome Induced by Cardiopulmonary Resuscitation After Cardiac Arrest

OBJECTIVE

Cardiopulmonary resuscitation (CPR) after cardiac arrest (CA) is one of the main causes of capillary leakage syndrome (CLS). This study aimed to establish a stable CLS model following the CA and cardiopulmonary resuscitation (CA-CPR) model in Sprague-Dawley (SD) rats.

METHODS

We conducted a prospective, randomized, animal model study. All adult male SD rats were randomly divided into a normal group (group N), a sham operation group (group S), and a cardiopulmonary resuscitation group (group T). The SD rats of the three groups were all inserted with 24-G needles through their left femoral arteries and right femoral veins. In group S and group T, the endotracheal tube was intubated. In group T, CA induced by asphyxia (AACA) was caused by vecuronium bromide with the endotracheal tube obstructed for 8 min, and the rats were resuscitated with manual chest compression and mechanical ventilation. Preresuscitation and postresuscitation measurements, including basic vital signs (BVS), blood gas analysis (BG), routine complete blood count (CBC), wet-to-dry ratio of tissues (W/D), and the HE staining results after 6 h were evaluated.

RESULTS

In group T, the success rate of the CA-CPR model was 60% (18/30), and CLS occurred in 26.6% (8/30) of the rats. There were no significant differences in the baseline characteristics, including BVS, BG, and CBC, among the three groups (P>0.05). Compared with pre-asphyxia, there were significant differences in BVS, CBC, and BG, including temperature, oxygen saturation (SpO2), mean arterial pressure (MAP), central venous pressure (CVP), white blood cell count (WBC), hemoglobin, hematocrit, pH, pCO2, pO2, SO2, lactate (Lac), base excess (BE), and Na+ (P<0.05) after the return of spontaneous circulation (ROSC) in group T. At 6 h after ROSC in group T and at 6 h after surgery in groups N and S, there were significant differences in temperature, heart rate (HR), respiratory rate (RR), SpO2, MAP, CVP, WBC, pH, pCO2, Na+, and K+ among the three groups (P<0.05). Compared with the other two groups, the rats in group T showed a significantly increased W/D weight ratio (P<0.05). The HE-stained sections showed consistent severe lesions in the lung, small intestine, and brain tissues of the rats at 6 h after ROSC following AACA.

CONCLUSION

The CA-CPR model in SD rats induced by asphyxia could reproduce CLS with good stability and reproducibility.

Changes of antioxidant enzymes in the kidney after cardiac arrest in the rat model

Globally, cardiac arrest (CA) is a leading cause of death and disability. Asphyxial CA (ACA)-induced kidney damage is a crucial factor in reducing the survival rate. The purpose of this study was to investigate the role of antioxidant enzymes in histopathological renal damage in an ACA rat model at different time points. A total of 88 rats were divided into five groups and exposed to ACA except for the sham group. To evaluate glomerular function and oxidative stress, serum levels of blood urea nitrogen (BUN) and creatinine (Crtn) and malondialdehyde (MDA) levels in renal tissues were measured. To determine histopathological damage, hematoxylin and eosin staining, periodic acid-Schiff staining, and Masson's trichrome staining were performed. Expression levels of antioxidant enzymes including superoxide dismutase-1 (SOD-1), superoxide dismutase-2 (SOD-2), catalase (CAT), and glutathione peroxidase (GPx) were measured by immunohistochemistry (IHC). Survival rate of the experimental rats was reduced to 80% at 6 h, 55% at 12 h, 42.9% at 1 day, and 33% at 2 days after return of spontaneous circulation. Levels of BUN, Crtn, and MDA started to increase significantly in the early period of CA induction. Renal histopathological damage increased markedly from 6 h until two days post-CA. Additionally, expression levels of antioxidant enzymes were significantly decreased at 6 h, 12 h, 1 day, and 2 days after CA. CA-induced oxidative stress and decreased levels of antioxidant enzymes (SOD-1, SOD-2, CAT, GPx) from 6 h to two days could be possible mediators of severe renal tissue damage and increased mortality rate.

Abnormal fatty acid metabolism and ceramide expression may discriminate myocardial infarction from strangulation death: A pilot study

Determining myocardial infarction (MI) and mechanical asphyxia (MA) was one of the most challenging tasks in forensic practice. The present study aimed to investigate the potential of fatty acid (FAs) metabolism, and lipid alterations in determining MI and MA. MA and MI mouse models were constructed, and metabolic profiles were obtained by LC-MS-based untargeted metabolomics. The metabolic alterations were explored using the PCA, OPLS-DA, the Wilcoxon test, and fold change analysis. The contents of lipid droplets (LDs) were detected by the transmission scanning electron microscope and Oil red O staining. The immunohistochemical assay was performed to detect CD36 and dysferlin. The ceramide was assessed by LC-MS. PCA showed considerable differences in the metabolite profiles, and the well-fitting OPLS-DA model was developed to screen differential metabolites. Thereinto, 9 metabolites in the MA were reduced, while metabolites were up- and down-regulated in MI. The increased CD36 suggested that MI and MA could enhance the intake of FAs and disturb energy metabolism. The increased LDs, decreased dysferlin, and increased ceramide (C18:0, C22:0, and C24:0) were observed in MI groups, confirming the lipid deposition. The present study indicated significant differences in myocardial FAs metabolism and lipid alterations between MI and MA, suggesting that FAs metabolism and related proteins, certain ceramide may harbor the potential as biomarkers for discrimination of MI and MA.

Rat model of asphyxia-induced cardiac arrest and resuscitation

Neurologic injury after cardiopulmonary resuscitation is the main cause of the low survival rate and poor quality of life among patients who have experienced cardiac arrest. In the United States, as the American Heart Association reported, emergency medical services respond to more than 347,000 adults and more than 7,000 children with out-of-hospital cardiac arrest each year. In-hospital cardiac arrest is estimated to occur in 9.7 per 1,000 adult cardiac arrests and 2.7 pediatric events per 1,000 hospitalizations. Yet the pathophysiological mechanisms of this injury remain unclear. Experimental animal models are valuable for exploring the etiologies and mechanisms of diseases and their interventions. In this review, we summarize how to establish a standardized rat model of asphyxia-induced cardiac arrest. There are four key focal areas: (1) selection of animal species; (2) factors to consider during modeling; (3) intervention management after return of spontaneous circulation; and (4) evaluation of neurologic function. The aim was to simplify a complex animal model, toward clarifying cardiac arrest pathophysiological processes. It also aimed to help standardize model establishment, toward facilitating experiment homogenization, convenient interexperimental comparisons, and translation of experimental results to clinical application.

Extracorporeal cardiopulmonary resuscitation (eCPR) and cerebral perfusion: A narrative review

Extracorporeal cardiopulmonary resuscitation (eCPR) is emerging as an effective, lifesaving resuscitation strategy for select patients with prolonged or refractory cardiac arrest. Currently, a paucity of evidence-based recommendations is available to guide clinical management of eCPR patients. Despite promising results from initial clinical trials, neurological injury remains a significant cause of morbidity and mortality. Neuropathology associated with utilization of an extracorporeal circuit may interact significantly with the consequences of a prolonged low-flow state that typically precedes eCPR. In this narrative review, we explore current gaps in knowledge about cerebral perfusion over the course of cardiac arrest and resuscitation with a focus on patients treated with eCPR. We found no studies which investigated regional cerebral blood flow or cerebral autoregulation in human cohorts specific to eCPR. Studies which assessed cerebral perfusion in clinical eCPR were small and limited to near-infrared spectroscopy. Furthermore, no studies prospectively or retrospectively evaluated the relationship between epinephrine and neurological outcomes in eCPR patients. In summary, the field currently lacks a comprehensive understanding of how regional cerebral perfusion and cerebral autoregulation are temporally modified by factors such as pre-eCPR low-flow duration, vasopressors, and circuit flow rate. Elucidating these critical relationships may inform future strategies aimed at improving neurological outcomes in patients treated with lifesaving eCPR.

Therapeutic Administration of Oxcarbazepine Saves Cerebellar Purkinje Cells from Ischemia and Reperfusion Injury Induced by Cardiac Arrest through Attenuation of Oxidative Stress

Research reports using animal models of ischemic insults have demonstrated that oxcarbazepine (a carbamazepine analog: one of the anticonvulsant compounds) extends neuroprotective effects against cerebral or forebrain injury induced by ischemia and reperfusion. However, research on protective effects against ischemia and reperfusion cerebellar injury induced by cardiac arrest (CA) and the return of spontaneous circulation has been poor. Rats were assigned to four groups as follows: (Groups 1 and 2) sham asphyxial CA and vehicle- or oxcarbazepine-treated, and (Groups 3 and 4) CA and vehicle- or oxcarbazepine-treated. Vehicle (0.3% dimethyl sulfoxide/saline) or oxcarbazepine (200 mg/kg) was administered intravenously ten minutes after the return of spontaneous circulation. In this study, CA was induced by asphyxia using vecuronium bromide (2 mg/kg). We conducted immunohistochemistry for calbindin D-28kDa and Fluoro-Jade B histofluorescence to examine Purkinje cell death induced by CA. In addition, immunohistochemistry for 4-hydroxy-2-nonenal (4HNE) was carried out to investigate CA-induced oxidative stress, and immunohistochemistry for Cu, Zn-superoxide dismutase (SOD1) and Mn-superoxide dismutase (SOD2) was performed to examine changes in endogenous antioxidant enzymes. Oxcarbazepine treatment after CA significantly increased the survival rate and improved neurological deficit when compared with vehicle-treated rats with CA (survival rates ≥ 63.6 versus 6.5%), showing that oxcarbazepine treatment dramatically protected cerebellar Purkinje cells from ischemia and reperfusion injury induced by CA. The salvation of the Purkinje cells from ischemic injury by oxcarbazepine treatment paralleled a dramatic reduction in 4HNE (an end-product of lipid peroxidation) and increased or maintained the endogenous antioxidant enzymes (SOD1 and SOD2). In brief, this study shows that therapeutic treatment with oxcarbazepine after CA apparently saved cerebellar neurons (Purkinje cells) from CA-induced neuronal death by attenuating oxidative stress and suggests that oxcarbazepine can be utilized as a therapeutic medicine for ischemia and reperfusion brain (cerebellar) injury induced by CA.

Resuscitation with epinephrine worsens cerebral capillary no-reflow after experimental pediatric cardiac arrest: An in vivo multiphoton microscopy evaluation

Epinephrine is the principal resuscitation therapy for pediatric cardiac arrest (CA). Clinical data suggest that although epinephrine increases the rate of resuscitation, it fails to improve neurological outcome, possibly secondary to reductions in microvascular flow. We characterized the effect of epinephrine vs. placebo administered at resuscitation from pediatric asphyxial CA on microvascular and macrovascular cortical perfusion assessed using in vivo multiphoton microscopy and laser speckle flowmetry, respectively, and on brain tissue oxygenation (PbO₂), behavioral outcomes, and neuropathology in 16-18-day-old rats. Epinephrine-treated rats had a more rapid return of spontaneous circulation and brisk immediate cortical reperfusion during 1-3 min post-CA vs. placebo. However, at the microvascular level, epinephrine-treated rats had penetrating arteriole constriction and increases in both capillary stalling (no-reflow) and cortical capillary transit time 30-60 min post-CA vs. placebo. Placebo-treated rats had increased capillary diameters post-CA. The cortex was hypoxic post-CA in both groups. Epinephrine treatment worsened reference memory performance vs. shams. Hippocampal neuron counts did not differ between groups. Resuscitation with epinephrine enhanced immediate reperfusion but produced microvascular alterations during the first hour post-resuscitation, characterized by vasoconstriction, capillary stasis, prolonged cortical transit time, and absence of compensatory cortical vasodilation. Targeted therapies mitigating the deleterious microvascular effects of epinephrine are needed.

Inhaled Carbon Dioxide Improves Neurological Outcomes by Downregulating Hippocampal Autophagy and Apoptosis in an Asphyxia‐Induced Cardiac Arrest and Resuscitation Rat Model

Background

Protracted cerebral hypoperfusion following cardiac arrest (CA) may cause poor neurological recovery. We hypothesized that inhaled carbon dioxide (CO₂) could augment cerebral blood flow (CBF) and improve post‐CA neurological outcomes.

Methods and Results

After 6‐minute asphyxia‐induced CA and resuscitation, Wistar rats were randomly allocated to 4 groups (n=25/group) and administered with different inhaled CO₂ concentrations, including control (0% CO₂), 4% CO₂, 8% CO₂, and 12% CO₂. Invasive monitoring was maintained for 120 minutes, and neurological outcomes were evaluated with neurological function score at 24 hours post‐CA. After the 120‐minute experiment, CBF was 242.3% (median; interquartile range, 221.1%–267.4%) of baseline in the 12% CO₂ group while CBF fell to 45.8% (interquartile range, 41.2%–58.1%) of baseline in the control group (P<0.001). CBF increased along with increasing inhaled CO₂ concentrations with significant linear trends (P<0.001). At 24 hours post‐CA, compared with the control group (neurological function score, 9 [interquartile range, 8–9]), neurological recovery was significantly better in the 12% CO₂ group (neurological function score, 10 [interquartile range, 9.8–10]) (P<0.001) while no survival difference was observed. Brain tissue malondialdehyde (P=0.02) and serum neuron‐specific enolase (P=0.002) and S100β levels (P=0.002) were significantly lower in the 12% CO₂ group. TUNEL (terminal deoxynucleotidyl transferase–mediated biotin–deoxyuridine triphosphate nick‐end labeling)‐positive cell densities in hippocampal CA1 (P<0.001) and CA3 (P<0.001) regions were also significantly reduced in the 12% CO₂ group. Western blotting showed that beclin‐1 (P=0.02), p62 (P=0.02), and LAMP2 (lysosome‐associated membrane protein 2) (P=0.01) expression levels, and the LC3B‐II:LC3B‐I ratio (P=0.02) were significantly lower in the 12% CO₂ group.

Conclusions

Administering inhaled CO₂ augmented post‐CA CBF, mitigated oxidative brain injuries, ameliorated neuronal injury, and downregulated apoptosis and autophagy, thereby improving neurological outcomes.

Effects of Sodium Nitroprusside Administered Via a Subdural Intracranial Catheter on the Microcirculation, Oxygenation, and Electrocortical Activity of the Cerebral Cortex in a Pig Cardiac Arrest Model

Background

Postischemic cerebral hypoperfusion has been indicated as an important contributing factor to secondary cerebral injury after cardiac arrest. We evaluated the effects of sodium nitroprusside administered via a subdural intracranial catheter on the microcirculation, oxygenation, and electrocortical activity of the cerebral cortex in the early postresuscitation period using a pig model of cardiac arrest.

Methods and Results

Twenty‐nine pigs were resuscitated with closed cardiopulmonary resuscitation after 14 minutes of untreated ventricular fibrillation. Thirty minutes after restoration of spontaneous circulation, 24 pigs randomly received either 4 mg of sodium nitroprusside (IT‐SNP group) or saline placebo (IT‐saline group) via subdural intracranial catheters and were observed for 5 hours. The same dose of sodium nitroprusside was administered intravenously in another 5 pigs. Compared with the IT‐saline group, the IT‐SNP group had larger areas under the curve for tissue oxygen tension and percent changes of arteriole diameter and number of perfused microvessels from baseline (all P<0.05) monitored on the cerebral cortex during the 5‐hour period, without severe hemodynamic instability. This group also showed faster recovery of electrocortical activity measured using amplitude‐integrated electroencephalography. Repeated‐measures analysis of variance revealed significant group–time interactions for these parameters. Intravenously administered sodium nitroprusside caused profound hypotension but did not appear to increase the cerebral parameters.

Conclusions

Sodium nitroprusside administered via a subdural intracranial catheter increased post–restoration of spontaneous circulation cerebral cortical microcirculation and oxygenation and hastened electrocortical activity recovery in a pig model of cardiac arrest. Further studies are required to determine its impact on the long‐term neurologic outcomes.

Olanzapine-Induced Therapeutic Hypothermia Attenuates Renal Injury in Rats after Asphyxial Cardiac Arrest and Resuscitation

Return of spontaneous circulation (ROSC) through cardiopulmonary resuscitation (CPR) after cardiac arrest (CA) causes post-cardiac arrest syndrome (PCAS) due to dysfunction in various organs, which provokes acute kidney injury because of renal ischemia-reperfusion injury. Therapeutic hypothermia (TH) can reduce PCAS after CA and ROSC. However, it needs to be more sophisticated and effective. Hence, we aimed to elucidate the protective effects of olanzapine-induced TH against renal injury in asphyxial CA-induced rats. Every rat’s body temperature was maintained at 33 °C for 6 h after administering olanzapine post-CA and ROSC. Olanzapine-induced TH dramatically increased the survival rate of the rats and ameliorated renal tissue damage. Moreover, it suppressed oxidative stress responses through preservation of mitochondrial function and endoplasmic reticulum stress as the main contributor of oxidative stress. Notably, these actions of olanzapine-induced TH were mediated through the Sirt3-related signaling pathway, including the maintenance of Sirt3 and FOXO3a protein expression and the activation of AMPKα and superoxide dismutase 1 (SOD2, a mitochondrial antioxidant). This study is the first to disclose the protective effects of olanzapine-induced TH against renal injury after CA and ROSC, suggesting that olanzapine-induced TH could be utilized for treating CA followed by ROSC.

Early Thalamocortical Reperfusion Leads to Neurologic Recovery in a Rodent Cardiac Arrest Model

BACKGROUND

Cerebral blood flow (CBF) plays an important role in neurological recovery after cardiac arrest (CA) resuscitation. However, the variations of CBF recovery in distinct brain regions and its correlation with neurologic recovery after return of spontaneous circulation (ROSC) have not been characterized. This study aimed to investigate the characteristics of regional cerebral reperfusion following resuscitation in predicting neurological recovery.

METHODS

Twelve adult male Wistar rats were studied, ten resuscitated from 7-min asphyxial CA and two uninjured rats, which were designated as healthy controls (HCs). Dynamic changes in CBF in the cerebral cortex, hippocampus, thalamus, brainstem, and cerebellum were assessed by pseudocontinuous arterial spin labeling magnetic resonance imaging, starting at 60 min after ROSC to 156 min (or time to spontaneous arousal). Neurologic outcomes were evaluated by the neurologic deficit scale at 24 h post-ROSC in a blinded manner. Correlations between regional CBF (rCBF) and neurological recovery were undertaken.

RESULTS

All post-CA animals were found to be nonresponsive during the 60-156 min post ROSC, with reductions in rCBF by 24-42% compared with HC. Analyses of rCBF during the post-ROSC time window from 60 to 156 min showed the rCBF recovery of hippocampus and thalamus were positively associated with better neurological outcomes (rs = 0.82, p = 0.004 and rs = 0.73, p < 0.001, respectively). During 96 min before arousal, thalamic and cortical rCBF exhibited positive correlations with neurological recovery (rs = 0.80, p < 0.001 and rs = 0.65, p < 0.001, respectively); for predicting a favorable neurological outcome, the thalamic rCBF threshold was above 50.84 ml/100 g/min (34% of HC) (area under the curve of 0.96), whereas the cortical rCBF threshold was above 60.43 ml/100 g/min (38% of HC) (area under the curve of 0.88).

CONCLUSIONS

Early magnetic resonance imaging analyses showed early rCBF recovery in thalamus, hippocampus, and cortex post ROSC was positively correlated with neurological outcomes at 24 h. Our findings suggest new translational insights into the regional reperfusion and the time window that may be critical in neurological recovery and warrant further validation.

Effects of NLRP3 inflammasome blockade on postresuscitation cerebral function in a rat model of cardiopulmonary resuscitation

Cardiac arrest (CA) remains a major public health issue. Inflammatory responses with overproduction of interleukin-1β regulated by NLRP3 inflammasome activation play a crucial role in cerebral ischemia/reperfusion injury. We investigated the effects of the selective NLRP3-inflammasome inhibitor MCC950 on post-resuscitation cerebral function and neurologic outcome in a rat model of cardiac arrest. Thirty-six male rats were randomized into the MCC950 group, the control group, or the sham group (N = 12 of each group). Each group was divided into a 6 h non-survival subgroup (N = 6) and a 24 h survival subgroup (N = 6). Ventricular fibrillation (VF) was electrically induced and untreated for 6 min, followed by 8 min of precordial compressions and mechanical ventilation. Resuscitation was attempted with a 4J defibrillation. Either MCC950 (10 mg/kg) or vehicle was injected intraperitoneally immediately after the return of spontaneous circulation (ROSC). Rats in the sham group underwent the same surgical procedures without VF and CPR. Brain edema, cerebral microcirculation, plasma interleukin Iβ (IL-1β), and neuron-specific enolase (NSE) concentration were measured at 6 h post-ROSC of non-survival subgroups, while 24 h survival rate, neurological deficits were measured at 24 h post-ROSC of survival subgroups. Post-resuscitation brain edema was significantly reduced in animals treated with MCC950 (p < 0.05). Cerebral perfused vessel density (PVD) and microcirculatory flow index (MFI) values were significantly higher in the MCC950 group compared with the control group (p < 0.05). The plasma concentrations of IL-1β and NSE were significantly decreased in animals treated with MCC950 compared with the control group (p < 0.05). 24 h-survival rate and neurological deficits score (NDS) was also significantly improved in the MCC950 group compared with the control group (p < 0.05). NLRP3 inflammasome blockade with MCC950 at ROSC reduces the circulatory level of IL-1β, preserves cerebral microcirculation, mitigates cerebral edema, improves the 24 h-survival rate, and neurological deficits.

Increased cerebral endothelium-dependent vasodilation in rats in the postcardiac arrest period

Cardiovascular lability is common after cardiac arrest. We investigated whether altered endothelial function is present in cerebral and mesenteric arteries 2 and 4 h after resuscitation. Male Sprague-Dawley rats were anesthetized, intubated, ventilated, and intravascularly catheterized whereupon rats were randomized into four groups. Following 7 min of asphyxial cardiac arrest and subsequent resuscitation, cardiac arrest and sham rats were observed for either 2 or 4 h. Neuron-specific enolase levels were measured in blood samples. Middle cerebral artery segments and small mesenteric arteries were isolated and examined in microvascular myographs. qPCR and immunofluorescence analysis were performed on cerebral arteries. In cerebral arteries, bradykinin-induced vasodilation was inhibited in the presence of either calcium-activated K⁺ channel blockers (UCL1684 and senicapoc) or the nitric oxide (NO) synthase inhibitor, N^ω-nitro-L-arginine methyl ester hydrochloride (l-NAME), whereas the combination abolished bradykinin-induced vasodilation across groups. Neuron-specific enolase levels were significantly increased in cardiac arrest rats. Cerebral vasodilation was comparable between the 2-h groups, but markedly enhanced in response to bradykinin, NS309 (an opener of small and intermediate calcium-activated K⁺ channels), and sodium nitroprusside 4 h after cardiac arrest. Endothelial NO synthase and guanylyl cyclase subunit α-1 mRNA expression was unaltered after 2 h, but significantly decreased 4 h after resuscitation. In mesenteric arteries, the endothelium-dependent vasodilation was comparable between corresponding groups at both 2 and 4 h. Our findings show enhanced cerebral endothelium-dependent vasodilation 4 h after cardiac arrest mediated by potentiated endothelial-derived hyperpolarization and NO pathways. Altered cerebral endothelium-dependent vasodilation may contribute to disturbed cerebral perfusion after cardiac arrest.NEW & NOTEWORTHY This is the first study, to our knowledge, to demonstrate enhanced endothelium-dependent vasodilation in middle cerebral arteries in a cardiac arrest rat model. The increased endothelium-dependent vasodilation was a result of potentiated endothelium-derived hyperpolarization and endothelial nitric oxide pathways. Immunofluorescence microscopy confirmed the presence of relevant receptors and eNOS in cerebral arteries, whereas qPCR showed altered expression of genes related to guanylyl cyclase and eNOS. Altered endothelium-dependent vasoregulation may contribute to disturbed cerebral blood flow in the postcardiac arrest period.

Precision Cardiac Arrest Resuscitation Based on Etiology

Cardiac arrest results from a broad range of etiologies that can be broadly grouped as sudden and asphyxial. Animal studies point to differences in injury pathways invoked in the heart and brain that drive injury and outcome after these different forms of cardiac arrest. Present guidelines largely ignore etiology in their management recommendations. Existing clinical data reveal significant heterogeneity in the utility of presently employed resuscitation and postresuscitation strategies based on etiology. The development of future neuroprotective and cardioprotective therapies should also take etiology into consideration to optimize the chances for successful translation.

Quantitative magnetic resonance imaging assessment of brain injury after successful cardiopulmonary resuscitation in a rat model of asphyxia cardiac arrest

The aim of this study was to use dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and diffusion-weighted magnetic resonance imaging (DWI) to measure changes in blood-brain barrier (BBB) permeability and cerebral edema over time in a rat model of asphyxial cardiac arrest (ACA). ACA was established by endotracheal tube clamping. Male rats were randomized into a sham group (n = 5) and three ACA groups (n = 18). After return of spontaneous circulation (ROSC), the rats were randomized to perform DWI and DCE-MRI exam in the 6 h, 24 h and 72 h timepoint (ROSC + 6 h, ROSC + 24 h, and ROSC + 72 h). Results shows that fifteen of 18 animals achieved successful resuscitation in the ACA groups. The average apparent diffusion coefficient(ADC) value of the whole brain in ROSC + 6 h was markedly lower than those of the sham, ROSC + 24 h, and ROSC + 72 h. The aquaporin-4(AQP4) score in ROSC + 6 h was significantly higher than those in the other groups, which were negatively correlated with the ADC values. The ratio of whole brain to masseter muscle of volume transfer constant (rK^trans), tissue interstitium-to-plasma rate constant(rK_ep), and fractional extra-cellular space volume(rV_e) in ROSC + 6 h were all significantly higher than those in the sham, ROSC + 24 h, and ROSC + 72 h. The transforming growth factor β1(TGF-β1) and vascular endothelial growth factor A(VEGF-a) scores in ROSC + 6 h were significantly higher than those in the other groups, which were all positively correlated with rK^trans and rK_ep. In conclusions, brain injury is a frequent complication after CA and resuscitation. DWI and DCE-MRI can quantitatively evaluate brain injury in term of cerebral edema and BBB permeability after successful CPR.

Changes of renal histopathology and the role of Nrf2/HO-1 in asphyxial cardiac arrest model in rats

PURPOSE

To investigate the role of Nrf2/HO-1 in renal histopathological ailments time-dependently in asphyxial cardiac arrest (CA) rat model.

METHODS

Eighty-eight Sprague Dawley male rats were divided into five groups of eight rats each. Asphyxial CA was induced in all the experimental rats except for the sham group. The rats were sacrificed at 6 hours, 12 hours, one day and two days post-CA. Serum blood urea nitrogen (BUN), creatinine (Crtn) and malondialdehyde from the renal tissues were evaluated. Hematoxylin and eosin and periodic acid-Schiff staining were done to evaluate the renal histopathological changes in the renal cortex. Furthermore, Nrf2/HO-1 immunohistochemistry (ihc) and western blot analysis were performed after CA.

RESULTS

The survival rate of rats decreased in a time-dependent manner: 66.6% at 6 hours, 50% at 12 hours, 38.1% in one day, and 25.8% in two days. BUN and serum Crtn markedly increased in CA-operated groups. Histopathological ailments of the renal cortical tissues increased significantly from 6 hours until two days post-CA. Furthermore, Nrf2/HO-1 expression level significantly increased at 6 hours, 12 hours, and one day.

CONCLUSIONS

The survival rate decreased time-dependently, and Nrf/HO-1 expression increased from 6 hours with the peak times at 12 hours, and one day post-CA.

Therapeutic hypothermia effect on asphyxial cardiac arrest-induced renal ischemia/reperfusion injury via change of Nrf2/HO-1 levels

The present study aimed to investigate the renoprotective effect of therapeutic hypothermia (TH) on renal ischemia-reperfusion injury (RI/RI) induced by asphyxial cardiac arrest (CA) in rats. A total of 48 male rats were randomly divided into five groups: i) Sham (n=6); ii) Normothermia + CA (Normo.) (n=14); iii) Normo. and 2 h of TH after return of spontaneous circulation (ROSC) (n=12); iv) Normo. and 4 h of TH after ROSC (n=9); and v) Normo. and 6 h of TH after ROSC (n=7). All rats except the Sham group underwent asphyxia CA and were sacrificed 1 day after ROSC. The survival rate increased from 42.8% in the Normo. group to 50, 66.6 and 85.7% in the groups with 2, 4 and 6 h of TH after CA, respectively. TH attenuated the histopathological changes of the renal tissues following ROSC and the levels of blood urea nitrogen, serum creatinine and malondialdehyde in renal tissues. On immunohistochemistry, the relative optical density of nuclear erythroid-related factor-2 (Nrf2) and heme oxygenase (HO-1) expression in renal tissues increased in the Normo. group compared with that in the Sham group and exhibited further significant increases at 6 h of TH after ROSC. In conclusion, TH attenuated renal injury and increased the expression of Nrf2 and HO-1 in a TH treatment time-dependent manner.

Development and Evaluation of a Novel Mouse Model of Asphyxial Cardiac Arrest Revealed Severely Impaired Lymphopoiesis After Resuscitation

Background Animal disease models represent the cornerstone in basic cardiac arrest (CA) research. However, current experimental models of CA and resuscitation in mice are limited. In this study, we aimed to develop a mouse model of asphyxial CA followed by cardiopulmonary resuscitation (CPR), and to characterize the immune response after asphyxial CA/CPR. Methods and Results CA was induced in mice by switching from an O2/N2 mixture to 100% N2 gas for mechanical ventilation under anesthesia. Real-time measurements of blood pressure, brain tissue oxygen, cerebral blood flow, and ECG confirmed asphyxia and ensuing CA. After a defined CA period, mice were resuscitated with intravenous epinephrine administration and chest compression. We subjected young adult and aged mice to this model, and found that after CA/CPR, mice from both groups exhibited significant neurologic deficits compared with sham mice. Analysis of post-CA brain confirmed neuroinflammation. Detailed characterization of the post-CA immune response in the peripheral organs of both young adult and aged mice revealed that at the subacute phase following asphyxial CA/CPR, the immune system was markedly suppressed as manifested by drastic atrophy of the spleen and thymus, and profound lymphopenia. Finally, our data showed that post-CA systemic lymphopenia was accompanied with impaired T and B lymphopoiesis in the thymus and bone marrow, respectively. Conclusions In this study, we established a novel validated asphyxial CA model in mice. Using this new model, we further demonstrated that asphyxial CA/CPR markedly affects both the nervous and immune systems, and notably impairs lymphopoiesis of T and B cells.

Mild therapeutic hypothermia improves neurological outcomes in a rat model of cardiac arrest

Cardiac arrest (CA) is the leading cause of death in humans. Research has shown that mild therapeutic hypothermia (MTH) can reduce neurological sequelae and mortality after CA. Nevertheless, the mechanism remains unclear. This study aimed to determine whether MTH promotes neurogenesis, attenuates neuronal damage, and inhibits apoptosis of neurons in rats after CA. Sprague-Dawley rats were divided into the normothermia and mild hypothermia groups. The rats in the normothermia and hypothermia groups were exposed to 2 h of normothermia (36-37℃) and hypothermia (32-33℃), respectively, immediately after resuscitation from 5 min of asphyxial CA. Corresponding control groups not subjected to CA were included. On days 1-6, 5-bromodeoxyuridine (BrdU) 100 mg/kg/day was administered intraperitoneally. The animals were euthanized 1 week after CA. Compared with the normothermia group, the hypothermia group showed a significant increase in the number of doublecortin (DCX) immune-positive cells in the subgranular zone of the hippocampus 1 week after CA. Neurogenesis was assessed using double immunofluorescent labeling of BrdU with neuronal-specific nuclear protein (NeuN)/DCX. There was no marked change in the number of newborn mature (BrdU+-NeuN+) neurons, though there was a significant increase in the number of newborn immature (BrdU+-DCX+) neurons in the hypothermia than in the normothermia group 1 week after CA. Neuronal injury and apoptosis in the CA1 region of the hippocampus, assessed using NeuN immunofluorescence and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assays, were significantly reduced in the hypothermia group 1 week after CA. Moreover, mild hypothermia increased the expression of cold-shock protein RNA-binding motif protein 3 (RBM3) in the early stage (24 h/48 h) after CA. These results suggested that mild hypothermia promotes generation of neuronal cells, reduces neuronal injury, and inhibits apoptosis of neurons, which may be related to RBM3 expression.

Association of central arterial stiffness with hippocampal blood flow and N-acetyl aspartate concentration in hypertensive adult Dahl salt sensitive rats

BACKGROUND

Central arterial stiffness (CAS) is associated with elevated arterial blood pressure (BP) and is likely associated with stiffening of cerebral artery walls, with attendant cerebral hypoperfusion, neuronal density loss and cognitive decline. Dahl salt-sensitive (Dahl-S) rats exhibit age-associated hypertension and memory loss, even on a normal salt intake.

METHOD

We sought to explore whether central arterial pulse wave velocity (PWV), a marker of CAS, is associated with hippocampal cerebral blood flow (CBF) and neuronal density in hypertensive Dahl-S rats. We measured systolic BP (by tail-cuff plethysmography), aortic PWV (by echocardiography) and CBF and N-acetyl aspartate (NAA) (by magnetic resonance imaging) in 6 month-old male Dahl-S rats (n = 12).

RESULTS

Greater PWV was significantly associated with lower CBF and lower NAA concentration in the hippocampus, supporting a role of CAS in cerebrovascular dysfunction and decline in cognitive performance with aging.

CONCLUSION

These findings implicate increased CAS in cerebral hypoperfusion and loss of neuronal density and function in the Dahl-S model of age-associated cardiovascular dysfunction.

Effects of hypothermia on inflammatory cytokine expression in rat liver following asphyxial cardiac arrest

Hypothermic treatment is known to protect against cardiac arrest (CA) and improve survival rate. However, few studies have evaluated the CA-induced liver damage and the effects of hypothermia on this damage. Therefore, the aim of the present study was to determine possible protective effects of hypothermia on the liver after asphyxial CA. Rats were subjected to a 5-min asphyxial CA followed by return of spontaneous circulation (ROSC). The body temperature was controlled at 37±0.5˚C (normothermia group) or 33±0.5˚C (hypothermia group) for 4 h after ROSC. Livers were examined at 6, 12 h, 1 and 2 days after ROSC. Histopathological examination was performed by H&E staining. Alterations in the expression levels of pro-inflammatory (TNF-α and interleukin IL-2) and anti-inflammatory cytokines (IL-4 and IL-13) were investigated by immunohistochemistry. Sinusoidal dilatation and vacuolization were observed after asphyxial CA by histopathological examination. However, these CA-induced structural alterations were prevented by hypothermia. In immunohistochemical examination, the expression levels of pro-inflammatory cytokines were reduced in the hypothermia group compared with those in the normothermia group while the expression levels of anti-inflammatory cytokines were increased in the hypothermia group compared with those in the normothermia group. In conclusion, hypothermic treatment for 4 h following asphyxial CA in rats inhibited the increase of pro-inflammatory cytokines and stimulated the expression of anti-inflammatory cytokines compared with the normothermic group. The results of the present study suggested that hypothermic treatment after asphyxial CA reduced liver damage via the regulation of inflammation.

Relationship of common hemodynamic and respiratory target parameters with brain tissue oxygen tension in the absence of hypoxemia or hypotension after cardiac arrest: A post-hoc analysis of an experimental study using a pig model

Brain tissue oxygen tension (PbtO2)-guided care, a therapeutic strategy to treat or prevent cerebral hypoxia through modifying determinants of cerebral oxygen delivery, including arterial oxygen tension (PaO2), end-tidal carbon dioxide (ETCO2), and mean arterial pressure (MAP), has recently been introduced. Studies have reported that cerebral hypoxia occurs after cardiac arrest in the absence of hypoxemia or hypotension. To obtain preliminary information on the degree to which PbtO2 is responsive to changes in the common target variables for PbtO2-guided care in conditions without hypoxemia or hypotension, we investigated the relationships between the common target variables for PbtO2-guided care and PbtO2 using data from an experimental study in which the animals did not experience hypoxemia or hypotension after resuscitation. We retrospectively analyzed 170 sets of MAP, ETCO2, PaO2, PbtO2, and cerebral microcirculation parameters obtained during the 60-min post-resuscitation period in 10 pigs resuscitated from ventricular fibrillation cardiac arrest. PbtO2 and cerebral microcirculation parameters were measured on parietal cortices exposed through burr holes. Multiple linear mixed effect models were used to test the independent effects of each variable on PbtO2. Despite the absence of arterial hypoxemia or hypotension, seven (70%) animals experienced cerebral hypoxia (defined as PbtO2 <20 mmHg). Linear mixed effect models revealed that neither MAP nor ETCO2 were related to PbtO2. PaO2 had a significant linear relationship with PbtO2 after adjusting for significant covariates (P = 0.030), but it could explain only 17.5% of the total PbtO2 variance (semi-partial R2 = 0.175; 95% confidence interval, 0.086-0.282). In conclusion, MAP and ETCO2 were not significantly related to PbtO2 in animals without hypoxemia or hypotension during the early post-resuscitation period. PaO2 had a significant linear association with PbtO2, but its ability to explain PbtO2 variance was small.

The evaluation of pituitary damage associated with cardiac arrest: An experimental rodent model

The pituitary gland plays an important endocrinal role, however its damage after cardiac arrest (CA) has not been well elucidated. The aim of this study was to determine a pituitary gland damage induced by CA. Rats were subjected to 10-min asphyxia and cardiopulmonary resuscitation (CPR). Immunohistochemistry and ELISA assays were used to evaluate the pituitary damage and endocrine function. Samples were collected at pre-CA, and 30 and 120 min after cardio pulmonary resuscitation. Triphenyltetrazolium chloride (TTC) staining demonstrated the expansion of the pituitary damage over time. There was phenotypic validity between the pars distalis and nervosa. Both CT-proAVP (pars nervosa hormone) and GH/IGF-1 (pars distalis hormone) decreased over time, and a different expression pattern corresponding to the damaged areas was noted (CT-proAVP, 30.2 ± 6.2, 31.5 ± 5.9, and 16.3 ± 7.6 pg/mg protein, p < 0.01; GH/IGF-1, 2.63 ± 0.61, 0.62 ± 0.36, and 2.01 ± 0.41 ng/mg protein, p < 0.01 respectively). Similarly, the expression pattern between these hormones in the end-organ systems showed phenotypic validity. Plasma CT-proAVP (r = 0.771, p = 0.025) and IGF-1 (r = −0.775, p = 0.024) demonstrated a strong correlation with TTC staining area. Our data suggested that CA induces pathological and functional damage to the pituitary gland.

Therapeutic hypothermia reduces inflammation and oxidative stress in the liver after asphyxial cardiac arrest in rats

BACKGROUND

Few studies have evaluated the effects of hypothermia on cardiac arrest (CA)-induced liver damage. This study aimed to investigate the effects of hypothermic therapy on the liver in a rat model of asphyxial cardiac arrest (ACA).

METHODS

Rats were subjected to 5-minute ACA followed by return of spontaneous circulation (RoSC). Body temperature was controlled at 33°C±0.5°C or 37°C±0.5°C for 4 hours after RoSC in the hypothermia group and normothermia group, respectively. Liver tissues in each group were collected at 6 hours, 12 hours, 1 day, and 2 days after RoSC. To examine hepatic inflammation, mast cells were stained with toluidine blue. Superoxide anion radical production was evaluated using dihydroethidium fluorescence straining and expression of endogenous antioxidants (superoxide dismutase 1 [SOD1] and SOD2) was examined using immunohistochemistry.

RESULTS

There were significantly more mast cells in the livers of the normothermia group with ACA than in the hypothermia group with ACA. Gradual increase in superoxide anion radical production was found with time in the normothermia group with ACA, but production was significantly suppressed in the hypothermia group with ACA relative to the normothermia group with ACA. SOD1 and SOD2 levels were higher in the hypothermia group with ACA than in the normothermia group with ACA.

CONCLUSIONS

Experimental hypothermic treatment after ACA significantly inhibited inflammation and superoxide anion radical production in the rat liver, indicating that this treatment enhanced or maintained expression of antioxidants. Our findings suggest that hypothermic therapy after CA can reduce mast cell-mediated inflammation through regulation of oxidative stress and the expression of antioxidants in the liver.

Protective effects of therapeutic hypothermia on renal injury in an asphyxial cardiac arrest rat model

Cardiac arrest (CA) is a leading cause of mortality worldwide. Most of post-resuscitation related deaths are due to post-cardiac arrest syndrome (PCAS). After cardiopulmonary resuscitation (CPR), return of spontaneous circulation (ROSC) leads to renal ischemia-reperfusion injury, also known as PCAS. Many studies have focused on brain and heart injuries after ROSC, but renal failure has largely been ignored. Therefore, we investigated the protective effects of therapeutic hypothermia (TH) on asphyxial CA-induced renal injury in rats. Thirty rats were randomly divided into five groups: 1) the control group (sham); 2) the normothermic CA (nor.); 3) a normothermic CA group that received TH immediately within 2 h after CPR (Hypo. 2 hrs); 4) a normothermic CA group that received TH within 4 h after CPR (Hypo. 4 hrs); and 5) a normothermia CA group that received TH within 6 h after CPR (Hypo. 6 h). One day after CPR, all rats were sacrificed. Compared with the normothermic CA group, the TH groups demonstrated significantly increased survival rate (P < 0.05); decreased serum blood urea nitrogen, creatinine, and lactate dehydrogenase levels; and lower histological damage degree and malondialdehyde concentration in their renal tissue. Terminal deoxynucleotidyl transferase dUTP nick end labeling stain revealed that the number of apoptotic cells significantly decreased after 4 h and 6 h of TH compared to the results seen in the normothermic CA group. Moreover, TH downregulated the expression of cyclooxygenase-2 in the renal cortex compared to the normothermic CA group one day after CPR. These results suggest that TH exerts anti-apoptotic, anti-inflammatory, and anti-oxidative effects immediately after ROSC that protect against renal injury.

Cerebral Blood Flow-Guided Manipulation of Arterial Blood Pressure Attenuates Hippocampal Apoptosis After Asphyxia-Induced Cardiac Arrest in Rats

Background In most post-cardiac arrest patients, the autoregulation mechanism of cerebral blood flow (CBF) is dysregulated. We examined whether recovery of CBF by adjusting mean arterial pressure mitigates post-cardiac arrest neuronal damage. Methods and Results Wistar rats that underwent 8-minute asphyxia-induced cardiac arrest and resuscitation were computer-randomized to norepinephrine or control groups. The CBF was measured at the dorsal hippocampal CA1 region of the left hemisphere. In the norepinephrine group, the mean arterial pressure was adjusted to recover CBF to 80% to 100% of baseline. Twenty-four hours following resuscitation, neurological outcomes were assessed, and brain tissues and blood samples were harvested for neuronal apoptosis and injury assessment. Thirty resuscitated rats were randomized into 2 groups, each containing 12 rats that completed the experiments. Norepinephrine infusion effectively prevented posthyperemia hypoperfusion and recovered CBF to pre-arrest baseline levels; a moderate positive linear correlation between mean arterial pressure and CBF during this period was also observed (P<0.001). There were no significant between-group differences in neurological recovery. In the norepinephrine group compared with the control group, upregulated cleaved caspase-3 protein expression in brain tissue determined by Western blot was reduced (P=0.02) and the densities of apoptotic cells in hippocampal CA1 and CA3 regions determined by terminal deoxynucleotidyl transferase-mediated dUTP biotin nick-end labeling were decreased (P<0.001). No significant differences in serum neuron-specific enolase or S100β levels were detected between the 2 groups. Conclusions CBF recovery demonstrated neuroprotective effects by reducing activation of cerebral apoptosis and number of apoptotic neurons. However, these effects did not significantly improve clinical neurological function, necessitating further investigation.

Effects of regional body temperature variation during asphyxial cardiac arrest on mortality and brain damage in a rat model

To date, hypothermia has focused on improving rates of resuscitation to increase survival in patients sustaining cardiac arrest (CA). Towards this end, the role of body temperature in neuronal damage or death during CA needs to be determined. However, few studies have investigated the effect of regional temperature variation on survival rate and neurological outcomes. In this study, adult male rats (12 week-old) were used under the following four conditions: (i) whole-body normothermia (37 ± 0.5 °C) plus (+) no asphyxial CA, (ii) whole-body normothermia + CA, (iii) whole-body hypothermia (33 ± 0.5 °C)+CA, (iv) body hypothermia/brain normothermia + CA, and (v) brain hypothermia/body normothermia + CA. The survival rate after resuscitation was significantly elevated in groups exposed to whole-body hypothermia plus CA and body hypothermia/brain normothermia plus CA, but not in groups exposed to whole-body normothermia combined with CA and brain hypothermia/body normothermia plus CA. However, the group exposed to hypothermia/brain normothermia combined with CA exhibited higher neuroprotective effects against asphyxial CA injury, i.e. improved neurological deficit and neuronal death in the hippocampus compared with those involving whole-body normothermia combined with CA. In addition, neurological deficit and neuronal death in the group of rat exposed to brain hypothermia/body normothermia and CA were similar to those in the rats subjected to whole-body normothermia and CA. In brief, only brain hypothermia during CA was not associated with effective survival rate, neurological function or neuronal protection compared with those under body (but not brain) hypothermia during CA. Our present study suggests that regional temperature in patients during CA significantly affects the outcomes associated with survival rate and neurological recovery.

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

OBJECTIVES

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.

DESIGN

Prospective observational human and randomized animal study.

SETTING

University laboratory and ICUs.

PATIENTS

Five-hundred forty-three cardiac arrest patients admitted to ICU.

SUBJECTS

Seventy-five male Sprague-Dawley rats.

INTERVENTIONS

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.

MEASUREMENTS AND MAIN RESULTS

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).

CONCLUSIONS

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.

Nitrite pharmacokinetics, safety and efficacy after experimental ventricular fibrillation cardiac arrest

INTRODUCTION

Besides therapeutic hypothermia or targeted temperature management no novel therapies have been developed to improve outcomes of patients after cardiac arrest (CA). Recent studies suggest that nitrite reduces neurological damage after asphyxial CA. Nitrite is also implicated as a new mediator of remote post conditioning produced by tourniquet inflation-deflation, which is under active investigation in CA. However, little is known about brain penetration or pharmacokinetics (PK). Therefore, to define the optimal use of this agent, studies on the PK of nitrite in experimental ventricular fibrillation (VF) are needed. We tested the hypothesis that nitrite administered after resuscitation from VF is detectable in cerebrospinal fluid (CSF), brain and other organ tissues, produces no adverse hemodynamic effects, and improves neurologic outcome in rats.

METHODS

After return of spontaneous circulation (ROSC) of 5 min untreated VF, adult male Sprague-Dawley rats were given intravenous nitrite (8 μM, 0.13 mg/kg) or placebo as a 5 min infusion beginning at 5 min after CA. Additionally, sham groups with and without nitrite treatment were also studied. Whole blood nitrite levels were serially measured. After 15 min, CSF, brain, heart and liver tissue were collected. In a second series, using a randomized and blinded treatment protocol, rats were treated with nitrite or placebo after arrest. Neurological deficit scoring (NDS) was performed daily and eight days after resuscitation, fear conditioning testing (FCT) and brain histology were assessed.

RESULTS

In an initial series of experiments, rats (n = 21) were randomized to 4 groups: VF-CPR and nitrite therapy (n = 6), VF-CPR and placebo therapy (n = 5), sham (n = 5), or sham plus nitrite therapy (n = 5). Whole blood nitrite levels increased during drug infusion to 57.14 ± 10.82 μM at 11 min post-resuscitation time (1 min after dose completion) in the VF nitrite group vs. 0.94 ± 0.58 μM in the VF placebo group (p < 0.001). There was a significant difference between the treatment and placebo groups in nitrite levels in blood between 7.5 and 15 min after CPR start and between groups with respect to nitrite levels in CSF, brain, heart and liver. In a second series (n = 25 including 5 shams), 19 out of 20 animals survived until day 8. However, NDS, FCT and brain histology did not show any statistically significant difference between groups.

CONCLUSIONS

Nitrite, administered early after ROSC from VF, was shown to cross the blood brain barrier after a 5 min VF cardiac arrest. We characterized the PK of intravenous nitrite administration after VF and were able to demonstrate nitrite safety in this feasibility study.

Novel Quantitative Contrast-Enhanced Ultrasound Detection of Hypoxic Ischemic Injury in Neonates and Infants: Pilot Study 1

OBJECTIVES

To investigate whether quantitative contrast-enhanced ultrasound (CEUS) can accurately identify neonates and infants with hypoxic ischemic brain injury.

METHODS

In this prospective cohort study, 8 neonates and infants with a suspicion of hypoxic ischemic injury were evaluated with CEUS.

RESULTS

An interesting trend was observed in the central gray nuclei-to-cortex perfusion ratios. The ratios at the peak enhancement, wash-in area under the curve, perfusion index, and maximum wash-in slopes were lower in all of the affected cases compared to the normal group but not statistically significant given the small sample size (P = .0571). Additionally, when the central gray nuclei-to-cortex perfusion ratio was plotted for all time points along the time-intensity curve, it was observed that the affected cases showed a trend that was qualitatively different from that of the normal cases. In the affected cases, the ratio time-intensity curves either stayed below 1.0 for the entire enhancement period or reached 1.0 close to peak wash-in before falling just below 1.0 for the remaining period of enhancement. However, in the unaffected patients, there was a steep wash-in that crossed the 1.0 threshold and remained above 1.0 for most of the enhancement period.

CONCLUSIONS

Bedside CEUS is an easily obtainable brain-imaging modality that has the potential to effectively identify infants and neonates with evolving brain injury. A larger prospective study evaluating the correlation between CEUS findings and the reference standard of diffusion- and perfusion-weighted magnetic resonance imaging is needed to establish it as a diagnostic tool.

Croix CM, Alexander H, Gibson GA, Loughran PA, Kirisci L, Clark RSB, Kochanek PM, Vazquez AL, Manole MD. Cerebral microcirculatory alterations and the no-reflow phenomenon in vivo after experimental pediatric cardiac arrest

Decreased cerebral blood flow (CBF) after cardiac arrest (CA) contributes to secondary ischemic injury in infants and children. We previously reported cortical hypoperfusion with tissue hypoxia early in a pediatric rat model of asphyxial CA. In order to identify specific alterations as potential therapeutic targets to improve cortical hypoperfusion post-CA, we characterize the CBF alterations at the cortical microvascular level in vivo using multiphoton microscopy. We hypothesize that microvascular constriction and disturbances of capillary red blood cell (RBC) flow contribute to cortical hypoperfusion post-CA. After resuscitation from 9 min asphyxial CA, transient dilation of capillaries and venules at 5 min was followed by pial arteriolar constriction at 30 and 60 min (19.6 ± 1.3, 19.3 ± 1.2 µm at 30, 60 min vs. 22.0 ± 1.2 µm at baseline, p < 0.05). At the capillary level, microcirculatory disturbances were highly heterogeneous, with RBC stasis observed in 25.4% of capillaries at 30 min post-CA. Overall, the capillary plasma mean transit time was increased post-CA by 139.7 ± 51.5%, p < 0.05. In conclusion, pial arteriolar constriction, the no-reflow phenomenon and increased plasma transit time were observed post-CA. Our results detail the microvascular disturbances in a pediatric asphyxial CA model and provide a powerful platform for assessing specific vascular-targeted therapies.

Effect of mild hypothermia on cerebral microcirculation in a murine cardiopulmonary resuscitation model

BACKGROUND

We hypothesized that mild hypothermia may improve brain microcirculation by reducing cerebral microvascular endothelial cells apoptosis, and this effect may be maximized by moving up the initiation of mild hypothermia from after return of spontaneous circulation (ROSC) to the start of cardiopulmonary resuscitation (CPR).

METHODS

A total of 35 rats were randomized into the intra-arrest hypothermia group (IAH), post-resuscitation hypothermia group (PRH), normothermia group (NT), or the sham control group. A craniotomy exposed the parietal cortex for visualization of microcirculation. Ventricular fibrillation was electrically induced and untreated for 8 minutes, followed by 8 minutes of precordial compression and mechanical ventilation. Hypothermia (33 ± 0.5°C) in the IAH and PRH group was induced and maintained for 6 hours at the beginning of CPR or after ROSC, respectively. At baseline, 1, 3, and 6 hours, hemodynamic parameters were measured and the pial microcirculations were visualized with a sidestream dark field imaging video microscope. Microvascular flow index and perfused microvessel density (PMD) were calculated. Rats were euthanized, and brain tissues were removed at 3 and 6 hours separately. Expression of Bax, Bcl-2, and Caspase 3 in brain microvascular endothelial cells was examined by Western blot.

RESULTS

Microvascular flow index and PMD were significantly reduced after cardiac arrest and resuscitation (all P < 0.05), and the former was largely preserved by hypothermia regardless when the hypothermia treatment was induced (P < 0.05). Bax and Caspase 3 increased and Bcl-2 decreased significantly after resuscitation, and hypothermia treatment reversed the trend partly (all P < 0.05). A moderate correlation was observed between MFI and those proteins (Bcl-2/BAX: 3 hours: r = 0.730, P = 0.002; 6 hours: r = 0.743, P = 0.002).

CONCLUSION

Mild hypothermia improves cerebral microcirculatory blood supply, partly by inhibiting endothelial cell apoptosis. Mild hypothermia induced simultaneously with CPR has shown no additional benefit in microcirculation or endothelial cell apoptosis.

Selective beta-blocker esmolol improves cerebral cortex microcirculation in a swine ventricular fibrillation model

OBJECTIVE

This study aimed to identify whether esmolol attenuates cerebral cortex microcirculation blood flow due to epinephrine in prolonged ventricular fibrillation (VF) and cardiopulmonary resuscitation (CPR), and may improve neurological prognosis.

METHODS

Male pigs were randomized into the esmolol+epinephrine group (group EE), the epinephrine group (group EP), and the normal saline group (group NS) (n = 8 each group). Untreated VF for 8 minutes was induced in pigs. After CPR for 2 minutes, group EE received esmolol (500 µg/kg)+epinephrine (20 µg/kg), group EP received epinephrine 20 µg/kg, and group NS received 5 mL normal saline. Then, a 120 J electric shock was delivered. If the return of spontaneous circulation (ROSC) failed, epinephrine (20 µg/kg) was repeated in group EP and EE, followed by another 2 minutes of CPR, a 150 J electric shock was delivered every 2 minutes until ROSC. Cerebral microcirculation images were obtained at 0.5, 6, 12, and 24 hours by cranial windows after ROSC. Cerebral performance category scores and neurological deficit scores (NDS) were calculated. The frontal cortices were harvested after the animals were euthanized.

RESULTS

The NDS, the perfused vessel density, and the microcirculatory flow index of group EE were better than other two groups. The morphology of endothelial cells in the group EE remained intact; however, it was destroyed in the group EP.

CONCLUSIONS

Administration of esmolol with epinephrine may alleviate the impairment of cerebral microcirculation blood flow caused by the administration of epinephrine in prolonged VF and thereby improves neurological outcomes in a swine model.

Extracorporeal Life Support Increases Survival After Prolonged Ventricular Fibrillation Cardiac Arrest in the Rat

Background:

Extracorporeal life support (ECLS) for cardiopulmonary resuscitation (CPR) may increase end organ perfusion and thus survival when conventional CPR fails. The aim was to investigate, if after ventricular fibrillation cardiac arrest in rodents ECLS improves outcome compared with conventional CPR.

Methods:

In 24 adult male Sprague–Dawley rats (460–510 g) resuscitation was started after 10 min of no-flow with ECLS (consisting of an open reservoir, roller pump, and membrane oxygenator, connected to cannulas in the jugular vein and femoral artery, n = 8) or CPR (mechanical chest compressions plus ventilations, n = 8) and compared with a sham group (n = 8). After return of spontaneous circulation (ROSC), all rats were maintained at 33°C for 12 h. Survival to 14 days, neurologic deficit scores and overall performance categories were assessed.

Results:

ECLS leads to sustained ROSC in 8 of 8 (100%) and neurological intact survival to 14 days in 7 of 8 rats (88%), compared with 5 of 8 (63%) and 1 of 8 CPR rats. The median survival time was 14 days (IQR: 14–14) in the ECLS and 1 day (IQR: 0 to 5) for the CPR group (P = 0.004).

Conclusion:

In a rat model of prolonged ventricular fibrillation cardiac arrest, ECLS with mild hypothermia produces 100% resuscitability and 88% long-term survival, significantly better than conventional CPR.

The relationship between low survival and acute increase of tumor necrosis factor α expression in the lung in a rat model of asphyxial cardiac arrest

Cardiac arrest (CA) is sudden loss of heart function and abrupt stop in effective blood flow to the body. The patients who initially achieve return of spontaneous circulation (RoSC) after CA have low survival rate. It has been known that multiorgan dysfunctions after RoSC are associated with high morbidity and mortality. Most previous studies have focused on the heart and brain in RoSC after CA. Therefore, the aim of this research was to perform serological, physiological, and histopathology study in the lung and to determine whether or how pulmonary dysfunction is associated with low survival rate after CA. Experimental animals were divided into sham-operated group (n=14 at each point in time), which was not subjected to CA operation, and CA-operated group (n=14 at each point in time), which was subjected to CA. The rats in each group were sacrificed at 6 hours, 12 hours, 24 hours, and 2 days, respectively, after RoSC. Then, pathological changes of the lungs were analyzed by hematoxylin and eosin staining, Western blot and immunohistochemistry for tumor necrosis factor α (TNF-α). The survival rate after CA was decreased with time past. We found that histopathological score and TNF-α immunoreactivity were significantly increased in the lung after CA. These results indicate that inflammation triggered by ischemia-reperfusion damage after CA leads to pulmonary injury/dysfunctions and contributes to low survival rate. In addition, the finding of increase in TNF-α via inflammation in the lung after CA would be able to utilize therapeutic or diagnostic measures in the future.

Evaluation of small intestinal damage in a rat model of 6 Minutes cardiac arrest

BACKGROUND

Contribution of the small intestine to systemic inflammation after cardiac arrest (CA) is poorly understood. The objective was to evaluate whether an in vivo rat model of 6 min CA is suitable to initiate intestinal ischaemia-reperfusion-injury and to evaluate histomorphological changes and inflammatory processes in the small intestinal mucosa resp. in sera.

METHODS

Adult male Wistar rats were subjected to CA followed by cardio-pulmonary resuscitation. Proximal jejunum and serum was collected at 6 h, 24 h, 72 h and 7 d post return of spontaneous circulation (ROSC) and from a control group. The small intestine was evaluated histomorphologically. Cytokine concentrations were measured in jejunum lysates and sera.

RESULTS

Histomorphological evaluation revealed a significant increase in mucosal damage in the jejunum at all timepoints compared to controls (p < 0.0001). In jejunal tissues, concentrations of IL-1α, IL-1β, IL-10, and TNF-α showed significant peaks at 24 h and were 1.5- to 5.7-fold higher than concentrations at 6 h and in the controls (p < 0.05). In serum, a significant higher amount of cytokine was detected only for IL-1β at 24 h post-ROSC compared to controls (15.78 vs. 9.76 pg/ml).

CONCLUSION

CA resulted in mild small intestinal tissue damage but not in systemic inflammation. A rat model of 6 min CA is not capable to comprehensively mimic a post cardiac arrest syndrome (PCAS). Whether there is a vital influence of the intestine on the PCAS still remains unclear.

Dynamic Changes of Mitochondrial Fusion and Fission in Brain Injury after Cardiac Arrest in Rats

Mitochondria change their morphology dynamically by continual fusion and fission processes to fulfill their function. However, little is known about the effect of cardiac arrest on mitochondrial dynamics. This study aimed to investigate time-dependent change of the mitochondrial dynamics after brain ischemic injury in rats of cardiac arrest. After resuscitation, obvious neuronal injury, reduced adenosine triphosphate (ATP) levels, excessive reactive oxygen species (ROS) generation, decreased mitochondrial membrane potential (MMP), and increased release of mitochondrial cytochrome c were observed at 12 h and 24 h after cardiac arrest. Moreover, we found that elongation of mitochondria was observed at 4 h after cardiac arrest, whereas fragmented mitochondria were significantly increased, along with concomitant increase in the fission proteins Drp1 and Fis1 and a reduction in the fusion proteins Mfn1 and Mfn2 at 12 h and 24 h after cardiac arrest. Taken together, these findings suggest that imbalance in mitochondrial dynamics probably contributes to brain injury after cardiac arrest.

Neurocardiology: Cardiovascular Changes and Specific Brain Region Infarcts

There are complex and dynamic reflex control networks between the heart and the brain, including cardiac and intrathoracic ganglia, spinal cord, brainstem, and central nucleus. Recent literature based on animal model and clinical trials indicates a close link between cardiac function and nervous systems. It is noteworthy that the autonomic nervous-based therapeutics has shown great potential in the management of atrial fibrillation, ventricular arrhythmia, and myocardial remodeling. However, the potential mechanisms of postoperative brain injury and cardiovascular changes, particularly heart rate variability and the presence of arrhythmias, are not understood. In this chapter, we will describe mechanisms of brain damage undergoing cardiac surgery and focus on the interaction between cardiovascular changes and damage to specific brain regions.

Post-anoxic quantitative MRI changes may predict emergence from coma and functional outcomes at discharge

BACKGROUND

Traditional predictors of neurological prognosis after cardiac arrest are unreliable after targeted temperature management. Absence of pupillary reflexes remains a reliable predictor of poor outcome. Diffusion-weighted imaging has emerged as a potential predictor of recovery, and here we compare imaging characteristics to pupillary exam.

METHODS

We identified 69 patients who had MRIs within seven days of arrest and used a semi-automated algorithm to perform quantitative volumetric analysis of apparent diffusion coefficient (ADC) sequences at various thresholds. Area under receiver operating characteristic curves (ROC-AUC) were estimated to compare predictive values of quantitative MRI with pupillary exam at days 3, 5 and 7 post-arrest, for persistence of coma and functional outcomes at discharge. Cerebral Performance Category scores of 3-4 were considered poor outcome.

RESULTS

Excluding patients where life support was withdrawn, ≥2.8% diffusion restriction of the entire brain at an ADC of ≤650×10^-6m²/s was 100% specific and 68% sensitive for failure to wake up from coma before discharge. The ROC-AUC of ADC changes at ≤450×10^-6mm²/s and ≤650×10^-6mm²/s were significantly superior in predicting failure to wake up from coma compared to bilateral absence of pupillary reflexes. Among survivors, >0.01% of diffusion restriction of the entire brain at an ADC ≤450×10^-6m²/s was 100% specific and 46% sensitive for poor functional outcome at discharge. The ROC curve predicting poor functional outcome at ADC ≤450×10^-6mm²/s had an AUC of 0.737 (0.574-0.899, p=0.04).

CONCLUSION

Post-anoxic diffusion changes using quantitative brain MRI may aid in predicting persistent coma and poor functional outcomes at hospital discharge.

Neuronal injury and tumor necrosis factor-alpha immunoreactivity in the rat hippocampus in the early period of asphyxia-induced cardiac arrest under normothermia

Low survival rate occurs in patients who initially experience a spontaneous return of circulation after cardiac arrest (CA). In this study, we induced asphyxial CA in adult male Sprague-Daley rats, maintained their body temperature at 37 ± 0.5°C, and then observed the survival rate during the post-resuscitation phase. We examined neuronal damage in the hippocampus using cresyl violet (CV) and Fluore-Jade B (F-J B) staining, and pro-inflammatory response using ionized calcium-binding adapter molecule 1 (Iba-1), glial fibrillary acidic protein (GFAP), and tumor necrosis factor-alpha (TNF-α) immunohistochemistry in the hippocampus after asphyxial CA in rats under normothermia. Our results show that the survival rate decreased gradually post-CA (about 63% at 6 hours, 37% at 1 day, and 8% at 2 days post-CA). Rats were sacrificed at these points in time post-CA, and no neuronal damage was found in the hippocampus until 1 day post-CA. However, some neurons in the stratum pyramidale of the CA region in the hippocampus were dead 2 days post-CA. Iba-1 immunoreactive microglia in the CA1 region did not change until 1 day post-CA, and they were activated (enlarged cell bodies with short and thicken processes) in all layers 2 days post-CA. Meanwhile, GFAP-immunoreactive astrocytes did not change significantly until 2 days post-CA. TNF-α immunoreactivity decreased significantly in neurons of the stratum pyramidale in the CA1 region 6 hours post-CA, decreased gradually until 1 day post-CA, and increased significantly again 2 days post-CA. These findings suggest that low survival rate of normothermic rats in the early period of asphyxia-induced CA is related to increased TNF-α immunoreactivity, but not to neuronal damage in the hippocampal CA1 region.