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

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.

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.

Post-cardiac arrest temporal evolution of left ventricular function in a rat model: speckle-tracking echocardiography and cardiac circulating biomarkers

Aims

There is little information from experimental studies regarding the evolution of post-resuscitation cardiac arrest [post-return of spontaneous circulation (post-ROSC)] myocardial dysfunction during mid-term follow-up. For this purpose, we assessed left ventricular (LV) function and circulating cardiac biomarkers at different time points in a rat model of cardiac arrest (CA).

Methods and results

Rats were divided into two groups: control and post-ROSC rats. Eight minutes of untreated ventricular fibrillation were followed by 8 min of cardiopulmonary resuscitation. Conventional and speckle-tracking echocardiographic (STE) parameters and cardiac circulating biomarkers concentrations were assessed, at 3, 4, 72, and 96 h post-ROSC. At 3 and 4 h post-ROSC, LV systolic function was severely impaired, and high-sensitivity cardiac troponin T and N-terminal pro-atrial natriuretic peptide (NT-proANP) plasma concentrations were significantly increased, compared with control rats (P < 0.0001 for all). At 72 and 96 h post-ROSC, LV ejection fraction (LVEF) normalized. At 96 h, the following variables were significantly different from control rats: early trans-mitral peak velocity, 56.8 ± 3.1 vs. 87.8 ± 3.8 cm/s, P < 0.0001; late trans-mitral peak velocity, 50.6 ± 4.7 vs. 73.7 ± 4.2 cm/s, P < 0.0001; mean s' wave velocity, 4.6 ± 0.3 vs. 5.9 ± 0.3 cm/s, P < 0.0001, global longitudinal strain (GLS) -7.5 ± 0.5 and vs. -11 ± 1.2%, P < 0.01; GLS rate (GLSR) -0.9 ± 0.4 and -2.3 ± 0.2 1/s, P < 0.01; and NT-proANP concentration, 2.5 (0.2; 6.0) vs. 0.4 (0.01; 1.0) nmol/L, P < 0.01.

Conclusion

s' velocity, GLS, and GLSR indicated that LV systolic function was still impaired 96 h post-ROSC. These findings agree with NT-proANP concentrations, which continue to be high. Normalization of LVEF supports the use of STE for its greater sensitivity for monitoring post-CA cardiac function. Further investigations are needed to provide evidence of the post-ROSC LV diastolic function pattern.

Interpretable machine learning model for imaging-based outcome prediction after cardiac arrest

INTRODUCTION

Early identification of brain injury patterns in computerized tomography (CT) imaging is crucial for post-cardiac arrest prognostication. Lack of interpretability of machine learning prediction reduces trustworthiness by clinicians and prevents translation to clinical practice. We aimed to identify CT imaging patterns associated with prognosis with interpretable machine learning.

METHODS

In this IRB-approved retrospective study, we included consecutive comatose adult patients hospitalized at a single academic medical center after resuscitation from in- and out-of-hospital cardiac arrest between August 2011 and August 2019 who underwent unenhanced CT imaging of the brain within 24 hours of their arrest. We decomposed the CT images into subspaces to identify interpretable and informative patterns of injury, and developed machine learning models to predict patient outcomes (i.e., survival and awakening status) using the identified imaging patterns. Practicing physicians visually examined the imaging patterns to assess clinical relevance. We evaluated machine learning models using 80%-20% random data split and reported AUC values to measure the model performance.

RESULTS

We included 1284 subjects of whom 35% awakened from coma and 34% survived hospital discharge. Our expert physicians were able to visualize decomposed image patterns and identify those believed to be clinically relevant on multiple brain locations. For machine learning models, the AUC was 0.710 ± 0.012 for predicting survival and 0.702 ± 0.053 for predicting awakening, respectively.

DISCUSSION

We developed an interpretable method to identify patterns of early post-cardiac arrest brain injury on CT imaging and showed these imaging patterns are predictive of patient outcomes (i.e., survival and awakening status).

Clinical presentation, diagnosis, treatment, and outcome in 8 dogs and 2 cats with global hypoxic-ischemic brain injury (2010-2022)

BACKGROUND

Global hypoxic-ischemic brain injury (GHIBI) results in variable degrees of neurological dysfunction. Limited data exists to guide prognostication on likelihood of functional recovery.

HYPOTHESIS

Prolonged duration of hypoxic-ischemic insult and absence of neurological improvement in the first 72 hours are negative prognostic indicators.

ANIMALS

Ten clinical cases with GHIBI.

METHODS

Retrospective case series describing 8 dogs and 2 cats with GHIBI, including clinical signs, treatment, and outcome.

RESULTS

Six dogs and 2 cats experienced cardiopulmonary arrest or anesthetic complication in a veterinary hospital and were promptly resuscitated. Seven showed progressive neurological improvement within 72 hours of the hypoxic-ischemic insult. Four fully recovered and 3 had residual neurological deficits. One dog presented comatose after resuscitation at the primary care practice. Magnetic resonance imaging confirmed diffuse cerebral cortical swelling and severe brainstem compression and the dog was euthanized. Two dogs suffered out-of-hospital cardiopulmonary arrest, secondary to a road traffic accident in 1 and laryngeal obstruction in the other. The first dog was euthanized after MRI that identified diffuse cerebral cortical swelling with severe brainstem compression. In the other dog, spontaneous circulation was recovered after 22 minutes of cardiopulmonary resuscitation. However, the dog remained blind, disorientated, and ambulatory tetraparetic with vestibular ataxia and was euthanized 58 days after presentation. Histopathological examination of the brain confirmed severe diffuse cerebral and cerebellar cortical necrosis.

CONCLUSIONS AND CLINICAL IMPORTANCE

Duration of hypoxic-ischemic insult, diffuse brainstem involvement, MRI features, and rate of neurological recovery could provide indications of the likelihood of functional recovery after GHIBI.

Recent developments and controversies in therapeutic hypothermia after cardiopulmonary resuscitation

Therapeutic hypothermia was recommended as the only neuroprotective treatment in comatose patients after return of spontaneous circulation (ROSC). With new evidence suggesting a similar neuroprotective effect of 36 °C and 33 °C, the term "therapeutic hypothermia" was substituted by "targeted temperature management" in 2011, which in turn was replaced by the term "temperature control" in 2022 because of new evidence of the similar effects of target normothermia and 33 °C. However, there is no clear consensus on the efficacy of therapeutic hypothermia. In this article, we provide an overview of the recent evidence from basic and clinical research related to therapeutic hypothermia and re-evaluate its application as a post-ROSC neuroprotective intervention in clinical settings.

Association of Blood-Based Brain Injury Biomarker Concentrations With Outcomes After Pediatric Cardiac Arrest

IMPORTANCE

Families and clinicians have limited validated tools available to assist in estimating long-term outcomes early after pediatric cardiac arrest. Blood-based brain-specific biomarkers may be helpful tools to aid in outcome assessment.

OBJECTIVE

To analyze the association of blood-based brain injury biomarker concentrations with outcomes 1 year after pediatric cardiac arrest.

DESIGN, SETTING, AND PARTICIPANTS

The Personalizing Outcomes After Child Cardiac Arrest multicenter prospective cohort study was conducted in pediatric intensive care units at 14 academic referral centers in the US between May 16, 2017, and August 19, 2020, with the primary investigators blinded to 1-year outcomes. The study included 120 children aged 48 hours to 17 years who were resuscitated after cardiac arrest, had pre-cardiac arrest Pediatric Cerebral Performance Category scores of 1 to 3 points, and were admitted to an intensive care unit after cardiac arrest.

EXPOSURE

Cardiac arrest.

MAIN OUTCOMES AND MEASURES

The primary outcome was an unfavorable outcome (death or survival with a Vineland Adaptive Behavior Scales, third edition, score of <70 points) at 1 year after cardiac arrest. Glial fibrillary acidic protein (GFAP), ubiquitin carboxyl-terminal esterase L1 (UCH-L1), neurofilament light (NfL), and tau concentrations were measured in blood samples from days 1 to 3 after cardiac arrest. Multivariate logistic regression and area under the receiver operating characteristic curve (AUROC) analyses were performed to examine the association of each biomarker with outcomes on days 1 to 3.

RESULTS

Among 120 children with primary outcome data available, the median (IQR) age was 1.0 (0-8.5) year; 71 children (59.2%) were male. A total of 5 children (4.2%) were Asian, 19 (15.8%) were Black, 81 (67.5%) were White, and 15 (12.5%) were of unknown race; among 110 children with data on ethnicity, 11 (10.0%) were Hispanic, and 99 (90.0%) were non-Hispanic. Overall, 70 children (58.3%) had a favorable outcome, and 50 children (41.7%) had an unfavorable outcome, including 43 deaths. On days 1 to 3 after cardiac arrest, concentrations of all 4 measured biomarkers were higher in children with an unfavorable vs a favorable outcome at 1 year. After covariate adjustment, NfL concentrations on day 1 (adjusted odds ratio [aOR], 5.91; 95% CI, 1.82-19.19), day 2 (aOR, 11.88; 95% CI, 3.82-36.92), and day 3 (aOR, 10.22; 95% CI, 3.14-33.33); UCH-L1 concentrations on day 2 (aOR, 11.27; 95% CI, 3.00-42.36) and day 3 (aOR, 7.56; 95% CI, 2.11-27.09); GFAP concentrations on day 2 (aOR, 2.31; 95% CI, 1.19-4.48) and day 3 (aOR, 2.19; 95% CI, 1.19-4.03); and tau concentrations on day 1 (aOR, 2.44; 95% CI, 1.14-5.25), day 2 (aOR, 2.28; 95% CI, 1.31-3.97), and day 3 (aOR, 2.04; 95% CI, 1.16-3.57) were associated with an unfavorable outcome. The AUROC models were significantly higher with vs without the addition of NfL on day 2 (AUROC, 0.932 [95% CI, 0.877-0.987] vs 0.871 [95% CI, 0.793-0.949]; P = .02) and day 3 (AUROC, 0.921 [95% CI, 0.857-0.986] vs 0.870 [95% CI, 0.786-0.953]; P = .03).

CONCLUSIONS AND RELEVANCE

In this cohort study, blood-based brain injury biomarkers, especially NfL, were associated with an unfavorable outcome at 1 year after pediatric cardiac arrest. Additional evaluation of the accuracy of the association between biomarkers and neurodevelopmental outcomes beyond 1 year is needed.

Long-term prognosis and clinical course of choking-induced cardiac arrest in patients without the return of spontaneous circulation at hospital arrival: a population-based community study from the Shizuoka Kokuho Database

Background

The risk of choking increases with aging, and the number of cases of choking-induced cardiac arrest is increasing. However, few studies have examined the prognosis of choking-induced cardiac arrest. The aim of this study was to reveal the rates of survival and dependence on devices in the long term after choking-induced cardiac arrest.

Methods

We analyzed data from the Shizuoka Kokuho Database, which consists of claims data of approximately 2.2 million people, from April 2012 to September 2018. We selected patients with choking-induced cardiac arrest who received cardiopulmonary resuscitation in the hospital. Patients were excluded if they were less than 20 years old, had an upper airway tumor, received ventilation assistance, or received enteral nutrition in the month prior to cardiac arrest. The primary outcome was death, and the secondary outcomes were the rates of survival at 3-months and independence on devices. Descriptive statistics are presented and compared among age groups (20–64 years, 65–74 years, 75–84 years, 85 years and older), and survival time analysis (Kaplan-Meier method) was performed.

Results

In total, 268 patients were analyzed, including 26 patients in the 20–64 age group, 33 patients in the 65–74 age group, 70 patients in the 75–84 age group, and 139 patients in the ≥85 age group. The overall 3-month survival rate was 5.6% (15/268). The 3-month survival rates were 3.8% (1/26) in the 20–64 age group, 15.2% (5/33) in the 65–74 age group, 8.6% (6/70) in the 75–84 age group, and 2.2% (3/139) in the ≥85 age group. The overall 12-month survival rate was 2.6% (7/268). Of the 7 patients who survived for 12 months, 3 received ventilation management and 5 received tube or intravenous feedings at 3 months. These survivors were still receiving ventilation assistance and tube feedings in the hospital and had not been discharged at 12 months.

Conclusions

The prognosis of choking-induced cardiac arrest was extremely poor when patients were not resuscitated before hospital arrival. Those who survived were mostly dependent on assistive devices. Additionally, none of the survivors dependent on assistive devices had discontinued the use of the devices at the long-term follow-up.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12873-022-00676-8.

Omecamtiv mecarbil treatment improves post-resuscitation cardiac function and neurological outcome in a rat model

Background

Myocardial dysfunction is a major cause of poor outcomes in the post-cardiac arrest period. Omecamtiv mecarbil (OM) is a selective small molecule activator of cardiac myosin that prolongs myocardial systole and increases stroke volume without apparent effects on myocardial oxygen demand. OM administration is safe and improves cardiac function in patients with acute heart failure. Whether OM improves post-resuscitation myocardial dysfunction remains unclear. This study investigated the effect of OM treatment on post-resuscitation myocardial dysfunction and outcomes.

Methods and results

Adult male rats were resuscitated after 9.5 min of asphyxia-induced cardiac arrest. OM and normal saline was continuously intravenously infused after return of spontaneous circulation (ROSC) at 0.25 mg/kg/h for 4 h in the experimental group and control group, respectively (n = 20 in each group). Hemodynamic parameters were measured hourly and monitored for 4 h after cardiac arrest. Recovery of neurological function was evaluated by neurological functioning scores (0–12; favorable: 11–12) for rats 72 h after cardiac arrest. OM treatment prolonged left ventricular ejection time and improved post-resuscitation cardiac output. Post-resuscitation heart rate and left ventricular systolic function (dp/dt₄₀) were not different between groups. Kaplan-Meier analysis showed non-statistically higher 72-h survival in the OM group (72.2% [13/18] and 58.8% [10/17], p = 0.386). The OM group had a higher chance of having favorable neurological outcomes in surviving rats 72 h after cardiac arrest (84.6% [11/13] vs. 40% [4/10], p = 0.026). The percentage of damaged neurons was lower in the OM group in a histology study at 72 h after cardiac arrest (55.5±2.3% vs. 76.2±10.2%, p = 0.004).

Conclusions

OM treatment improved post-resuscitation myocardial dysfunction and neurological outcome in an animal model. These findings support further pre-clinical studies to improve outcomes in post-cardiac arrest care.

Brain injury after cardiac arrest

As more people are surviving cardiac arrest, focus needs to shift towards improving neurological outcomes and quality of life in survivors. Brain injury after resuscitation, a common sequela following cardiac arrest, ranges in severity from mild impairment to devastating brain injury and brainstem death. Effective strategies to minimise brain injury after resuscitation include early intervention with cardiopulmonary resuscitation and defibrillation, restoration of normal physiology, and targeted temperature management. It is important to identify people who might have a poor outcome, to enable informed choices about continuation or withdrawal of life-sustaining treatments. Multimodal prediction guidelines seek to avoid premature withdrawal in those who might survive with a good neurological outcome, or prolonging treatment that might result in survival with severe disability. Approximately one in three admitted to intensive care will survive, many of whom will need intensive, tailored rehabilitation after discharge to have the best outcomes.

Cardiopulmonary resuscitation in special circumstances

Cardiopulmonary resuscitation prioritises treatment for cardiac arrests from a primary cardiac cause, which make up the majority of treated cardiac arrests. Early chest compressions and, when indicated, a defibrillation shock from a bystander give the best chance of survival with a good neurological status. Cardiac arrest can also be caused by special circumstances, such as asphyxia, trauma, pulmonary embolism, accidental hypothermia, anaphylaxis, or COVID-19, and during pregnancy or perioperatively. Cardiac arrests in these circumstances represent an increasing proportion of all treated cardiac arrests, often have a preventable cause, and require additional interventions to correct a reversible cause during resuscitation. The evidence for treating these conditions is mostly of low or very low certainty and further studies are needed. Irrespective of the cause, treatments for cardiac arrest are time sensitive and most effective when given early-every minute counts.

High-resolution respirometry for evaluation of mitochondrial function on brain and heart homogenates in a rat model of cardiac arrest and cardiopulmonary resuscitation

The physiology and physiopathology process of mitochondrial function following cardiac arrest remains poorly understood. We aimed to assess mitochondrial respiratory function on the heart and brain homogenates from cardiac arrest rats. The expression level of SIRT1/PGC-1α pathway was measured by immunoblotting. 30 rats were assigned to the CA group and the sham group. Rats of CA were subjected to 6 min of untreated ventricular fibrillation (VF) followed by 8 min of cardiopulmonary resuscitation (CPR). Mitochondrial respiratory function was compromised following CA and I/R injury, as indicated by CIL (451.46 ± 71.48 vs. 909.91 ± 5.51 pmol/min*mg for the heart and 464.14 ± 8.22 vs. 570.53 ± 56.33 pmol/min*mg for the brain), CI (564.04 ± 64.34 vs. 2729.52 ± 347.39 pmol/min*mg for the heart and 726.07 ± 85.78 vs. 1762.82 ± 262.04 pmol/min*mg for the brain), RCR (1.88 ± 0.46 vs. 3.57 ± 0.38 for the heart and 2.05 ± 0.19 vs. 3.49 ± 0.19, for the brain) and OXPHOS coupling efficiency (0.45 ± 0.11 vs. 0.72 ± 0.03 for the heart and 0.52 ± 0.05 vs. 0.71 ± 0.01 for the brain). However, routine respiration was lower in the heart and comparable in the brain after CA. CIV did not change in the heart but was enhanced in the brain. Furthermore, both SIRT1 and PGC-1α were downregulated concurrently in the heart and brain. The mitochondrial respiratory function was compromised following CA and I/R injury, and the major affected respiratory state is complex I-linked respiration. Furthermore, the heart and the brain respond differently to the global I/R injury after CA in mitochondrial respiratory function. Inhibition of the SIRT1/PGC-1α pathway may be a major contributor to the impaired mitochondrial respiratory function.

Upregulation of hemeoxygenase enzymes HO-1 and HO-2 following ischemia-reperfusion injury in connection with experimental cardiac arrest and cardiopulmonary resuscitation: Neuroprotective effects of methylene blue

Oxidative stress plays an important role in neuronal injuries after cardiac arrest. Increased production of carbon monoxide (CO) by the enzyme hemeoxygenase (HO) in the brain is induced by the oxidative stress. HO is present in the CNS in two isoforms, namely the inducible HO-1 and the constitutive HO-2. Elevated levels of serum HO-1 occurs in cardiac arrest patients and upregulation of HO-1 in cardiac arrest is seen in the neurons. However, the role of HO-2 in cardiac arrest is not well known. In this review involvement of HO-1 and HO-2 enzymes in the porcine brain following cardiac arrest and resuscitation is discussed based on our own observations. In addition, neuroprotective role of methylene blue- an antioxidant dye on alterations in HO under in cardiac arrest is also presented. The biochemical findings of HO-1 and HO-2 enzymes using ELISA were further confirmed by immunocytochemical approach to localize selective regional alterations in cardiac arrest. Our observations are the first to show that cardiac arrest followed by successful cardiopulmonary resuscitation results in significant alteration in cerebral concentrations of HO-1 and HO-2 levels indicating a prominent role of CO in brain pathology and methylene blue during CPR followed by induced hypothermia leading to superior neuroprotection after return of spontaneous circulation (ROSC), not reported earlier.

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.

Cardiopulmonary Resuscitation and Rescue Therapies

The history of cardiopulmonary resuscitation and the Society of Critical Care Medicine have much in common, as many of the founders of the Society of Critical Care Medicine focused on understanding and improving outcomes from cardiac arrest. We review the history, the current, and future state of cardiopulmonary resuscitation.

European Resuscitation Council and European Society of Intensive Care Medicine guidelines 2021: post-resuscitation care

The European Resuscitation Council (ERC) and the European Society of Intensive Care Medicine (ESICM) have collaborated to produce these post-resuscitation care guidelines for adults, which are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. The topics covered include the post-cardiac arrest syndrome, diagnosis of cause of cardiac arrest, control of oxygenation and ventilation, coronary reperfusion, haemodynamic monitoring and management, control of seizures, temperature control, general intensive care management, prognostication, long-term outcome, rehabilitation and organ donation.

European Resuscitation Council and European Society of Intensive Care Medicine Guidelines 2021: Post-resuscitation care

The European Resuscitation Council (ERC) and the European Society of Intensive Care Medicine (ESICM) have collaborated to produce these post-resuscitation care guidelines for adults, which are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. The topics covered include the post-cardiac arrest syndrome, diagnosis of cause of cardiac arrest, control of oxygenation and ventilation, coronary reperfusion, haemodynamic monitoring and management, control of seizures, temperature control, general intensive care management, prognostication, long-term outcome, rehabilitation, and organ donation.

Opioid-Associated Out-of-Hospital Cardiac Arrest: Distinctive Clinical Features and Implications for Health Care and Public Responses: A Scientific Statement From the American Heart Association

Opioid overdose is the leading cause of death for Americans 25 to 64 years of age, and opioid use disorder affects >2 million Americans. The epidemiology of opioid-associated out-of-hospital cardiac arrest in the United States is changing rapidly, with exponential increases in death resulting from synthetic opioids and linear increases in heroin deaths more than offsetting modest reductions in deaths from prescription opioids. The pathophysiology of polysubstance toxidromes involving opioids, asphyxial death, and prolonged hypoxemia leading to global ischemia (cardiac arrest) differs from that of sudden cardiac arrest. People who use opioids may also develop bacteremia, central nervous system vasculitis and leukoencephalopathy, torsades de pointes, pulmonary vasculopathy, and pulmonary edema. Emergency management of opioid poisoning requires recognition by the lay public or emergency dispatchers, prompt emergency response, and effective ventilation coupled to compressions in the setting of opioid-associated out-of-hospital cardiac arrest. Effective ventilation is challenging to teach, whereas naloxone, an opioid antagonist, can be administered by emergency medical personnel, trained laypeople, and the general public with dispatcher instruction to prevent cardiac arrest. Opioid education and naloxone distributions programs have been developed to teach people who are likely to encounter a person with opioid poisoning how to administer naloxone, deliver high-quality compressions, and perform rescue breathing. Current American Heart Association recommendations call for laypeople and others who cannot reliably establish the presence of a pulse to initiate cardiopulmonary resuscitation in any individual who is unconscious and not breathing normally; if opioid overdose is suspected, naloxone should also be administered. Secondary prevention, including counseling, opioid overdose education with take-home naloxone, and medication for opioid use disorder, is important to prevent recurrent opioid overdose.

Cardiac Arrest Induced by Asphyxia Versus Ventricular Fibrillation Elicits Comparable Early Changes in Cytokine Levels in the Rat Brain, Heart, and Serum

Background

Current postresuscitative care after cardiac arrest (CA) does not address the cause of CA. We previously reported that asphyxial CA (ACA) and ventricular fibrillation CA (VFCA) elicit unique injury signatures. We hypothesized that the early cytokine profiles of the serum, heart, and brain differ in response to ACA versus VFCA.

Methods and Results

Adult male rats were subjected to 10 minutes of either ACA or VFCA. Naives and shams (anesthesia and surgery without CA) served as controls (n=12/group). Asphyxiation produced an ≈4‐minute period of progressive hypoxemia followed by a no‐flow duration of ≈6±1 minute. Ventricular fibrillation immediately induced no flow. Return of spontaneous circulation was achieved earlier after ACA compared with VFCA (42±18 versus 105±22 seconds; P<0.001). Brain cytokines in naives were, in general, low or undetectable. Shams exhibited a modest effect on select cytokines. Both ACA and VFCA resulted in robust cytokine responses in serum, heart, and brain at 3 hours. Significant regional differences pinpointed the striatum as a key location of neuroinflammation. No significant differences in cytokines, neuron‐specific enolase, S100b, and troponin T were observed across CA models.

Conclusions

Both models of CA resulted in marked systemic, heart, and brain cytokine responses, with similar degrees of change across the 2 CA insults. Changes in cytokine levels after CA were most pronounced in the striatum compared with other brain regions. These collective observations suggest that the amplitude of the changes in cytokine levels after ACA versus VFCA may not mediate the differences in secondary injuries between these 2 CA phenotypes.

Targeted temperature management after cardiac arrest. A systematic review and meta-analysis of animal studies

AIM

Animal studies are an important knowledge base when information from clinical trials is missing or conflicting. The goal of this systematic review and meta-analysis was to investigate the effect of conventional targeted temperature management (TTM) between 32-36 °C in animal cardiac arrest models, and to estimate the influence of effect modifiers on the pooled effect of TTM.

DATA SOURCES

We searched Medline and Scopus from inception to May 2020 for randomised controlled animal trials assessing the effect of conventional TTM versus normothermia on neurologic outcome after cardiac arrest. We extracted data on study characteristics, study quality data, neurologic outcome, mortality, and potential effect modifiers.

RESULTS

We retrieved 1635 studies, 45 studies comprising data of 981 animals met the inclusion criteria. Risk of bias was high in 17 studies and moderate in 28 studies. We undertook random-effects meta-analyses and meta-regression analyses to calculate the pooled effect and the influence of effect modifiers. There was a strong beneficial effect of TTM as compared to normothermia on neurologic outcome (standardised mean difference of 1.4 [95% CI -1.7 to -1.1; I² = 75%]). Faster cooling rates, lower target temperature of TTM within the range of 32-36 °C, and shorter duration of cooling were independently associated with an increasing effect size of TTM.

CONCLUSIONS

This systematic review of animal cardiac arrest studies showed a consistent favourable effect of postresuscitation TTM as compared to normothermia on neurologic outcome that increased with lower target temperatures.

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.

Factors associated with shockable versus non-shockable rhythms in patients with in-hospital cardiac arrest

AIM

To identify factors associated with the initial rhythm in patients with in-hospital cardiac arrest and to assess whether potential differences in outcomes based on the initial rhythm can be explained by patient and event characteristics.

METHODS

Adult patients (≥18 years old) with in-hospital cardiac arrest in 2017 and 2018 were included from the Danish In-Hospital Cardiac Arrest Registry (DANARREST). We used population-based registries to obtain data on comorbidities, cardiac procedures, and medications. Unadjusted and adjusted risk ratios (RRs) for initial rhythm, return of spontaneous circulation (ROSC), and survival were estimated in separate models including an incremental number of prespecified variables.

RESULTS

A total of 3422 patients with in-hospital cardiac arrest were included, of which 639 (19%) had an initial shockable rhythm. Monitored cardiac arrest, witnessed cardiac arrest, and specific cardiac diseases (i.e. ischemic heart disease, dysrhythmias, and valvular heart disease) were associated with initial shockable rhythm. Conversely, higher age, female sex, and specific non-cardiovascular comorbidities (e.g. overweight and obesity, renal disease, and pulmonary cancer) were associated with an initial non-shockable rhythm. Initial shockable rhythm remained strongly associated with increased ROSC (RR = 1.63, 95%CI 1.51-1.76), 30-day survival (RR = 2.31, 95%CI 2.02-2.64), and 1-year survival (RR = 2.36, 95%CI 2.02-2.76) compared to initial non-shockable rhythm in the adjusted analyses.

CONCLUSION

In this study, specific patient and cardiac arrest characteristics were associated with initial rhythm in patients with in-hospital cardiac arrest. However, differences in patient and cardiac arrest characteristics did not fully explain the association with survival for initial shockable rhythm compared to a non-shockable rhythm.

Near-Infrared Spectroscopy to Assess Cerebral Autoregulation and Optimal Mean Arterial Pressure in Patients With Hypoxic-Ischemic Brain Injury: A Prospective Multicenter Feasibility Study

Supplemental Digital Content is available in the text.

We provide preliminary multicenter data to suggest that recruitment and collection of physiologic data necessary to quantify cerebral autoregulation and individualized blood pressure targets are feasible in postcardiac arrest patients. We evaluated the feasibility of a multicenter protocol to enroll patients across centers, as well as collect continuous recording (≥ 80% of monitoring time) of regional cerebral oxygenation and mean arterial pressure, which is required to quantify cerebral autoregulation, using the cerebral oximetry index, and individualized optimal mean arterial pressure thresholds. Additionally, we conducted an exploratory analysis to assess if an increased percentage of monitoring time where mean arterial pressure was greater than or equal to 5 mm Hg below optimal mean arterial pressure, percentage of monitoring time with dysfunctional cerebral autoregulation (i.e., cerebral oximetry index ≥ 0.3), and time to return of spontaneous circulation were associated with an unfavorable neurologic outcome (i.e., 6-mo Cerebral Performance Category score ≥ 3).

Cardiac function after cardiac arrest: what do we know?

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

Salvianolic Acid B Improves Postresuscitation Myocardial and Cerebral Outcomes in a Murine Model of Cardiac Arrest: Involvement of Nrf2 Signaling Pathway

Survival and outcome of cardiac arrest (CA) are dismal despite improvements in cardiopulmonary resuscitation (CPR). Salvianolic acid B (Sal B), extracted from Salvia miltiorrhiza, has been investigated for its cardioprotective properties in cardiac remodeling and ischemic heart disease, but less is known about its role in CA. The aim of this study was to learn whether Sal B improves cardiac and neurologic outcomes after CA/CPR in mice. Female C57BL/6 mice were subjected to eight minutes of CA induced by an intravenous injection of potassium chloride (KCl), followed by CPR. After 30 seconds of CPR, mice were blindly randomized to receive either Sal B (20 mg/kg) or vehicle (normal saline) intravenously. Hemodynamic variables and indices of left ventricular function were determined before CA and within three hours after CPR, the early postresuscitation period. Sal B administration resulted in a remarkable decrease in the time required for the return of spontaneous circulation (ROSC) in animals that successfully resuscitated compared to the vehicle-treated mice. Myocardial performance, including cardiac output and left ventricular systolic (dp/dt_max) and diastolic (dp/dt_min) function, was clearly ameliorated within three hours of ROSC in the Sal B-treated mice. Moreover, Sal B inhibited CA/CPR-induced cardiomyocyte apoptosis and preserved mitochondrial morphology and function. Mechanistically, Sal B dramatically promoted Nrf2 nuclear translocation through the downregulation of Keap1, which resulted in the expression of antioxidant enzymes, including HO-1 and NQO1, thereby counteracted the oxidative damage in response to CA/CPR. The aforementioned antiapoptotic and antioxidant effects of Sal B were impaired in the setting of gene silencing of Nrf2 with siRNA in vitro model. These improvements were associated with better neurological function and increased survival rate (75% vs. 40%, p < 0.05) up to 72 hours postresuscitation. Our findings suggest that the administration of Sal B improved cardiac function and neurological outcomes in a murine model of CA via activating the Nrf2 antioxidant signaling pathway, which may represent a novel therapeutic strategy for the treatment of CA.

Resuscitating the Globally Ischemic Brain: TTM and Beyond

Cardiac arrest (CA) afflicts ~ 550,000 people each year in the USA. A small fraction of CA sufferers survive with a majority of these survivors emerging in a comatose state. Many CA survivors suffer devastating global brain injury with some remaining indefinitely in a comatose state. The pathogenesis of global brain injury secondary to CA is complex. Mechanisms of CA-induced brain injury include ischemia, hypoxia, cytotoxicity, inflammation, and ultimately, irreversible neuronal damage. Due to this complexity, it is critical for clinicians to have access as early as possible to quantitative metrics for diagnosing injury severity, accurately predicting outcome, and informing patient care. Current recommendations involve using multiple modalities including clinical exam, electrophysiology, brain imaging, and molecular biomarkers. This multi-faceted approach is designed to improve prognostication to avoid "self-fulfilling" prophecy and early withdrawal of life-sustaining treatments. Incorporation of emerging dynamic monitoring tools such as diffuse optical technologies may provide improved diagnosis and early prognostication to better inform treatment. Currently, targeted temperature management (TTM) is the leading treatment, with the number of patients needed to treat being ~ 6 in order to improve outcome for one patient. Future avenues of treatment, which may potentially be combined with TTM, include pharmacotherapy, perfusion/oxygenation targets, and pre/postconditioning. In this review, we provide a bench to bedside approach to delineate the pathophysiology, prognostication methods, current targeted therapies, and future directions of research surrounding hypoxic-ischemic brain injury (HIBI) secondary to CA.

Esmolol for cardioprotection during resuscitation with adrenaline in an ischaemic porcine cardiac arrest model

Background

The effectiveness of adrenaline during resuscitation continues to be debated despite being recommended in international guidelines. There is evidence that the β-adrenergic receptor (AR) effects of adrenaline are harmful due to increased myocardial oxygen consumption, post-defibrillation ventricular arrhythmias and increased severity of post-arrest myocardial dysfunction. Esmolol may counteract these unfavourable β-AR effects and thus preserve post-arrest myocardial function. We evaluated whether a single dose of esmolol administered prior to adrenaline preserves post-arrest cardiac output among successfully resuscitated animals in a novel, ischaemic cardiac arrest porcine model.

Methods

Myocardial infarction was induced in 20 anaesthetized pigs by inflating a percutaneous coronary intervention (PCI) balloon in the circumflex artery 15 min prior to induction of ventricular fibrillation. After 10 min of untreated VF, resuscitation with veno-arterial extracorporeal membrane oxygenation (VA-ECMO) was initiated and the animals were randomized to receive an injection of either 1 mg/kg esmolol or 9 mg/ml NaCl, prior to adrenaline. Investigators were blinded to allocation. Successful defibrillation was followed by a 1-h high-flow VA-ECMO before weaning and an additional 1-h stabilization period. The PCI-balloon was deflated 40 min after inflation. Cardiac function pre- and post-arrest (including cardiac output) was assessed by magnetic resonance imaging (MRI) and invasive pressure measurements. Myocardial injury was estimated with MRI, triphenyl tetrazolium chloride (TTC) staining and serum concentrations of cardiac troponin T.

Results

Only seven esmolol and five placebo-treated pigs were successfully resuscitated and available for post-arrest measurements (p = 0.7). MRI revealed severe but similar reductions in post-arrest cardiac function with cardiac output 3.5 (3.3, 3.7) and 3.3 (3.2, 3.9) l/min for esmolol and control (placebo) groups, respectively (p = 0.7). The control group had larger left ventricular end-systolic and end-diastolic ventricular volumes compared to the esmolol group (75 (65, 100) vs. 62 (53, 70) ml, p = 0.03 and 103 (86, 124) vs. 87 (72, 91) ml, p = 0.03 for control and esmolol groups, respectively). There were no other significant differences in MRI characteristics, myocardial infarct size or other haemodynamic measurements between the two groups.

Conclusions

We observed similar post-arrest cardiac output with and without a single dose of esmolol prior to adrenaline administration during low-flow VA-ECMO in an ischaemic cardiac arrest pig model.

Minocycline fails to improve neurologic and histologic outcome after ventricular fibrillation cardiac arrest in rats

BACKGROUND

Prolonged cardiac arrest (CA) produces extensive neuronal death and microglial proliferation and activation resulting in neuro-cognitive disabilities. Among other potential mechanisms, microglia have been implicated as triggers of neuronal death after hypoxic-ischemic insults. Minocycline is neuroprotective in some brain ischemia models, either by blunting the microglial response or by a direct effect on neurons.

AIM

To improve survival, attenuate neurologic deficits, neuroinflammation, and histological damage after ventricular fibrillation (VF) CA in rats.

METHODS

Adult male isoflurane-anesthetized rats were subjected to 6 min VF CA followed by 2 min resuscitation including chest compression, epinephrine, bicarbonate, and defibrillation. After return of spontaneous circulation (ROSC), rats were randomized to two groups: (1) Minocycline 90 mg/kg intraperitoneally (i.p.) at 15 min ROSC, followed by 22.5 mg/kg i.p. every 12 h for 72 h; and (2) Controls, receiving the same volume of vehicle (phosphate-buffered saline). The rats were kept normothermic during the postoperative course. Neurologic injury was assessed daily using Overall Performance Category (OPC; 1 = normal, 5 = dead) and Neurologic Deficit Score (NDS; 0% = normal, 100% = dead). Rats were sacrificed at 72 h. Neuronal degeneration (Fluoro-Jade C staining) and microglia proliferation (anti-Iba-1 staining) were quantified in four selectively vulnerable brain regions (hippocampus, striatum, cerebellum, cortex) by three independent reviewers masked to the group assignment.

RESULTS

In the minocycline group, 8 out of 14 rats survived to 72 h compared to 8 out of 19 rats in the control group (P = 0.46). The degree of neurologic deficit at 72 h [median, (interquartile range)] was not different between survivors in minocycline vs controls: OPC 1.5 (1-2.75) vs 2 (1.25-3), P = 0.442; NDS 12 (2-20) vs 17 (7-51), P = 0.328) or between all studied rats. The number of degenerating neurons (minocycline vs controls, mean ± SEM: Hippocampus 58 ± 8 vs 76 ± 8; striatum 121 ± 43 vs 153 ± 32; cerebellum 20 ± 7 vs 22 ± 8; cortex 0 ± 0 vs 0 ± 0) or proliferating microglia (hippocampus 157 ± 15 vs 193 cortex 0 ± 0 vs 0 ± 0; 16; striatum 150 ± 22 vs 161 ± 23; cerebellum 20 ± 7 vs 22 ± 8; cortex 26 ± 6 vs 31 ± 7) was not different between groups in any region (all P > 0.05). Numerically, there were approximately 20% less degenerating neurons and proliferating microglia in the hippocampus and striatum in the minocycline group, with a consistent pattern of histological damage across the individual regions of interest.

CONCLUSION

Minocycline did not improve survival and failed to confer substantial benefits on neurologic function, neuronal loss or microglial proliferation across multiple brain regions in our model of rat VF CA.

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.

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.

72-h therapeutic hypothermia improves neurological outcomes in paediatric asphyxial out-of-hospital cardiac arrest-An exploratory investigation

BACKGROUND

Recent studies suggest that a 48-h therapeutic hypothermia protocol does not improve outcomes in paediatric out-of-hospital cardiac arrest survivors. The aim of this study was to evaluate the effect of 72-h therapeutic hypothermia at 33 °C compared to normothermia at 35.5 °C-37.5 °C on outcomes and the incidence of adverse events in paediatric asphyxial out-of-hospital cardiac arrest survivors.

METHODS

We conducted this retrospective cohort study at a tertiary paediatric intensive care unit between January 2010 and June 2017. All children from 1 month to 18 years of age with asphyxial out-of-hospital cardiac arrest and a history of at least 3 min of chest compressions who survived for 12 h or more after the return of circulation were eligible.

RESULTS

Sixty-four patients met the eligibility criteria for the study. Forty-nine (76.6%) of the 64 children were male, and the mean age was 4.86+/-5.26 years. Twenty-four (37.5%) of the children had underlying disorders. The overall 1-month survival rate was 43.2%. Twenty-five (39.1%) of the children received therapeutic hypothermia at 33 °C for 72 h. The 1-month survival rate was significantly higher (p = 0.037) in the therapeutic hypothermia group (15/25, 60%) than in the normothermia group (12/39, 30.8%). The therapeutic hypothermia group had significantly better neurological outcomes (7/15, 46.7%) than the normothermia group (1/12, 8.3%) (p = 0.043).

CONCLUSION

Paediatric asphyxial out-of-hospital cardiac arrest was associated with high mortality and morbidity. Seventy-two-hour therapeutic hypothermia was associated with a better 1-month survival rate and 6-month neurological outcomes than normothermia in our paediatric patients with asphyxial out-of-hospital cardiac arrest.

Effect of neuromonitor-guided titrated care on brain tissue hypoxia after opioid overdose cardiac arrest

INTRODUCTION

Brain tissue hypoxia may contribute to preventable secondary brain injury after cardiac arrest. We developed a porcine model of opioid overdose cardiac arrest and post-arrest care including invasive, multimodal neurological monitoring of regional brain physiology. We hypothesized brain tissue hypoxia is common with usual post-arrest care and can be prevented by modifying mean arterial pressure (MAP) and arterial oxygen concentration (PaO2).

METHODS

We induced opioid overdose and cardiac arrest in sixteen swine, attempted resuscitation after 9 min of apnea, and randomized resuscitated animals to three alternating 6-h blocks of standard or titrated care. We invasively monitored physiological parameters including brain tissue oxygen (PbtO2). During standard care blocks, we maintained MAP > 65 mmHg and oxygen saturation 94-98%. During titrated care, we targeted PbtO2 > 20 mmHg.

RESULTS

Overall, 10 animals (63%) achieved ROSC after a median of 12.4 min (range 10.8-21.5 min). PbtO2 was higher during titrated care than standard care blocks (unadjusted β = 0.60, 95% confidence interval (CI) 0.42-0.78, P < 0.001). In an adjusted model controlling for MAP, vasopressors, sedation, and block sequence, PbtO2 remained higher during titrated care (adjusted β = 0.75, 95%CI 0.43-1.06, P < 0.001). At three predetermined thresholds, brain tissue hypoxia was significantly less common during titrated care blocks (44 vs 2% of the block duration spent below 20 mmHg, P < 0.001; 21 vs 0% below 15 mmHg, P < 0.001; and, 7 vs 0% below 10 mmHg, P = .01).

CONCLUSIONS

In this model of opioid overdose cardiac arrest, brain tissue hypoxia is common and treatable. Further work will elucidate best strategies and impact of titrated care on functional outcomes.