Thrombolytic-Enhanced Extracorporeal Cardiopulmonary Resuscitation After Prolonged Cardiac Arrest

Extracorporeal cardiopulmonary resuscitation: a comparison of two experimental approaches and systematic review of experimental models

BACKGROUND

In patients requiring extracorporeal cardiopulmonary resuscitation (ECPR), there is a need for studies to assess the potential benefits of therapeutic interventions to improve survival and reduce hypoxic-ischemic brain injuries. However, conducting human studies may be challenging. This study aimed to describe two experimental models developed in our laboratory and to conduct a systematic review of existing animal models of ECPR reported in the literature.

RESULTS

In our experiments, pigs were subjected to 12 min (model 1) or 5 min (model 2) of untreated ventricular fibrillation, followed by 18 min (model 1) or 25 min (model 2) of conventional cardiopulmonary resuscitation. Results showed severe distributive shock, decreased brain oxygen pressure and increased intracranial pressure, with model 1 displaying more pronounced brain perfusion impairment. A systematic review of 52 studies, mostly conducted on pigs, revealed heterogeneity in cardiac arrest induction methods, cardiopulmonary resuscitation strategies, and evaluated outcomes.

CONCLUSIONS

This review emphasizes the significant impact of no-flow and low-flow durations on brain injury severity following ECPR. However, the diversity in experimental models hinders direct comparisons, urging the standardization of ECPR models to enhance consistency and comparability across studies.

Leukocyte filtration and leukocyte modulation therapy during extracorporeal cardiopulmonary resuscitation in a porcine model of prolonged cardiac arrest

Extracorporeal cardiopulmonary resuscitation (ECPR) is emerging as a feasible and effective rescue strategy for prolonged cardiac arrest (CA). However, prolonged total body ischemia and reperfusion can cause microvascular occlusion that prevents organ reperfusion and recovery of function. One hypothesized mechanism of microvascular "no-reflow" is leukocyte adhesion and formation of neutrophil extracellular traps. In this study we tested the hypothesis that a leukocyte filter (LF) or leukocyte modulation device (L-MOD) could reduce NETosis and improve recovery of heart and brain function in a swine model of prolonged cardiac arrest treated with ECPR. Thirty-six swine (45.5 ± 2.5 kg, evenly distributed sex) underwent 8 min of untreated ventricular fibrillation CA followed by 30 min of mechanical CPR with subsequent 8 h of ECPR. Two females were later excluded from analysis due to CPR complications. Swine were randomized to standard care (Control group), LF, or L-MOD at the onset of CPR. NET formation was quantified by serum dsDNA and citrullinated histone as well as immunofluorescence staining of the heart and brain for citrullinated histone in the microvasculature. Primary outcomes included recovery of cardiac function based on cardiac resuscitability score (CRS) and recovery of neurologic function based on the somatosensory evoked potential (SSEP) N20 cortical response. In this model of prolonged CA treated with ECPR we observed significant increases in serum biomarkers of NETosis and immunohistochemical evidence of microvascular NET formation in the heart and brain that were not reduced by LF or L-MOD therapy. Correspondingly, there were no significant differences in CRS and SSEP recovery between Control, LF, and L-MOD groups 8 h after ECPR onset (CRS = 3.1 ± 2.7, 3.7 ± 2.6, and 2.6 ± 2.6 respectively; p = 0.606; and SSEP = 27.9 ± 13.0%, 36.7 ± 10.5%, and 31.2 ± 9.8% respectively, p = 0.194). In this model of prolonged CA treated with ECPR, the use of LF or L-MOD therapy during ECPR did not reduce microvascular NETosis or improve recovery of myocardial or brain function. The causal relationship between microvascular NETosis, no-reflow, and recovery of organ function after prolonged cardiac arrest treated with ECPR requires further investigation.

Coagulofibrinolytic effects of recombinant soluble thrombomodulin in prolonged porcine cardiac arrest

Aim

To evaluate coagulofibrinolytic abnormalities and the effects of ART-123 (recombinant human thrombomodulin alpha) in a porcine model of cardiac arrest and prolonged cardiopulmonary resuscitation (CA/CPR).

Methods

Fifteen pigs (n = 5 per group) underwent 8 minutes of no-flow CA followed by 50 minutes of mechanical CPR, while 2 pigs underwent sham arrest. CA/CPR animals were randomized to receive saline or 1 mg/kg ART-123 pre-arrest (5 minutes prior to ventricular fibrillation) or post-arrest (2 minutes after initiation of CPR). Arterial and venous blood samples were drawn at multiple time points for blood gas analysis and measurement of plasma and whole blood markers of coagulation and fibrinolysis.

Results

In saline-treated CA/CPR, but not sham animals, robust and persistent activation of coagulation and fibrinolysis was observed throughout resuscitation. After 50 minutes of CPR, plasma tests and thromboelastography indicated a mix of hypercoagulability and consumptive coagulopathy. ART-123 had a robust anticoagulant effect, reducing both thrombin-antithrombin (TAT) complexes and d-dimer (p < 0.05 for each). The duration of anticoagulant effect varied depending on the timing of ART-123 administration. Similarly, ART-123 when given prior to cardiac arrest was found to have pro-fibrinolytic effects, increasing free tissue plasminogen activator (tPA, p = 0.02) and decreasing free plasminogen activator inhibitor-1 (PAI-1, p = 0.04).

Conclusion

A porcine model of prolonged CA/CPR reproduces many of the coagulofibrinolytic abnormalities observed in human cardiac arrest patients. ART-123 demonstrates a combination of anticoagulant and profibrinolytic effects, depending on the timing of its administration relative to cardiac arrest.

R. Whitman G, Cho SM. A recommended preclinical extracorporeal cardiopulmonary resuscitation model for neurological outcomes: A scoping review

Background

Despite the high prevalence of neurological complications and mortality associated with extracorporeal cardiopulmonary resuscitation (ECPR), neurologically-focused animal models are scarce. Our objective is to review current ECPR models investigating neurological outcomes and identify key elements for a recommended model.

Methods

We searched PubMed and four other engines for animal ECPR studies examining neurological outcomes. Inclusion criteria were: animals experiencing cardiac arrest, ECPR/ECMO interventions, comparisons of short versus long cardiac arrest times, and neurological outcomes.

Results

Among 20 identified ECPR animal studies (n = 442), 13 pigs, 4 dogs, and 3 rats were used. Only 10% (2/20) included both sexes. Significant heterogeneity was observed in experimental protocols. 90% (18/20) employed peripheral VA-ECMO cannulation and 55% (11/20) were survival models (median survival = 168 hours; ECMO duration = 60 minutes). Ventricular fibrillation (18/20, 90%) was the most common method for inducing cardiac arrest with a median duration of 15 minutes (IQR = 6-20). In two studies, cardiac arrests exceeding 15 minutes led to considerable mortality and neurological impairment. Among seven studies utilizing neuromonitoring tools, only four employed multimodal devices to evaluate cerebral blood flow using Transcranial Doppler ultrasound and near-infrared spectroscopy, brain tissue oxygenation, and intracranial pressure. None examined cerebral autoregulation or neurovascular coupling.

Conclusions

The substantial heterogeneity in ECPR preclinical model protocols leads to limited reproducibility and multiple challenges. The recommended model includes large animals with both sexes, standardized pre-operative protocols, a cardiac arrest time between 10-15 minutes, use of multimodal methods to evaluate neurological outcomes, and the ability to survive animals after conducting experiments.

Therapeutic Effect of Argatroban During Cardiopulmonary Resuscitation and Streptokinase During Extracorporeal Cardiopulmonary Resuscitation in a Porcine Model of Prolonged Cardiac Arrest

Prolonged cardiac arrest (CA) causes microvascular thrombosis which is a potential barrier to organ reperfusion during extracorporeal cardiopulmonary resuscitation (ECPR). The aim of this study was to test the hypothesis that early intra-arrest anticoagulation during cardiopulmonary resuscitation (CPR) and thrombolytic therapy during ECPR improve recovery of brain and heart function in a porcine model of prolonged out-of-hospital CA.

DESIGN

Randomized interventional trial.

SETTING

University laboratory.

SUBJECTS

Swine.

INTERVENTIONS

In a blinded study, 48 swine were subjected to 8 minutes of ventricular fibrillation CA followed by 30 minutes of goal-directed CPR and 8 hours of ECPR. Animals were randomized into four groups (n = 12) and given either placebo (P) or argatroban (ARG; 350 mg/kg) at minute 12 of CA and either placebo (P) or streptokinase (STK, 1.5 MU) at the onset of ECPR.

MEASUREMENTS AND MAIN RESULTS

Primary outcomes included recovery of cardiac function measured by cardiac resuscitability score (CRS: range 0-6) and recovery of brain function measured by the recovery of somatosensory-evoked potential (SSEP) cortical response amplitude. There were no significant differences in recovery of cardiac function as measured by CRS between groups (p = 0.16): P + P 2.3 (1.0); ARG + P = 3.4 (2.1); P + STK = 1.6 (2.0); ARG + STK = 2.9 (2.1). There were no significant differences in the maximum recovery of SSEP cortical response relative to baseline between groups (p = 0.73): P + P = 23% (13%); ARG + P = 20% (13%); P + STK = 25% (14%); ARG + STK = 26% (13%). Histologic analysis demonstrated reduced myocardial necrosis and neurodegeneration in the ARG + STK group relative to the P + P group.

CONCLUSIONS

In this swine model of prolonged CA treated with ECPR, early intra-arrest anticoagulation during goal-directed CPR and thrombolytic therapy during ECPR did not improve initial recovery of heart and brain function but did reduce histologic evidence of ischemic injury. The impact of this therapeutic strategy on the long-term recovery of cardiovascular and neurological function requires further investigation.

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.

Investigating the Airway Opening Index during Cardiopulmonary Resuscitation

INTRODUCTION

Chest compressions during CPR induce oscillations in capnography (E_TCO₂) waveforms. Studies suggest E_TCO₂ oscillation characteristics are associated with intrathoracic airflow dependent on airway patency. Oscillations can be quantified by the Airway Opening Index (AOI). We sought to evaluate multiple methods of computing AOI and their association with return of spontaneous circulation (ROSC).

METHODS

We conducted a retrospective study of 307 out-of-hospital cardiac arrest (OHCA) cases in Seattle, WA during 2019. E_TCO₂ and chest impedance waveforms were annotated for the presence of intubation and CPR. We developed four methods for computing AOI based on peak E_TCO₂ and the oscillations in E_TCO₂ during CCs (ΔE_TCO₂). We examined the feasibility of automating ΔE_TCO₂ and AOI calculation and evaluated differences in AOI across the methods using nonparametric testing (p=0.05).

RESULTS

Median [interquartile range] AOI across all cases using Methods 1-4 was 28.0% [17.9-45.5%], 20.6% [13.0-36.6%], 18.3% [11.4-30.4%], and 22.4% [12.8-38.5%], respectively (p<0.001). Cases with ROSC had a higher median AOI than those without ROSC across all methods, though not statistically significant. Cases with ROSC had a significantly higher median [interquartile range] ΔE_TCO₂ of 7.3 mmHg [4.5-13.6 mmHg] compared to those without ROSC (4.8 mmHg [2.6-9.1 mmHg], p<0.001).

CONCLUSION

We calculated AOI using four proposed methods resulting in significantly different AOI. Additionally, AOI and ΔE_TCO₂ were larger in cases achieving ROSC. Further investigation is required to characterize AOI's ability to predict OHCA outcomes, and whether this information can improve resuscitation care.

Brain vulnerability and viability after ischaemia

The susceptibility of the brain to ischaemic injury dramatically limits its viability following interruptions in blood flow. However, data from studies of dissociated cells, tissue specimens, isolated organs and whole bodies have brought into question the temporal limits within which the brain is capable of tolerating prolonged circulatory arrest. This Review assesses cell type-specific mechanisms of global cerebral ischaemia, and examines the circumstances in which the brain exhibits heightened resilience to injury. We suggest strategies for expanding such discoveries to fuel translational research into novel cytoprotective therapies, and describe emerging technologies and experimental concepts. By doing so, we propose a new multimodal framework to investigate brain resuscitation following extended periods of circulatory arrest.

Early Coronary Reperfusion Facilitates Return of Spontaneous Circulation and Improves Cardiovascular Outcomes After Ischemic Cardiac Arrest and Extracorporeal Resuscitation in Pigs

Background

Extracorporeal cardiopulmonary resuscitation (ECPR) is widely proposed for the treatment of refractory cardiac arrest. It should be associated with coronary angiography if coronary artery disease is suspected. However, the prioritization of care remains unclear in this situation. Our goal was to determine whether coronary reperfusion should be instituted as soon as possible in such situations in a pig model.

Methods and Results

Anesthetized pigs were instrumented and submitted to coronary artery occlusion and ventricular fibrillation. After 5 minutes of untreated cardiac arrest, conventional cardiopulmonary resuscitation (CPR) was started. Fifteen minutes later, ECPR was initiated for a total duration of 240 minutes. Animals randomly underwent either early or late coronary reperfusion at 20 or 120 minutes of ECPR, respectively. This timing was adapted to the kinetic of infarct extension in pigs. Return of spontaneous circulation was determined as organized electrocardiogram rhythm with systolic arterial pressure above 80 mm Hg. During conventional CPR, hemodynamic parameters were not different between groups. Carotid blood flow then increased by 70% after the onset of ECPR in both groups. No animal (0 of 7) elicited return of spontaneous circulation after late reperfusion versus 4 of 7 after early reperfusion (P=0.025). The hemodynamic parameters, such as carotid blood flow, were also improved in early versus late reperfusion groups (113±20 vs 43±17 mL/min after 240 minutes of ECPR, respectively; P=0.030), along with infarct size decrease (71±4% vs 84±2% of the risk zone, respectively; P=0.013).

Conclusions

Early reperfusion improved hemodynamic status and facilitated return of spontaneous circulation in a porcine model of ischemic cardiac arrest treated by ECPR.