Twenty minutes of normothermic cardiac arrest in a pig model: the role of short-term hypothermia for neurological outcome

Neuroprotection with hypothermic reperfusion and extracorporeal cardiopulmonary resuscitation - A randomized controlled animal trial of prolonged ventricular fibrillation cardiac arrest in rats

Extracorporeal cardiopulmonary resuscitation (ECPR) facilitates resuscitation with immediate and precise temperature control. This study aimed to determine the optimal reperfusion temperature to minimize neurological damage after ventricular fibrillation cardiac arrest (VFCA). Twenty-four rats were randomized (n = 8 per group) to normothermia (NT = 37°C), mild hypothermia (MH = 33°C) or moderate hypothermia (MOD = 27°C). The rats were subjected to 10 minutes of VFCA, before 15 minutes of ECPR at their respective target temperature. After ECPR weaning, rats in the MOD group were rapidly rewarmed to 33°C, and temperature maintained at 33°C (MH/MOD) or 37°C (NT) for 12 hours before slow rewarming to normothermia (MH/MOD). The primary outcome was 30-day survival with overall performance category (OPC) 1 or 2 (1 = normal, 2 = slight disability, 3 = severe disability, 4 = comatose, 5 = dead). Secondary outcomes included awakening rate (OPC ≤ 3) and neurological deficit score (NDS, from 0 = normal to 100 = brain dead). The survival rate did not differ between reperfusion temperatures (NT = 25%, MH = 63%, MOD = 38%, p = 0.301). MH had the lowest NDS (NT = 4[IQR 3-4], MH = 2[1-2], MOD = 5[3-5], p = 0.044) and highest awakening rate (NT = 25%, MH = 88%, MOD = 75%, p = 0.024). In conclusion, ECPR with 33°C reperfusion did not statistically significantly improve survival after VFCA when compared with 37°C or 27°C reperfusion but was neuroprotective as measured by awakening rate and neurological function.

Controlled automated reperfusion of the whole body after cardiac arrest: Device profile of the CARL system

BACKGROUND

Cardiac arrest is associated with high mortality rates and severe neurological impairments. One of the underlying mechanisms is global ischemia-reperfusion injury of the body, particularly the brain. Strategies to mitigate this may thus improve favorable neurological outcomes. The use of extracorporeal cardiopulmonary membrane oxygenation (ECMO) during CA has been shown to improve survival, but available systems are vastly unable to deliver goal-oriented resuscitation to control patient's individual physical and chemical needs during reperfusion. Recently, controlled automated reperfusion of the whoLe body (CARL), a pulsatile ECMO with arterial blood-gas analysis, has been introduced to deliver goal-directed reperfusion therapy during the post-arrest phase.

METHODS

This review focuses on the device profile and use of CARL. Specifically, we reviewed the published literature to summarize data regarding its technical features and potential benefits in ECPR.

RESULTS

Peri-arrest, mitigating severe IRI with ECMO, might be the next step toward augmenting survival rates and neurological recovery. To this end, CARL is a promising extracorporeal oxygenation device that improves the early reperfusion phase after resuscitation.

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.

Treatment of Refractory Cardiac Arrest by Controlled Reperfusion of the Whole Body: A Multicenter, Prospective Observational Study

Background: Survival following cardiac arrest (CA) remains poor after conventional cardiopulmonary resuscitation (CCPR) (6-26%), and the outcomes after extracorporeal cardiopulmonary resuscitation (ECPR) are often inconsistent. Poor survival is a consequence of CA, low-flow states during CCPR, multi-organ injury, insufficient monitoring, and delayed treatment of the causative condition. We developed a new strategy to address these issues. Methods: This all-comers, multicenter, prospective observational study (69 patients with in- and out-of-hospital CA (IHCA and OHCA) after prolonged refractory CCPR) focused on extracorporeal cardiopulmonary support, comprehensive monitoring, multi-organ repair, and the potential for out-of-hospital cannulation and treatment. Result: The overall survival rate at hospital discharge was 42.0%, and a favorable neurological outcome (CPC 1+2) at 90 days was achieved for 79.3% of survivors (CPC 1+2 survival 33%). IHCA survival was very favorable (51.7%), as was CPC 1+2 survival at 90 days (41%). Survival of OHCA patients was 35% and CPC 1+2 survival at 90 days was 28%. The subgroup of OHCA patients with pre-hospital cannulation showed a superior survival rate of 57.1%. Conclusions: This new strategy focusing on repairing damage to multiple organs appears to improve outcomes after CA, and these findings should provide a sound basis for further research in this area.

The Impact of Head Position on Neurological and Histopathological Outcome Following Controlled Automated Reperfusion of the Whole Body (CARL) in a Pig Model

Introduction: Based on extracorporeal circulation, targeted reperfusion strategies have been developed to improve survival and neurologic recovery in refractory cardiac arrest: Controlled Automated Reperfusion of the whoLe Body (CARL). Furthermore, animal and human cadaver studies have shown beneficial effects on cerebral pressure due to head elevation during conventional cardiopulmonary resuscitation. Our aim was to evaluate the impact of head elevation on survival, neurologic recovery and histopathologic outcome in addition to CARL in an animal model. Methods: After 20 min of ventricular fibrillation, 46 domestic pigs underwent CARL, including high, pulsatile extracorporeal blood flow, pH-stat acid-base management, priming with a colloid, mannitol and citrate, targeted oxygen, carbon dioxide and blood pressure management, rapid cooling and slow rewarming. N = 25 were head-up (HUP) during CARL, and N = 21 were supine (SUP). After weaning from ECC, the pigs were extubated and followed up in the animal care facility for up to seven days. Neuronal density was evaluated in neurohistopathology. Results: More animals in the HUP group survived and achieved a favorable neurological recovery, 21/25 (84%) versus 6/21 (29%) in the SUP group. Head positioning was an independent factor in neurologically favorable survival (p < 0.00012). Neurohistopathology showed no significant structural differences between HUP and SUP. Distinct, partly transient clinical neurologic deficits were blindness and ataxia. Conclusions: Head elevation during CARL after 20 min of cardiac arrest independently improved survival and neurologic outcome in pigs. Clinical follow-up revealed transient neurologic deficits potentially attributable to functions localized in the posterior perfusion area, whereas histopathologic findings did not show corresponding differences between the groups. A possible explanation of our findings may be venous congestion and edema as modifiable contributing factors of neurologic injury following prolonged 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.

The use of induced hypothermia in extracorporeal membrane oxygenation: A narrative review

Despite venovenous or venoarterial extracorporeal membrane oxygenation (ECMO) being increasingly used in patients with severe acute respiratory disease syndrome, severe cardiogenic shock, and refractory cardiac arrest, mortality rates still remain high mainly because of the severity of the underlying disease and the numerous complications associated with initiation of ECMO. Induced hypothermia might minimize several pathological pathways present in patients requiring ECMO; even though numerous studies conducted in the experimental setting have reported promising results, there are currently no recommendations suggesting the routine use of this therapy in patients requiring ECMO. In this review, we summarized the existing evidence on the use of induced hypothermia in patients requiring ECMO. Induced hypothermia was a feasible and relatively safe intervention in this setting; however, the effects on clinical outcomes remain uncertain. Whether controlled normothermia has an impact on these patients compared with no temperature control remains unknown. Further randomized controlled trials are required to better understand the role and impact of such therapy in patients requiring ECMO according to the underlying disease.

CARL – kontrollierte Reperfusion des ganzen Körpers

Hintergrund

Inzidenz und Letalität des akuten Herz-Kreislauf-Stillstands sind seit Jahrzehnten gleichbleibend hoch.

Fragestellung

Wie lassen sich die derzeit unbefriedigenden Ergebnisse nach einer Reanimation mit Blick auf das Überleben und die neurologischen, v. a. mit Blick auf die zerebralen Folgeschäden verbessern?

Material und Methoden

Entwicklung eines therapeutischen Verfahrens zur Eindämmung des Ischämie‑/Reperfusionsschadens im Tiermodell. Entwicklung eines für die Reanimation optimierten Gerätesystems, mit dem sich eine kontrollierte Ganzkörperreperfusion auch außerklinisch umsetzen lässt.

Ergebnisse

Etablierung der CARL-Therapie in der Klinik und in der Behandlung von OHCA-Patienten. Übernahme der Therapie und des CARL-Systems in eine klinische Beobachtungsstudie. Erste Fallberichte, in denen Patienten einen OHCA auch nach Ischämiezeiten bis zu 2 h ohne Schädigung des Gehirns überlebten.

Schlussfolgerungen

Die CARL-Therapie eignet sich potenziell zur Behandlung reanimationspflichtiger Patienten mit einem auch über längere Zeit therapierefraktären Herz-Kreislauf-Stillstand.

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.

Targeted temperature management and early neuro-prognostication after cardiac arrest

Targeted temperature management (TTM) is a recommended neuroprotective intervention for coma after out-of-hospital cardiac arrest (OHCA). However, controversies exist concerning the proper implementation and overall efficacy of post-CA TTM, particularly related to optimal timing and depth of TTM and cooling methods. A review of the literature finds that optimizing and individualizing TTM remains an open question requiring further clinical investigation. This paper will summarize the preclinical and clinical trial data to-date, current recommendations, and future directions of this therapy, including new cooling methods under investigation. For now, early induction, maintenance for at least 24 hours, and slow rewarming utilizing endovascular methods may be preferred. Moreover, timely and accurate neuro-prognostication is valuable for guiding ethical and cost-effective management of post-CA coma. Current evidence for early neuro-prognostication after TTM suggests that a combination of initial prediction models, biomarkers, neuroimaging, and electrophysiological methods is the optimal strategy in predicting neurological functional outcomes.

Controlled automated reperfusion of the whole body after cardiac arrest

Background

Sudden circulatory arrest (CA) requiring cardiopulmonary resuscitation (CPR) has for decades been associated with high mortality and frequent neurological sequelae in the rarer survivors. The high mortality and morbidity are potentially related to a severe and global ischemia/reperfusion injury (IRI) of the whole body, especially the brain. Consequently, strategies to counteract this severe IRI may improve survival and neurological recovery of affected patients.

Methods

Based on the target to limit IRI in single organs, suitable parameters and methods were composed to form a global treatment concept, the CARL method (controlled automated reperfusion of the whole body). The concept centers on extracorporeal circulation, enhanced with readily available online monitoring. It allows for targeted adaption of different parameters (i.e., blood pressure and flow, temperature, oxygen content, electrolytes) during the reperfusion process, in the sense of a controlled reperfusion. Parameters and elements of the CARL method were extensively tested in a chronic animal model. An appropriate medical device, the system configuration "CIRD 1.0" (Controlled Integrated Resuscitation Device) is approved to be applied to patients.

Results

A set of parameters that support a limitation of a global IRI have been identified in over 250 animal experiments. Their specific targets and surveillance using adequate monitoring features are described. Using the CIRD in a single center, 14 patients with witnessed, but extremely prolonged CPR (51-120 minutes) have been treated with CARL. The outcome of these patients was favorable, with 7 of 14 patients regaining full consciousness and 6 of 7 allocated to Cerebral Performance Class (CPC) "1".

Conclusions

CA followed by CPR is associated with a very high mortality and frequent neurological sequelae. Limiting the occurring severe and global IRI may be a key to an improved survival and neurological recovery. Therefore, the therapeutic approach of CARL, which stands for a personalized, comprehensive therapy based on a readily available set of monitoring data and diagnostic findings, has been developed. First experience in patients indicates beneficial effects that call for further studies in the field of CARL.

Type 2 diabetes mellitus worsens neurological injury following cardiac arrest: an animal experimental study

Background

Cardiac arrest carries a poor prognosis. The typical cardiac arrest patient is comorbid, and studies have shown that diabetes mellitus is an independent risk factor for increased mortality after cardiac arrest. Despite this, animal studies lack to investigate cardiac arrest in the setting of diabetes mellitus.

We hypothesize that type 2 diabetes mellitus in a rat model of cardiac arrest is associated with increased organ dysfunction when compared with non-diabetic rats.

Methods

Zucker diabetic fatty (ZDF) rats (n = 13), non-diabetic Zucker lean control (ZLC) rats (n = 15), and non-diabetic Sprague Dawley (SprD) rats (n = 8), underwent asphyxia-induced cardiac arrest. Animals were resuscitated and monitored for 180 min after return of spontaneous circulation (ROSC).

Blood levels of neuron-specific enolase were measured to assess neurological injury. Cardiac function was evaluated by echocardiography.

Results

No differences in cardiac output or neuron-specific enolase existed between the groups at baseline. Median levels of neuron-specific enolase 180 min after ROSC was 10.8 μg/L (Q₂₅;Q₇₅—7.6;11.3) in the ZDF group, which was significantly higher compared to the ZLC group at 2.0 μg/L (Q₂₅;Q₇₅—1.7;2.3, p < 0.05) and the SprD group at 2.8 μg/L (Q₂₅;Q₇₅—2.3;3.4, p < 0.05). At 180 min after ROSC, cardiac output was 129 mL/min/kg (SD 45) in the ZDF group, which was not different from 106 mL/min/kg (SD 31) in the ZLC group or 123 mL/min/kg (SD 26, p = 0.72) in the SprD group.

Conclusions

In a cardiac arrest model, neuronal injury is increased in type 2 diabetes mellitus animals compared with non-diabetic controls. Although this study lacks to uncover the specific mechanisms causing increased neuronal injury, the establishment of a cardiac arrest model of type 2 diabetes mellitus lays the important foundation for further experimental investigations within this field.