Improved haemodynamics and restoration of spontaneous circulation with constant aortic occlusion during experimental cardiopulmonary resuscitation

A protocol for the ERICA-ARREST feasibility study of Emergency Resuscitative Endovascular Balloon occlusion of the Aorta in Out-of-Hospital Cardiac Arrest

Background

Fewer than one in ten out-of-hospital cardiac arrest (OHCA) patients survive to hospital discharge in the UK. For prehospital teams to improve outcomes in patients who remain in refractory OHCA despite advanced life support (ALS); novel strategies that increase the likelihood of return of spontaneous circulation, whilst preserving cerebral circulation, should be investigated. Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) has been shown to improve coronary and cerebral perfusion during cardiopulmonary resuscitation. Early, prehospital initiation of REBOA may improve outcomes in patients who do not respond to standard ALS. However, there are significant clinical, technical, and logistical challenges with rapidly delivering prehospital REBOA in OHCA; and the feasibility of delivering this intervention in the UK urban-rural setting has not been evaluated.

Methods

The Emergency Resuscitative Endovascular Balloon Occlusion of the Aorta in Out-of-Hospital Cardiac Arrest (ERICA-ARREST) study is a prospective, single-arm, interventional feasibility study. The trial will enrol 20 adult patients with non-traumatic OHCA. The primary objective is to assess the feasibility of performing Zone I (supra-coeliac) aortic occlusion in patients who remain in OHCA despite standard ALS in the UK prehospital setting. The trial's secondary objectives are to describe the hemodynamic and physiological responses to aortic occlusion; to report key time intervals; and to document adverse events when performing REBOA in this context.

Discussion

Using compressed geography, and targeted dispatch, alongside a well-established femoral arterial access programme, the ERICA-ARREST study will assess the feasibility of deploying REBOA in OHCA in a mixed UK urban and rural setting.Trial registration.ClinicalTrials.gov (NCT06071910), registration date October 10, 2023, https://classic.clinicaltrials.gov/ct2/show/NCT06071910.

Endovascular aortic occlusion improves return of spontaneous circulation after longer periods of cardiopulmonary resuscitation: A translational study in pigs

Introduction

Resuscitative endovascular balloon occlusion of the aorta (REBOA) has emerged as an adjunct to CPR for nontraumatic cardiac arrest (NTCA). This translational study investigated the impact of varying low-flow duration (15- vs 30-mins) on REBOA's hemodynamic performance and ability to achieve return of spontaneous circulation (ROSC) in a porcine model.

Methods

Thirty-two pigs were anesthetized and placed into ventricular fibrillation. All animals received a 4-min no-flow period before CPR was initiated. Animals were randomized into four groups: 15- vs 30-minutes of CPR; REBOA vs. no-REBOA. After completion of 15- or 30-minute low-flow, ACLS was initiated and REBOA was inflated in experimental animals.

Results

In the 15-mins groups, there were no differences in the rates of ROSC between REBOA (4/8, 50%) and control (4/8, 50%; p = 0.99). However, in the 30-min groups, the REBOA animals had a significantly higher rate of ROSC (6/8, 75%) compared to control (1/8, 12.5%; p = 0.04). In the 7-mins after REBOA deployment in the 30-min animals there was a statistically significant difference in coronary perfusion pressure (REBOA 42.1 mmHg, control 3.6 mmHg, p = 0.038). Importantly, 5/6 animals that obtained ROSC in the 30-min group with REBOA re-arrested at least once, with 3/6 maintaining ROSC until study completion.

Conclusion

In our porcine model of NTCA, REBOA preferentially improved hemodynamics and ROSC after a 30-mins period of low-flow CPR. REBOA may be a viable strategy to improve ROSC after prolonged downtime, however, more hemodynamic support will be required to maintain ROSC.

Haemodynamic impact of aortic balloon occlusion combined with percutaneous left ventricular assist device during cardiopulmonary resuscitation in a swine model of cardiac arrest

AIM

To investigate the effect of tandem use of transient balloon occlusion of the descending aorta (AO) and percutaneous left ventricular assist device (pl-VAD) during cardiopulmonary resuscitation in a large animal model of prolonged cardiac arrest.

METHODS

Ventricular fibrillation was induced and left untreated for 8 minutes followed by 16 minutes of mechanical CPR (mCPR) in 24 swine, under general anesthesia. Animals were randomized to 3 treatment groups (n = 8 per group): A) pL-VAD (Impella CP®) B) pL-VAD+AO, and C) AO. Impella CP® and the aortic balloon catheter were inserted via the femoral arteries. mCPR was continued during treatment. Defibrillation was attempted 3 times starting at minute 28 and then every 4 minutes. Haemodynamic, cardiac function and blood gas measurements were recorded for up to 4 hours.

RESULTS

Coronary perfusion pressure (CoPP) in the pL-VAD+AO Group increased by a mean (SD) of 29.2(13.94) mmHg compared to an increase of 7.1(12.08) and 7.1(5.95) mmHg for groups pL-VAD and AO respectively (p = 0.02). Similarly, cerebral perfusion pressure (CePP) in pL-VAD+AO increased by a mean (SD) of 23.6 (6.11), mmHg compared with 0.97 (9.07) and 6.9 (7.98) mmHg for the other two groups (p < 0.001). The rate of return of spontaneous heartbeat (ROSHB) was 87.5%, 75%, and 100% for pL-VAD+AO, pL-VAD, and AO.

CONCLUSION

Combined AO and pL-VAD improved CPR hemodynamics compared to either intervention alone in this swine model of prolonged cardiac arrest.

Resuscitation Strategies for Maximizing Survival

There is no single resuscitation strategy that will uniformly improve cardiac arrest outcomes. Traditional vital signs cannot be relied on in cardiac arrest, and the use of continuous capnography, regional cerebral tissue oxygenation, and continuous arterial monitoring are options for use early defibrillation are critical elements of resuscitation. Cardio-cerebral perfusion may be improved with the use of active compression-decompression CPR, an impedance threshold device, and head-up CPR. In refractory shockable arrest, if ECPR is not an option, consider changing defibrillator pad placement and/or double defibrillation, additional medication options, and possibly stellate ganglion block.

Intra-aortic and Intra-caval Balloon Pump Devices in Experimental Non-traumatic Cardiac Arrest and Cardiopulmonary Resuscitation

Intra-aortic balloon pump (IABP) use during CPR has been scarcely studied. Intra-caval balloon pump (ICBP) may decrease backward venous flow during CPR. Mechanical chest compressions (MCC) were initiated after 10 min of cardiac arrest in anesthetized pigs. After 5 min of MCC, IABP (n = 6) or ICBP (n = 6) was initiated. The MCC device and the IABP/ICBP had slightly different frequencies, inducing a progressive peak pressure phase shift. IABP inflation 0.15 s before MCC significantly increased mean arterial pressure (MAP) and carotid blood flow (CBF) compared to inflation 0.10 s after MCC and to MCC only. Coronary perfusion pressure significantly increased with IABP inflation 0.25 s before MCC compared to inflation at MCC. ICBP inflation before MCC significantly increased MAP and CBF compared to inflation after MCC but not compared to MCC only. This shows the potential of IABP in CPR when optimally synchronized with MCC. The effect of timing of intra-aortic balloon pump (IABP) inflation during mechanical chest compressions (MCC) on hemodynamics. Data from12 anesthetized pigs.

Extremity tourniquets raise blood pressure and maintain heart rate

BACKGROUND

Tourniquets have been modified and used for centuries to occlude blood flow to control hemorrhage. More recently, the occlusion of peripheral vessels has been linked to resultant increases in blood pressure, which may provide additional therapeutic potential, particularly during states of low cardiac output.

OBJECTIVE

The objective of this study was to investigate a causal relationship between tourniquet application and blood pressure in healthy adults.

METHODS

Healthy adult volunteers were recruited to participate in this IRB-approved study. Each participant met inclusion criteria and demonstrated baseline normotension. Brachial cuff blood pressure and heart rate were recorded pre- and post-tourniquet application to the bilateral legs.

RESULTS

Twenty-seven adults aged 22 to 35 years participated and were included in analysis. The average systolic blood pressure was 122 ± 7 mmHg, diastolic blood pressure was 72 ± 9 mmHg, and heart rate was 70 ± 13 bpm. Following bilateral tourniquet application over the femoral vasculature, we observed a statistically significant increase in systolic (7 mmHg, p < 0.001) and diastolic (4 mmHg, p = 0.05) blood pressures with no significant change in heart rate (2 bpm, p > 0.05).

CONCLUSIONS

The elevations in systolic and diastolic blood pressures establish a dependent relationship between tourniquet application to the lower extremities and blood pressure elevation. These results may support new indications for tourniquet-use or extremity vessel occlusion in settings of hemodynamic instability.

A single-center, nonblinded, clinical trial comparing blood pressures before and after tourniquet application in healthy humans: A study protocol

INTRODUCTION

Cardiac arrest is the leading cause of natural death in the United States, and most surviving patients suffer from neurological dysfunction. Although this is recognized as a problem, there have been very few changes to the cardiopulmonary resuscitation (CPR) procedure. Tourniquets have been recognized for their ability to increase truncal blood pressure and have been shown to improve CPR outcomes in animal models. However, the relationship between tourniquet application and blood pressure elevation has not been adequately explored in healthy human adults.

OBJECTIVES

The objective of this study is to demonstrate that bilateral, non-invasive, peripheral vascular occlusion in the thighs results in an increased proximal systolic blood pressure ≥ 10 mmHg.

METHODS

This is a single-center, non-blinded clinical trial. Volunteers will be screened for eligibility at least 24 hours before the day of the trial. On the day of the trial, volunteers will undergo an informed consent process. If they choose to participate in the trial after informed consent, their baseline blood pressure will be measured. Volunteers will then have a Combat Application Tourniquet (CAT) applied to each thigh, and the windlasses will be tightened by IRB-approved personnel. Once no pulse can be felt in the lower extremity, blood pressure will be measured in the arm. This will be replicated three times, and the tourniquets will be loosened between trials to allow the volunteers to rest. Any complications that arise during the trial will be handled by the physician that is present.

ANALYSIS

Changes in systolic blood pressure and diastolic blood pressure will be analyzed using a Shapiro-Wilk test. Then, a one-way repeated measures analysis of variance (ANOVA) will be performed with a Holm-Sidak post-hoc test to determine the mean differences. The significance level will be set to 5% for statistical significance.

REGISTRY AND REGISTRATION NUMBER

Clinicaltrials.gov, NCT05324306.

The role of REBOA in patients in traumatic cardiac arrest subsequent to hemorrhagic shock: a scoping review

Purpose

Resuscitative endovascular balloon occlusion of the aorta (REBOA) is a useful adjunct in treatment of patients in severe hemorrhagic shock. Hypothetically, REBOA could benefit patients in traumatic cardiac arrest (TCA) as balloon occlusion of the aorta increases afterload and may improve myocardial performance leading to return of spontaneous circulation (ROSC). This scoping review was conducted to examine the effect of REBOA on patients in TCA.

Methods

This scoping review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis Extension for Scoping Reviews (PRISMA-ScR) Statement. PubMed, EMBASE.com and the Web of Science Core Collection were searched. Articles were included if they reported any data on patients that underwent REBOA and were in TCA. Of the included articles, data regarding SBP, ROSC and survival were extracted and summarized.

Results

Of 854 identified studies, 26 articles met criteria for inclusion. These identified a total of 785 patients in TCA that received REBOA (presumably less because of potential overlap in patients). This review shows REBOA elevates mean SBP in patients in TCA. The achievement of ROSC after REBOA deployment ranged from 18.2% to 67.7%. Survival to discharge ranged from 3.5% to 12.1%.

Conclusion

Overall, weak evidence is available on the use of REBOA in patients in TCA. This review, limited by selection bias, indicates that REBOA elevates SBP and may benefit ROSC and potentially survival to discharge in patients in TCA. Extensive further research is necessary to further clarify the role of REBOA during TCA.

Automated aortic endovascular balloon volume titration prevents re-arrest immediately after return of spontaneous circulation in a swine model of nontraumatic cardiac arrest

Objectives

Endovascular aortic occlusion as an adjunct to cardiopulmonary resuscitation (CPR) for non-traumatic cardiac arrest is gaining interest. In a recent clinical trial, return of spontaneous circulation (ROSC) was achieved despite prolonged no-flow times. However, 66% of patients re-arrested upon balloon deflation. We aimed to determine if automated titration of endovascular balloon volume following ROSC can augment diastolic blood pressure (DBP) to prevent re-arrest.

Methods

Twenty swine were anesthetized and placed into ventricular fibrillation (VF). Following 7 minutes of no-flow VF and 5 minutes of mechanical CPR, animals were subjected to complete aortic occlusion to adjunct CPR. Upon ROSC, the balloon was either deflated steadily over 5 minutes (control) or underwent automated, dynamic adjustments to maintain a DBP of 60 mmHg (Endovascular Variable Aortic Control, EVAC).

Results

ROSC was obtained in ten animals (5 EVAC, 5 REBOA). Sixty percent (3/5) of control animals rearrested while none of the EVAC animals rearrested (p = 0.038). Animals in the EVAC group spent a significantly higher proportion of the post-ROSC period with a DBP > 60 mmHg [median (IQR)] [control 79.7 (72.5–86.0)%; EVAC 97.7 (90.8–99.7)%, p = 0.047]. The EVAC group had a statistically significant reduction in arterial lactate concentration [7.98 (7.4–8.16) mmol/L] compared to control [9.93 (8.86–10.45) mmol/L, p = 0.047]. There were no statistical differences between the two groups in the amount of adrenaline (epinephrine) required.

Conclusion

In our swine model of cardiac arrest, automated aortic endovascular balloon titration improved DBP and prevented re-arrest in the first 20 minutes after ROSC.

Targeted Regional Optimization: Increasing the Therapeutic Window for Endovascular Aortic Occlusion In Traumatic Hemorrhage

ABSTRACT

Resuscitative endovascular balloon occlusion of the aorta (REBOA) allows for effective temporization of exsanguination from non-compressible hemorrhage (NCTH) below the diaphragm. However, the therapeutic window for aortic occlusion is time-limited given the ischemia-reperfusion injury generated. Significant effort has been put into translational research to develop new strategies to alleviate the ischemia-reperfusion injury and extend the application of endoaortic occlusion. Targeted regional optimization (TRO) is a partial REBOA strategy to augment proximal aortic and cerebral blood flow while targeting minimal threshold of distal perfusion beyond the zone of partial aortic occlusion. The objective of TRO is to reduce the degree of ischemia caused by complete aortic occlusion while providing control of distal hemorrhage. This review provides a synopsis of the concept of TRO, pre-clinical, translational experiences with TRO and early clinical outcomes. Early results from TRO strategies are promising; however, further studies are needed prior to large-scale implementation into clinical practice.

REBOARREST, resuscitative endovascular balloon occlusion of the aorta in non-traumatic out-of-hospital cardiac arrest: a study protocol for a randomised, parallel group, clinical multicentre trial

Background

Survival after out-of-hospital cardiac arrest (OHCA) is poor and dependent on high-quality cardiopulmonary resuscitation. Resuscitative endovascular balloon occlusion of the aorta (REBOA) may be advantageous in non-traumatic OHCA due to the potential benefit of redistributing the cardiac output to organs proximal to the aortic occlusion. This theory is supported by data from both preclinical studies and human case reports.

Methods

This multicentre trial will enrol 200 adult patients, who will be randomised in a 1:1 ratio to either a control group that receives advanced cardiovascular life support (ACLS) or an intervention group that receives ACLS and REBOA. The primary endpoint will be the proportion of patients who achieve return of spontaneous circulation with a duration of at least 20 min. The secondary objectives of this trial are to measure the proportion of patients surviving to 30 days with good neurological status, to describe the haemodynamic physiology of aortic occlusion during ACLS, and to document adverse events.

Discussion

Results from this study will assess the efficacy and safety of REBOA as an adjunctive treatment for non-traumatic OHCA. This novel use of REBOA may contribute to improve treatment for this patient cohort.

Trial registration

The trial is approved by the Regional Committee for Medical and Health Research Ethics in Norway (reference 152504) and is registered at ClinicalTrials.gov (reference NCT04596514) and as Universal Trial Number WHO: U1111-1253-0322.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05477-1.

Optimizing hemodynamic function during cardiopulmonary resuscitation

PURPOSE OF REVIEW

The purpose of this narrative review is to provide an update on hemodynamics during cardiopulmonary resuscitation (CPR) and to describe emerging therapies to optimize perfusion.

RECENT FINDINGS

Cadaver studies have shown large inter-individual variations in blood distribution and anatomical placement of the heart during chest compressions. Using advanced CT techniques the studies have demonstrated atrial and slight right ventricular compression, but no direct compression of the left ventricle. A hemodynamic-directed CPR strategy may overcome this by allowing individualized hand-placement, drug dosing, and compression rate and depth. Through animal studies and one clinical before-and-after study head-up CPR has shown promising results as a potential strategy to improve cerebral perfusion. Two studies have demonstrated that placement of an endovascular balloon occlusion in the aorta (REBOA) can be performed during ongoing CPR.

SUMMARY

Modern imaging techniques may help increase our understanding on the mechanism of forward flow during CPR. This could provide new information on how to optimize perfusion. Head-up CPR and the use of REBOA during CPR are novel methods that might improve cerebral perfusion during CPR; both techniques do, however, still await clinical testing.

Resuscitative endovascular balloon occlusion of the aorta vs epinephrine in the treatment of non-traumatic cardiac arrest in swine

Background

The administration of epinephrine in the management of non-traumatic cardiac arrest remains recommended despite controversial effects on neurologic outcome. The use of resuscitative endovascular balloon occlusion of the aorta (REBOA) could be an interesting alternative. The aim of this study was to compare the effects of these 2 strategies on return of spontaneous circulation (ROSC) and cerebral hemodynamics during cardiopulmonary resuscitation (CPR) in a swine model of non-traumatic cardiac arrest.

Results

Anesthetized pigs were instrumented and submitted to ventricular fibrillation. After 4 min of no-flow and 18 min of basic life support (BLS) using a mechanical CPR device, animals were randomly submitted to either REBOA or epinephrine administration before defibrillation attempts. Six animals were included in each experimental group (Epinephrine or REBOA). Hemodynamic parameters were similar in both groups during BLS, i.e., before randomization. After epinephrine administration or REBOA, mean arterial pressure, coronary and cerebral perfusion pressures similarly increased in both groups. However, carotid blood flow (CBF) and cerebral regional oxygenation saturation were significantly higher with REBOA as compared to epinephrine administration (+ 125% and + 40%, respectively). ROSC was obtained in 5 animals in both groups. After resuscitation, CBF remained lower in the epinephrine group as compared to REBOA, but it did not achieve statistical significance.

Conclusions

During CPR, REBOA is as efficient as epinephrine to facilitate ROSC. Unlike epinephrine, REBOA transitorily increases cerebral blood flow and could avoid its cerebral detrimental effects during CPR. These experimental findings suggest that the use of REBOA could be beneficial in the treatment of non-traumatic cardiac arrest.

State-of-the-Art Review-Endovascular Resuscitation

ABSTRACT

The emerging concept of endovascular resuscitation applies catheter-based techniques in the management of patients in shock to manipulate physiology, optimize hemodynamics, and bridge to definitive care. These interventions hope to address an unmet need in the care of severely injured patients, or those with refractory non-traumatic cardiac arrest, who were previously deemed non-survivable. These evolving techniques include Resuscitative Endovascular Balloon Occlusion of Aorta, Selective Aortic Arch Perfusion, and Extracorporeal Membrane Oxygenation and there is a growing literature base behind them. This review presents the up-to-date techniques and interventions, along with their application, evidence base, and controversy within the new era of endovascular resuscitation.

Randomized blinded trial of automated REBOA during CPR in a porcine model of cardiac arrest

BACKGROUND

Resuscitative endovascular balloon occlusion of the aorta (REBOA) reportedly elevates arterial blood pressure (ABP) during non-traumatic cardiac arrest.

OBJECTIVES

This randomized, blinded trial of cardiac arrest in pigs evaluated the effect of automated REBOA two minutes after balloon inflation on ABP (primary endpoint) as well as arterial blood gas values and markers of cerebral haemodynamics and metabolism.

METHODS

Twenty anesthetized pigs were randomized to REBOA inflation or sham-inflation (n = 10 in each group) followed by insertion of invasive monitoring and a novel, automated REBOA catheter (NEURESCUE® Catheter & NEURESCUE® Assistant). Cardiac arrest was induced by ventricular pacing. Cardiopulmonary resuscitation was initiated three min after cardiac arrest, and the automated REBOA was inflated or sham-inflated (blinded to the investigators) five min after cardiac arrest.

RESULTS

In the inflation compared to the sham group, mean ABP above the REBOA balloon after inflation was higher (inflation: 54 (95%CI: 43-65) mmHg; sham: 44 (33-55) mmHg; P = 0.06), and diastolic ABP was higher (inflation: 38 (29-47) mmHg; sham: 26 (20-33) mmHg; P = 0.02), and the arterial to jugular oxygen content difference was lower (P = 0.04). After return of spontaneous circulation, mean ABP (inflation: 111 (95%CI: 94-128) mmHg; sham: 94 (95%CI: 65-123) mmHg; P = 0.04), diastolic ABP (inflation: 95 (95%CI: 78-113) mmHg; sham: 78 (95%CI: 50-105) mmHg; P = 0.02), CPP (P = 0.01), and brain tissue oxygen tension (inflation: 315 (95%CI: 139-491)% of baseline; sham: 204 (95%CI: 75-333)%; P = 0.04) were higher in the inflation compared to the sham group.

CONCLUSION

Inflation of REBOA in a porcine model of non-traumatic cardiac arrest improves central diastolic arterial pressure as a surrogate marker of coronary artery pressure, and cerebral perfusion.

INSTITUTIONAL PROTOCOL NUMBER

2017-15-0201-01371.

The use of resuscitative endovascular balloon occlusion of the aorta (REBOA) for non-traumatic cardiac arrest: A review

Resuscitative endovascular balloon occlusion of the aorta (REBOA) has been proposed as a novel approach to managing non-traumatic cardiac arrest (NTCA). During cardiac arrest, cardiac output ceases and perfusion of vital organs is compromised. Traditional advanced cardiac life support (ACLS) measures and cardiopulmonary resuscitation are often unable to achieve return of spontaneous circulation (ROSC). During insertion of REBOA a balloon-tipped catheter is placed into the femoral artery and advanced in a retrograde manner into the aorta while the patient is undergoing cardiopulmonary resuscitation (CPR). The balloon is then inflated to fully occlude the aorta. The literature surrounding the use of aortic occlusion in non-traumatic cardiac arrest is limited to animal studies, case reports and one recent non-controlled feasibility trial. In both human and animal studies, preliminary data show that REBOA may improve coronary and cerebral perfusion pressures and key physiologic parameters during cardiac arrest resuscitation, and animal data have demonstrated improved rates of ROSC. Multiple questions remain before REBOA can be considered as an adjunct to ACLS. If demonstrated to be effective clinically, REBOA represents a potentially cost-effective and generalizable intervention that may improve quality of life for patients with non-traumatic cardiac arrest.

The Effect of Chest Compression Location and Aortic Perfusion in a Traumatic Arrest Model

BACKGROUND

Recent evidence demonstrates that closed chest compressions directly over the left ventricle (LV) in a traumatic cardiac arrest (TCA) model improve hemodynamics and return of spontaneous circulation (ROSC) when compared to traditional compressions. Selective aortic arch perfusion (SAAP) also improves hemodynamics and controls hemorrhage in TCA. We hypothesized that chest compressions located over the LV would result in improved hemodynamics and ROSC in a swine model of TCA using SAAP.

MATERIALS AND METHODS

Transthoracic echo was used to mark the location of the aortic root (Traditional location) and the center of the LV on animals (n = 24), which were randomized to receive chest compressions in one of the two locations. After hemorrhage, ventricular fibrillation (VF) was induced to simulate TCA. After a period of 10 min of VF, basic life support (BLS) with mechanical CPR was initiated and performed for 10 min, followed by advanced life support (ALS) for an additional 10 min. SAAP balloons were inflated at min 6 of BLS. Hemodynamic variables were averaged over the final 2 min of the BLS and ALS periods. Survival was compared between this SAAP cohort and a control group without SAAP (No-SAAP) (n = 26).

RESULTS

There was no significant difference in ROSC between the two SAAP groups (P = 0.67). There was no ROSC difference between SAAP and No-SAAP (P = 0.74).

CONCLUSIONS

There was no difference in ROSC between LV and Traditional compressions when SAAP was used in this swine model of TCA. SAAP did not confer a survival benefit compared to historical controls.

Resuscitative Endovascular Balloon Occlusion of the Aorta in Experimental Cardiopulmonary Resuscitation: Aortic Occlusion Level Matters

Introduction:

Aortic occlusion during cardiopulmonary resuscitation (CPR) increases systemic arterial pressures. Correct thoracic placement during the resuscitative endovascular balloon occlusion of the aorta (REBOA) may be important for achieving effective CPR.

Hypothesis:

The positioning of the REBOA in the thoracic aorta during CPR will affect systemic arterial pressures.

Methods:

Cardiac arrest was induced in 27 anesthetized pigs. After 7 min of CPR with a mechanical compression device, REBOA in the thoracic descending aorta at heart level (zone Ib, REBOA-Ib, n = 9), at diaphragmatic level (zone Ic, REBOA-Ic, n = 9) or no occlusion (control, n = 9) was initiated. The primary outcome was systemic arterial pressures during CPR.

Results:

During CPR, REBOA-Ic increased systolic blood pressure from 86 mmHg (confidence interval [CI] 71–101) to 128 mmHg (CI 107–150, P < 0.001). Simultaneously, mean and diastolic blood pressures increased significantly in REBOA-Ic (P < 0.001 and P = 0.006, respectively), and were higher than in REBOA-Ib (P = 0.04 and P = 0.02, respectively) and control (P = 0.005 and P = 0.003, respectively). REBOA-Ib did not significantly affect systemic blood pressures. Arterial pH decreased more in control than in REBOA-Ib and REBOA-Ic after occlusion (P = 0.004 and P = 0.005, respectively). Arterial lactate concentrations were lower in REBOA-Ic compared with control and REBOA-Ib (P = 0.04 and P < 0.001, respectively).

Conclusions:

Thoracic aortic occlusion in zone Ic during CPR may be more effective in increasing systemic arterial pressures than occlusion in zone Ib. REBOA during CPR was found to be associated with a more favorable acid–base status of circulating blood. If REBOA is used as an adjunct in CPR, it may be of importance to carefully determine the aortic occlusion level.

The study was performed following approval of the Regional Animal Ethics Committee in Linköping, Sweden (application ID 418).

Zone 3 REBOA does not provide hemodynamic benefits during nontraumatic cardiac arrest

BACKGROUND

Resuscitative endovascular balloon occlusion of the aorta (REBOA) may be a novel intervention to improve cardiopulmonary resuscitation (CPR) quality during cardiac arrest. Zone 1 supraceliac aortic occlusion improves coronary and cerebral blood flow. It is unknown if Zone 3 occlusion distal to the renal arteries offers a similar physiologic benefit while maintaining blood flow to organs above the point of occlusion.

METHODS

Fifteen swine were anesthetized, instrumented, and placed into ventricular fibrillation. Mechanical CPR was immediately initiated. After 5 min of CPR, Zone 1 REBOA, Zone 3 REBOA, or no intervention (control) was initiated. Hemodynamic variables were continuously recorded for 30 min.

RESULTS

There were no significant differences between groups before REBOA deployment. Once REBOA was deployed, Zone 1 animals had statistically greater diastolic blood pressure compared to control (median [IQR]: 19.9 mmHg [9.5-20.5] vs 3.9 mmHg [2.4-4.8], p = .006). There were no differences in diastolic blood pressure between Zone 1 and Zone 3 (8.6 mmHg [5.1-13.1], p = .10) or between Zone 3 and control (p = .10). There were no significant differences in systolic blood pressure, cerebral blood flow, or time to return of spontaneous circulation (ROSC) between groups.

CONCLUSION

In our swine model of cardiac arrest, Zone 1 REBOA improved diastolic blood pressure when compared to control. Zone 3 does not offer a hemodynamic benefit when compared to no occlusion. Unlike prior studies, immediate use of REBOA after arrest did not result in an increase in ROSC rate, suggesting REBOA may be more beneficial in patients with prolonged no-flow time.

INSTITUTIONAL PROTOCOL NUMBER

FDG20180024A.

The Effect of Chest Compression Location and Occlusion of the Aorta in a Traumatic Arrest Model

BACKGROUND

Recent evidence demonstrates that closed chest compressions directly over the left ventricle (LV) in a traumatic cardiac arrest (TCA) model improve hemodynamics and return of spontaneous circulation (ROSC) when compared with traditional compressions. Resuscitative endovascular balloon occlusion of the aorta (REBOA) also improves hemodynamics and controls hemorrhage in TCA. We hypothesized that chest compressions located over the LV would result in improved hemodynamics and ROSC in a swine model of TCA using REBOA.

MATERIALS AND METHODS

Transthoracic echo was used to mark the location of the aortic root (traditional location) and the center of the LV on animals (n = 26), which were randomized to receive chest compressions in one of the two locations. After hemorrhage, ventricular fibrillation was induced to simulate TCA. After a period of 10 min of ventricular fibrillation, basic life support (BLS) with mechanical cardiopulmonary resuscitation was initiated and performed for 10 min followed by advanced life support for an additional 10 min. REBOA balloons were inflated at 6 min into BLS. Hemodynamic variables were averaged during the final 2 min of the BLS and advanced life support periods. Survival was compared between this REBOA cohort and a control group without REBOA (no-REBOA cohort) (n = 26).

RESULTS

There was no significant difference in ROSC between the two REBOA groups (P = 0.24). Survival was higher with REBOA group versus no-REBOA group (P = 0.02).

CONCLUSIONS

There was no difference in ROSC between LV and traditional compressions when REBOA was used in this swine model of TCA. REBOA conferred a survival benefit regardless of compression location.

A needs assessment of resuscitative endovascular balloon occlusion of the aorta (REBOA) in non-traumatic out-of-hospital cardiac arrest in Norway

Introduction

Out of hospital cardiac arrest (OHCA) carries an 86% mortality rate in Norway. Resuscitative endovascular balloon occlusion of the aorta (REBOA) is a potential adjunct in management of non-traumatic cardiac arrest and is feasible in pre-hospital setting without compromising standard cardiopulmonary resuscitation (CPR). However, number of patients potentially eligible for REBOA remain unknown. In preparation for a clinical trial to investigate any benefit of pre-hospital REBOA, we sought to assess the need for REBOA in Norway as an adjunct treatment in OHCA.

Methods

Retrospective observational cohort study of data from the Norwegian Cardiac Arrest Registry in the 3-year period 2016–2018. We identified number of patients potentially eligible for pre-hospital REBOA during CPR, defined by suspected non-traumatic origin, age 18–75 years, witnessed arrest, ambulance response time less than 15 min, treated by ambulance personnel and resuscitation effort over 30 min.

Results

In the 3-year period, ambulance personnel resuscitated 8339 cases. Of these, a group of 720 patients (8.6%) were eligible for REBOA. Only 18% in this group achieved return of spontaneous circulation and 7% survived for 30 days or more.

Conclusion

This national registry data analysis constitutes a needs assessment of REBOA in OHCA. We found that each year approximately 240 patients, or nearly 9% of ambulance treated OHCA, in Norway is potentially eligible for pre-hospital REBOA as an adjunct treatment to standard resuscitation. This needs assessment suggests that there is sufficient patient population in Norway to study REBOA as an adjunct treatment in OHCA.

Feasibility of Pre-Hospital Resuscitative Endovascular Balloon Occlusion of the Aorta in Non-Traumatic Out-of-Hospital Cardiac Arrest

Background

Few patients survive after out‐of‐hospital cardiac arrest and any measure that improve circulation during cardiopulmonary resuscitation is beneficial. Animal studies support that resuscitative endovascular balloon occlusion of the aorta (REBOA) during cardiopulmonary resuscitation might benefit patients suffering from out‐of‐hospital cardiac arrest, but human data are scarce.

Methods and Results

We performed an observational study at the helicopter emergency medical service in Trondheim (Norway) to assess the feasibility and safety of establishing REBOA in patients with out‐of‐hospital cardiac arrest. All patients received advanced cardiac life support during the procedure. End‐tidal CO₂ was measured before and after REBOA placement as a proxy measure of central circulation. A safety‐monitoring program assessed if the procedure interfered with the quality of advanced cardiac life support. REBOA was initiated in 10 patients. The mean age was 63 years (range 50–74 years) and 7 patients were men. The REBOA procedure was successful in all cases, with 80% success rate on first cannulation attempt. Mean procedural time was 11.7 minutes (SD 3.2, range 8–16). Mean end‐tidal CO₂ increased by 1.75 kPa after 60 seconds compared with baseline (P<0.001). Six patients achieved return of spontaneous circulation (60%), 3 patients were admitted to hospital, and 1 patient survived past 30 days. The safety‐monitoring program identified no negative influence on the advanced cardiac life support quality.

Conclusions

To our knowledge, this is the first study to demonstrate that REBOA is feasible during non‐traumatic out‐of‐hospital cardiac arrest. The REBOA procedure did not interfere with the quality of the advanced cardiac life support. The significant increase in end‐tidal CO₂ after occlusion suggests improved organ circulation during cardiopulmonary resuscitation.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT03534011.

Resuscitative Endovascular Balloon Occlusion of the Aorta Improves Cardiac Compression Fraction Versus Resuscitative Thoracotomy in Patients in Traumatic Arrest

STUDY OBJECTIVE

Resuscitative endovascular balloon occlusion of the aorta (REBOA) is emerging as an alternative to resuscitative thoracotomy for proximal aortic control in select patients with exsanguinating hemorrhage below the diaphragm. The purpose of this study is to compare interruptions in closed chest compression or open chest cardiac massage during REBOA versus resuscitative thoracotomy.

METHODS

From May 2014 to December 2016, patients in arrest who received aortic occlusion with REBOA or resuscitative thoracotomy were included. Total cardiac compression time was defined as the total time that closed chest compression was performed for REBOA patients and the total time that closed chest compression (before resuscitative thoracotomy) and open chest cardiac massage (after thoracotomy) were performed for resuscitative thoracotomy patients. Cardiac compression fraction was defined as the time compressions occurred during the entire resuscitation phase. All resuscitations were captured by multiview, time-stamped videography.

RESULTS

Fifty patients with aortic occlusion after arrest were enrolled: 22 REBOA and 28 resuscitative thoracotomy. Most were men (86%) (median age 30.2 years, interquartile range [IQR] 24.9 to 42.3; median Injury Severity Score 27, IQR 16 to 42; neither differed between groups). The median duration of total cardiac compression time was 945 seconds (IQR 697 to 1,357) for REBOA versus 496 seconds (IQR 375 to 933) for resuscitative thoracotomy. During initial resuscitation, compressions occurred 86.5% of the time (SD 9.7%) during resuscitation with REBOA versus 35.7% of the time (SD 16.4%) in patients receiving resuscitative thoracotomy. Cardiac compression fraction improved after open cross clamp in resuscitative thoracotomy patients to 73.2% of the time (SD 18.0%) but remained significantly less than the same period for REBOA (86.7%; SD 9.4%). Mean cardiac compression fraction for REBOA was significantly improved over that for resuscitative thoracotomy (86.2% [SD 9.1%] versus 55.3 [SD 17.1%]; mean difference 31.0%; 95% confidence interval for difference 22.7% to 39.23%; P<.001). Median pause in resuscitation related to procedural tasks was 0 seconds (IQR 0 to 13) for REBOA and 148 seconds (IQR 118 to 223) in resuscitative thoracotomy.

CONCLUSION

Total duration of interruptions of cardiac compressions is shorter for patients receiving REBOA versus resuscitative thoracotomy before and during resuscitation with aortic occlusion. Markers for perfusion during resuscitation must be examined to understand the effects of cardiac compressions and aortic occlusion on patients in arrest because of hemorrhagic shock.

Resuscitative Endovascular Balloon Occlusion of the Aorta: Review of the Literature and Applications to Veterinary Emergency and Critical Care

While hemorrhagic shock might be the result of various conditions, hemorrhage control and resuscitation are the corner stone of patient management. Hemorrhage control can prove challenging in both the acute care and surgical settings, especially in the abdomen, where no direct pressure can be applied onto the source of bleeding. Resuscitative endovascular balloon occlusion of the aorta (REBOA) has emerged as a promising replacement to resuscitative thoracotomy (RT) for the management of non-compressible torso hemorrhage in human trauma patients. By inflating a balloon at specific levels (or zones) of the aorta to interrupt blood flow, hemorrhage below the level of the balloon can be controlled. While REBOA allows for hemorrhage control and augmentation of blood pressure cranial to the balloon, it also exposes caudal tissue beds to ischemia and the whole body to reperfusion injury. We aim to introduce the advantages of REBOA while reviewing known limitations. This review outlines a step-by-step approach to REBOA implementation, and discusses common challenges observed both in human patients and during translational large animal studies. Currently accepted and debated indications for REBOA in humans are discussed. Finally, we review possible applications for veterinary patients and how REBOA has the potential to be translated into clinical veterinary practice.

Use of resuscitative balloon occlusion of the aorta in a swine model of prolonged cardiac arrest

AIM

We examined the use of a Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) catheter during cardiopulmonary resuscitation (CPR) after cardiac arrest (CA) to assess its effect on haemodynamics such as coronary perfusion pressure (CPP), common carotid artery blood flow (CCA-flow) and end-tidal CO₂ (PetCO₂) which are associated with increased return of spontaneous circulation (ROSC).

METHODS

Six male swine were instrumented to measure CPP, CCA-Flow, and PetCO₂. A 7Fr REBOA was advanced into zone-1 of the aorta through the femoral artery. Ventricular fibrillation was induced and untreated for 8 min. CPR (manual then mechanical) was initiated for 24 min. Continuous infusion of adrenaline (epinephrine) was started at minute-4 of CPR. The REBOA balloon was inflated at minute-16 for 3 min and then deflated/inflated every 3 min for 3 cycles. Animals were defibrillated up to 6 times after the final cycle. Animals achieving ROSC were monitored for 25 min.

RESULTS

Data showed significant differences between balloon deflation and inflation periods for CPP, CCA-Flow, and PetCO₂ (p < 0.0001) with an average difference (SD) of 13.7 (2.28) mmHg, 15.5 (14.12) mL min^-1 and -4 (2.76) mmHg respectively. Three animals achieved ROSC and had significantly higher mean CPP (54 vs. 18 mmHg), CCA-Flow (262 vs. 135 mL min^-1) and PetCO₂ (16 vs. 8 mmHg) (p < 0.0001) throughout inflation periods than No-ROSC animals. Aortic histology did not reveal any significant changes produced by balloon inflation.

CONCLUSION

REBOA significantly increased CPP and CCA-Flow in this model of prolonged CA. These increases may contribute to the ability to achieve ROSC.

Resuscitative endovascular balloon occlusion of the aorta (REBOA) in non-traumatic out-of-hospital cardiac arrest: evaluation of an educational programme

BACKGROUND

Out-of-hospital cardiac arrest (OHCA) is a critical incident with a high mortality rate. Augmentation of the circulation during cardiopulmonary resuscitation (CPR) might be beneficial. Use of resuscitative endovascular balloon occlusion of the aorta (REBOA) redistribute cardiac output to the organs proximal to the occlusion. Preclinical data support that patients in non-traumatic cardiac arrest might benefit from REBOA in the thoracic level during CPR. This study describes a training programme to implement the REBOA procedure to a prehospital working team, in preparation to a planned clinical study.

METHODS

We developed a team-based REBOA training programme involving the physicians and paramedics working on the National Air Ambulance helicopter base in Trondheim, Norway. The programme consists of a four-step approach to educate, train and implement the REBOA procedure in a simulated prehospital setting. An objective structured assessment of prehospital REBOA application scoring chart and a special designed simulation mannequin was made for this study.

RESULTS

Seven physicians and 3 paramedics participated. The time needed to perform the REBOA procedure was 8.5 (6.3-12.7) min. The corresponding time from arrival at scene to balloon inflation was 12.0 (8.8-15) min. The total objective assessment scores of the candidates' competency was 41.8 (39-43.5) points out of 48. The advanced cardiovascular life support (ACLS) remained at standard quality, regardless of the simultaneous REBOA procedure.

CONCLUSION

This four-step approach to educate, train and implement the REBOA procedure to a prehospital working team ensures adequate competence in a simulated OHCA setting. The use of a structured training programme and objective assessment of skills is recommended before utilising the procedure in a clinical setting. In a simulated setting, the procedure does not add significant time to the prehospital resuscitation time nor does the procedure interfere with the quality of the ACLS.

TRIAL REGISTRATION NUMBER

NCT03534011.

Extended resuscitative endovascular balloon occlusion of the aorta (REBOA)-induced type 2 myocardial ischemia: a time-dependent penalty

Background

Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) increases cardiac-afterload and is used for patients in hemorrhagic shock. The cardiac tolerance of prolonged afterload augmentation in this context is unknown. The aim of this study is to quantify cardiac injury, if any, following 2, 3 and 4 hours of REBOA.

Methods

Anesthetized swine (70-90 kg) underwent a 40% controlled hemorrhage, followed by supraceliac resuscitative endovascular balloon occlusion of the aorta (REBOA) for 2 (n=5), 3 (n=5), and 4 hours (n=5). High-fidelity arterial wave form data were collected, and signal processing techniques were used to extract key inflection points. The adjusted augmentation index (AIx@75; augmentation pressure/pulse pressure, normalized for heart rate) was derived for use as a measure of aortic compliance (higher ratio = less compliance). Endpoints consisted of electrocardiographic, biochemical, and histologic markers of myocardial injury/ischemia. Regression modeling was used to assess the trend against time.

Results

All animals tolerated instrumentation, hemorrhage, and REBOA. The mean (±SD) systolic blood pressure (mm Hg) increased from 65±11 to 212±39 (p<0.001) during REBOA. The AIx@75 was significantly higher during REBOA than baseline, hemorrhage, and resuscitation phases (p<0.05). A time-dependent rise in troponin (R²=0.95; p<0.001) and T-wave deflection (R²=0.64; p<0.001) was observed. The maximum mean troponin (ng/mL) occurred at 4 hours (14.6±15.4) and maximum T-wave deflection (mm) at 65 minutes (3.0±1.8). All animals demonstrated histologic evidence of acute injury with increasing degrees of cellular myocardial injury.

Discussion

Prolonged REBOA may result in type 2 myocardial ischemia, which is time-dependent. This has important implications for patients where prolonged REBOA may be considered beneficial, and strategies to mitigate this effect require further investigation.

Level of evidence

II.

Traumatic cardiac arrest and resuscitative endovascular balloon occlusion of the aorta (REBOA): a preliminary analysis utilizing high fidelity invasive blood pressure recording and videography

PURPOSE

Aortic occlusion (AO) increases proximal perfusion and may improve rates of return of spontaneous circulation (ROSC). The objective of this study was to investigate the hemodynamic effects of cardiopulmonary resuscitation (CPR) and AO by REBOA on patients in traumatic cardiac arrest.

METHODS

Patients admitted between February 2013 and May 2017 at a tertiary center who suffered traumatic arrest, had an arterial line placed during resuscitation, and received CPR and REBOA which were included. In-hospital CPR data were obtained from videography. Arterial waveforms were recorded at 240 Hz.

RESULTS

11 consecutive patients were included, 82% male; mean (± SD) age 37 ± 19 years. 55% suffered blunt trauma and the remaining penetrating injuries. 64% arrested out of hospital. During compressions with AO, the mean systolic blood pressure (SBP) was 70 ± 22 mmHg, mean arterial pressure (MAP) 43 ± 19 mmHg, and diastolic blood pressure (DBP) 26 ± 17 mmHg. Nine (82%) had ROSC, with eight having multiple periods of ROSC and arrest in the initial period. In-hospital mortality was 82%. Cardiac ultrasonography was used during arrest in 73%. In two patients with arterial line data before and after AO, SBP (mmHg) improved from 51 to 73 and 55 to 96 during arrest after AO.

CONCLUSIONS

High-quality chest compressions coupled with aortic occlusion may generate adequate perfusion pressures to increase the rate of ROSC. New technology capable of transducing central arterial pressure may help us to understand the effectiveness of CPR with and without aortic occlusion. REBOA may be a useful adjunct to high-quality chest compressions during arrest.

The role of resuscitative endovascular balloon occlusion of the aorta (REBOA) as an adjunct to ACLS in non-traumatic cardiac arrest

Non-traumatic cardiac arrest is a major public health problem that carries an extremely high mortality rate. If we hope to increase the survivability of this condition, it is imperative that alternative methods of treatment are given due consideration. Balloon occlusion of the aorta can be used as a method of circulatory support in the critically ill patient. Intra-aortic balloon pumps have been used to temporize patients in cardiogenic shock for decades. More recently, resuscitative endovascular balloon occlusion of the aorta (REBOA) has been utilized in the patient in hemorrhagic shock or cardiac arrest secondary to trauma. Aortic occlusion in non-traumatic cardiac arrest has the effect of reducing the vascular volume that the generated cardiac output is distributed across. This augments myocardial and cerebral perfusion, increasing the probability of a return to a good quality of life for the patient. This phenomenon has been the subject of numerous animal studies dating back to the early 1980s; however, the human evidence is limited to several small case series. Animal research has demonstrated improvements in cerebral and coronary perfusion pressure during ACLS that lead to statistically significant differences in mortality. Several case series in humans have replicated these findings, suggesting the efficacy of this procedure. The objectives of this review are to: 1) introduce the reader to REBOA 2) review the physiology of NTCA and examine the current limitations of traditional ACLS 3) summarize the literature regarding the efficacy and feasibility of aortic balloon occlusion to support traditional ACLS.

Western Trauma Association critical decisions in trauma: resuscitative thoracotomy

BACKGROUND

In the past three decades, there has been a significant clinical shift in the performance of resuscitative thoracotomy (RT), from a nearly obligatory procedure before declaring any trauma patient deceased to a more selective application of RT. We have sought to formulate an evidence-based guideline for the current indications for RT after injury in the patient.

METHODS

The Western Trauma Association Critical Decisions Committee queried the literature for studies defining the appropriate role of RT in the trauma patient. When good data were not available, the Committee relied on expert opinion.

RESULTS

There are no published PRCT and it is not likely that there will be; recommendations are based on published prospective observational and retrospective studies, as well as expert opinion of Western Trauma Association members. Patients undergoing cardiopulmonary resuscitation (CPR) on arrival to the hospital should be stratified based on injury and transport time. Indications for RT include the following: blunt trauma patients with less than 10 minutes of prehospital CPR, penetrating torso trauma patients with less than 15 minutes of CPR, patients with penetrating trauma to the neck or extremity with less than 5 minutes of prehospital CPR, and patients in profound refractory shock. After RT, the patient's intrinsic cardiac activity is evaluated; patients in asystole without cardiac tamponade are declared dead. Patients with a cardiac wound, tamponade, and associated asystole are aggressively treated. Patients with an intrinsic rhythm following RT should be treated according to underlying primary pathology. Following several minutes of such treatment as well as generalized resuscitation, salvageability is reassessed; we define this as the patient's ability to generate a systolic blood pressure of greater than 70 mm Hg with an aortic cross-clamp if necessary.

CONCLUSION

The success of RT approximates 35% for the patient arriving in shock with a penetrating cardiac wound and 15% for all patients with penetrating wounds. Conversely, patient outcome is relatively poor when RT is performed for blunt trauma, 2% survival for patients in shock and less than 1% survival for patients with no vital signs. Patients undergoing CPR on arrival to the hospital should be stratified based on injury and transport time to determine the utility of RT. This algorithm represents a rational approach that could be followed at trauma centers with the appropriate resources; it may not be applicable at all hospitals caring for the injured. There will be patient, personnel, institutional, and situational factors that may warrant deviation from the recommended guideline. The annotated algorithm is intended to serve as a quick bedside reference for clinicians.

Drug administration in animal studies of cardiac arrest does not reflect human clinical experience

INTRODUCTION

To date, there is no evidence showing a benefit from any advanced cardiac life support (ACLS) medication in out-of-hospital cardiac arrest (OOHCA), despite animal data to the contrary. One explanation may be a difference in the time to first drug administration. Our previous work has shown the mean time to first drug administration in clinical trials is 19.4min. We hypothesized that the average time to drug administration in large animal experiments occurs earlier than in OOHCA clinical trials.

METHODS

We conducted a literature review between 1990 and 2006 in MEDLINE using the following MeSH headings: swine, dogs, resuscitation, heart arrest, EMS, EMT, ambulance, ventricular fibrillation, drug therapy, epinephrine, vasopressin, amiodarone, lidocaine, magnesium, and sodium bicarbonate. We reviewed the abstracts of 331 studies and 197 full manuscripts. Exclusion criteria included: non-peer reviewed, all without primary animal data, and traumatic models. From these, we identified 119 papers that contained unique information on time to medication administration. The data are reported as mean, ranges, and 95% confidence intervals. Mean time to first drug administration in animal laboratory studies and clinical trials was compared with a t-test. Regression analysis was performed to determine if time to drug predicted ROSC.

RESULTS

Mean time to first drug administration in 2378 animals was 9.5min (range 3.0-28.0; 95% CI around mean 2.78, 16.22). This is less than the time reported in clinical trials (19.4min, p<0.001). Time to drug predicted ROSC (odds ratio 0.844; 95% CI 0.738, 0.966).

CONCLUSION

Shorter drug delivery time in animal models of cardiac arrest may be one reason for the failure of animal studies to translate successfully into the clinical arena.

Emergency department thoracotomy for the critically injured patient: Objectives, indications, and outcomes

In the past three decades there has been a significant clinical shift in the performance of emergency department thoracotomy (EDT), from a nearly obligatory procedure before declaring any trauma patient to select patients undergoing EDT. The value of EDT in resuscitation of the patient in profound shock but not yet dead is unquestionable. Its indiscriminate use, however, renders it a low-yield and high-cost procedure. Overall analysis of the available literature indicates that the success of EDT approximates 35% in the patient arriving in shock with a penetrating cardiac wound, and 15% for all penetrating wounds. Conversely, patient outcome is relatively poor when EDT is done for blunt trauma; 2% survival in patients in shock and less than 1% survival with no vital signs. Patients undergoing CPR upon arrival to the emergency department should be stratified based upon injury and transport time to determine the utility of EDT. The optimal application of EDT requires a thorough understanding of its physiologic objectives, technical maneuvers, and the cardiovascular and metabolic consequences.

Effect of intra-aortic occlusion balloon in external thoracic compressions during CPR in pigs

This study was performed to compare the effectiveness of external thoracic compressions with and without intra-aortic occlusion balloon with capnography and coronary and cerebral perfusion pressure (CPP) in the normothermic and traumatic-less cardiopulmonary arrest provoked by a ventricular fibrillation in pigs. This was an experimental study (cross-over study) in 14 pigs with similar characteristics (23 +/- 2 kg, 10-12 weeks of age). After an 8-minute nonintervention period, the cardiopulmonary resuscitation (CPR) consists of 4 periods of 5 minutes alternating CPR with and without intra-aortic occlusion balloon. Main outcomes measured are end-tidal CO(2) (ETCO(2)); intra-aortic, coronary, and cerebral perfusion pressures; blood gas analysis; and blood lactate concentration. At the end of each period, levels are obtained. Postmortem study was made. Inflation of the occlusion balloon provokes an expansion in the ETCO(2) of about 38%. The coronary perfusion pressure initially goes from 10.21 to 29.0 mm Hg after the occlusion of the aorta, which means an increase of 150%. The CPP goes from 12.54 to 39.71 mm Hg after the balloon was inflated, which means an increase of 200%. In all cases the differences are statistically significant (P <.0001). These increases are less important in the final periods. Intra-aortic balloon occlusion increased ETCO(2), coronary, and cerebral perfusion pressures. An early application of this technique was important.

[New aspects and perspectives on cardiac arrest]

OBJECTIVES

To analyse the current knowledge based on the experimental and the clinical research studies focused on the main fields of cardiopulmonary resuscitation.

DATA SOURCES

International guidelines and recent review articles. Data collected from the Medline database with the key word: cardiac arrest.

STUDY SELECTION

Research studies published during the last ten years were reviewed. Relevant clinical information was extracted and discussed when it induced changes in guidelines.

DATA SYNTHESIS

Promising improvements on basic and advanced life supports are proposed. Chest compressions prevail over ventilation. Alternatives to classical chest compressions are tested. Ventilatory volume must be reduced from 1000 to approximatively 500 mL for each breath with oxygen. Biphasic waveform defibrillators and automated external defibrillators will be considered as the best devices in the near future. Some non-catecholaminergic vasopressors could reduce the use of epinephrine for advanced cardiac life support. Lidocaine could be replaced by amiodarone as anti-arrhythmic drug of choice. New post-resuscitation therapeutic strategies are evaluated, especially coronary reperfusion when the cause of cardiac arrest is cardiac.

CONCLUSION

Many fields of cardiopulmonary resuscitation are investigated. Some relevant informations are included in the last international guidelines published in 2000, but most of them need complementary studies before other changes could be recommended for routine practice.

Improved cerebral blood supply and oxygenation by aortic balloon occlusion combined with intra-aortic vasopressin administration during experimental cardiopulmonary resuscitation

BACKGROUND

Intravenous administration of vasopressin during cardiopulmonary resuscitation (CPR) has been shown to improve myocardial and cerebral blood flow. Aortic balloon occlusion during CPR may also augment myocardial and cerebral blood flow and can be used as a central route for the administration of resuscitative drugs. We hypothesized that, as compared with intravenously administered vasopressin, the administration of this drug above the site of an aortic balloon occlusion would result in a greater increase in cerebral perfusion and oxygenation during CPR and after restoration of spontaneous circulation (ROSC).

METHODS

Twenty piglets were subjected to 5 min of ventricular fibrillation followed by 8 min of closed-chest CPR and were treated with 0.4 U kg(-1) boluses of vasopressin intravenously (the IV-vasopressin group with sham aortic balloon) or above the site for an aortic balloon occlusion (the balloon-vasopressin group). The aortic balloon catheter was inflated in the latter group 1 min after commencement of CPR and was deflated within 1 min after ROSC. Systemic blood pressures, cerebral cortical blood flow, cerebral tissue pH and PCO2 were monitored continuously and the cerebral oxygen extraction ratio was calculated.

RESULTS

During CPR, arterial blood pressure and cerebral perfusion pressure were greater in the balloon-vasopressin group, as compared with the IV-vasopressin group. These pressures did not differ between the groups after ROSC. Cerebral cortical blood flow was not significantly greater in the balloon-vasopressin group during CPR, whereas significantly higher cortical blood flow levels were recorded after ROSC. Cerebral tissue pH decreased in the IV-vasopressin group during the post-resuscitation hypoperfusion period. In contrast, decreasing pressures during the hypoperfusion period did not result in increasing tissue acidosis in the balloon-vasopressin group.

CONCLUSIONS

During CPR, intra-aortic vasopressin combined with aortic balloon occlusion resulted in significantly greater perfusion pressures but not in greater cerebral cortical blood flow. After ROSC, however, a greater increase in cortical blood flow was recorded in the balloon-vasopressin group, even though the aortic balloon was deflated and perfusion pressures did not differ between the groups. This suggests that vasopressin predominantly gives vasoconstrictive effects on cerebral cortical vessels during CPR, but results in cerebral cortical vasodilatation after ROSC.