The Underlying Cardiovascular Mechanisms of Resuscitation and Injury of REBOA and Partial REBOA

Prehospital Partial Resuscitative Endovascular Balloon Occlusion of the Aorta for Exsanguinating Subdiaphragmatic Hemorrhage

Importance

Hemorrhage is the most common cause of preventable death after injury. Most deaths occur early, in the prehospital phase of care.

Objective

To establish whether prehospital zone 1 (supraceliac) partial resuscitative endovascular balloon occlusion of the aorta (Z1 P-REBOA) can be achieved in the resuscitation of adult trauma patients at risk of cardiac arrest and death due to exsanguination.

Design, Setting, and Participants

This was a prospective observational cohort study (Idea, Development, Exploration, Assessment and Long-term follow-up [IDEAL] 2A design) with recruitment from June 2020 to March 2022 and follow-up until discharge from hospital, death, or 90 days evaluating a physician-led and physician-delivered, urban prehospital trauma service in the Greater London area. Trauma patients aged 16 years and older with suspected exsanguinating subdiaphragmatic hemorrhage, recent or imminent hypovolemic traumatic cardiac arrest (TCA) were included. Those with unsurvivable injuries or who were pregnant were excluded. Of 2960 individuals attended by the service during the study period, 16 were included in the study.

Exposures

ZI REBOA or P-REBOA.

Main Outcomes and Measures

The main outcome was the proportion of patients in whom Z1 REBOA and Z1 P-REBOA were achieved. Clinical end points included systolic blood pressure (SBP) response to Z1 REBOA, mortality rate (1 hour, 3 hours, 24 hours, or 30 days postinjury), and survival to hospital discharge.

Results

Femoral arterial access for Z1 REBOA was attempted in 16 patients (median [range] age, 30 [17-76] years; 14 [81%] male; median [IQR] Injury Severity Score, 50 [39-57]). In 2 patients with successful arterial access, REBOA was not attempted due to improvement in clinical condition. In the other 14 patients (8 [57%] of whom were in traumatic cardiac arrest [TCA]), 11 successfully underwent cannulation and had aortic balloons inflated in Z1. The 3 individuals in whom cannulation was unsuccessful were in TCA (failure rate = 3/14 [21%]). Median (IQR) pre-REBOA SBP in the 11 individuals for whom cannulation was successful (5 [46%] in TCA) was 47 (33-52) mm Hg. Z1 REBOA plus P-REBOA was associated with a significant improvement in BP (median [IQR] SBP at emergency department arrival, 101 [77-107] mm Hg; 0 of 10 patients were in TCA at arrival). The median group-level improvement in SBP from the pre-REBOA value was 52 (95% CI, 42-77) mm Hg (P < .004). P-REBOA was feasible in 8 individuals (8/11 [73%]) and occurred spontaneously in 4 of these. The 1- and 3-hour postinjury mortality rate was 9% (1/11), 24-hour mortality was 27% (3/11), and 30-day mortality was 82% (9/11). Survival to hospital discharge was 18% (2/11). Both survivors underwent early Z1 P-REBOA.

Conclusions and Relevance

In this study, prehospital Z1 P-REBOA is feasible and may enable early survival, but with a significant incidence of late death.

Trial Registration

ClinicalTrials.gov Identifier: NCT04145271.

Propensity Score Analysis of Resuscitative Endovascular Balloon Occlusion of the Aorta: Zone-1 Versus Zone-3 Resuscitative Endovascular Balloon Occlusion of the Aorta Odds of Mortality

INTRODUCTION

There are two zones for the placement of a Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) in trauma patients: above the mesenteric vessels (Zone-1) or below the renal arteries (Zone-3). Zone-1 REBOA diverts blood away from the visceral organs which leads to a systemic inflammatory response and reperfusion injury. We hypothesized that patients undergoing Zone-1 REBOA placement had a higher odds of mortality.

METHODS

The 2017-2019 Trauma Quality Improvement Program database was queried for patients undergoing either Zone-1 or Zone-3 REBOA. We excluded all patients with prehospital cardiac arrest. We compared Zone-1 versus Zone-3 REBOA using a 1:2 propensity-score model, matching for age, mechanism, sex, hypotension, tachycardia, blunt solid organ injury grade, pelvic fracture, and injuries to the aorta, iliac artery, iliac vein, and inferior vena cava.

RESULTS

We matched 130 Zone-1 REBOA patients to 260 Zone-3 REBOA patients. There were no statistically significant differences in the matched variables (P > 0.05). Compared to Zone-3 REBOA, patients with Zone-1 REBOA who survived ≥48 h had similar rates of acute kidney injury (18.6% versus 10.9%, P = 0.19). Zone-1 REBOA patients had a higher mortality rate (71.4% versus 48.8%, P = 0.002) and mortality odds ratio (OR) (OR 1.85, OR 1.18-2.89, P = 0.007). Zone-1 REBOA remained associated with a higher odds of mortality after controlling for traumatic brain injury and injury severity score (OR 1.86, OR 1.18-2.92, P = 0.007).

CONCLUSIONS

Compared to Zone-3, using a REBOA in Zone-1 is associated with higher odds of mortality. The use of REBOA Zone-1 deployment should be done with caution.

Raising Systemic Blood Pressure to Delay Irreversible Intestinal Ischemia in a Swine Model of Proximal Superior Mesenteric ArteryOcclusion

INTRODUCTION

Acute proximal superior mesenteric artery (SMA) occlusion is highly lethal, and adjuncts are needed to mitigate ischemic injury until definitive therapy. We hypothesized that raising mean arterial pressure (MAP) >90 mmHg with norepinephrine may delay irreversible bowel ischemia by increasing gastroduodenal artery (GDA) flow despite possible pressor-induced vasospasm.

METHODS

12 anesthetized swine underwent laparotomy, GDA flow probe placement, and proximal SMA exposure and clamping. Animals were randomized between conventional therapy (CT) versus targeted MAP >90 mmHg (MAP push; MP) where norepinephrine was titrated after 45 min of SMA occlusion. Animals were followed until bowel death or 4 h. Kaplan-Meier bowel survival, mean normalized GDA flow, and histology were compared.

RESULTS

12 swine (mean 57.8 ± 7.6 kgs) were included, six per group. Baseline weight, HR, MAP and GDA flows were not different. Within 5 min following SMA clamping, all 12 animals had an increase in MAP without other intervention from 81.7 to 105.5 mmHg (29.1%, P < 0.01) with a concomitant 74.9% increase in GDA flow as compared to baseline (P < 0.01). Beyond 45 min postclamp, MAP was greater in the MP group as intended, as were GDA flows. Median time to irreversibly ischemic bowel was 31% longer for MAP push animals (CT: 178 versus MP: 233 min, P = 0.006), Hazard Ratio of CT 8.85 (95% CI: 1.86-42.06); 3/6 MP animals versus 0/6 CT animals with bowel survived to predetermined end point.

CONCLUSIONS

In this swine model of acute complete proximal SMA occlusion, increasing MAP >90 mmHg with norepinephrine was associated with an increase in macrovascular blood flow through the GDA and bowel survival. Norepinephrine was not associated with worse bowel survival and a MAP push may increase the time window where ischemic bowel can be salvaged.

Technical and analytical approach to biventricular pressure-volume loops in swine including a completely endovascular, percutaneous closed-chest large animal model

Pressure-volume (PV) loop analysis is a sophisticated invasive approach to quantifying load-dependent and independent measures of cardiac function. Biventricular (BV) PV loops allow left and right ventricular function to be quantified simultaneously and independently, which is important for conditions and certain physiologic states, such as ventricular decoupling or acute physiologic changes. BV PV loops can be performed in an entirely endovascular, percutaneous, and closed-chest setting. This technique is helpful in a survival animal model, as a percutaneous monitoring system during endovascular device experiments, or in cases where chest wall compliance is being tested or may be a confounder. In this article, we describe the end-to-end implementation of a completely endovascular, totally percutaneous, and closed-chest large animal model to obtain contemporaneous BV PV loops in 40 to 70 kg swine. We describe the associated surgical and technical challenges and our solutions to obtaining endovascular BV PV loops, closed-chest cardiac output, and stroke volume (including validation of the correction factor necessary for thermodilution), as well as how to perform endovascular inferior vena cava occlusion in this swine model. We also include techniques for data acquisition and analysis that are required for this method.

Prehospital Resuscitation: What Should It Be?

Prehospital resuscitation is a dynamic field now being energized by new technologies and a shift in thinking regarding intravascular resuscitation. Growing evidence discourages use of intravenous (IV) crystalloid and colloid solutions in trauma, whereas blood products, particularly whole blood, are becoming preferred. Although randomized clinical trials validating definitive resuscitative protocols are still lacking, most preclinical and clinical indicators support this approach. In addition, emerging technologies such as external and endovascular hemorrhage control devices and extracorporeal perfusion are now being used routinely, even in the prehospital setting in many countries, generating new lines of emerging investigations for trauma specialists.

Common complications and prevention strategies for resuscitative endovascular balloon occlusion of the aorta: A narrative review

Resuscitative endovascular balloon occlusion of the aorta (REBOA) is considered a key measure of treatment due to its use in stabilizing patients in shock through temporary inflow occlusion for noncompressible torso hemorrhage as well as its supportive role in myocardial and cerebral perfusion. Although its clinical efficacy in trauma has been widely recognized, concerns over related complications, such as vascular access and ischemia-reperfusion, are on the rise. This paper aims to investigate complications associated with REBOA and identify current and emerging prevention or mitigation strategies through a literature review based on human or animal data. Common complications associated with REBOA include ischemia/reperfusion injuries, vessel injuries, venous thromboembolism, and worsening proximal bleeding. REBOA treatment outcomes can be improved substantially with the help of precise selection of patients, better visualization tools, improvement in balloon catheters, blockage strategies, and medication intervention measures. Better understanding of REBOA-related complications and further research on the strategies to mitigate the occurrence of such complications will be of vital importance for the optimization of the clinical outcomes in patients.

Investigating the variability in pressure-volume relationships during hemorrhage and aortic occlusion

Introduction

The pressure-volume (P-V) relationships of the left ventricle are the classical benchmark for studying cardiac mechanics and pumping function. Perturbations in the P-V relationship (or P-V loop) can be informative and guide the management of heart failure, hypovolemia, and aortic occlusion. Traditionally, P-V loop analyses have been limited to a single-beat P-V loop or an average of consecutive P-V loops (e.g., 10 cardiac cycles). While there are several algorithms to obtain single-beat estimations of the end-systolic and end-diastolic pressure-volume relations (i.e., ESPVR and EDPVR, respectively), there remains a need to better evaluate the variations in P-V relationships longitudinally over time. This is particularly important when studying acute and transient hemodynamic and cardiac events, such as active hemorrhage or aortic occlusion. In this study, we aim to investigate the variability in P-V relationships during hemorrhagic shock and aortic occlusion, by leveraging on a previously published porcine hemorrhage model.

Methods

Briefly, swine were instrumented with a P-V catheter in the left ventricle of the heart and underwent a 25% total blood volume hemorrhage over 30 min, followed by either Zone 1 complete aortic occlusion (i.e., REBOA), Zone 1 endovascular variable aortic control (EVAC), or no occlusion as a control, for 45 min. Preload-independent metrics of cardiac performance were obtained at predetermined time points by performing inferior vena cava occlusion during a ventilatory pause. Continuous P-V loop data and other hemodynamic flow and pressure measurements were collected in real-time using a multi-channel data acquisition system.

Results

We developed a custom algorithm to quantify the time-dependent variance in both load-dependent and independent cardiac parameters from each P-V loop. As expected, all pigs displayed a significant decrease in the end-systolic pressures and volumes (i.e., ESP, ESV) after hemorrhage. The variability in response to hemorrhage was consistent across all three groups. However, upon introduction of REBOA, we observed significantly high levels of variability in both load-dependent and independent cardiac metrics such as ESP, ESV, and the slope of ESPVR (Ees). For instance, pigs receiving REBOA experienced a 342% increase in ESP from hemorrhage, while pigs receiving EVAC experienced only a 188% increase. The level of variability within the EVAC group was consistently less than that of the REBOA group, which suggests that the EVAC group may be more supportive of maintaining healthier cardiac performance than complete occlusion with REBOA.

Discussion

In conclusion, we successfully developed a novel algorithm to reliably quantify the single-beat and longitudinal P-V relations during hemorrhage and aortic occlusion. As expected, hemorrhage resulted in smaller P-V loops, reflective of decreased preload and afterload conditions; however, the cardiac output and heart rate were preserved. The use of REBOA and EVAC for 44 min resulted in the restoration of baseline afterload and preload conditions, but often REBOA exceeded baseline pressure conditions to an alarming level. The level of variability in response to REBOA was significant and could be potentially associated to cardiac injury. By quantifying each P-V loop, we were able to capture the variability in all P-V loops, including those that were irregular in shape and believe that this can help us identify critical time points associated with declining cardiac performance during hemorrhage and REBOA use.

How to TEVAR swine for scientific research: Technical, anatomic, and device considerations to translate human TEVAR techniques into the large animal laboratory

OBJECTIVE

Thoracic Endovascular Aortic Repair (TEVAR) is well established in humans. Despite widespread use, additional research questions related to thoracic aortic stenting and endovascular innovation require large animal models. Translating human TEVAR devices and techniques into animal models, however, is a challenge even for experienced endovascular surgeons looking to develop a large animal TEVAR model.This article describes swine-specific strategies to deploy human TEVAR stent grafts, delineate how to select, size, prepare, and re-use human stents and deployment systems in swine, and how to translate human imaging modalities to large animal TEVAR.

METHODS

We describe a selection of related TEVAR models and techniques in Yorkshire swine to support scientific inquiry. This includes an animal husbandry and pre-operative preparation and planning program. All imaged specimens in this paper are castrated male Yorkshire swine in the 60-80 kg range and underwent TEVAR with the Medtronic Navion stent and deployment system.

RESULTS

To study human aortic stent grafts in swine, the animals generally must be at least 50 kgs to guarantee a 2 cm internal aortic diameter at the left subclavian, and for the iliac arteries to accommodate the human deployment system. Swine will have longer torsos and shorter iliofemoral segments than a human of the same weight which can make human deployment systems too short to reach the left subclavian from the femoral arteries in larger animals. We provide techniques to overcome this, including open iliac access or upside-down carotid TEVAR, which may be particularly useful if the scientific data would be confounded by iliofemoral access.Unlike humans that present clinically with axial imaging, swine will generally not have preoperative imaging, and many translational research laboratories do not have access to inexpensive preoperative CT, or any intraoperative CT scanning, which we are fortunate to have. We describe, therefore, several strategies for imaging in this setting including TEVAR via C-arm fluoroscopy and with or without in-laboratory CT scanning. Due to the low-resource setting of most large animal laboratories, as compared to a human hybrid room, we also describe several techniques to reduce cost and reuse materials, including the stent grafts, which at the end of non-survival experiments can be recovered during necropsy, cleaned, reinserted into the deployment device and reused on additional animals.

CONCLUSIONS

This article describes a collection of related techniques and tips to translate human TEVAR imaging, sizing/selection, deployment, and anatomy to swine research. Using this framework alone, an experienced human vascular or endovascular surgeon may develop a complete aortic stenting animal model with strategies for scientific data acquisition.

Autologous blood resuscitation for large animals in a research setting using the Hemafuse device: Preliminary data of device use for controlled and real-world hemorrhage

Introduction

New low-cost technologies are needed to salvage lost blood in low-resource settings and large animal laboratories. The Hemafuse device is a simple mechanical device that can recover lost blood during surgery. The aim of this study is to assess the feasibility of this device for resuscitating large animals with controlled and unintended hemorrhage and to provide device considerations for use in this context.

Methods

This study had two experimental components: (1) the Hemafuse device was kept on-shelf and used as needed to assess real-world use for unintended hemorrhage during experiments, and (2) animals underwent a controlled hemorrhage protocol, where four anesthetized swine underwent aortic and external jugular vein catheterization for pressure monitoring. Animals were hemorrhaged into the pelvis, and the Hemafuse device was used to suction the blood through a filter and pushed into a heparinized bag for subsequent retransfusion. Blood samples were collected at baseline, hemorrhage, within the device, and post-retransfusion and laboratory tests were performed.

Results

Animals that underwent controlled hemorrhage had a baseline mean arterial pressure of 83.6 ± 7.8 mmHg, and central venous pressure of 12.8 ± 1.9 mmHg, with expected changes throughout hemorrhage and resuscitation. Following resuscitation, pH was similar to baseline (7.39 ± 0.05 vs. 7.31 ± 0.03, p = 0.24). Lactate increased throughout the experiment with no significant differences after autotransfusion compared to baseline (2.7 ± 0.7 vs. 4.1 ± 1.4 mmol/L, p = 0.37). There were no significant changes in metabolic physiology. Compared to baseline, the hemoglobin (7.8 ± 2.4 vs. 7.3 ± 1.8 g/dL, p = 0.74), hematocrit (23% ± 6.9 vs. 21.3% ± 5.6, p = 0.71), and activated clotting time (268.5 ± 44.5 vs. 193 ± 24.6 s, p = 0.35) were similar after retransfusion. When used for unintended hemorrhage, the animals were resuscitated using the device with a mean time to retransfusion time of 128.7 ± 13.3 s and 100% survival throughout the experiment.

Conclusion

The Hemafuse device is feasible and efficacious for supporting large animal resuscitation. This is preliminary evidence that the device is a low-risk and low-cost off-the-shelf option for resuscitation using autologous blood with no significant effect on physiology post-retransfusion. We recommend that research laboratories consider the Hemafuse device for emergency use, particularly for highly invasive surgical laboratories where banked blood is not readily available.

Class of hemorrhagic shock is associated with progressive diastolic coronary flow reversal and diminished left ventricular function

Introduction: The relationship between coronary artery flow and left ventricular (LV) function during hemorrhagic shock remains unknown. The aim of this study was to quantify coronary artery flow directionality alongside left ventricular function through the four classes of hemorrhage shock. Methods: Following baseline data collection, swine were exsanguinated into cardiac arrest via the femoral artery using a logarithmic bleed, taking each animal through the four classes of hemorrhagic shock based on percent bleed (class I: 15%; class II: 15%-30%; class III: 30%-40%; class IV: >40%). Telemetry data, left ventricular pressure-volume loops, and left anterior descending artery flow tracings over numerous cardiac cycles were collected and analyzed for each animal throughout. Results: Five male swine (mean 72 ± 12 kg) were successfully exsanguinated into cardiac arrest. Mean left ventricular end-diastolic volume, end-diastolic pressure, and stroke work decreased as the hemorrhagic shock class progressed (p < 0.001). The proportion of diastole spent with retrograde coronary flow was also associated with class of hemorrhagic shock (mean 5.6% of diastole in baseline, to 63.9% of diastole in class IV; p < 0.0001), worsening at each class from baseline through class IV. Preload recruitable stroke work (PRSW) decreased significantly in classes II through IV (p < 0.001). Systemic Vascular Resistance (SVR) is associated with class of hemorrhage shock (p < 0.001). Conclusion: With progressive classes of hemorrhagic shock left ventricular function progressively decreased, and the coronary arteries spent a greater proportion of diastole in retrograde flow, with progressively more negative total coronary flow. Preload recruitable stroke work, a load-independent measure of inotropy, also worsened in severe hemorrhagic shock, indicating the mechanism extends beyond the drop in preload and afterload alone.