Michael Austin Johnson

Partial resuscitative balloon occlusion of the aorta (P-REBOA): Clinical technique and rationale

Resuscitative endovascular balloon occlusion of the aorta (REBOA) has continued to evolve as a viable tool of modern trauma resuscitation. Developed from the convergence of trauma and endovascular surgery, REBOA has increasingly been used at select centers as a resuscitative adjunct for trauma patients with life-threatening noncompressible truncal hemorrhage. Even as prospective registry data seek to capture and analyze outcomes of early use of REBOA, ongoing device innovation and technique refinement seek to mitigate potential risks associated with aortic occlusion. It is hypothesized that early use of REBOA preserves cerebral perfusion and coronary filling in the setting of lifethreatening hypotension and hypovolemia secondary to hemorrhage. Laboratory data have demonstrated that the use of REBOA in the setting of hemorrhagic shock results in increased central aortic pressure, carotid flow, and brain oxygenation, and early reports suggest REBOA may improve outcomes in select patient populations. These benefits of REBOAmust be weighed against the consequence of sustained complete aortic occlusion, primarily profound distal ischemia and associated reperfusion

Emerging Endovascular Therapies for Non-Compressible Torso Hemorrhage

ABSTRACT Management of non-compressible torso hemorrhage (NCTH) remains a challenge despite continued advancements in trauma resuscitation. Resuscitative thoracotomy with aortic cross-clamping and recent advances in endovascular aortic occlusion, including resuscitative endovascular occlusion of the aorta, have finite durations of therapy due to the inherent physiologic stressors that accompany complete occlusion. Here, we attempt to illuminate the current state of aortic occlusion for trauma resuscitation including explanation of the deleterious consequences of complete occlusion, potential methods and limitations of existing technology to overcome these consequences, and a description of innovative methods to improve the resuscitation of NCTH. By explaining the complexity and potential deleterious effects of resuscitation augmented with aortic occlusion, our goal is to provide practitioners with a real-world perspective on current endovascular technology and to encourage the continued innovation required to overcome existing obstacles.

Extending resuscitative endovascular balloon occlusion of the aorta: Endovascular variable aortic control in a lethal model of hemorrhagic shock

BACKGROUND The duration of use and efficacy of resuscitative endovascular balloon occlusion of the aorta (REBOA) is limited by distal ischemia. We developed a hybrid endovascular-extracorporeal circuit variable aortic control (VAC) device to extend REBOA duration in a lethal model of hemorrhagic shock to serve as an experimental surrogate to further the development of endovascular VAC (EVAC) technologies. METHODS Nine Yorkshire-cross swine were anesthetized, instrumented, splenectomized, and subjected to 30% liver amputation. Following a short period of uncontrolled hemorrhage, REBOA was instituted for 20 minutes. Automated variable occlusion in response to changes in proximal mean arterial pressure was applied for the remaining 70 minutes of the intervention phase using the automated extracorporeal circuit. Damage-control surgery and whole blood resuscitation then occurred, and the animals were monitored for a total of 6 hours. RESULTS Seven animals survived the initial surgical preparation. After 20 minutes of complete REBOA, regulated flow was initiated through the extracorporeal circuit to simulate VAC and provide perfusion to distal tissue beds during the 90-minute intervention phase. Two animals required circuit occlusion for salvage, while five animals tolerated sustained, escalating restoration of distal blood flow before surgical hemorrhage control. Animals tolerating distal flow had preserved renal function, maintained proximal blood pressure, and rapidly weaned from complete REBOA. CONCLUSION We combined a novel automated, extracorporeal circuit with complete REBOA to achieve EVAC in a swine model of uncontrolled hemorrhage. Our approach regulated proximal aortic pressure, alleviated supranormal values above the balloon, and provided controlled distal aortic perfusion that reduced ischemia without inducing intolerable bleeding. This experimental model serves as a temporary surrogate to guide future EVAC catheter designs that may provide transformational approaches to hemorrhagic shock.

Automated variable aortic control versus complete aortic occlusion in a swine model of hemorrhage

BACKGROUND Future endovascular hemorrhage control devices will require features that mitigate the adverse effects of vessel occlusion. Permissive regional hypoperfusion (PRH) with variable aortic control (VAC) is a novel strategy to minimize hemorrhage and reduce the ischemic burden of complete aortic occlusion (AO). The objective of this study was to compare PRH with VAC to AO in a lethal model of hemorrhage. METHODS Twenty-five swine underwent cannulation of the supraceliac aorta, with diversion of aortic flow through an automated extracorporeal circuit. After creation of uncontrolled liver hemorrhage, animals were randomized to 90 minutes of treatment: Control (full, unregulated flow; n = 5), AO (no flow; n = 10), and PRH with VAC (dynamic distal flow initiated after 20 minutes of AO; n = 10). In the PRH group, distal flow rates were regulated between 100 and 300 mL/min based on a desired, preset range of proximal mean arterial pressure (MAP). At 90 minutes, damage control surgery, resuscitation, and restoration of full flow ensued. Critical care continued for 4.5 hours or until death. Hemodynamic parameters and markers of ischemia were recorded. RESULTS Study survival was 0%, 50%, and 90% for control, AO, and VAC, respectively (p < 0.01). During intervention, VAC resulted in more physiologic proximal MAP (84 ± 18 mm Hg vs. 105 ± 9 mm Hg, p < 0.01) and higher renal blood flow than AO animals (p = 0.02). During critical care, VAC resulted in higher proximal MAP (73 ± 8 mm Hg vs. 50 ± 6 mm Hg, p < 0.01), carotid and renal blood flow (p < 0.01), lactate clearance (p < 0.01), and urine output (p < 0.01) than AO despite requiring half the volume of crystalloids to maintain proximal MAP ≥50 mm Hg (p < 0.01). CONCLUSION Permissive regional hypoperfusion with variable aortic control minimizes the adverse effects of distal ischemia, optimizes proximal pressure to the brain and heart, and prevents exsanguination in this model of lethal hemorrhage. These findings provide foundational knowledge for the continued development of this novel paradigm and inform next-generation endovascular designs.

High ratio plasma resuscitation does not improve survival in pediatric trauma patients

BACKGROUND Damage control resuscitation including balanced resuscitation with high ratios of plasma (PLAS) and platelets (PLT) to packed red blood cells (PRBC) improves survival in adult patients. We sought to evaluate the effect of a high ratio PLAS to PRBC resuscitation strategy in massively transfused pediatric patients with combat injuries. METHODS The Department of Defense Trauma Registry was queried from 2001 to 2013 for pediatric trauma patients (<18 years). Burns, drowning, isolated head trauma, and older teens were excluded. Those who received massive transfusion (≥40 mL/kg total blood products in 24 hours) and early deaths who received any blood products were then evaluated. Primary outcomes were mortality at 24 hours and in-hospital. Secondary outcomes included blood product utilization over 24 hours, ventilator-free days, intensive care unit–free days, and hospital length of stay. RESULTS The Department of Defense Trauma Registry yielded 4,980 combat-injured pediatric trauma patients, of whom 364 met inclusion criteria. Analysis of PLAS/PRBC ratios across the entire spectrum of possible ratios in these patients demonstrated no clear inflection point for mortality. Using a division between low (LO) and high (HI) ratios of PLAS/PRBC 1:2, there was no difference in all-cause mortality at 24 hours (LO, 9.2% vs. HI, 8.0%; p = 0.75) and hospital discharge (LO, 21.5% vs. HI, 17.1%; p = 0.39). HI ratio patients received less PRBC but more PLAS and PLT and more total blood products. Those in the HI ratio group also had longer hospital length of stay. Regression analysis demonstrated no associated mortality benefit with a HI ratio (hazards ratio, 2.04; 95% confidence interval, 0.48–8.73; p = 0.34). CONCLUSION In combat-injured children undergoing a massive transfusion, a high ratio of PLAS/PRBC was not associated with improved survival. Further prospective studies should be performed to determine the optimal resuscitation strategy in critically injured pediatric patients. LEVEL OF EVIDENCE Therapeutic study, level III.

Resuscitative endovascular balloon occlusion of the aorta during non-ST elevation myocardial infarction: A case report:

Resuscitative endovascular balloon occlusion of the aorta (REBOA) is a hemorrhage control technique that is increasingly being adopted for the management of noncompressible bleeding. In addition to limiting hemorrhage, REBOA increases blood flow to the heart, lungs, and brain. A small number of case reports and animal studies describe the use of REBOA to increase coronary perfusion during cardiopulmonary resuscitation. We report a case in which REBOA may have reversed ST-segment abnormalities during a Type II non-ST elevation myocardial infarction (NSTEMI) in a patient with previous trauma. We describe the presentation, course, and decision making that contributed to the use of REBOA in this case. Additionally, we will present a review of the literature on the effects of REBOA on coronary perfusion.

Patient, provider, and environmental factors associated with adherence to cardiovascular and cerebrovascular clinical practice guidelines in the emergency department

Objectives: Myocardial infarction and stroke are two of the leading causes of death in the U.S. Both diseases have clinical practice guidelines (CPGs) specific to the emergency department (ED) that improve patient outcomes. Our primary objectives were to estimate differences in ED adherence across CPGs for these diseases and identify patient, provider, and environmental factors associated with adherence. Methods: Design: Retrospective study at 3 hospitals in Colorado using standard medical record review. Population: Consecutive adults (≥ 18) hospitalized for acute coronary syndrome (ACS), ST‐elevation myocardial infarction (STEMI), or acute ischemic stroke (AIS), who were admitted to the hospital from the ED and for whom the ED diagnosed or initiated treatment. Outcome: ED adherence to the CPG (primary); in‐hospital mortality and length‐of‐stay (secondary). Analysis: Multivariable logistic regression using generalized estimating equations was used. Results: Among 1053 patients, ED care was adherent in 84% with significant differences in adherence between CPGs (p < 0.001) and across institutions (p = 0.04). When patients presented with atypical chief complaints, the odds of receiving adherent care was 0.6 (95% CI 0.4–0.9). When the primary ED diagnosis was associated but not specific to the CPG, the odds of receiving adherent care was 0.5 (95% CI 0.3–0.9) and 0.3 (95% CI 0.2–0.5) for unrelated primary diagnoses. Conclusions: Adherence to ED CPGs for ACS, STEMI and AIS differs significantly between cardiovascular and cerebrovascular diseases and is more likely to occur when the diagnosis is highly suggested by the patients complaint and acknowledged as the primary diagnosis by the treating ED physician.