BACKGROUND Administering antithrombotics (AT) to the multiply injured patient with blunt cerebrovascular injury (BCVI) requires a thoughtful assessment of the risk of stroke and death associated with nontreatment. Large, multicenter analysis of outcomes stratified by injury grade and vessel injured is needed to inform future recommendations. METHODS Nine hundred and seventy-one BCVIs were identified from the PROspective Vascular Injury Treatment registry in this retrospective analysis. Using multivariate analysis, we identified predictors of BCVI-related stroke and death. We then stratified these risks by injury grade and vessel injured. We compared the risk of adverse outcomes in the nontreatment group with those treated with antiplatelet agents and/or anticoagulants. RESULTS Stroke was identified in 7% of cases. Overall mortality was 12%. Both increased with increasing BCVI grade. Treatment with ATs was associated with lower mortality and was not significantly affected by the choice of agent. Withholding ATs was associated with an increased risk of stroke and/or death across all subgroups (Grade I/II: odds ratio [OR], 4.66; 95% confidence interval [CI], 2.48-8.75; Grade III: OR, 7.0; 95% CI, 2.01-24.5; Grade IV: OR, 4.43; 95% CI, 1.76-11.1) even after controlling for covariates. Predictors of death included more severe trauma, Grade IV injury, and the occurrence of stroke. Arterial occlusion, hypotension, and endovascular intervention were significant predictors of stroke. Patients that experienced a BCVI-related stroke were at a 4.2x increased risk of death. The data set lacked the granularity necessary to evaluate AT timing or dosing regimen, which limited further analysis of stroke prevention strategies. CONCLUSION Stroke and death remain significant risks for all BCVI grades regardless of the vessel injured. Antithrombotics represent the only management strategy that is consistently associated with a lower incidence of stroke and death in all BCVI categories. In the multi-injured BCVI patient with a high risk of bleeding on anticoagulation, antiplatelet agents are an efficacious alternative. Given the 40% mortality rate in patients who survived their initial trauma and developed a BCVI-related stroke, nontreatment may no longer be a viable option. LEVEL OF EVIDENCE Epidemiological III; Therapeutic IV.

Partial resuscitative balloon occlusion of the aorta (P-REBOA) has emerged as an alternative technique to complete aortic occlusion (REBOA). As it is currently utilized, REBOA is a simple “all-or-none” phenomenon. The balloon is inflated causing exclusion of downstream tissue beds from blood flow. P-REBOA differs from REBOA in that it allows a limited amount of blood flow beyond the aortic occlusion balloon in order to mitigate the negative effects of complete aortic occlusion. P-REBOA is guided by the underlying concept that lowering the pressure and flow to a hemorrhaging tissue bed will allow clot to form around the source of hemorrhage. This clot formation, along with vasospasm, will minimize ongoing bleeding. Furthermore, the small amount of blood flow beyond the balloon may lessen the ischemic burden and allow aerobic metabolism within distal tissue beds, while simultaneously mitigating the supraphysiologic proximal blood pressures observed during conventional REBOA. This variation of REBOA may serve to extend the tolerable duration of intervention. This chapter will discuss the technique of P-REBOA including the physiology of partial aortic occlusion, translational and early clinical data of P-REBOA, as well as future considerations for continued refinement of the technique.

Russo, Rachel M. MD, MS; Franklin, Curtis J. BS; Davidson, Anders J. MD; Carlisle, Patricia L. PhD; Iancu, Ariella M. MSEd; Baer, David G. PhD; Alam, Hasan B. MD Author Information

Background: Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) in the management of pediatric abdomino-pelvic hemorrhage from trauma or iatrogenic injury is limited by a lack of appropriately sized balloon catheters that can be delivered through a less than 7-Fr sheath.Methods: We bench tested the occlusion capability of eight commercially available balloon catheters deliverable through 4-Fr, 5-Fr, and 6-Fr sheaths in an anatomic pulsatile flow model of the pediatric aorta with variable luminal diameters (5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, and 12 mm). Inflated balloon migration and the deflated balloon’s effect on aortic flow were recorded. The flow chamber was calibrated to an approximate size-appropriate physiologic aortic blood flow.Results: Seven of the eight devices were able to occlude the test lumen diameter corresponding to their manufactured specifications. Deflated luminal flow restriction in the smallest test lumen was lowest in the Fogarty devices (0–3%) followed by Cordis (8–10%) and Numed (14–26%) devices. The Fogarty devices demonstrated the most distal migration (10–15 mm) followed by Numed (1–5 mm). Device migration was undetectable in the Cordis devices.Conclusion: There are commercially available balloon catheters, deliverable through smaller than 7-Fr sheaths, which can occlude pediatric sized aortic test lumens in the setting of physiologic pulsatile flow. While the use of these catheters for occlusion represents off-label use, these results will help inform future research, device development, and practice in the field of pediatric REBOA.

ABSTRACT Background: The resuscitation of patients in shock is materially intensive and many patients are refractory to maximal therapy. We hypothesized that partial inflation of an intra-aortic balloon, termed Endovascular Perfusion Augmentation for Critical Care (EPACC), would minimize material requirements while improving physiologic metrics. Methods: Swine underwent a 25% controlled bleed and 45 min of complete aortic occlusion to create a severe ischemia–reperfusion shock state. Animals received either standardized critical care (SCC) composed of IV fluids and norepinephrine delivered through an algorithmically controlled platform or EPACC in addition to SCC. Physiologic parameters were collected, and blood was sampled for analysis. Primary outcomes were total IV fluids and average MAP during the critical care phase. Differences ( P < 0.05) were measured with t test (continuous data) and Wilcoxon rank-sum test (ordinal data). Results: There were no differences in baseline characteristics. There were no differences in the maximum lactate; however, animals in the EPACC group had a higher average MAP (EPACC 65 mmHg, 95% confidence interval [CI], 65–66; SCC 60 mmHg, 95% CI, 57–63; P < 0.01) and remained within goal MAP for a greater period of time (EPACC 95.3%, 95% CI, 93.2–97.4; SCC 51.0%, 95% CI, 29.5–72.6; P < 0.01). EPACC animals required less IV fluids when compared with the SCC group (EPACC 21 mL/kg, 95% CI, 0–42; SCC 96 mL/kg, 95% CI, 76–117; P < 0.01). There were no differences in final lactate. Animals in the EPACC group had a higher final creatinine (EPACC 2.3 mg/dL, 95% CI, 2.1–2.5; SCC 1.7 mg/dL, 95% CI, 1.4–2.0; P < 0.01), but there were no differences in renal cellular damage on histology ( P = 0.16). Conclusion: Using a swine model of severe shock, the addition of EPACC to SCC significantly reduced fluid resuscitation requirements and improved blood pressure. This is the first description of a new therapy for patients in refractory shock or in resource-limited settings.

Background: Endovascular methods for hemorrhage control, including resuscitative endovascular balloon occlusion of the aorta (REBOA), are evolving and are increasingly being applied clinically. Partial flow strategies to mitigate the consequences of complete aortic occlusion have been demonstrated in pre-clinical models to enhance REBOA and expand its application to various shock states. Initial studies demonstrated that controlled partial flow requires precision beyond the capabilities of manual balloon volume adjustment, therefore automation is required. Our group previously developed a proof-of-concept computer-controlled extracorporeal flow circuit capable of precision aortic flow regulation, but it was not clinically applicable. To bring this concept closer to clinical applicability, we have developed the first endovascular strategy to achieve precision aortic flow regulation, termed endovascular variable aortic control (EVAC). Methods: Following instrumentation, five Yorkshire-cross swine were subjected to controlled 25% hemorrhage, followed by precision low volume aortic flow regulation using a commercially available compliant balloon catheter pre-positioned in the descending thoracic aorta, connected to a custom, wireless syringe pump. Closed-loop feed-back algorithms based on streaming physiologic data were used to determine balloon volume changes. Results: The EVAC syringe pump was highly eff ective at maintaining precise aortic fl ow throughout the 45-minute intervention period during steady-state conditions as well as during rapid fluid administration. Aortic flow and distal mean arterial pressure remained stable during EVAC, despite changing proximal hemodynamics. Balloon volume was dynamic, averaging over 500 changes during intervention, with a mean volume change of 6.7 μL and a maximal change of 100 μL. Conclusions: The EVAC syringe pump is capable of achieving aortic flow regulation with high precision, beyond what is achievable with manual control. This serves as a model for future device design, enabling as of yet unachievable clinical therapies for hemorrhage and shock states. Future technological development is required to fully translate this into clinical use.

The surgical guidelines for male breast cancer (MBC) have been largely guided by female-predominant clinical trials. Because no clinical trial has been conducted to examine the surgical treatment of MBC, we performed a systematic review comparing the survival of patients with MBC who had undergone breast conserving surgery (BCS) and those who had undergone mastectomy and evaluated the patients' radiotherapy compliance after BCS. We performed a systematic search of electronic databases to find MBC cohort studies that had reported ≥ 1 survival outcome (disease-free survival [DFS], disease-specific survival [DSS], or overall survival [OS]) stratified by surgical treatment (BCS and/or mastectomy) and/or radiotherapy compliance with BCS. A total of 1 prospective and 9 retrospective cohort studies were included, with the number of patients ranging from 7 to 6039. Of the BCS patients, compliance with postoperative radiotherapy was low (range, 27%-46%), with the exception of 1 single-institution prospective study that reported 86% compliance (6 of 7 patients). The pooled estimate for all patients with MBC was 83% (95% confidence interval [CI], 78%-88%) for 5-year DSS and 66% (95% CI, 63%-70%) for 5-year OS. Most studies reported no differences in DFS, DSS, or OS for BCS and mastectomy. BCS is a reasonable treatment approach for MBC because it was associated with oncologic outcomes similar to those with mastectomy. However, the low rates of radiotherapy compliance among male patients who underwent BCS is concerning and highlights the importance of shared decision-making with patients with MBC when selecting a surgical treatment strategy.

A 16-year-old boy presented to a level I trauma center after multiple gun shot wounds and a motorcycle crash. He was in profound hemorrhagic shock and had multiple traumatic injuries, including a right common iliac arterial injury. The vessel was shunted for damage control and subsequently repaired primarily. On hospital day 18, he experienced dehiscence of the anastomosis requiring urgent surgery. The artery was ultimately repaired with an expandable polytetrafluoroethylene stent graft deployed in an open fashion through the site of injury. We discuss the use of stent grafts as an interesting alternative to suture repair after anastomotic disruption.

BACKGROUND:Intravenous (IV) tranexamic acid (TXA) is an adjunct for resuscitation in hemorrhagic shock; however, IV access in these patients may be difficult or impossible. Intraosseous (IO) or intramuscular (IM) administration could be quickly performed with minimal training. We investigated the pharmacokinetics of TXA via IV, IO, and IM routes in a swine model of controlled hemorrhagic shock.METHODS:Fifteen swine were anesthetized and bled of 35% of their blood volume before randomization to a single 1g/10mL dose of IV, IO, or IM TXA. Serial serum samples were obtained after TXA administration. These were analyzed with high-pressure liquid chromatography-mass spectrometry to determine drug concentration at each time point and define the pharmacokinetics of each route.RESULTS:There were no significant differences in baseline hemodynamics or blood loss between the groups. Peak concentration (Cmax) was significantly higher in IV and IO routes compared with IM (p = .005); however, the half-life of TXA was similar across all routes (p = .275).CONCLUSION:TXA administration via IO and IM routes during hemorrhagic shock achieves serum concentrations necessary for inhibition of fibrinolysis and may be practical alternatives when IV access is not available.

BACKGROUND The cardiac effects of resuscitative endovascular balloon occlusion of the aorta (REBOA) are largely unknown. We hypothesized that increased afterload from REBOA would lead to cardiac injury, and that partial flow using endovascular variable aortic control (EVAC) would mitigate this injury. METHODS Eighteen anesthetized swine underwent controlled 25% blood volume hemorrhage. Animals were randomized to either Zone 1 REBOA, Zone 1 EVAC, or no intervention (control) for 45 minutes. Animals were then resuscitated with shed blood, observed during critical care, and euthanized after a 6-hour total experimental time. Left ventricular function was measured with a pressure-volume catheter, and blood samples were drawn at routine intervals. RESULTS The average cardiac output during the intervention period was higher in the REBOA group (9.3 [8.6–15.4] L/min) compared with the EVAC group (7.2 [5.8–8.0] L/min, p = 0.01) and the control group (6.8 [5.8–7.7] L/min, p < 0.01). At the end of the intervention, the preload recruitable stroke work was significantly higher in both the REBOA and EVAC groups compared with the control group (111.2 [102.5–148.6] and 116.7 [116.6–141.4] vs. 67.1 [62.7–87.9], p = 0.02 and p < 0.01, respectively). The higher preload recruitable stroke work was maintained throughout the experiment in the EVAC group, but not in the REBOA group. Serum troponin concentrations after 6 hours were higher in the REBOA group compared with both the EVAC and control groups (6.26 ± 5.35 ng/mL vs 0.92 ± 0.61 ng/mL and 0.65 ± 0.38 ng/mL, p = 0.05 and p = 0.03, respectively). Cardiac intramural hemorrhage was higher in the REBOA group compared with the control group (1.67 ± 0.46 vs. 0.17 ± 0.18, p = 0.03), but not between the EVAC and control groups. CONCLUSION In a swine model of hemorrhagic shock, complete aortic occlusion resulted in cardiac injury, although there was no direct decrease in cardiac function. EVAC mitigated the cardiac injury and improved cardiac performance during resuscitation and critical care.

Current treatment guidelines for male breast cancer are predominantly guided by female-only clinical trials. With scarce research, it is unclear whether breast-conserving therapy (BCT) is equivalent to mastectomy in men. We sought to compare overall survival (OS) among male breast cancer patients who underwent BCT versus mastectomy.

INTRODUCTION:Trauma patients are predisposed to kidney injury. We hypothesized that in shock, zone 3 REBOA would increase renal blood flow (RBF) compared to control and that a period of zone 3 occlusion following zone 1 occlusion would improve renal function compared to zone 1 occlusion alone. MATERIALS AND METHODS:Twenty-four anesthetized swine underwent hemorrhagic shock, 45 min of zone 1 REBOA (Z1, supraceliac), zone 3 REBOA (Z3, infrarenal), or no intervention (control) followed by resuscitation with shed blood and 5 h of critical care. In a fourth group (Z1Z3), animals underwent 55 min of zone 3 REBOA following zone 1 occlusion. Physiologic parameters were recorded, blood and urine were collected at specified intervals. RESULTS:During critical care, there were no differences in RBF between the Z1 and Z3 groups. The average RBF during critical care in Z1Z3 was significantly lower than in Z3 alone (98.2 ± 23.9 and 191.9 ± 23.7 mL/min; p = 0.046) and not different than Z1. There was no difference in urinary neutrophil gelatinase-associated lipocalin-to-urinary creatinine ratio between Z1 and Z1Z3. Animals in the Z1Z3 group had a significant increase in the ratio at the end of the experiment compared to baseline [median (IQR)] [9.2 (8.2-13.2) versus 264.5 (73.6-1174.6)]. Following Z1 balloon deflation, RBF required 45 min to return to baseline. CONCLUSION:Neither zone 3 REBOA alone nor zone 3 REBOA following zone 1 REBOA improved renal blood flow or function. Following zone 1 occlusion, RBF is restored to baseline levels after approximately 45 min.

The use of topical negative pressure dressings in temporary abdominal closure has been readily adopted worldwide; however, a method of continuous suction is typically required to provide a seal. We describe a method of temporary abdominal closure using readily available materials in the forward surgical environment which does not require continuous suction after application. This method of temporary abdominal closure provides the benefits of negative pressure temporary abdominal closure after damage control surgery without the need for continuous suction or specialised equipment. Its application in damage control surgery in austere or far-forward settings is suggested. The technique has potential applications for military surgeons as well as in humanitarian settings where the logistic supply chain may be fragile.

BACKGROUND: Resuscitative endovascular balloon occlusion of the aorta (REBOA) is effective at limiting hemorrhage from noncompressible sources and restoring but causes progressive distal ischemia, supraphysiologic pressures, and increased cardiac afterload. Endovascular variable aortic control (EVAC) addresses these limitations, while still controlling hemorrhage. Previous work demonstrated improved outcomes following a 90-minute intervention period in an uncontrolled hemorrhage model. The present study compares automated EVAC to REBOA over an occlusion period reflective of contemporary REBOA usage. METHODS: Following instrumentation, 12 Yorkshire-cross swine underwent controlled 25% hemorrhage, a 45-minute intervention period of EVAC or REBOA, and subsequent resuscitation with whole blood and critical care for the remainder of a 6-hour experiment. Hemodynamics were acquired continuously, and laboratory parameters were assessed at routine intervals. Tissue was collected for histopathologic analysis. RESULTS: No differences were seen in baseline parameters. During intervention, EVAC resulted in more physiologic proximal pressure augmentation compared with REBOA (101 vs. 129 mm Hg; 95% confidence interval [CI], 105-151 mm Hg; p = 0.04). During critical care, EVAC animals required less than half the amount of crystalloid (3,450 mL; 95% CI, 1,215-5,684 mL] vs. 7,400 mL [95% CI, 6,148-8,642 mL]; p < 0.01) and vasopressors (21.5 ng/kg [95% CI, 7.5-35.5 ng/kg] vs. 50.5 ng/kg [95% CI, 40.5-60.5 ng/kg]; p = 0.05) when compared with REBOA animals. Endovascular variable aortic control resulted in lower peak and final lactate levels. Endovascular variable aortic control animals had less aortic hyperemia from reperfusion with aortic flow rates closer to baseline (36 mL/kg per minute [95% CI, 30-44 mL/kg per minute] vs. 51 mL/kg per minute [95% CI, 41-61 mL/kg per minute]; p = 0.01). CONCLUSIONS: For short durations of therapy, EVAC produces superior hemodynamics and less ischemic insult than REBOA in this porcinecontrolled hemorrhage model, with improved outcomes during critical care. This study suggests EVAC is a viable strategy for inhospital management of patients with hemorrhagic shock from noncompressible sources. Survival studies are needed to determine if these early differences persist over time. Copyright (C) 2018 Wolters Kluwer Health, Inc. All rights reserved.

Background: Resuscitative endovascular balloon occlusion of the aorta (REBOA) may be beneficial in the management of traumatic and iatrogenic vascular and solid organ injuries in children, but requires an understanding of vessel diameter at the access site and landing zones. We adapted the Broselow Tape method to estimate aortic and femoral artery diameters for this purpose.Methods: Computed tomography scans from trauma and non-trauma pediatric patients at a level 1 trauma center were reviewed for vascular dimensions at aorta Zone I, Zone III, and the common femoral artery (CFA). Vessel size was measured by two providers using a vascular software suite with a 10% interobserver comparison. Height was used to create linear regression equations for each location and calculate ranges for each Broselow Tape category.Results: We reviewed scans from 110 patients ages 2–14 years with less than 8% interobserver variability. Of these, 64% were male and 46% were trauma patients. Height-based regression equations were closely correlated with vessel diameter: Zone I (mm) = [0.093 ± 0.006 ⋅ height (cm)] + 0.589 ± 0.768; R2 = 0.714, p < 0.001; Zone III (mm) = [0.083 ± 0.005 ⋅ height (cm)] – 0.703 ± 0.660; and R2 = 0.728, p < 0.001; CFA (mm) = [0.043 ± 0.003 ⋅ height (cm)] + 0.644 ± 0.419; R2 = 0.642, p < 0.001. These equations, along with the minimum and maximum length for each Broselow Tape color, were used to define color-coded normal ranges for each REBOA landing zone and access site.Conclusion: Knowledge of the access vessel and occlusion zone diameters in pediatric patients is crucial for future research and application of REBOA in this population. Furthermore, an adapted Broselow Tape including these measurements would assist in appropriate sheath and balloon catheter selection in emergent settings.

Background: One limitation of resuscitative endovascular balloon occlusion of the aorta (REBOA) is hemodynamic instability upon balloon deflation due to distal hyperemia and washout of ischemic metabolites. We sought to determine whether stepwise reperfusion after supraceliac (Zone 1) REBOA by transitioning to infrarenal (Zone 3) occlusion would mitigate the physiologic consequences of balloon deflation and decrease hemodynamic instability. Methods: Twelve anesthetized swine underwent controlled hemorrhage of 25% blood volume, 45 minutes of Zone 1 REBOA, then resuscitation with shed blood. Standardized critical care began with deflation of the Zone 1 balloon in all animals, and continued for six hours. Half of the animals were randomly assigned to Zone 3 REBOA for an additional 55 minutes following Zone 1 balloon deflation. Results: There were no differences in physiology at baseline, during the initial 30 minutes of hypotension, or during the 45 minutes of Zone 1 occlusion. After Zone 1 balloon deflation, there was no difference in proximal mean arterial pressure (pMAP) with or without Zone 3 occlusion or percentage of critical care time spent within the target pMAP range between 65 and 75 mm Hg. There were also no significant differences in peak lactate concentration or resuscitation requirements. Conclusions: In an animal model of hemorrhagic shock and Zone 1 REBOA, subsequent Zone 3 aortic occlusion did not add a significant ischemic burden, but it also did not provide significant hemodynamic support. The effect of this strategy on functional outcomes warrants further study. Continued investigation is necessary to determine optimal resuscitative support strategies during reperfusion following Zone 1 REBOA.

Background:Acute traumatic coagulopathy (ATC) is a common condition after traumatic injury and is known to be associated with an increase in morbidity and mortality in trauma patients. ATC has been implicated as a causative factor in both early hemorrhage and late organ failure in this population, yet the pathophysiology remains largely unknown. Additionally, acute kidney injury (AKI) is a common condition among critically injured trauma patients. AKI has been associated with an elevated International Normalized Ratio (INR) and warfarin use, but its development has not been well studied in the setting of ATC. We hypothesized that the presence of ATC influences the development of AKI and may mediate mortality in combat casualties.Methods:Data were obtained from the Department of Defense Trauma Registry, Medical Data Store and Composite Healthcare System, and the Armed Forces Medical Examiner System. A retrospective review was conducted of US service members injured in Iraq or Afghanistan between February 1, 2002 and February 1, 2011, who required ICU level care and survived evacuation out of theater. Exclusions were made for missing data. Cox proportional hazard regression was performed to determine the effect of ATC (a priori defined as first INR > 1.3) on the development of AKI. Further analysis was conducted to determine the influence of these variables on 30-d mortality, and multiple sensitivity analyses were performed to determine the effect of ATC on both AKI and mortality.Results:A total of 1,288 patients were identified for analysis. ATC was a risk factor for subsequent AKI after adjustment (HR 1.67, 95% CI 1.28-2.18; p < 0.001). However, ATC was not a risk factor for mortality after adjustment in the full model (HR 1.87, 95% CI 0.95-3.65; p = 0.069). On sensitivity analyses exploring alternate definitions of ATC, an INR of 1.2 remained associated with AKI (HR 1.46, 95% CI 1.13-1.88; p = 0.004) and an INR of 1.5 became significant for mortality (HR 1.76, 95% CI 1.32-2.35; p < 0.001).Conclusion:ATC is independently associated with the development of AKI. Although ATC is associated with mortality in the unadjusted model, it is not significant after adjustment for AKI. This implies that the kidneys may play a role in the adverse outcomes observed after ATC. Increased awareness and monitoring for coagulopathy and the subsequent development of AKI in combat casualty patients may lead to earlier diagnosis and treatment of these conditions, possibly decreasing morbidity and mortality.

Stewart, Amy MD; Tat, Christine MD; Origenes, Rovi MSN, NP-C, CCRN, TNS; Amjad, Sohaib; Dabbous, Firas PhD; Shah, Manoj R. MD, FACS; Origenes, Andrea Kristin Author Information

INTRODUCTION:The effect of presenting hypertension is poorly studied in combat casualties. We hypothesized that elevated mean arterial pressure (MAP) on presentation to combat hospitals would be associated with poor outcomes.METHODS:Data was obtained from the Department of Defense Trauma Registry and the Armed Forces Medical Examiner System. Variables analyzed included presenting vital signs to Role II-III military theater hospital, demographic variables, injury severity score (ISS), location and mechanism of injury, presence of traumatic brain injury (TBI), acute kidney injury (AKI), and mortality. Patients were stratified by decile of MAP and logistic regression analysis was employed to adjust for confounders.RESULTS:A total of 4072 subjects injured from February 2002 to February 2011 were identified. Compared to patients in the middle deciles of presenting MAP, patients in the highest and lowest MAP deciles were the only groups that demonstrated a higher mortality on univariate analysis (OR 2.06, 95% CI 1.16-2.31 and OR 2.86, 95% CI 1.76-4.67, respectively), and this relationship persisted after adjustment for ISS, HR, temperature, presence of burn injury, TBI, and AKI. Burn injury was associated with mortality in the full multivariate analysis. However, further analysis limited to patients without burn injury did not demonstrate an association between high MAP and mortality (OR 0.84, 95% CI 0.36-1.99; p=0.70). Conversely, when limited to patients with burn injury, high MAP was associated with mortality (OR 3.78, 95% CI 1.74-8.20; p=0.001).CONCLUSION:The relationship between mortality and presenting MAP appears to be U-shaped, demonstrating increased mortality in the lowest and highest deciles. However, mortality in the highest MAP decile appears to be limited to casualties with associated burn injury, even after adjustment for TBI, AKI, and ISS, which takes into account the severity of the burn injury. Physicians should recognize that burn patients presenting with an elevated MAP are at an increased risk for poor outcomes.LEVEL OF EVIDENCE:III.

Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) results in large increases in cardiac afterload, which may lead to heart failure. Endovascular Variable Aortic Control (EVAC) is a strategy to mitigate the adverse effects of REBOA by allowing titrated distal blood flow with an automated balloon catheter. The objective of this study was to characterize, quantify, and compare the effects of REBOA and EVAC on cardiac function. Eighteen swine underwent controlled hemorrhage of 25% blood volume over 30 minutes, followed by randomization to either 45 minutes of Zone 1 REBOA (complete occlusion) or EVAC. Balloon volume in the EVAC arm was autonomously titrated to maintain an aortic flow of 300 mL/min. Animals were then resuscitated with shed blood, intra-aortic balloons were deflated, and 5 hours of critical care ensued. Cardiac function was measured continuously with a pressure-volume catheter placed in the left ventricle under fluoroscopic guidance. Physiologic parameters were recorded continuously. Repeated measures ANOVA and rank-sum tests were used to test for significance. There were no differences in cardiac output at the start of experiment (REBOA 5.3±3.6 L/min versus EVAC 4.1±1.4 L/min, p=0.39) or at the end of the hemorrhage phase (REBOA 5.7±1.9 L/min versus EVAC 5.9±1.9 L/min, p=0.81). During the intervention, there was a trend towards increased average cardiac output with REBOA (11.5±4.5 L/min) compared to EVAC (7.5±2.8 L/min, p=0.09) and with maximal cardiac output (REBOA 14.5±5.3 L/min versus EVAC 9.3±3.1 L/min, p=0.08). During the critical care phase, cardiac output was higher in the REBOA cohort (10.2±5.3 L/min) compared to the EVAC cohort (6.2±2.9 L/min), p=0.02. Despite a lower cardiac output, the end systolic pressure volume relationship (ESPVR), a marker of LV contractile strength, was significantly higher in the EVAC cohort at Time 120 (REBOA 1.6±1.0 versus EVAC 4.7±3.3, p=0.08) and Time 240 (REBOA 1.8±0.9 versus EVAC 5.0±2.8, p=0.02); this difference was no longer observed at the end of the study (p=0.14). Peak lactate concentration during the critical care phase was higher in the REBOA cohort (9.6±1.0 mmol/L) compared to the EVAC cohort (7.9±1.1 mmol/L, p=0.02) and remained significantly elevated through the end of the study period (REBOA 5.2±1.5 mmol/L versus EVAC 3.0±0.6, p=0.01). The physiologic impact of REBOA on the heart results in decreased left ventricular contractile strength and increased cardiac output compared to EVAC. Elevated ischemic metabolites may blunt the contractile strength of the heart while simultaneously requiring greater cardiac output to maintain goal blood pressure. Titrated partial distal flow via EVAC may place less strain on the heart and improves cardiac performance. Further studies are needed to determine if EVAC is a suitable intervention for patients suffering from non-compressible torso hemorrhage.