The degree of aortic occlusion in the setting of trauma alters the extent of acute kidney injury associated with mitochondrial preservation.

Resuscitative endovascular balloon occlusion of the aorta (REBOA) is used to control noncompressible hemorrhage not addressed with traditional tourniquets. However, REBOA is associated with acute kidney injury (AKI) and subsequent mortality in severely injured trauma patients. Here, we investigated how the degree of aortic occlusion altered the extent of AKI in a porcine model. Female Yorkshire-cross swine (n = 16, 68.1 ± 0.7 kg) were anesthetized and had carotid and bilateral femoral arteries accessed for REBOA insertion and distal and proximal blood pressure monitoring. Through a laparotomy, a 6-cm liver laceration was performed and balloon inflation was performed in zone 1 of the aorta for 90 min, during which animals were randomized to target distal mean arterial pressures of 25 or 45 mmHg via balloon volume adjustment. Blood draws were taken at baseline, end of occlusion, and time of death, at which point renal tissues were harvested 6 h after balloon deflation for histological and molecular analyses. Renal blood flow was lower in the 25-mmHg group (48.5 ± 18.3 mL/min) than in the 45-mmHg group (177.9 ± 27.2 mL/min) during the occlusion phase, which recovered and was not different after balloon deflation. AKI was more severe in the 25-mmHg group, as evidenced by circulating creatinine, blood urea nitrogen, and urinary neutrophil gelatinase-associated lipocalin. The 25-mmHg group had increased tubular necrosis, lower renal citrate synthase activity, increased tissue and circulating syndecan-1, and elevated systemic inflammatory cytokines. The extent of renal ischemia-induced AKI is associated with the magnitude of mitochondrial biomass and systemic inflammation, highlighting potential mechanistic targets to combine with partial REBOA strategies to prevent AKI.NEW & NOTEWORTHY Large animal models of ischemia-reperfusion acute kidney injury (IR-AKI) are lacking. This report establishes a titratable IR-AKI model in swine in which a balloon catheter can be used to alter distal pressures experienced by the kidney, thus controlling renal blood flow. Lower blood flow results in greater renal dysfunction and structural damage, as well as lower mitochondrial biomass, elevated systemic inflammation, and vascular dysfunction.

A Novel Sutureless Anastomotic Device in a Swine Model: A Proof of Concept Study.

INTRODUCTION: Vascular reconstruction requires technical expertise and is often time consuming. As a novel alternative to traditional hand-sewn vascular anastomoses, the VasoLock (VL), is a nonabsorbable, sutureless anastomosis device with traction anchors designed to hold free artery ends together. These anchors do not penetrate the vessel wall but adhere by leveraging the elasticity of the vessels to fasten blood vessels together. This pilot study assesses the performance and patency of this novel device in a porcine model of femoral artery injury. METHODS: Female swine (n = 7) underwent femoral artery exposure for a total of 10 VL implanted. Study animals underwent hemodilution to a target hematocrit of 15% and ROTEM was used to assess coagulopathy, followed by an arterial injury via transection. The VL was inserted without any sutures. Flow-probe monitors were positioned proximal and distal to the device and flow rates were measured continuously for a total of 90 min. Flow was analyzed and presented as a ratio of distal to proximal flow with the slope of this ratio across time subsequently determined. Angiographic assessment was completed to evaluate for patency and technical complications after 90 min of implant. RESULTS: The average animal weight was 44.1 ± 3.2 kg. The average mean arterial pressure at the time of implant was 51.2 ± 7.8 mmHg, median heart rate was 77.4 (IQR = 77.25-157.4) beats per minute, and average temperature was 36.1 ± 1.5°C. The baseline hematocrit was 13.5 ± 3.0%, average pH was 7.20 ± 0.1, average clotting time was 154.1 ± 58.7 s and average clot formation time was 103.4 ± 10.9 s all demonstrating the acidotic, hypothermic, and coagulopathic state of the swine at the time of insertion. During the 90-min observation period, the average flow gradient identified across the VL was 0.99 ± 0.24, indicating no significant change in flow across the VL. The average slope of the gradients was 0.0005 (P = 0.22), suggesting the ratio of proximal and distal flow did not change over the 90 min. Following 90 min of dwell time, all VL were patent without technical complication. Angiographic assessment at 90 min demonstrated no evidence of dissection, device migration, arterial extravasation, or thromboembolism with any of the 10 devices. CONCLUSIONS: This pilot study demonstrated technical feasibility of the novel VL device over a 90-min observation period. All VL were patent and no negative events or complications were identified. This technology demonstrated significant promise in a coagulopathic state: additional investigation, involving long-term survival, is warranted for further validation.

Impact of Ischemia Duration on Lower Limb Salvage in Combat Casualties.

INTRODUCTION: The 6-hour threshold to revascularization of an ischemic limb is ubiquitous in the trauma literature, however, contemporary evidence suggests that this threshold should be less. This study aims to characterize the relationship between the duration of limb ischemia and successful limb salvage following lower extremity arterial trauma. METHODS: This is a cohort study of the United States and UK military service members injured while serving in Iraq or Afghanistan between 2003 and 2013. Consecutive patients who sustained iliac, femoral, or popliteal artery injuries, and underwent surgery to attempt revascularization, were included. The association between limb outcome and the duration of limb ischemia was assessed using the Kaplan-Meier method. RESULTS: One hundred twenty-two patients (129 limbs) who sustained iliac (2.3%), femoral (56.6%), and popliteal (41.1%) arterial injuries were included. Overall, 87 limbs (67.4%) were successfully salvaged. The probability of limb salvage was 86.0% when ischemia was ≤1 hour; 68.3% when between 1 and 3 hours; 56.3% when between 3 and 6 hours; and 6.7% when >6 hours ( P <0.0001). Shock more than doubled the risk of failed limb salvage [hazard ratio=2.42 (95% confidence interval: 1.27-4.62)]. CONCLUSIONS: Limb salvage is critically dependent on the duration of ischemia with a 10% reduction in the probability of successful limb salvage for every hour delay to revascularization. The presence of shock significantly worsens this relationship. Military trauma systems should prioritize rapid hemorrhage control and early limb revascularization within 1 hour of injury.

Characterizing Brain Perfusion in a Swine Model of Raised Intracranial Pressure.

INTRODUCTION: Perfusion of the brain is critical, but this can be compromised due to focal space occupying lesions (SOL). SOLs can raise intracranial pressure (ICP), resulting in reduced cerebral blood flow (CBF). Most gyrencephalic models of brain injury focus on parenchymal injury, with few models of acutely elevated ICP. We hypothesized that we could employ a SOL technique to develop a titratable ICP model and sought to quantitate the resulting decrease in brain perfusion. METHODS: Six swine were anesthetized and instrumented. A Fogarty balloon catheter was inserted intracranially. Blood CO2 partial pressure was maintained between 35 and 45 mmHg. The Fogarty balloon was infused with normal saline at 1 mL/min to ICP targets of 10, 20, 30, and 40 mmHg. CBF (mL/100 g/min) were assessed at each ICP level using computed tomography perfusion (CTP). Data are presented as the mean ± standard deviation with all pressures measured in mmHg. CBF values were compared between baseline and each ICP level using analysis of variance. RESULTS: Baseline ICP was 5 ± 2 and systolic blood pressure was 106 ± 7. Balloon volumes (mL) required to achieve each incremental ICP level were 2.4 ± 0.5, 4.9 ± 1.7, 7.6 ± 1.6, and 9.9 ± 1.7. CBF decreased with each raised ICP level, with CBF being significantly less than baseline at ICP values of 30 (56.1 ± 34.7 versus 20.6 ± 11.0, P < 0.05) and 40 (56.1 ± 34.7 versus 6.5 ± 10.6, P < 0.05). CONCLUSIONS: An intracranial balloon catheter can be used to increase ICP, delivering a proportionate reduction in CBF. This model can be used in the future studies to examine adjuncts that manipulate intracranial pressure and their effect on brain perfusion.

Next-Generation REBOA (Resuscitative Endovascular Balloon Occlusion of the Aorta) Device Precisely Achieves Targeted Regional Optimization in a Porcine Model of Hemorrhagic Shock.

INTRODUCTION: Limitations such as time-dependent distal ischemia have slowed the adoption of resuscitative endovascular balloon occlusion of the aorta (REBOA) for noncompressible hemorrhage. Next-generation REBOA technologies may allow for controlled partial flow, known as targeted regional optimization, to reduce distal ischemia. We aimed to characterize the efficacy of one such catheter in a porcine model of lethal hemorrhagic shock. METHODS: Noncompressible hemorrhage from an iliac injury was induced in anesthetized swine (Sus scrofa) (70-90 kg), targeting 30% total blood volume. Animals were then randomized to partial aortic occlusion (PO) with targeted distal mean arterial pressure (MAP) of 35-40 mm of mercury (mm Hg) and complete aortic occlusion (CO) (n = 8 per group) for 90 min. All groups were then resuscitated during a two-h critical care (CC) phase, with flow rate and MAP recorded continuously at the distal infrarenal aorta and proximal carotid artery, and analyzed with two-way repeated measures analysis of variance with S-N-K post-hoc test. RESULTS: During aortic occlusion, MAP distal to the balloon was consistently maintained at 35.8 ± 0.3 mm Hg in the PO group compared to 27.1 ± 0.3 mm Hg in the CO group (P < 0.05), which also corresponded to higher flow rates (202.9 ± 4.8 mL/min PO versus 25.9 ± 0.8 mL/min CO; P < 0.05). MAP proximal to the balloon was significantly higher with CO versus PO (109.2 ± 2.3 mm Hg versus 85.2 ± 2.3 mm Hg; P < 0.05). During the CC phase, distal aortic flow and MAP were not significantly different between groups. However, creatinine returned to baseline levels by the end of the study in the PO group, but not the CO group. One animal died in the CO group, whereas none died in the PO group. CONCLUSIONS: This is the first examination of the next-generation pREBOA-PRO in a porcine model of lethal hemorrhagic shock. We show technical feasibility of this technique to precisely achieve targeted regional optimization without device failure or complication. The ability to titrate balloon inflation and thus distal flow/pressure may extend the therapeutic window of REBOA by mitigating distal ischemia.

Preliminary Experience With the Human Acellular Vessel: A Descriptive Case Series Detailing Early Use of a Bioengineered Blood Vessel for Arterial Repair.

BACKGROUND: An infection-resistant, immediately available conduit for trauma and urgent vascular reconstruction remains a critical need for successful limb salvage. While autologous vein remains the gold standard, vein-limited patients and size mismatch are common issues. The Human Acellular Vessel (HAV) (Humacyte, Inc., Durham, NC) is a bioengineered conduit with off-the-shelf availability and resistance to infection, ideal characteristics for patients with challenging revascularization scenarios. This report describes HAV implantation in patients with complex limb-threatening ischemia and limited conduit options who may have otherwise faced limb loss. METHODS: The Food and Drug Administration (FDA) expanded-access program was used to allow urgent implantation of the HAV for arterial reconstruction. Electronic medical records were reviewed with extraction of relevant data including patient demographics, surgical implantation, patency, infectious complications, and mortality. RESULTS: The HAV was implanted in 8 patients requiring vascular reconstruction. Graft or soft tissue infection was present in 2 patients. One patient with severe penetrating pelvic injury had 4 HAV placed to repair bilateral external iliac artery and vein injuries. There was 1 technical failure due to poor outflow, 2 patients died unrelated to HAV use, and 5 lower extremity bypasses maintained patency at an average of 11.4 months (range: 4-20 months). No HAV infectious complications were identified. CONCLUSIONS: This report is the first United States series describing early outcomes using the HAV under the FDA expanded-access program for urgent vascular reconstruction. The HAV demonstrates resistance to infection, reliable patency, and offers surgeons an immediate option when confronted with complex revascularization scenarios. Assessment of long-term outcomes will be important for future studies.

Temporary intravascular shunt use improves early limb salvage after extremity vascular injury.

OBJECTIVE: The use of temporary intravascular shunts (TIVSs) allow for restoration of distal perfusion and reduce ischemic time in the setting of arterial injury. As a damage control method, adjunct shunts restore perfusion during treatment of life-threatening injuries, or when patients require evacuation to a higher level of care. Single-center reports and case series have demonstrate that TIVS use can extend the opportunity for limb salvage. However, few multi-institutional studies on the topic have been reported. The objective of the present study was to characterize TIVS use through a multi-institutional registry and define its effects on early limb salvage. METHODS: Data from the Prospective Observation Vascular Injury Treatment registry was analyzed. Civilian patients aged ≥18 years who had sustained an extremity vascular injury from September 2012 to November 2018 were included. Patients who had a TIVS used in the management of vascular injury were included in the TIVS group and those who had received treatment without a TIVS served as the control group. An unadjusted comparison of the groups was conducted to evaluate the differences in the baseline and outcome characteristics. Double robust estimation combining logistic regression with propensity score matching was used to evaluate the effect of TIVS usage on the primary end point of limb salvage. RESULTS: TIVS use was identified in 78 patients from 24 trauma centers. The control group included 613 patients. Unmatched analysis demonstrated that the TIVS group was more severely injured (mean ± standard deviation injury severity score, 18.83 ± 11.76 for TIVS vs 14.93 ± 10.46 for control; P = .002) and had more severely mangled extremities (mean ± standard deviation abbreviated injury scale, extremity, score 3.23 ± 0.80 for TIVS vs 2.95 ± 0.87 for control; P = .008). Logistic regression demonstrated that propensity-matched control patients had a three times greater likelihood of amputation compared with the TIVS patients (odds ratio, 3.6; 95% confidence interval, 1.2-11.1; P = .026). Concomitant nerve injury and orthopedic fracture were associated with a greater risk of amputation. The median follow-up for the TIVS group was 12 days (interquartile range, 4-25 days) compared with 9 days (interquartile range, 4-18 days) for the control group. CONCLUSIONS: To the best of our knowledge, the present study is the first multicenter, matched-cohort study to characterize early limb salvage as a function of TIVS use in the setting of extremity vascular injury. Shunts expedite limb perfusion and resulted in lower rates of amputation during the early phase of care. The use of TIVS should be one part of a more aggressive approach to restore perfusion in the most injured patients and ischemic limbs.

Partial Resuscitative Endovascular Balloon Occlusion of the Aorta: A Systematic Review of the Preclinical and Clinical Literature.

BACKGROUND: Resuscitative endovascular balloon occlusion of the aorta (REBOA) has become a standard adjunct for the management of life-threatening truncal hemorrhage, but the technique is limited by the sequalae of ischemia distal to occlusion. Partial REBOA addresses this limitation, and the recent Food and Drug Administration approval of a device designed to enable partial REBOA will broaden its application. We conducted a systematic review of the available animal and clinical literature on the methods, impacts, and outcomes associated with partial REBOA as a technique to enable targeted proximal perfusion and limit distal ischemic injury. We hypothesize that a systematic review of the published animal and human literature on partial REBOA will provide actionable insight for the use of partial REBOA in the context of future wider clinical implementation of this technique. METHODS: Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses for Protocols guidelines, we conducted a search of the available literature which used partial inflation of a REBOA balloon catheter. Findings from 22 large animal studies and 14 clinical studies met inclusion criteria. RESULTS: Animal and clinical results support the benefits of partial REBOA including extending the resuscitative window extended safe occlusion time, improved survival, reduced proximal hypertension, and reduced resuscitation requirements. Clinical studies provide practical physiologic targets for partial REBOA including a period of total occlusion followed by gradual balloon deflation to achieve a target proximal pressure and/or target distal pressure. CONCLUSIONS: Partial REBOA has several benefits which have been observed in animal and clinical studies, most notably reduced ischemic insult to tissues distal to occlusion and improved outcomes compared with total occlusion. Practical clinical protocols are available for the implementation of partial REBOA in cases of life-threatening torso hemorrhage.

A New Pressure-Regulated, Partial Resuscitative Endovascular Balloon Occlusion of the Aorta Device Achieves Targeted Distal Perfusion.

BACKGROUND: Resuscitative endovascular balloon occlusion of the aorta (REBOA) reduces blood loss and improves hemodynamics. Complete occlusion results in distal ischemia, limiting its use for prolonged care. This study evaluated two next-generation partial REBOA (pREBOA) catheters and their ability to achieve targeted distal aortic flow. MATERIALS AND METHODS: Swine underwent hemorrhagic shock, complete aortic occlusion, controlled continuous balloon deflation, and targeted distal perfusion (TDP; 300-mL/min) phases. They were randomized into three groups (n = 6/group), one managed with the current ER-REBOA (ER), and two with the new pREBOA technologies: a bilobed (BL) device and a semicompliant pREBOA-PRO (PRP). Hemodynamics including flow rates and mean arterial pressures at the carotid artery and infrarenal aorta were recorded. RESULTS: Hemodynamics were comparable between groups during hemorrhage and complete occlusion phases. During the controlled continuous balloon deflation phase, the distal aortic flow rate strongly correlated with percent balloon volume in BL and PRP groups, suggesting a precise control of distal perfusion. The slope of flow-balloon-volume curves was greater in the ER group than BL and PRP groups, indicating the change in distal aortic flow rate was more sensitive to the balloon volume (less titratable) when using ER. During the TDP phase, variation in distal aortic flow and mean arterial pressure with respect to the target flow was lower in ER and PRP groups, than the BL group. CONCLUSIONS: Pressure-regulated occlusion using the next-generation pREBOA catheters is more controlled than the first-generation ER-REBOA catheter and allow for targeted and precise distal perfusion.

Anatomic Variation of the Phrenic Nerve and Brachial Plexus Encountered during 100 Supraclavicular Decompressions for Neurogenic Thoracic Outlet Syndrome with Associated Postoperative Neurologic Complications.

BACKGROUND: The objective of this study was to characterize phrenic nerve and brachial plexus variation encountered during supraclavicular decompression for neurogenic thoracic outlet syndrome and to identify associated postoperative neurologic complications. METHODS: A multicenter retrospective review was performed to evaluate anatomic variation of the phrenic nerve and brachial plexus from November 2010 to July 2018. After initial characterization, the following two groups were identified: variant anatomy (VA) group and standard anatomy (SA) group. Complications were analyzed and compared between the two groups. RESULTS: In total, 105 patients were identified, and 100 patients met inclusion criteria. Any anatomic variation of the standard course or configuration of the phrenic nerve and/or brachial plexus was encountered in 47 (47%) patients. Phrenic nerve anatomic variations were identified in 28 (28%) patients. These included 9 duplicated nerves, 6 lateral accessory nerves, 8 medial displacement, and 5 lateral displacement. Brachial plexus anatomic variation was found in 34 (34%) patients. The most common variant configuration of a fused middle and inferior trunk was identified in 25 (25%) patients. Combined phrenic nerve and brachial plexus anatomic variation was demonstrated in 15 (15%) patients. The VA and SA groups consisted of 47 and 53 patients, respectively. Transient phrenic nerve injury with postoperative elevation of the ipsilateral hemidiaphragm was documented in 3 (6.4%) patients in the VA group and 6 (11.3%) patients in the SA group (P = 0.49). Permanent phrenic nerve injury was identified in 1 (2.1%) patient in the VA group (P = 0.47) and none in the SA group. Transient brachial plexopathy was encountered in 1 (1.9%) patient in the SA group (P = 1.0) with full recovery to normal function. CONCLUSIONS: Anatomic variability of the phrenic nerve and brachial plexus are encountered more frequently than previously reported. While the incidence of nerve injury is low, surgeons operating within the thoracic aperture should be familiar with variant anatomy to reduce postoperative complications.

Epidemiology of Upper Extremity Vascular Injury in Contemporary Combat.

BACKGROUND: The incidence of wartime upper-extremity vascular injury (UEVI) has been stable for the past century. The objective of this study is to provide a contemporary review of wartime UEVI, including epidemiologic characterization and description of early limb loss. METHODS: The Department of Defense Trauma Registry (DoDTR) was queried to identify US service members who sustained a battle-related UEVI in Afghanistan between January 2009 and December 2015. Anatomic distribution of injury, mechanism of injury (MOI), associated injuries, early management, and early limb loss were analyzed. RESULTS: Analysis identified 247 casualties who sustained 308 UEVIs. The most common injury was to the vessels distal to the brachial bifurcation (63.3%, n = 195), followed by the brachial vessels (27.3%, n = 84) and the axillary vessels (9.4%, n = 29). The predominant MOIs were penetrating explosive fragments (74.1%, n = 183) and gunshot wounds (25.9%, n = 64). Associated fractures were identified in 151 (61.1%) casualties and nerve injuries in 133 (53.8%). Angiography was performed in 91 (36.8%) casualties, and endovascular treatment was performed 10 (4%) times. Temporary vascular shunts were placed in 39 (15.8%) casualties. Data on surgical management were available for 171 injuries and included repair (48%, n = 82) and ligation (52%, n = 89). The early limb loss rate was 12.1% (n = 30). For all casualties sustaining early limb loss, the MOI was penetrating fragments from an explosion; the average injury severity score (ISS) was 32.3, and the mortality was 6.7% (n = 2). In those without amputation, the ISS and mortality were low at 20 and 4.6% (n = 10), respectively. Overall mortality was 4.9% (n = 12). CONCLUSIONS: The early limb loss rate was increased compared with initial descriptions from Operation Iraqi Freedom. Amputations are associated with a higher ISS. Improved data capture and fidelity, or differing MOIs, may account for this trend. Proficiency with open and endovascular therapy remains a critical focus for combat casualty care.

Infraclavicular Thoracic Outlet Decompression Compared to Supraclavicular Thoracic Outlet Decompression for the Management of Venous Thoracic Outlet Syndrome.

BACKGROUND: The treatment of venous thoracic outlet syndrome (VTOS) requires surgical decompression often combined with catheter-directed thrombolysis and venoplasty. Surgical options include transaxillary, supraclavicular, or infraclavicular approaches to first rib resection. The optimal method, however, has yet to be defined. The purpose of this study is to compare the outcomes of patients who underwent infraclavicular versus supraclavicular surgical decompression for VTOS. METHODS: A retrospective review of patients who underwent surgical management for VTOS from December 2010 to November 2017 was performed. During the study period, supraclavicular and infraclavicular approaches were chosen according to surgeon preference. Patient demographics, pre- and postdecompression interventions, perioperative outcomes for each group of patients were analyzed. RESULTS: Thirty patients underwent surgical management of VTOS, of which 15 (50%) underwent infraclavicular decompression and 15 (50%) supraclavicular decompression. The mean age of patients was 32.1 ± 13.6 years and 80% were male. Twenty-six patients (86.7%) presented with thrombotic VTOS. Acute axillosubclavian vein thrombosis was present in 20 (76.9%) of these patients, 10 patients in each group. Subacute or chronic thrombosis was encountered in the remaining 6 (23%) patients, 2 patients in the infraclavicular group and 4 patients in the supraclavicular group. Preoperative thrombolysis was utilized in 7 (46.7%) and 6 (40%) patients in the infraclavicular and supraclavicular groups, respectively (P = 1.00). Patients without postdecompression venography were removed from analysis and included 1 patient in the infraclavicular group and 5 patients in the supraclavicular group. Initial postdecompression venogram, prior to any endovascular intervention, demonstrated a residual axillosubclavian vein stenosis of greater than 50% in 6 (42.9%) patients in the infraclavicular decompression group and 7 (70%) patients in the supraclavicular decompression group (P = 0.24). Crossing the stenosis after surgical decompression was more easily accomplished in the infraclavicular group, 14 (100%) versus 5 (50%), (P = 0.01). Following endovascular venoplasty, calculated residual stenosis greater than 50% was found in 0 (0%) and 3 (30%) patients in the infraclavicular and supraclavicular approaches, respectively (P = 0.047). Infraclavicular thoracic outlet decompression was associated with fewer patients with postoperative symptoms, 0 of 15 (0%) versus 8 of 15 (53.3%), (P = 0.0022), and infraclavicular thoracic outlet decompression demonstrated improved patency, 15 of 15 (100%) versus 8 of 15 (53.3%), (P = 0.028) at a mean combined follow-up of 8.47 ± 10.8 months. CONCLUSIONS: Infraclavicular thoracic outlet decompression for the surgical management of VTOS was associated with fewer postoperative symptoms and improved axillosubclavian vein patency compared to the supraclavicular approach. Prospective analysis is warranted to determine long-term outcomes following infraclavicular decompression.

Improving the safety of resuscitative endovascular balloon occlusion of the aorta - Compliant versus semi-compliant balloon systems.

OBJECTIVES: Resuscitative endovascular balloon occlusion of the aorta is an alternative to resuscitative thoracotomy in non-compressible torso haemorrhage. Low-profile, compliant balloon catheter systems have been developed, which can be deployed without the need for fluoroscopy. However, concern exists for over inflation and aortic injury, especially as compliant balloon material can stretch reducing syringe feedback and limiting the effectiveness of a safety valve. An alternative material would be a semi-compliant balloon material, but its performance is unknown. The aim of this study was to compare the inflation characteristics of compliant versus semi-compliant balloon systems and to determine whether a pressure relief safety valve can be practically applied to a semi-compliant balloon catheter as a safety device. METHODS: This was an ex vivo study using porcine segments of thoracic aorta. The study consisted of two phases. The first phase involved intermittent inflation of six compliant balloon and six semi-compliant balloon balloons until balloon or aortic rupture. In the second phase, six semi-compliant balloons with the pressure-relief valve set at 0.45 atmospheres were inflated in the aortas until the valve release, followed by injection with additional 30 mL. Data including pressure, volume, balloon working length, diameter and circumferential stretch ratio were collected. RESULTS: At failure, mean balloon volume was almost double in compliant balloon group vs semi-compliant balloon group - 49.83 mL (±23.25) and 25.16 mL (±8.93), respectively (p = 0.004), with 36% increase in working length in the compliant balloon group - 81.17 mm (±19.11) vs 59.49 (±4.86) for semi-compliant balloon (p = 0.023). When plotted, the relationship pattern between volume and pressure fit a linear model for the compliant balloon, and a quadratic model for the semi-compliant balloon. Following attempted over inflation with the pressure valve, there was no change in parameters before and after attempted over inflation. CONCLUSIONS: The inflation profile differs between balloon designs. In contrast to semi-compliant balloons, compliant balloons will accommodate more volume to mitigate increase in pressure. This does not completely eliminate the risk of over inflation. The inflation characteristics of the semi-compliant balloon permit pairing it with a safety valve, which could lead to a development of a safer balloon technology in the future.

Management and outcome of 597 wartime penetrating lower extremity arterial injuries from an international military cohort.

OBJECTIVE: Vascular injury is a leading cause of death and disability in military and civilian settings. Most wartime and an increasing amount of civilian vascular trauma arises from penetrating mechanisms of injury due to gunshot or explosion. The objective of this study was to provide a comprehensive examination of penetrating lower extremity arterial injury and to characterize long-term limb salvage and differences related to mechanisms of injury. METHODS: The military trauma registries of the United States and the United Kingdom were analyzed to identify service members who sustained penetrating lower limb arterial injury (2001-2014). Treatment and limb salvage data were studied and comparisons made of patients whose penetrating vascular trauma arose from explosion (group 1) vs gunshot (group 2). Standardized statistical testing was used, with Bonferroni corrections for multiple comparisons. RESULTS: The cohort consisted of 568 combat casualties (mean age, 25.2 years) with 597 injuries (explosion, n = 416; gunshot, n = 181). Group 1 had higher Injury Severity Score (P < .05) and Mangled Extremity Severity Score (P < .0001), required more blood transfusion (P < .05), and had more tibial (P < .01) and popliteal (P < .05) arterial injuries; group 2 had more profunda femoris injuries (P < .05). Initial surgical management for the whole cohort included vein interposition graft (33%), ligation (31%), primary repair with or without patch angioplasty (16%), temporary vascular shunting (15%), and primary amputation (6%). No difference in patency of arterial reconstruction was found between group 1 and group 2, although group 1 had a higher incidence of primary (13% vs 2%; P < .05) and secondary (19% vs 9%; P < .05) amputation. Similarly, longer term freedom from amputation was lower for group 1 than for group 2 (68% vs 89% at 5.5 years; Cox hazard ratio, 0.30; P < .0001), as was physical functioning (36-Item Short Form Health Survey data; mean, 39.80 vs 43.20; P < .05). CONCLUSIONS: The majority of wartime lower extremity arterial injuries result from an explosive mechanism that preferentially affects the tibial vasculature and results in poorer long-term limb salvage compared with those injured with firearms. The mortality associated with immediate limb salvage attempts is low, and delayed amputations occur weeks later, affording the patient involvement in the decision-making and rehabilitation planning. We recommend assertive attempts at vascular repair and limb salvage for service members injured by explosive and gunshot mechanisms.

A contemporary, 7-year analysis of vascular injury from the war in Afghanistan.

OBJECTIVE: Vascular injury is a leading cause of death and disability in military and civilian trauma. Although a previous interim study defined the distribution of vascular injury during the wars in Iraq and Afghanistan, a contemporary epidemiologic assessment has not been performed. The objective of this study was to provide a current analysis of vascular injury during the final 7 years of the war in Afghanistan, including characterization of anatomic injury patterns, mechanisms of injury, and methods of acute management. METHODS: The Department of Defense Trauma Registry was analyzed to identify U.S. military service members who sustained a battle-related vascular injury and survived to be treated at a surgical facility in Afghanistan between January 1, 2009, and December 31, 2015. All battle-related injuries (nonreturn to duty) were used as a denominator to establish the injury rate. Mechanism and anatomic distribution of injury as well as the acute management strategies of revascularization, ligation, and use of endovascular techniques were defined. RESULTS: Of 3900 service members who sustained a battle-related injury, 685 patients (17.6%) had 1105 vascular injuries (1.6 vascular injuries per patient). Extremity trauma accounted for 72% (n = 796) of vascular injuries, followed by the torso (17%; n = 188) and cervical (11%; n = 118) regions. Lower extremity vascular injury was the most prevalent anatomic location (45%; 501/1105). Explosion with fragment penetration accounted for 70% (477/685) of injuries, whereas gunshot wounds accounted for 30% (205/685). Open repair was performed in 559 cases (57%; 554/981), whereas ligation was the initial management strategy in 40% (395/981) of cases. In addition, 374 diagnostic endovascular procedures were completed, 27 therapeutic endovascular interventions to include stent placement and angioplasty were performed and 55 inferior vena cava filters were placed. Mortality of the vascular injury cohort was 5%. CONCLUSIONS: The rate of vascular injury in modern combat is higher than that reported in previous wars. Open reconstruction is performed in half of cases, although ligation is an important damage control option, especially for minor or distal vessel injuries. Angiographic techniques are increasingly being used and documented within wartime registries more than ever. Proficiency with open and endovascular methods of vascular injury management remains a critical need for the U.S. military and will require partnership with civilian institutions to attain and maintain.

Critical Limb Ischemia Secondary to Antiphospholipid Syndrome in a Pediatric Patient: Case Report and Review.

BACKGROUND: Antiphospholipid syndrome (APS) is a condition that manifests as venous or arterial thrombosis, as well as complications of pregnancy. APS affecting primarily the arteries is less common when compared to venous complications. We present a case of arterial occlusion resulting in critical limb ischemia (CLI) in a pediatric patient. METHODS: A 14-year old boy presented with worsening right lower extremity pain and ulcerative lesions of his foot. Laboratory analysis revealed a diagnosis of APS. This case report and review of the literature expands our understanding of arterial manifestations of APS in the pediatric patient. RESULTS: The patient was discovered to have proximal occlusion of the superficial femoral artery (SFA), the distal popliteal artery, the anterior tibial artery at the mid-calf, and the posterior tibial artery at the ankle. He underwent a common femoral artery to above-knee-popliteal artery bypass with reversed greater saphenous graft. Follow up after over one-year demonstrated an ABI of 1.0 and no evidence of stenosis in the bypass graft on duplex ultrasound (DUS). CONCLUSIONS: APS is a complex syndrome with a variety of clinical presentations. This case highlights arterial manifestations of APS and reviews the expanding literature to guide improved patient outcomes.

Intraoperative duplex ultrasound criteria for performing interposition bypass in the treatment of popliteal artery entrapment syndrome.

We present a case series of 3 surgical procedures (2 patients) in which intraoperative duplex ultrasound (IDUS) was used to determine whether the chronic compression of the popliteal artery caused by popliteal artery entrapment syndrome had injured the artery to such a degree that interposition bypass was required. Patients initially underwent standard clinical evaluation including history and physical examination and noninvasive diagnostic testing including postexercise ankle-brachial indexes and angiography with evocative maneuvers before surgery. IDUS was performed. Doppler was used to calculate peak systolic velocities (PSVs) and velocity ratios (VRs) across areas of suspected injury. B-mode was used to assess arterial wall thickness (AWT) and sclerotic changes. Patients were followed in the postoperative period with surveillance duplex ultrasound (US). Three limbs (2 patients) underwent IDUS evaluation after popliteal decompression. Limb 1 demonstrated an elevated intraoperative PSV of 295 cm/sec with an elevated VR of 2.52 (295/117 cm/sec) and AWT of 1.1 mm. Interposition bypass was performed after popliteal decompression. Postoperative surveillance duplex US revealed a reduction of the PSV to 90 cm/sec. Limb 2 showed a mildly elevated intraoperative PSV of 211.5 cm/sec with a VR of 1.86 (211.5/114 cm/sec) and AWT of 0.8 mm. An interposition bypass was not performed. Limb 3 demonstrated an elevated intraoperative PSV of 300 cm/sec with an elevated VR of 2.51 (300/119.5 cm/sec) and AWT of 1.0. Interposition bypass was performed. Postoperative surveillance duplex US revealed a reduction of the PSV to 115 cm/sec. IDUS was very helpful in the operative management and intraoperative decision making process for popliteal artery entrapment. An elevated PSV of 250-275 cm/sec or greater on IDUS and a VR of 2.0 or greater, in conjunction with B-mode demonstration of arterial wall injury, was useful in identifying severely injured popliteal arterial segments. Additional prospective studies are warranted to further investigate objective criteria that indicate the need for bypass.

Real-Time Measurements of Oral Mucosal Carbon Dioxide (POMCO2) Reveals an Inverse Correlation With Blood Pressure in a Porcine Model of Coagulopathic Junctional Hemorrhage.

INTRODUCTION: Shock states that occur during, for example, profound hemorrhage can cause global tissue hypoperfusion leading to organ failure. There is an unmet need for a reliable marker of tissue perfusion during hemorrhage that can be followed longitudinally. Herein, we investigated whether longitudinal POMCO2 tracks changes in hemodynamics in a swine model of coagulopathic uncontrolled junctional hemorrhage. MATERIALS AND METHODS: Female Yorkshire-crossbreed swine (n = 7, 68.1 ± 0.7 kg) were anesthetized and instrumented for continuous measurement of mean arterial pressure (MAP). Coagulopathy was induced by the exchange of 50 to 60% of blood volume with 6% Hetastarch over 30 minutes to target a hematocrit of <15%. A 4.5-mm arteriotomy was made in the right common femoral artery with 30 seconds of free bleeding. POMCO2 was continuously measured from baseline through hemodilution, hemorrhage, and a subsequent 3-h intensive care unit period. Rotational thromboelastometry and blood gases were measured. RESULTS: POMCO2 and MAP showed no significant changes during the hemodilution phase of the experiment, which produced coagulopathy evidenced by prolonged clot formation times. However, POMCO2 increased because of the uncontrolled hemorrhage by 11.3 ± 3.1 mmHg and was inversely correlated with the drop (17.9 ± 5.9 mmHg) in MAP (Y = -0.4122*X + 2.649, P = .02, r2 = 0.686). In contrast, lactate did not significantly correlate with the changes in MAP (P = .35) or POMCO2 (P = .37). CONCLUSIONS: Despite the logical appeal of measuring noninvasive tissue CO2 measurement as a surrogate for gastrointestinal perfusion, prior studies have only reported snapshots of this readout. The present investigation shows real-time longitudinal measurement of POMCO2 to confirm that MAP inversely correlates to POMCO2 in the face of coagulopathy. The simplicity of measuring POMCO2 in real time can provide an additional practical option for military or civilian medics to monitor trends in hypoperfusion during hemorrhagic shock.

Surgical outcomes for occluded venous thoracic outlet syndrome following transaxillary first rib resection.

OBJECTIVE: Surgical decompression via transaxillary first rib resection (TFRR) is often performed in patients presenting with venous thoracic outlet syndrome (VTOS). We aimed to evaluate the outcomes of TFRR based on chronicity of completely occluded axillosubclavian veins in VTOS. METHODS: We performed a retrospective institutional review of all patients who underwent TFRR for VTOS and had a completely occluded axillosubclavian vein between 2003 and 2022. Patients were categorized into three groups based on the time of inciting VTOS event to TFRR acuity of their venous occlusion: <4 weeks, 4 to 12 weeks, and >12 weeks. We evaluated the association of TFRR timing with 1-year outcomes, including patency and symptomatic improvement. We used the χ2 test to compare baseline characteristics and postoperative outcomes. RESULTS: Overall, 103 patients underwent TFRR for VTOS with a completely occluded axillosubclavian vein (median age, 30.0 years; 42.7% female; 8.8% non-White), of whom 28 had occlusion at <4 weeks, 36 had occlusion at 4 to 12 weeks, and 39 had occlusion at >12 weeks. Postoperative venogram performed 2 to 3 weeks after TFRR demonstrated that 78.6% in the <4 weeks group, 72.2% in the 4- to 12-weeks group, and 61.5% in the >12 weeks group had some degree of recanalization (P = .76). Postoperative balloon angioplasty was successfully performed in 60 patients with stenosed or occluded axillosubclavian vein at the time of postoperative venogram. At the 10- to 14-month follow-up, 79.2% of the <4 weeks group, 73.3% of the 4- to 12-weeks group, and 73.3% of the >12 weeks group had patent axillosubclavian veins based on duplex ultrasound examination (P = .86). Among patients who underwent postoperative balloon angioplasty, 80.0%, 85.0% and 100% in the <4 weeks, 4- to 12-weeks, and >12 weeks groups respectively demonstrated patency at 10 to 14 months (P = .31). Symptomatic improvement was reported in 95.7% in the <4 weeks group, 96.7% in the 4- to 12-weeks group, and 93.5% in the >12 weeks group (P = .84). CONCLUSIONS: TFRR offers excellent postoperative outcomes for patients with symptomatic VTOS, even in cases of completely occluded axillosubclavian veins, regardless of the chronicity of the occlusion. By 14 months, 95.2% of patients experienced symptomatic improvement, and 75% attained venous patency.

Use of MEDEVAC Resources in Austere Settings: Paget-Schroetter in the Deployed Environment.

Medical evacuation (MEDEVAC) from a combat zone requires complex decision-making and coordination of assets. A MEDEVAC helicopter team transports not only battle-injured patients but also patients with urgent non-battle-related medical diagnoses from extremely remote locations and are at the mercy of terrain, weather, and enemy contact. The military represents a young population particularly susceptible to venous thoracic outlet syndrome (vTOS) given the rigorous physical activity demands. Current literature supports immediate anticoagulation and surgical decompression within 14 days of diagnosis of vTOS to prevent long-term morbidity. Presented is a case of service member with vTOS presenting at an extremely remote military clinic who underwent a prompt evacuation ∼7,000 miles utilizing rotary-wing transport, followed by three to four more fixed-wing flights to a military treatment facility in the United States. Immediate recognition and ultrasound of this patient to confirm vTOS upon presentation and effective communication to non-medical military commanders and the receiving medical personnel at each Echelon was necessary to ensure an expedited evacuation. The surgeons treating this patient recommend prompt evacuation of deployed service members with suspected vTOS, venogram at the Role 3 if ultrasound is inconclusive, anticoagulation, and return to a Role 4 CONUS facility for definitive surgical management within 14 days. This case is an example of the efficiency of the military MEDEVAC system on a global scale, ensuring optimum medical care for all service members deployed.