Composite Graft Pretreatment With Hydrogen Sulfide Delays the Onset of Acute Rejection.

INTRODUCTION: Vascularized composite allotransplantation can reconstruct devastating tissue loss by replacing like-with-like tissues, most commonly in the form of hand or face transplantation. Unresolved technical and ethical challenges have meant that such transplants remain experimental treatments. The most significant barrier to expansion of this field is the requirement for systemic immunosuppression, its toxicity and effect on longevity.Hydrogen sulfide (H2S) has been shown experimentally to ameliorate the ischemia reperfusion injury associated with composite tissue autotransplantation, which has been linked to acute rejection in solid organ transplantation. In this protocol, a large-animal model was used to evaluate the effect of H2S on acute rejection after composite tissue allotransplantation. MATERIALS AND METHODS: A musculocutaneous flap model in SLA-mismatched swine was used to evaluate acute rejection of allotransplants in 2 groups: control animals (n = 8) and a treatment group in which the allografts were pretreated with hydrogen sulfide (n = 8). Neither group was treated with systemic immunosuppression. Acute rejection was graded clinically and histopathologically by an independent, blinded pathologist. Data were analyzed by t tests with correction for multiple comparisons by the Holm-Sídák method. RESULTS: Clinically, H2S-treated tissue composites showed a delay in the onset of rejection that was statistically significant from postoperative day 6. Histopathologically, this difference between groups was also apparent, although evidence of a difference in groups disappeared beyond day 10. CONCLUSIONS: Targeted hydrogen sulfide treatment of vascularized composite allografts immediately before transplantation can delay acute rejection. This may, in turn, reduce or obviate the requirement for systemic immunosuppression.

C1 esterase inhibitor ameliorates ischemia reperfusion injury in a swine musculocutaneous flap model.

PURPOSE: Free tissue transfer is a powerful reconstructive surgical technique. The ischemia reperfusion injury (IRI) at revascularization affects the flap and the patient; reducing this insult could improve outcomes. This study evaluated the effect of C1 esterase inhibitor (C1-inh) on IRI in a porcine musculocutaneous flap model. MATERIALS AND METHODS: A musculocutaneous flap was transferred from the limb to the neck of 12 swine. Flaps underwent a 3-hour ischemic interval prior to revascularization. Intervention group flaps (n = 6) were perfused intra-arterially with 100U C1-inh at the commencement of the ischemic period; controls (n = 6) received heparinized saline solution. Protocol duration was 14 days; markers of reperfusion injury (creatine kinase [CK], aspartate transaminase [AST], tumor necrosis factor-alpha) were evaluated. RESULTS: All flaps from the intervention group were viable at 14 days; five of six control flaps were viable at 14 days (P = 1). Systemic levels of biomarkers of tissue necrosis and inflammation were reduced in the intervention group. On post-operative day one, statistically significant reductions in mean levels of AST and CK were demonstrated (2,293 ± 1 × 103 U/L vs. 1,586 ± 767 U/L [P = 0.04] and 429 × 103 ± 214 × 103 U/L vs. 213 × 103 ± 156 × 103 U/L [P = 0.002], respectively). Flaps of both groups healed in their recipient locations, no adverse reactions were observed. CONCLUSIONS: C1-inh is protective of IRI and may have utility in free tissue transfer, vascularized composite allotransplantation, and spare parts surgery. © 2016 Crown copyright. Microsurgery © 2016 Wiley Periodicals, Inc. Microsurgery 37:142-147, 2017.

Prophylactic fasciotomy in a porcine model of extremity trauma.

BACKGROUND: Extremity injury, with concomitant hemorrhagic shock, can result in ischemia-reperfusion injury and the formation of compartment syndrome requiring fasciotomy. As the benefit of prophylactic fasciotomy is unclear, the objective of this study is to determine the functional recovery of an ischemic limb with hemorrhagic shock after prophylactic fasciotomy. MATERIAL AND METHODS: Yorkshire swine underwent 35% blood volume hemorrhage, followed by 1, 3, and 6 h of ischemia (n = 17; 1HR, 3HR, and 6HR) via iliac artery occlusion followed by repair and reperfusion. A second cohort (n = 18) underwent fasciotomy of the anterior compartment of the hind limb following vascular repair (1HR-F, 3HR-F, and 6HR-F). Compartment pressures, measures of electromyographic (EMG) recovery, and a validated gait score (modified Tarlov) were performed throughout a 14-d survival period. RESULTS: Increasing ischemic intervals resulted in incremental increases in compartment pressure (P < 0.05), although the mean did not exceed 30 mm Hg. EMG studies did not show a significant improvement comparing the 3HR with 6HR groups. There was a significant improvement in the EMG studies within the 3HR-F, when compared with 6HR-F. There was a trend toward sensory improvement between the 3HR-F and 3HR groups. However, this did not translate to a difference in functional outcome as measured by the Tarlov gait score. CONCLUSIONS: Within this swine model of hemorrhagic shock and hind limb ischemia, the use of prophylactic fasciotomies did not improve functional outcome.

The inflammatory sequelae of aortic balloon occlusion in hemorrhagic shock.

BACKGROUND: Resuscitative endovascular balloon occlusion of the aorta (REBOA) is a hemorrhage control and resuscitative adjunct that has been demonstrated to improve central perfusion during hemorrhagic shock. The aim of this study was to characterize the systemic inflammatory response associated and cardiopulmonary sequelae with 30, 60, and 90 min of balloon occlusion and shock on the release of interleukin 6 (IL-6) and tumor necrosis factor alpha. MATERIALS AND METHODS: Anesthetized female Yorkshire swine (Sus scrofa, weight 70-90 kg) underwent a 35% blood volume-controlled hemorrhage followed by thoracic aortic balloon occlusion of 30 (30-REBOA, n = 6), 60 (60-REBOA, n = 8), and 90 min (90-REBOA, n = 6). This was followed by resuscitation with whole blood and crystalloid over 6 h. Animals then underwent 48 h of critical care with sedation, fluid, and vasopressor support. RESULTS: All animals were successfully induced into hemorrhagic shock without mortality. All groups responded to aortic occlusion with a rise in blood pressure above baseline values. IL-6, as measured (picogram per milliliter) at 8 h, was significantly elevated from baseline values in the 60-REBOA and 90-REBOA groups: 289 ± 258 versus 10 ± 5; P = 0.018 and 630 ± 348; P = 0.007, respectively. There was a trend toward greater vasopressor use (P = 0.183) and increased incidence of acute respiratory distress syndrome (P = 0.052) across the groups. CONCLUSIONS: REBOA is a useful adjunct in supporting central perfusion during hemorrhagic shock; however, increasing occlusion time and shock results in a greater IL-6 release. Clinicians must anticipate inflammation-mediated organ failure in post-REBOA use patients.

Hydrogen sulfide mitigates reperfusion injury in a porcine model of vascularized composite autotransplantation.

BACKGROUND: Devastating extremity injuries are prevalent but often survivable on the modern battlefield. These complex injuries require advanced methods of reconstruction, involving prolonged ischemic periods and reperfusion injury. Using our group's validated porcine model of gracilis myocutaneous flap transplantation, this study demonstrates that an interim perfusion of hydrogen sulfide (H2S) mitigates the effects of reperfusion injury in the setting of delayed restoration of blood flow. METHODS: A gracilis myocutaneous flap (200-400 g; surface area, 250 cm²) was procured from the hind limb of a Yorkshire swine (70-90 kg, n=16). The right external carotid artery and the internal jugular vein are the recipient axis. Group 1 (control, n = 6) underwent delayed anastomosis with a 3-hour ischemic period. Group 2 (n=10) underwent a similar delayed anastomosis with an interim perfusion of H2S during the ischemic period. The animals survived for 14 days. Systemic biomarker assays for skeletal muscle tissue injury (creatine kinase, lactate dehydrogenase, and aspartate transaminase) and proinflammatory markers (tumor necrosis factor α and interleukin 6) provide assessment of reperfusion injury at the cellular level. RESULTS: The control animals (3 hours of ischemia with an interim perfusion of heparinized saline) demonstrated increased levels of injury biomarkers and proinflammatory cytokines compared with the animals receiving H2S infusion and identical ischemic interval. The control flaps had a mean creatine kinase level of 280³×10 U/L (±80×10³), compared with the H2S group, which had a mean of 99×10³ U/L (±14×10³; P=0.0007 at postoperative day 2). lactate dehydrogenase levels (mean) were 26×10³ U/L (±8×10³) versus 9×10³ U/L (±3×10³; P=0.0004) and aspartate transaminase levels (mean) were 1651 U/L (±324) versus (873 U/L [±279]; P=0.0013) for the control and treatment groups, respectively. Similarly, an intergroup difference in IL-6 was found, although not statistically significant. Tumor necrosis factor α levels (mean) were 93 pg/mL (±14) versus 39 pg/mL (±4; P=0.0013) for the control and treatment groups, respectively. CONCLUSIONS: This study demonstrated the mitigating properties of H2S on reperfusion injury. Interim perfusion with H2S resulted in diminution of ischemia-dependent biomarkers after 3 hours of ischemia. Follow-up studies will translate these findings as an evolving method for reconstructing previously unreconstructable injuries.

Microvascular porcine model for the optimization of vascularized composite tissue transplantation.

BACKGROUND: Devastating extremity injuries are prevalent but most often survivable on the modern battlefield. The complexity of these injuries requires advanced methods of reconstruction. This study is designed to validate the feasibility of gracilis myocutaneous flap transplantation via microvascular free tissue transfer in a porcine model. This model will facilitate study of autotransplant physiology as well as vascularized composite allotransplantation as an evolving method for reconstructing previously nonreconstructable injuries. MATERIAL AND METHODS: A donor gracilis myocutaneous flap is procured from Yorkshire swine. The right external carotid artery and internal jugular vein are prepared as the recipient axis for microvascular anastomoses. Group 1 undergoes immediate microvascular anastomosis with resultant 1-h ischemic period. Group 2 undergoes delayed anastomosis with 3-h ischemic period. Markers of ischemia-reperfusion injury are evaluated after anastomosis and on postoperative days 1, 2, 7, and 14. RESULTS: A novel porcine model for microvascular composite tissue transplantation is demonstrated. Ischemia period-dependent elevations in circulating biomarkers (lactate dehydrogenase [LDH], creatine kinase [CK], and aspartate transaminase [AST]) demonstrate the effects of prolonged ischemia. Both groups showed marked LDH elevation without significant statistical intergroup difference (P=0.250). The difference in CK and AST levels at 24h showed strong significance (P<0.0001). CONCLUSIONS: A novel method of vascularized gracilis myocutaneous flap transplantation was validated in the Yorkshire swine. Assays for skeletal muscle tissue injury (LDH, CK, and AST) showed ischemia period-dependent response providing assessment of ischemia-reperfusion injury at the cellular level. Subsequent studies will evaluate agents that mitigate ischemia-reperfusion injury and transition these findings to potentiate vascularized composite allotransplantation.

Aortic balloon occlusion is effective in controlling pelvic hemorrhage.

BACKGROUND: The objective of this study was to evaluate the efficacy of resuscitative endovascular aortic balloon occlusion (REBOA) of the distal aorta in a porcine model of pelvic hemorrhage. METHODS: Swine were entered into three phases of study: injury (iliac artery), hemorrhage (45 s), and intervention (180 min). Three groups were studied: no intervention (NI, n = 7), a kaolin-impregnated gauze (Combat Gauze) (CG, n = 7), or REBOA (n = 7). The protocol was repeated with a dilutional coagulopathy (CG-C, n = 7, and REBOA-C, n = 7). Measures of physiology, rates of hemorrhage, and mortality were recorded. RESULTS: Rate of hemorrhage was greatest in the NI group, followed by the REBOA and CG groups (822 ± 415 mL/min versus 11 ± 13 and 0.2 ± 0.4 mL/min respectively; P < 0.001). MAP following intervention (at 15 min) was the same in the CG and REBOA groups and higher than in the NI group (70 ± 4 and 70 ± 11 mm Hg versus 5 ± 13 mm Hg respectively; P < 0.001). There was 100% mortality in the NI group, with no deaths in the CG or REBOA group. In the setting of coagulopathy, the rate of bleeding was higher in the CG-C versus the REBOA-C group (229 ± 295 mL/min versus 20 ± 7 mL/min, P = 0.085). MAP following intervention (15 min) was higher in the REBOA-C than the CG-C group (71 ± 12 mm Hg versus 28 ± 31 mm Hg; P = 0.005). There were 5 deaths (71.4%) in the CG-C group, but none in the REBOA-C group (P = 0.010). CONCLUSION: Balloon occlusion of the aorta is an effective method to control pelvic arterial hemorrhage. This technique should be further developed as an adjunct to manage noncompressible pelvic hemorrhage.

The impact of ischemic intervals on neuromuscular recovery in a porcine (Sus scrofa) survival model of extremity vascular injury.

BACKGROUND: Despite advances in revascularization following extremity vascular injury, the relationship between time to restoration of flow and functional limb salvage is unknown. The objectives of this study are to describe a large animal survival model of hind limb ischemia/reperfusion and define neuromuscular recovery following increasing ischemic periods. METHODS: Sus scrofa swine (N = 38; weight, 87 ± 6.2 kg) were randomized to iliac artery occlusion for 0 (Control), 1 (1HR), 3 (3HR), or 6 (6HR) hours, followed by vessel repair and 14 days of recovery. Additionally, one group underwent iliac artery division with no restoration of flow (Ligation), and one group underwent iliac artery exposure only without intervention (Sham). A composite physiologic measure of recovery (PMR) was generated to assess group differences over 14 days of survival. PMR included limb function (Tarlov score) and electrophysiologic measures (compound muscle action potential amplitude, sensory nerve action potential amplitude, and nerve conduction velocity). Using the PMR and extrapolating the point at which recovery following ligation crosses the slope connecting recovery after 3 and 6 hours of ischemia, an estimate of the ischemic threshold for the hind limb is made. These results were correlated with peroneus muscle and peroneal nerve histology. RESULTS: Baseline physiologic characteristics were similar between groups. Neuromuscular recovery in groups with early restoration of flow (Control, 1HR, 3HR) was similar and nearly complete (92%, 98%, and 88%, respectively; P > .45). While recovery was diminished in both 6HR and Ligation, Ligation, rather than repair, exhibited greater recovery (68% vs 53%; P < .05). These relationships correlated with the pathologic grade of degeneration, necrosis, and fibrosis (P < .05). The PMR model predicts minimal and similar persistent loss of function in groups undergoing early surgical restoration of flow (Control 8%, 1HR 1%, 3HR 12%; P > .45). In contrast, the Ligation group exhibited the greatest degree of injury early in the reperfusion period, followed by more complete recovery and at a faster rate than 6HR. Extrapolating from the PMR the point at which Ligation (68% recovery) crosses the slope connecting 3 hours (84% recovery) and 6 hours (53% recovery) of ischemia estimates the ischemic threshold to be 4.7 hours. Restoration of flow at ischemic intervals exceeding this are associated with less physiologic recovery than ligation. CONCLUSION: In this model, surgical and therapeutic adjuncts to restore extremity perfusion early (1-3 hours) after extremity vascular injury are most likely to provide outcomes benefit compared with delayed restoration of flow or ligation. Furthermore, the ischemic threshold of the extremity after which neuromuscular recovery is significantly diminished is less than 5 hours. Additional studies are necessary to determine the effect of other factors such as shock or therapeutic measures on this ischemic threshold.

A porcine model for evaluating the management of noncompressible torso hemorrhage.

BACKGROUND: Noncompressible hemorrhage from central vascular injuries remains the leading cause of preventable death in modern combat. This report introduces a large animal model of noncompressible torso hemorrhage, which permits assessment of the various approaches to this problem. METHODS: Yorkshire swine were anesthetized and monitoring devices for central aortic pressure, carotid flow, and intracerebral and transcutaneous brain oximetry were applied. Class IV hemorrhagic shock was induced through an iliac arterial injury and animals were subjected to different vascular control methods including thoracic aortic clamping, supraceliac aortic clamping, direct vascular control, and proximal endovascular balloon occlusion. After vascular control, the injury was shunted, and damage control resuscitation was continued. Serum markers, intravenous fluid volumes, and vasopressor requirements were tracked over a subsequent resuscitation period. Postmortem tissue analysis was performed to compare levels of acute ischemic injury between groups. RESULTS: The protocol for animal preparation, hemorrhage volume, open surgical technique, and posthemorrhage resuscitation was developed using four animals. The endovascular approach was developed using two additional animals. After model development, treatment animals subsequently underwent noncompressible hemorrhage with thoracic aortic clamping, supraceliac aortic clamping, direct vascular control, and endovascular aortic occlusion. Premature death occurred in one animal in the direct vascular control group. CONCLUSION: This study presents a large animal model of class IV hemorrhagic shock from noncompressible hemorrhage, which permits comparison of various vascular control methods to address this challenging problem. Future studies using this model as the standard will allow further development of strategies for the management of noncompressible hemorrhage.

Direct vascular control results in less physiologic derangement than proximal aortic clamping in a porcine model of noncompressible extrathoracic torso hemorrhage.

BACKGROUND: The optimal method of vascular control and resuscitation in patients with life-threatening, extrathoracic torso hemorrhage remains debated. Guidelines recommend emergency department thoracotomy (EDT) with aortic clamping, although transabdominal aortic clamping followed by vascular control and direct vascular control (DVC) without aortic clamping are alternatives. The objective of this study is to compare the effectiveness of three approaches to extrathoracic torso hemorrhage in a large animal model. METHODS: Adolescent swine (Sus Scrofa) (mean weight = 80.9 kg) were randomized into three groups all of which had class IV shock established by hemorrhage from an iliac artery injury. Group 1: EDT with thoracic aortic clamping (N = 6); group 2: transabdominal supraceliac aortic clamping (SCC; N = 6); and group 3: DVC of bleeding site without aortic clamping (N = 6). After hemorrhage, EDT or SCC was performed in groups 1 and 2, respectively, with subsequent exploration of the bleeding site and placement of a temporary vascular shunt (TVS). Group 3 (DVC) underwent direct exploration of the injury and placement of a TVS. All groups were resuscitated to predefined physiologic endpoints over 6 hours with repeated measures of central and cerebral perfusion and end-organ function at standardized time points. Postmortem tissue analysis was performed to quantify injury to critical tissue beds. RESULTS: There was no difference in mortality among the groups and no TVS failures. Central aortic pressure, carotid flow, and partial pressure brain tissue oximetry, all demonstrated increases in EDT and SCC after application of the aortic clamp relative to DVC (p < 0.05). During resuscitation, serum lactate levels were higher in EDT compared with SCC and DVC (6.85 vs. 3.08 and 2.15, respectively; p < 0.05) and serum pH in EDT reflected greater acidosis than SCC and DVC (7.24 vs. 7.36 and 7.39, respectively; p < 0.05). EDT and SCC required more intravenous fluid than DVC (2,166 mL and 2,166 mL vs. 667 mL, respectively; p < 0.05) and more vasopressors were used in EDT and SCC compared with DVC (52.1 µg and 43.5 µg vs. 12.4 µg, respectively; p < 0.05). Brain and myocardial tissue stains demonstrated the same degree of acute ischemic changes in all groups. CONCLUSION: Although aortic clamping increases central and cerebral perfusion, DVC results in less physiologic derangement. The optimal method of aortic control would incorporate the benefits of maintained central pressure with less associated morbidity. Clinical studies evaluating DVC are warranted.

A large animal survival model (Sus scrofa) of extremity ischemia/reperfusion and neuromuscular outcomes assessment: a pilot study.

BACKGROUND: Extremity ischemia/reperfusion has been studied mostly in small-animal models with limited characterization of neuromuscular or functional outcome. The objective of this experiment was to report a large-animal survival model of extremity ischemia/reperfusion using circulating, electromyographic (EMG), gate, and histologic measures of injury and limb recovery. METHODS: Sus scrofa swine (n = 6; mean, 83 kg) were randomized to iliac artery occlusion for 0 (control), 1 (1 HR), 3 (3 HR), or 6 (6 HR) hours. Restoration of flow after a standard large-vessel reconstructive technique (thrombectomy, heparin irrigation, and patch angioplasty) was performed in each of the control, 1HR, 3HR, and 6HR animals, whereas one animal had iliac artery segment excision with no restoration (NR) of axial flow. One animal had operative exposure but no intervention on the iliac artery (sham). Animals were recovered and closely monitored for 2 weeks. Indicators of ischemia/reperfusion and functional recovery, including circulating markers, EMG measures (complex motor action potential), and Tarlov gate scoring (0-4; 0, insensate/paralyzed to 4, normal posture and no gait abnormality) were measured at 24 hours and 72 hours and 7 days and 14 days. Muscle (peroneus) and nerve (peroneal) were collected during necropsy at 14 days to assess gross and histologic changes. Duplex ultrasound was performed serially during the recovery period to confirm patency of vascular reconstruction. RESULTS: There were no deaths or failures of vascular reconstruction. Control had a Tarlov score of 4 and normal EMG measures at each point during recovery (same as sham). Tarlov scores at 1, 3, and 14 days recovery in each of the animals were as follows: 1HR: 3, 3, and 4; 3HR: 1, 2, and 4; 6HR: 1, 2, and 3; and NR: 1, 2, and 4. Complex motor action potential as a percentage of baseline at 1, 2, and 14 days recovery was as follows: 1HR: 56%, 55%, and 84%; 3HR: 9%, 8%, and 57%; 6HR: 5%, 5%, and 16%; and NR: 22%, 28%, and 33%. Muscle and nerve histology was the same in sham, control, and 1HR animals. Moderate degeneration and necrosis was observed in peroneus muscle of the 3HR animals. The peroneal nerve in 3HR demonstrated minimal Wallerian degeneration. Severe necrosis was present, as was minimal regeneration, and peroneal nerve demonstrated moderate Wallerian degeneration in 6HR. CONCLUSION: This study reports a new large-animal survival model of extremity ischemia/reperfusion using circulating, functional, and histologic markers of neuromuscular recovery. Findings provide insight into an extremity ischemic threshold after which functional neuromuscular recovery is lost. Additional study is necessary to define this threshold and factors that may move it to a more or less favorable position in the setting of extremity injury.

Early versus delayed restoration of flow with temporary vascular shunt reduces circulating markers of injury in a porcine model.

BACKGROUND: Temporary vascular shunting to restore flow after vascular injury has been advocated. The effectiveness of this adjunct in protecting against ischemic injury has not been established. This study will assess the temporal impact of shunts on ischemic injury and arterial flow. METHODS: A porcine model of hind-limb ischemia via iliac artery occlusion was used (N = 36; weight [kg] +/- SD: 89 +/- 4.4). Animals were randomized into one control (Iscctrl) and four study groups (Isc0, Isc1, Isc3, and Isc6) according to ischemic time. Shunt placement followed ischemia, and flow and circulating injury markers were collected incrementally during 18 hours of reperfusion. Flow proportions and a calculated Ischemia Injury Index were used to characterize group differences. RESULTS: There were no intergroup differences concerning initial weight, hemodynamic, or laboratory values. Shunt patency was 92% in the absence of anticoagulation. The proportion of common femoral arterial flow to baseline flow in the Isc6 group was lower than the Iscctrl group (p = 0.02). There was a similar trend with the Isc1 and Isc3 groups. The Ischemia Injury Index demonstrated that there was a difference in the Isc3 and Isc6 groups (late shunt placement) compared with the Iscctrl, Isc0, and Isc1 groups (early shunt placement) (p < 0.001). CONCLUSION: This study provides physiologic insight into the benefit of shunts in a model of extremity ischemia. Early shunting protects the extremity from further ischemic insult and reduces circulating markers of tissue injury. Additionally, the presence of a shunt does not increase the Ischemic Injury Index and patency is maintained in the absence of heparinization.

A Porcine Orthotopic Forelimb Vascularized Composite Allotransplantation Model: Technical Considerations and Translational Implications.

BACKGROUND: The restoration of complex tissue deficits with vascularized composite allotransplantation is a paradigm shift in reconstructive surgery. Clinical adoption of vascularized composite allotransplantation is limited by the need for systemic immunosuppression, with associated morbidity and mortality. Small-animal models lack the biological fidelity and preclinical relevance to enable translation of immunologic insights to humans. Large-animal models have been described; however, limitations persist, including the inability of heterotopic models to evaluate functional nerve regeneration, and the sensitivity of primates to toxicity of immunosuppressive drugs. The authors' novel orthotopic porcine limb transplant model has broad applicability and translational relevance to both immunologic and functional outcomes after vascularized composite allotransplantation. METHODS: Recipients underwent amputation at a level corresponding to the mid forearm. Replantation or transplantation of grafts was performed by plate fixation of the radio-ulna, microsurgical repair of brachial artery and median nerve, and extensor and flexor tendon repairs. Viability of replants was monitored clinically and radiologically. Transplants were monitored for clinicopathologic signs of rejection. Animals mobilized freely postoperatively. RESULTS: Replantations remained viable until the endpoint of 14 days. Transplants developed Banff grade 4 acute rejection by postoperative day 7. Doppler sonography and angiography confirmed vascular patency. Serial biopsy specimens of skin and histopathology of replants at endpoint confirmed tissue viability and bone healing. CONCLUSIONS: An orthotopic load-bearing porcine forelimb vascularized composite allotransplantation model was successfully established. Technical, procedural, and logistic considerations were optimized to allow model use for immunologic, bone healing, functional nerve regeneration, and other translational studies.

Endovascular Skills for Trauma and Resuscitative Surgery (ESTARS) course: curriculum development, content validation, and program assessment.

BACKGROUND: The management of hemorrhage shock requires support of central aortic pressure including perfusion to the brain and heart as well as measures to control bleeding. Emerging endovascular techniques including resuscitative endovascular balloon occlusion of the aorta serve as potential lifesaving adjuncts in this setting. The Endovascular Skills for Trauma and Resuscitative Surgery (ESTARS) course was developed to provide fundamental endovascular training for trauma surgeons. METHODS: ESTARS 2-day course incorporated pretest/posttest examinations, precourse materials, lectures, endovascular and open vascular instruments, Vascular Intervention System Trainer endovascular simulator, and live animal laboratories for training and testing. Curriculum included endovascular techniques for trauma; review of wires, sheaths, and catheters; as well as regional vascular injury management. Animal laboratories integrated arterial access, angiography, coil embolization, resuscitative endovascular balloon occlusion of the aorta, control of iliac artery injury, and vascular shunt placement. Students completed a knowledge test (precourse/postcourse) and a summative skills assessment. The test measured knowledge and judgment in vascular injury management as defined in the course objectives. Vascular Intervention System Trainer and animal laboratory were used for final examinations. Subjective performance was graded by expert observers using a global assessment scale and performance metrics. RESULTS: Four pilot ESTARS courses were completed, with four participants each. Knowledge and performance significantly improved after ESTARS. Mean test examination scores increased by 77% to 85%, with a mean change of 9 percentage points [paired t (15) = 7.82, p < 0.0001]. The test was unidimensional (Cronbach's α = 0.67). Technical skill significantly improved for both endovascular simulation and live animal laboratory examinations. All participants passed the live animal laboratory practical examination. CONCLUSION: The ESTARS curriculum is effective at teaching a basic set of endovascular skills for resuscitation and hemorrhage control to trauma surgeons. ESTARS was confirmed as a stepwise and hierarchical curriculum demonstrating measurable improvements in performance metrics and should serve as a model for future competency-based structured training in endovascular trauma skills.

Physiologic tolerance of descending thoracic aortic balloon occlusion in a swine model of hemorrhagic shock.

BACKGROUND: Resuscitative endovascular balloon occlusion of the aorta (REBOA) is an emerging technique in trauma; however, the physiologic sequelae have not been well quantified. The objectives of this study were to characterize the burden of reperfusion and organ dysfunction of REBOA incurred during 30 or 90 min of class IV shock in a survivable porcine model of hemorrhage. METHODS: After induction of shock, animals were randomized into 4 groups (n = 6): 30 min of shock alone (30-Shock) or with REBOA (30-REBOA) and 90 min of shock alone (90-Shock) or with REBOA (90-REBOA). Cardiovascular homeostasis was then restored with blood, fluid, and vasopressors for 48 h. Outcomes included mean central aortic pressure (MCAP), lactate concentration, organ dysfunction, histologic evaluation, and resuscitation requirements. RESULTS: Both REBOA groups had greater MCAPs throughout their shock phase compared to controls (P < .05) but accumulated a significantly greater serum lactate burden, which returned to control levels by 150 min in the 30-REBOA groups and 320 min in the 90-REBOA group. There was a greater level of renal dysfunction and evidence of liver necrosis seen in the 90-REBOA group compared to the 90-Shock group. There was no evidence of cerebral or spinal cord necrosis in any group. The 90-REBOA group required more fluid resuscitation than the 90-Shock group (P = .05). CONCLUSION: REBOA in shock improves MCAP and is associated with a greater lactate burden; however, this lactate burden returned to control levels within the study period. Ultimately, prolonged REBOA is a survivable and potentially life-saving intervention in the setting of hemorrhagic shock and cardiovascular collapse in the pig.

A novel fluoroscopy-free, resuscitative endovascular aortic balloon occlusion system in a model of hemorrhagic shock.

BACKGROUND: Resuscitative endovascular balloon occlusion of the aorta (REBOA) is a potentially lifesaving maneuver in the setting of hemorrhagic shock. However, emergent use of REBOA is limited by existing technology, which requires large sheath arterial access and fluoroscopy-guided balloon positioning. The objectives of this study were to describe a new, fluoroscopy-free REBOA system and to compare its efficacy to existing technology. An additional objective was to characterize the survivability of 60 minutes of REBOA using these systems in a model of hemorrhagic shock. METHODS: Swine (70-88 kg) in shock underwent 60 minutes of REBOA using either a self-centering, one component prototype balloon system (PBS, n = 8) inserted (8 Fr) and inflated without fluoroscopy or a two-component, commercially available balloon system (CBS, n = 8) inserted (14 Fr) with fluoroscopic guidance. Following REBOA, resuscitation occurred for 48 hours with blood, crystalloid, and vasopressors. End points included accurate balloon positioning, hemodynamics, markers of ischemia, resuscitation requirements, and mortality. RESULTS: Posthemorrhage mean arterial pressure (mm Hg) was similar in the CBS and PBS groups (35 [8] vs. 34 [5]; p = 0.89). Accurate balloon positioning and inflation occurred in 100% of the CBS and 88% of the PBS group. Following REBOA, mean arterial pressure increased comparably in the CBS and PBS groups (81 [20] vs. 89 [16]; p = 0.21). Lactate peaked in the CBS and PBS groups (10.8 [1.4] mmol/L vs. 13.2 [2.1] mmol/L; p = 0.01) 45 minutes following balloon deflation but returned to baseline by 24 hours. Mortality was similar between the CBS and PBS groups (12% vs. 25%, p = 0.50). CONCLUSION: This study reports the feasibility and efficacy of a novel, fluoroscopy-free REBOA system in a model of shock. Despite a significant physiologic insult, 60 minutes of REBOA is tolerated and recoverable. Development of lower profile, fluoroscopy-free endovascular balloon occlusion catheters may allow proactive aortic control in patients at risk for hemorrhagic shock and cardiovascular collapse.

Endovascular balloon occlusion of the aorta is superior to resuscitative thoracotomy with aortic clamping in a porcine model of hemorrhagic shock.

BACKGROUND: Noncompressible torso hemorrhage is the leading cause of potentially preventable death on the modern battlefield. The objective of this study is to characterize resuscitative aortic balloon occlusion (BO) compared to thoracotomy with aortic clamping in a model of hemorrhagic shock. METHODS: A total of 18 swine (3 groups; 6 animals/group) were used in this study. Swine in class IV shock underwent no aortic occlusion (NO), thoracotomy and clamp occlusion (CO), or endovascular BO. Animals in the NO group underwent direct placement of a temporary vascular shunt (TVS) at the injury site, whereas animals in the CO and BO groups underwent aortic occlusion before TVS placement. Hemodynamic and physiologic measures were collected. RESULTS: The central aortic pressure, carotid blood flow and brain oxygenation as measured by oximetry increased in the CO and BO groups compared to the NO group (P < .05). During resuscitation, the BO group was less acidotic than the CO group (pH,7.35 vs 7.24; P < .05) with a lower serum lactate level (4.27 vs 6.55; P < .05) and pCO2 level (43.5 vs 49.9; P < .05). During resuscitation, the BO group required less fluid (667 mL vs 2,166 mL; P < .05) and norepinephrine (0 mcg vs 52.1 mcg; P < .05) than the CO group. CONCLUSION: Resuscitative aortic BO increases central perfusion pressures with less physiologic disturbance than thoracotomy with aortic clamping in a model of hemorrhagic shock. Endovascular BO of the aorta should be explored further as an option in the management of noncompressible torso hemorrhage.