Gabriel E. Burkhardt

The Epidemiology of Vascular Injury in the Wars in Iraq and Afghanistan

Background:Blood vessel trauma leading to hemorrhage or ischemia presents a significant cause of morbidity and mortality after battlefield injury. The objective of this study is to characterize the epidemiology of vascular injury in the wars of Iraq and Afghanistan, including categorization of anatomic patterns, mechanism, and management of casualties. Methods:The Joint Theater Trauma Registry was interrogated (2002–2009) for vascular injury in US troops to identify specific injury (group 1) and operative intervention (group 2) groups. Battle-related injuries (nonreturn to duty) were used as the denominator to establish injury rates. Mechanism of injury was compared between theaters of war and the management strategies of ligation versus revascularization (repair and interposition grafting) reported. Results:Group 1 included 1570 Troops injured in Iraq (OIF) (n = 1390) and Afghanistan (OEF) (n = 180). Mechanism included explosive (73%), gunshot (27%), and other (<1%) with explosive more common in OIF than OEF (P < 0.05). During this period, 13,076 battle-related injuries occurred resulting in a specific rate of 12% (1570 of 13,076), which was higher in OIF than OEF (12.5% vs 9% respectively; P < 0.05). Of group 1, 60% (n = 940) sustained injury to major or proximal vessels and 40% (n = 630) to minor or distal vessels (unknown vessel, n = 27). Group 2 (operative) comprised 1212 troops defining an operative rate of 9% (1212 of 13,076) and included ligation (n = 660; 54%) or repair (n = 552; 46%). Peak rates in OIF and OEF occurred in November 2004 (15%) and August 2009 (11%), respectively and correlated with combat operational tempo. Conclusion:The rate of vascular injury in modern combat is 5 times that reported in previous wars and varies according to theater of war, mechanism of injury and operational tempo. Methods of reconstruction are now applied to nearly half of the vascular injuries and should be a focus of training for combat surgery. Selective ligation of vascular injury remains an important management strategy, especially for minor or distal vessel injuries.

Effect of temporary shunting on extremity vascular injury: An outcome analysis from the Global War on Terror vascular injury initiative

OBJECTIVE Extremity vascular injury during the current war has been defined by anecdotal description and case series. These reports focused on estimation of short-term limb viability and technical description of commonly used adjuncts. Temporary vascular shunting (TVS) has been advocated in current care structures, yet mostly due to war environments, broader statistical scrutiny is lacking. This studys purpose is to provide perspective on TVSs impact on limb salvage, and estimate longer-term freedom from amputation. METHODS Data from the Joint Theater Trauma Registry (JTTR), Balad Vascular Registry (BVR), Walter Reed Vascular Registry (WRVR), electronic medical records, and patient interviews were collected on American Troops sustaining extremity vascular injury from June 2003 through December 2007. Those in whom arterial TVS utilization was identified comprise the TVS group. These were compared with controls with similar injury date and anatomic location managed without TVS. Descriptive statistics were employed establishing overall univariate predictors of amputation and comparison between groups. Proportional-hazards modeling, with propensity score adjustment for systemic injury severity and Level 2 care, characterized risk factors of limb loss and effect of TVS. Freedom from amputation was estimated using Kaplan Meier log-rank methods. RESULTS Cases and controls consisted of 64 and 61 extremity arterial injuries, respectively. Mean follow-up was 22 months (range: 1-54 months). The TVS group was more severely injured (mean injury severity score [ISS]: 18 [SD = 10] TVS vs. 15 [SD = 10] control, P = .05) and more likely to receive Level 2 care (TVS: 26%; control: 10%, P = .02). Overall, a total of 26 amputations occurred (21%). Penetrating blasts, compared with gunshot wounds, were associated with amputation (30% vs. 6%, P = .002). After propensity score adjustment, use of TVS suggested a reduced risk of amputation (relative risk [RR] = 0.47; 95% confidence interval [CI] [0.18-1.19]; P = .11). Venous repair was associated with limb salvage (RR = 0.2; 95% CI [0.04-0.99], P = .05). Associated fracture (RR = 5.0; 95% CI [1.45-17.28], P = .01), and elevated mangled extremity severity score (MESS) ([MESS 5-7] RR = 3.5, 95% CI [0.97-12.36], P = .06; [MESS 8-12] RR = 16.4; 95% CI (3.79-70.79), P < .001) predicted amputation. Amputation-free survival was 78% in the TVS group and 77% in the control group at three years (P = .5). CONCLUSION Temporary vascular shunting used as a damage control adjunct in management of wartime extremity vascular injury does not lead to worse outcomes. Benefit from TVS is suggested, but not statistically significant. Injury specific variables of venous ligation, associated fracture, and penetrating blast mechanism are associated with amputation. Amputation-free survival after vascular injury in Operation Iraqi Freedom is 79% at three years. Further studies to statistically define any possible benefits of TVS are needed.

Hemorrhagic shock worsens neuromuscular recovery in a porcine model of hind limb vascular injury and ischemia-reperfusion

BACKGROUND In order to advance beyond basic statistical limb salvage to improved functional or quality limb salvage, a better understanding of the ischemic threshold of the limb is required. To date, models of extremity ischemia and reperfusion involve small animals and few include survival with physiologic measures of nerve and muscle recovery. In addition, the effect of hemorrhagic shock on the ischemic threshold of the extremity is unknown. This study characterized the effect of class III hemorrhagic shock on the ischemic threshold of the extremity in a large-animal model of neuromuscular recovery. METHODS Yorkshire/Landrace-cross swine (weight, 70-90 kg) were randomized to iliac artery repair either immediately or at 1, 3, or 6 hours after vessel loop occlusion and arteriotomy. A fifth group underwent excision of the arterial segment without repair to represent ligation. Class III shock was created by removing 35% of total blood volume using a variable rate model. Animals were monitored for 14 days to serially collect markers of functional recovery. RESULTS Animals with ≤1 hour ischemia (control) had clinically normal limb function by the end of the 2-week observation period, with minimal muscle and nerve changes on histology. Separate analysis of contralateral, nonexperimental limbs revealed normal histology and function. After 3 hours of ischemia, functional recovery was impaired, with moderate-to-severe degeneration of nerve and muscle noted on histology. Animals undergoing 6 hours of ischemia or ligation had minimal electromyelography response and severe systemic inflammation, which correlated with severe muscle and nerve degeneration. Concurrent class III hemorrhagic shock was associated with a decrement in neuromuscular recovery across all groups but was greatest in groups undergoing ≥3 hours of extremity ischemia (P < .01). CONCLUSIONS This study demonstrates the feasibility of combined hemorrhagic shock and extremity ischemia-reperfusion in a large-animal survival model. The presence of hemorrhagic shock compounds the effect of extremity ischemia, reducing the ischemic threshold of the limb to <3 hours. Strategies to improve functional salvage after extremity vascular injury in the setting of shock should include attempts at restoration of flow ≤60 minutes.

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.

Endovascular treatment of a blunt aortic injury in Iraq: extension of innovative endovascular capabilities to the modern battlefield.

BACKGROUND The management of blunt descending thoracic aortic injury remains controversial. Despite emerging evidence touting the advantage of endovascular repair in civilian trauma, there have been no reports on the application of this management strategy in the austere environment of war. We provide a case report from the 332nd EMDG/Air Force Theater Hospital, Balad Air Base, Iraq. METHODS An Iraqi policeman presented with traumatic aortic disruption following blunt trauma. The patient arrived with hemoperitoneum, a Le Fort III facial fracture, a left humerus fracture, and a thoracic aortic disruption. Following facial packing, fracture stabilization, and damage control laparotomy, aortography was performed, confirming aortic disruption beyond the left subclavian artery. The injury was treated with three aortic cuffs (Gore Excluder AAA Aortic Extender Endoprostheses) placed in sequence from the origin of the left subclavian across the disruption. A type III endoleak was successfully managed with placement of one additional aortic cuff. RESULTS The patient was discharged after 1 month following the successful treatment of his other injuries. Computed tomography angiography at 10 and 30 days following the procedure revealed no endoleak and a resolved periaortic hematoma. CONCLUSION This report details the first endovascular treatment of blunt aortic injury in wartime and represents a sustained commitment to advance innovative endovascular capability closer to the time of injury. Although controversial, this less invasive approach is appealing in patients with high injury severity scores, making its availability in wartime especially germane.

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.

Temporal changes of aortic neck morphology in abdominal aortic aneurysms

OBJECTIVES This study characterized temporal changes in the infrarenal aortic aneurysm neck in patients with small, untreated abdominal aortic aneurysms (AAA). METHODS Patients with infrarenal AAA who had contrast-enhanced computed tomography (CT) scans separated by >6 months were identified and their images reviewed. Infrarenal neck diameter and length were measured along with aneurysm diameter. Comparisons between the interval CT scans were made and analysis of factors affecting neck changes performed. RESULTS Sixty patients met inclusion criteria with an imaging interval of 3.8 years (median, 3.4 years; range, 0.75-9.6 years). During the interval, there was an increase in proximal and distal neck diameters of 1.1 mm (SD, 2.2) (0.28 mm/y) and 1.0 mm (SD, 3.0) (0.26 mm/y), respectively. During the same interval, the neck length decreased by 4 mm (SD, 11) (1 mm/y). A neck length of <15 mm was present in 10 patients (17%) at the initial imaging. Four of the remaining 50 patients experienced an interval decrease in neck length to <15 mm, all of whom had initial lengths of 15 to 20 mm. Medications had no association with changes in neck morphology; however, diabetes correlated with a slower rate of neck shortening (P = .001). CONCLUSION The natural history of the aneurysm neck is one of expansion and shortening that will not affect most patients under surveillance. Patients with marginal neck lengths (range, 15-20 mm) at the initial imaging are more likely to experience loss of neck length that may negatively affect endovascular suitability.