Temporary vascular shunts

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.

Contemporary management and time to revascularization in upper extremity arterial injury

INTRODUCTION

Upper extremity arterial injury is associated with significant morbidity and mortality for trauma patients, but there is a paucity of data to guide the clinician in the management of these injuries. The goals of this review were to characterize the demographics, presentation, clinical management, and outcomes, and to evaluate how time to intervention associates with outcomes in trauma patients with upper extremity vascular injuries.

METHODS

The National Trauma Data Bank (NTDB) Research Data Set for the years 2007-2016 was queried in order to identify adult patients (age ≥ 18) with an upper extremity arterial injury. Patients with brachiocephalic, subclavian, axillary, or brachial artery injury using the 1998 and 2005 versions of the Abbreviated Injury Scale were included. Patients with non-survivable injuries to the brain, traumatic amputation, or other major arterial injuries to the torso or lower extremities were excluded.

RESULTS

The data from 7908 patients with upper extremity arterial injuries was reviewed. Of those, 5407 (68.4%) underwent repair of the injured artery. The median Injury Severity Score (ISS) was 10 (IQR = 7-18), and 7.7% of patients had a severe ISS (≥ 25). Median time to repair was 120 min (IQR = 60-240 min). Management was open repair in 52.3%, endovascular repair in 7.3%, and combined open and endovascular repairs in 8.8%; amputation occurred in 1.8% and non-operative management was used in 31.6% of patients. Blunt mechanism of injury, crush injury, concomitant fractures/dislocations, and nerve injuries were associated with amputation, whereas simultaneous venous injury was not. There was a significant decrease in the rate of amputation when patients undergoing surgical revascularization did so within 90 min of injury (P = 0.007).

CONCLUSION

Injuries to arteries of the upper extremity are managed with open repair, endovascular repair, and, rarely, amputation. Expeditious transport to the operating room for revascularization is the key for limb salvage.

Update in combined musculoskeletal and vascular injuries of the extremities

Combined musculoskeletal and vascular injuries of the extremities are conditions in which a multidisciplinary approach is a sine qua non to ensure life initially and limb viability secondarily. Vascular injuries as part of musculoskeletal trauma are usually the result of the release of a high energy load in the wound site so that the prognosis is determined by the degree of soft-tissue damage, duration of limb ischemia, patient’s medical status and presence of associated injuries. The management of these injuries is challenging and requires a specific algorithm of action, because they are usually characterized by increased morbidity, amputation rate, infection, neurological and functional deficits, and they could be life threatening. Although vascular injuries are rare and occur either isolated or in the context of major combined musculoskeletal trauma, the high index of suspicion, imaging control, and timely referral of the patient to organized trauma centers ensure the best functional outcome of the extremity in such challenging cases. Even after a successful initial treatment of a combined trauma pattern, long-term follow-up is crucial to prevent and detect early possible complications. The purpose of this manuscript is to provide an update on diagnosis and treatment of combined musculoskeletal and vascular injuries of the extremities, from an orthopedic point of view.

Long-term intra-arterial shunt

This is a case report of a patient who sustained a stab wound to the right axilla with injuries to the right axillary artery and vein. The patient had near-exsanguination in the field and no recordable blood pressure upon admission to the trauma center. Resuscitation was performed with endotracheal intubation, a left anterolateral resuscitative thoracotomy with cross-clamping of the descending thoracic aorta, and the rapid infusion of crystalloid solutions and packed red cells. In the operating room, the third portion of the right axillary artery and the adjacent right axillary vein were found to be transected. As part of a ‘damage control’ procedure, the ends of the right axillary vein were ligated. A 14 French intra-arterial shunt was inserted into the transected ends of the right axillary artery to restore the flow to the right upper extremity. The patient’s postoperative course was complicated by a coagulopathy, adult respiratory distress syndrome (ARDS), and anuria. The coagulopathy and anuria resolved within the first 48 hours, but the patient’s ARDS was slow to resolve. On the 10th postinjury day, the patient was returned to the operating room for a definitive repair of the right axillary artery. After the intra-arterial shunt was removed, a reversed greater saphenous vein graft was inserted between the ends of the right axillary artery in a medial intermuscular (extra-anatomic) tunnel. The patient made an uneventful recovery and was discharged home on the 16th postinjury day.

The following principles of advanced trauma care were part of the management of this patient: (1) occasional need for resuscitative thoracotomy with cross-clamping of the descending thoracic aorta in a patient without a thoracic injury; (2) ‘damage control’ operation with ligation of the right axillary vein and placement of a temporary intra-arterial shunt to restore the flow to the right upper extremity; and (3) vascular reconstruction with an extra-anatomic bypass in a previously contaminated field.

Development of a Puncture Technique for Implanting Temporary Vascular Shunts in a Porcine Model

BACKGROUND

Temporary vascular shunts (TVSs) are an effective tool for rapidly restoring blood flow to a limb or organ that has experienced vascular injury and ischemia and for which revascularization is not an immediate option. Usually, through an opening in the skin, the TVS is positioned within the proximal and distal stumps of the injured vessel, restoring perfusion and stopping the ischemia. The aim of this study is to compare standard TVS technique and a developed puncture technique for implanting TVS and to evaluate the utility and feasibility of this protocol after arterial lesions, in pigs.

METHODS

Vascular injuries were inflicted in both hind limbs of 30 pigs, and vascular interventions were performed, using standard and puncture TVS. Because each pig was implanted with both types of TVSs, it was possible to simultaneously monitor, analyze, and compare parameters such as, the mean arterial pressure (MAP, in mm Hg), blood flow (mL/min), and insertion times, in the same animal.

RESULTS

It was observed that the MAP in the limbs recovered and approached systemic MAP, in 100% of the experiments, in both groups. Analysis of the blood flow data showed that this parameter was significantly reduced in the puncture TVS group (110.36 ± 9.99 mL/min vs. 153.20 ± 18.57 mL/min, P = 0.001). On the other hand, the insertion time for the standard TVS was significantly greater than that of the puncture shunt (15.32 ± 3.08 min vs. 10.37 ± 1.7 min, P = 0.001). Furthermore, it was found that the primary and secondary patency and complication rates were similar for both TVS types.

CONCLUSION

Thus, given the adequate MAP recovery and reduction in implantation time observed in this experimental and in an animal model study, the use of the puncture TVS technique is effective and feasible.

For the patient-Evolution in the management of vascular trauma

There has been an evolution in the diagnosis and management of vascular trauma over the past 100 years. The primary stimulus to these changes has been the increased volume of patients with cervical, truncal, and peripheral vascular injuries during military conflicts and in civilian life. Patients with "hard" signs of a vascular injury are taken to surgery emergently with a few exceptions to be described. In contrast, patients with "soft" signs of a vascular injury undergo a careful physical examination including measurement of vascular index to determine if radiologic imaging is necessary. Computed tomography arteriography has become the most commonly used method of imaging, whereas duplex ultrasonography is used in some centers. Nonoperative management is now common for nonocclusive injuries diagnosed on computed tomography arteriography. Proximal tourniquets are commonly used to control exsanguinating hemorrhage from injuries to extremities, whereas balloons can be used to control hemorrhage from difficult to expose areas at operation. Temporary intraluminal shunts are now used in 3% to 9% of arterial injuries. Operative techniques of repair have been refined and contribute to the excellent results noted in modern trauma centers.

Pitfalls in the management of peripheral vascular injuries

Over the past 65+ years, most civilian peripheral vascular injuries have been managed by trauma surgeons with training or experience in vascular repair or ligation. This is appropriate as the in-hospital trauma team is immediately available, and there are often other injuries present in the victim.

The pitfall to avoid during evaluation of the patient in the emergency center is a missed diagnosis. In the patient without ‘hard’ signs of a peripheral vascular injury, a careful history (bleeding), physical examination including measurement of ankle–brachial (ABI) or brachial–brachial index and liberal use of CT arteriography depending on an ABI <0.9 should essentially make the diagnosis if an arterial injury is present.

At operation, one pitfall is to limit skin preparation and draping, thereby eliminating the option of removing the greater saphenous vein if needed as a conduit from either the groin or ankle of an uninjured lower extremity. Another pitfall is to make a full longitudinal incision directly over a large pulsatile hematoma. Rather, separate shorter longitudinal incisions should be made to obtain proximal and distal vascular control before entering the hematoma. The failure to recognize patients who should be managed initially with insertion of a temporary intraluminal shunt is a major pitfall as well. Not following time-proven and results-proven ‘fine techniques’ of operative repair is another major pitfall. Such techniques include the following: use of small angioaccess vascular clamps or silastic vessel loops; passage of proximal and distal Fogarty catheters; administration of regional or systemic heparin during complex repairs; an open anastomosis technique; and completion arteriography after a complex arterial repair in a lower extremity.

Avoiding pitfalls should allow for success in peripheral vascular repair, particularly since most patients are young with non-diseased vessels.

Temporary arterial shunts in damage control: Experience and outcomes

BACKGROUND

Arterial shunting is a well-described method to control hemorrhage and rapidly reestablish flow, but optimal shunt dwell times remain controversial. We hypothesized that prolonged shunt dwell times of more than 6 hours are related to adverse outcomes after major arterial injury.

METHODS

A review (2005-2013) of all patients with arterial shunts placed after traumatic injury at our urban Level I trauma center was undertaken. Patients who died prior to shunt removal (n = 7) were excluded. Shunt complications were defined as dislodgement, thrombosis, and distal ischemia. Patients were compared on the basis of shunt complications with respect to clinical parameters.

RESULTS

The 42 patients who underwent arterial shunting after major vascular injury were primarily young (median, 26 years; interquartile range [IQR], 22-31 years) males (97.6%), severely injured (Injury Severity Score, 17.5 [IQR, 14-29]; shunted vessel Abbreviated Injury Scale score, 4 [IQR, 3-4]) by gunshot (85.7%) requiring neck/torso (33.3%) or upper-extremity (19.1%) or lower-extremity (47.6%) shunts. Thirty-five patients survived until shunt removal, and 5 (14.3%) of 35 developed shunt complications. Demographics and clinical characteristics were compared between those with shunt dwell times of less than 6 hours (n = 19) and more than 6 hours (n = 16). While patients appeared to have a greater injury burden overall in the group with dwell times of more than 6 hours, there were no statistical differences between groups with respect to age, gender, initial systolic blood pressure or hemodynamics during the shunt dwell period, use of vasopressors, Abbreviated Injury Scale score of the shunted vessel, Injury Severity Score, or outcomes including limb amputation or mortality. No patients (0/19) with shunt dwell times of less than 6 hours developed complications, whereas 5 (31.3%) of 16 patients with dwell times of more than 6 hours developed shunt complications (p = 0.05).

CONCLUSIONS

In this civilian series, 14% of patients with arterial shunts developed shunt complications. Our data suggest that limiting shunt dwell times to less than 6 hours when clinically feasible may decrease adverse outcomes.

LEVEL OF EVIDENCE

Therapeutic/care management study, level IV.

Vascular Injury in Orthopedic Trauma

Vascular injury in orthopedic trauma is challenging. The risk to life and limb can be high, and clinical signs initially can be subtle. Recognition and management should be a critical skill for every orthopedic surgeon. There are 5 types of vascular injury: intimal injury (flaps, disruptions, or subintimal/intramural hematomas), complete wall defects with pseudoaneurysms or hemorrhage, complete transections with hemorrhage or occlusion, arteriovenous fistulas, and spasm. Intimal defects and subintimal hematomas with possible secondary occlusion are most commonly associated with blunt trauma, whereas wall defects, complete transections, and arteriovenous fistulas usually occur with penetrating trauma. Spasm can occur after either blunt or penetrating trauma to an extremity and is more common in young patients. Clinical presentation of vascular injury may not be straightforward. Physical examination can be misleading or initially unimpressive; a normal pulse examination may be present in 5% to 15% of patients with vascular injury. Detection and treatment of vascular injuries should take place within the context of the overall resuscitation of the patient according to the established principles of the Advanced Trauma Life Support (ATLS) protocols. Advances in the field, made mostly during times of war, have made limb salvage the rule rather than the exception. Teamwork, familiarity with the often subtle signs of vascular injuries, a high index of suspicion, effective communication, appropriate use of imaging modalities, sound knowledge of relevant technique, and sequence of surgical repairs are among the essential factors that will lead to a successful outcome. This article provides a comprehensive literature review on a subject that generates significant controversy and confusion among clinicians involved in the care of trauma patients. [Orthopedics. 2016; 39(4):249-259.].