Chapter 1 Vascular Trauma: General Principles

This chapter will review the general principles of vascular injuries to the extremities and torso. Historical consideration, etiology, diagnosis, and principles of management will be presented.

Learning Objectives

By the end of the ASSET course, participants should be able to do the following:

1. Discuss the historical aspects of vascular injury and the influence of military surgical experience on modern care.
2. Describe the types of injury to extremity and torso vasculature that require surgical intervention.
3. List the hard and soft signs used to decide the further management of extremity vascular injuries.
4. Describe the role of adjunctive imaging techniques in the management of vascular injury.
5. Relate the immediate and delayed consequences of vascular injury.
6. Discuss which vessels can be safely ligated.
7. Describe the role of tourniquets and hemostatic agents in the management of vascular trauma.
8. Describe the indications and techniques for temporary shunting of blood vessels.
9. Discuss the basic principles of vascular repair and bypass.

Introduction

• Extremity vascular injuries have been documented as far back as classical Greece and Rome, with amputation being the most likely result.
• Many of our current management principles for the treatment of extremity vascular trauma come from military experience:
  • During World War II, extremity arterial injuries were routinely ligated, with a resultant amputation rate of 73 percent for popliteal injuries.
  • Hughes and Spencer performed formal repair of vascular injuries during the Korean War.
  • Rich and associates further refined arterial repair during the Vietnam War, with the amputation rate for popliteal injuries decreasing to 32 percent.
  • Modern civilian series report amputation rates of 3–7 percent.
  • Recent conflicts in Iraq and Afghanistan, as well as recent civilian mass casualty events, have established the benefits of liberal use of tourniquets and shunting of vessels for damage control.
• Prompt recognition and management of arterial hemorrhage is essential to obtaining optimal outcomes.

Etiology

• Penetrating injuries from the following mechanisms:
  • Gunshots
  • Knives
  • Industrial incidents (e.g., nail gun injuries)
  • Iatrogenic (vascular access procedures)
• Blunt injuries from the following mechanisms:
  • Motor vehicle crashes
  • Falls/crush incidents
  • Assault
• Fractured long bones or dislocated joints are frequently associated with vascular injury.
• Posterior knee dislocation is associated with injury to the popliteal artery.
• The incidence of extremity vascular injuries varies with the affected vessels and is as follows, in descending order: femoral > brachial > popliteal > radial and ulnar > tibioperoneal vessels.

Pathophysiology

• The vascular tree (both arterial and venous) appears to have some natural protection from stretching and bending; therefore, there are fewer vascular injuries associated with blunt injury.
• The smooth muscle of the arterial media layer protects from both stretch-type injuries and minor puncture wounds, which heal spontaneously in most cases.
• When an artery is transected, vascular spasm and low systemic pressure appear to promote clotting at the site of the injury. Spasm may limit the amount of bleeding. Aggressive fluid resuscitation may dislodge this clot and should be avoided until control of hemorrhage is achieved. In the absence of traumatic brain injury, permissive hypotension should be considered until bleeding is controlled.
• The immediate consequences of vascular injury are hemorrhage and acute ischemia:
  • Ischemia results from interruption of blood flow.
  • Oxygen supply is inadequate to meet demand, and anaerobic metabolism ensues with associated lactic acidosis.
  • Cellular and humoral inflammatory pathways are activated, and cell death occurs if blood flow is not reestablished in time.
  • Skeletal muscle can withstand ischemia for three to six hours and still recover function.
  • Peripheral nerves are more sensitive to ischemia and may suffer irreversible damage after lesser times of ischemia.
  • Compartment syndrome develops, as discussed in chapter 5.
• Delayed presentations of vascular injury include the following:
  • Delayed ischemia can result from arterial thrombosis or compartment syndrome.
  • Arteriovenous fistula occurs when an artery and an adjacent vein are both injured and arterial blood finds its way directly into the venous circulation.
  • Partial disruption of an artery leads to a hematoma and formation of a pseudoaneurysm, which may present in a delayed fashion.
• If arterial supply is restored to ischemic tissue, the sudden release of inflammatory mediators can precipitate both local and systemic inflammatory response (reperfusion injury).
• In the case of reperfusion of a large mass of ischemic tissue, liberation of intracellular potassium and hydrogen ions can result in cardiac dysrhythmia and cardiovascular collapse.

Diagnosis

• The diagnosis of significant vascular injury is, by and large, made on physical exam looking for «hard» and «soft» signs of injury.
• The «hard signs» of vascular injury mandate immediate action:
  • Observed pulsatile bleeding
  • Visible expanding hematoma
  • Signs of distal ischemia (absent distal pulses; cold, pale limb)
  • Palpable thrill (vibration) by manual palpation
  • Audible bruit over or near the artery by auscultation
• The «soft signs» of vascular injury should prompt further diagnostic evaluation or continued close observation:
  • A history of significant hemorrhage at the scene
  • Proximity of the penetrating wound, bony injury, or blunt trauma to a major artery
  • Decreased pulse compared with the uninjured extremity
  • Peripheral nerve deficit
  • Small nonpulsatile hematoma
  • Abnormal (<0.9) ankle-brachial index (ABI)
  • Abnormal flow-velocity waveform on Doppler ultrasound
  • Shock that is not the result of other injuries
• The physical exam is augmented by measurement of the ABI, arterial pressure index, or injured extremity index.
  • Patients with penetrating or blunt injury, normal extremity pulse, and an ABI of 1.0 or more are very unlikely to have a significant arterial injury and need no further evaluation except observation.
  • Most authors advocate observation for ABI > 0.9 and further evaluation for values below 0.9.
• Vascular injuries must be suspected with the following orthopaedic injuries:
  • Clavicular fracture—subclavian artery
  • Shoulder dislocation—axillary artery
  • Supracondylar humerus fracture— brachial artery
  • Femur fracture—superficial femoral artery
  • Posterior knee dislocation—popliteal artery

Diagnostic Adjuncts

• Doppler ultrasound
  • The presence of a Doppler signal in a pulseless limb can provide a false sense of security and does not imply an absence of significant vascular injury.
• Duplex ultrasound is highly operator dependent, but in the right hands, it can detect the following:
  • Arterial disruption or occlusion
  • Intimal flaps
  • Venous occlusion
  • Hematoma
  • Pseudoaneurysm
  • Arteriovenous fistula
• Pulse oximetry—the reduction in oximeter readings from one limb to another—is suggestive of, but neither confirms nor excludes significant vascular injury.
• Plain films are helpful as a rapid means of determining the presence of fractures and foreign bodies.
• CT angiography (CTA) has evolved into a highly sensitive and specific modality for identification and characterization of vascular injury. It has become the initial diagnostic modality of choice in most patients with suspected vascular injury. The sensitivity of this study for vascular injury is dependent on the protocol of contrast administration and image acquisition.
• Angiography
  • Angiography has long been considered the gold standard for identification and characterization of vascular injury. Angiographic images are less significantly impacted than CTA by the presence of foreign bodies and also provide real-time indication of flow patterns in the imaged arterial segment.
  • Angiography can also be therapeutic with endovascular techniques used to manage vascular injury if expertise and facilities are present.

Management: Immediate Control of Hemorrhage

• Apply direct pressure over the site of injury.
• Avoid large, bulky dressings.
• Tourniquets should be used if bleeding cannot be controlled with direct pressure or wound packing (Figure 1).
  • The use of tourniquets in recent conflicts has shown significant reduction in mortality, and their use is becoming commonplace in civilian prehospital care.
  • Tourniquets should be considered for initial intervention in patients with traumatic amputation and/or severe hemorrhage.
  • All health care providers should have a working knowledge on how to both apply and remove tourniquets.
• Blind clamping or probing in the depths of wounds is dangerous, likely to fail, and may injure other structures.
• A number of field dressings containing a variety of hemostatic agents have been approved for human use and are useful adjuncts for hemorrhage control.

Figure 1. Tourniquets have been applied to the lower legs of the two patients seen here to control active arterial hemorrhage as a result of blast injury (left) and a stab wound (right).

Volume Resuscitation

• Prior to hemorrhage control, fluid resuscitation should be judicious (permissive hypotension), as raising blood pressure may «pop the clot,» resulting in more bleeding and dilution of clotting factors.
• Two large-bore IVs should be placed in anticipation of resuscitation after hemorrhage control.
• After hemorrhage control is achieved, aggressive and balanced resuscitation with blood products should occur as necessary.

Operative Strategy/Considerations

• Vascular reconstruction (or restoration of flow with shunting) that occurs within three hours of injury is generally accepted to have the best outcome.
• The patient must be properly positioned on the operating table to allow on-table angiogram, exposure of all relevant vessels, and harvesting of vein grafts.
• The distal extremity (hand or foot) must also be prepped into the field as indicated to allow for assessment of distal perfusion
• The basic principle of all vascular surgery is attaining proximal and distal control of a vessel prior to exploring the injury. Obtaining both proximal and distal control may require separate incisions.
• Keep in mind that tourniquets can provide proximal control (Figure 1).
• Though it may be tempting to directly explore a wound that is not actively bleeding, this can dislodge a clot from the injury and result in profuse hemorrhage that obscures the field. So … «Don’t poke a skunk!»
• Control is best achieved by vessel loops passed twice around the vessel. If clamps are used, they should be atraumatic and applied with a minimum of force.
• In some circumstances, intraarterial balloon occlusion (e.g., Fogarty or REBOA) can be used to gain control.
• Selected use of balloon tamponade is useful for temporary control of hemorrhage from junctional or deep, difficult-to-access areas.
• Venous bleeding is more easily controlled with pressure than with loops or clamps.
• Large veins should be repaired (or shunted), and small veins can be ligated. The rule of thumb is that if the vein is tense, it should be repaired.
• In the setting of polytrauma with physiologic compromise, or if the surgeon is not experienced in vascular repairs, the default should be damage control shunting.
• If it is elected to repair the injury, the technique chosen will depend on the extent of damage to the vessel and the expertise of the surgeon.
• The first step is to debride devitalized tissue and define the edges of the wound.
• Next, an assessment of inflow and outflow is made. If flow is inadequate, a balloon (Fogarty) catheter is passed proximally and distally to extract any thrombus. 10–15 mL heparinized saline at 50 units/mL can be used to flush vessels distal and proximal to the injury for regional anticoagulation.
• Systemic anticoagulation should be avoided in patients with polytrauma.
• All vascular repairs should be followed by an assessment of the repair site, bypass, and distal perfusion. The repair or graft can be evaluated with duplex ultrasound or angiography. Consider performing angiography of the distal outflow prior to repair in order to identify potential thromboemboli.
• Completion arteriography is performed using a small angiocatheter puncturing the artery proximal to the anastomosis. Contrast dye is rapidly injected followed by either real-time fluoroscopic images or a “one-shot” plain X ray.
• Baseline Doppler signals should be documented following repair, and the location of the signal should be marked on the skin so that others may easily perform routine vascular checks.
• The patient should be assessed for development of compartment syndrome. Pain with certain movements, particularly passive stretching of the muscles, is the earliest clinical indicator of compartment syndrome (see chapter 5).
• Fasciotomy should be used early and liberally.

Temporary Vascular Shunting

• Temporary vascular shunting is a damage control technique that should be considered for the following circumstances:
  • In a patient who has developed the lethal triad of trauma (acidosis, hypothermia, and coagulopathy), to allow time for stabilization in the ICU prior to definitive repair
  • To allow for the initial repair of orthopaedic injuries prior to definitive vascular repair
  • As a temporizing measure to allow transfer to a higher level of care with the required resources and expertise to perform definitive repair
  • In multiple casualty events when operative resources are limited
• When possible, both the artery and vein should be shunted (Figure 2).
• Prior to placing a shunt, the distal vessel should be allowed to back-bleed, and a Fogarty catheter should be passed distal and proximal.

Figure 2. Temporary shunts using intravenous tubing have been placed in both the superficial femoral artery (red oxygenated blood) and the vein (dark blood) in this patient with vascular injury to the right thigh.

• There are commercially available shunts, but you can use IV tubing or chest tubes as well.
• Shunts should be carefully secured (ties or, less frequently, slings or clamps) to prevent dislodgement, especially if transporting the patient with a shunt in place (Figure 3).
• The largest possible arterial intraluminal shunt should be inserted.
• If available, papaverine can be topically applied to the transected ends of the artery, which are usually in spasm. The use of papaverine and gentle dilation of the arterial lumen may allow for insertion of a larger shunt.
• The shunt should be 4 cm longer than the gap between the two vessels such that 1.5 to 2 cm can be inserted into the lumen of each transected end of the artery.
• Once the shunt has been trimmed to the desired length, a 2-0 silk tie is placed securely in the middle of the shunt, with an occluding hemostat placed at the same spot to both mark and control the shunt (Figure 3a).
• The shunt is placed first into the proximal end of the transected artery inserting the tubing at least 1.5 cm. The proximal end of the artery is then secured to the shunt with a 2-0 silk tie placed approximately 5 mm from the cut end of the vessel.
• The hemostat in the mid-portion of the shunt is removed and the proximal vessel control released to confirm pulsatile flow of blood. Once confirmed, the clamp on the hemostat is reapplied.
• The shunt is then inserted 1.5 cm into the lumen of the distal end of the transected vessel, and the vessel is compressed down onto the shunt and secured with another 2-0 silk tie placed about 5 mm from the cut edge of the vessel (Figure 3b).
• The ties on the proximal and distal ends of the vessel are then joined together under slight tension, stabilizing the shunt and helping avoid dislodgement or migration (Figure 3c).
• The distal vascular control is released, and pulsatile flow distal to the shunt is confirmed (Figure 3d).
• When removing the shunt prior to definitive repair, the vessel will need to be debrided back to healthy tissue beyond the point where the shunt was secured.

Figure 3. A temporary shunt has been fashioned out of sterile intravenous tubing cut to appropriate size, with slight beveling of the ends, a suture marking the midpoint of the shunt marked with a suture, and a clamp providing control via occlusion (a). The shunt is placed first into the proximal end (a) and then the distal end of the partially transected vessel (b). The vessel is tied securely to the tube distally and proximally (b), and the ties on the vessel are tied to the suture at the midpoint, as seen in the partially transected artery (c). In a different case, an artery with several centimeters missing has been bridged with a shunt (d).

• Shunts should be removed as soon as the patient’s physiology will tolerate and appropriate vascular surgical expertise is available to perform definitive repair.
• It is not necessary to heparinize vascular shunts.
• Thrombosis rates for shunts placed in vessels below the elbow or below the knee are high, and limb loss rates are unchanged. This suggests that these vessels do not need to be shunted.
• Once a shunt is placed, it is important to document a thorough distal exam, as well as the time the shunt was placed.

Ligation

• Occasionally, it will be impossible or impractical to shunt or repair a vessel, and that vessel may require ligation to control life-threatening hemorrhage.
• There are very few vessels that cannot be ligated in extremis, with varying consequences.
• Vessels in which ligation may be tolerated include the following:
  • Common and external carotid arteries
  • Subclavian artery (as long as ligated distal to thyrocervical trunk)
  • Axillary artery
  • Brachial artery (distal to profunda branch)
  • Ulnar or radial artery individually (radial better tolerated as ulnar is the dominant vessel in most patients)
  • Celiac trunk
  • Internal iliac artery
• Vessels in which ligation is, or may be, poorly tolerated (e.g., leading to stroke or critical ischemia) include the following:
  • Internal carotid artery (15–20 percent incidence of stroke)
  • Superior mesenteric artery
  • External iliac artery
  • Common femoral artery
  • Popliteal artery
• It must be kept in mind that ischemia is much more likely to occur around ligated vessels if there is significant soft tissue injury and destruction of supporting collateral circulation.
• Almost all veins, including the inferior vena cava, can be ligated. The popliteal vein should be repaired or shunted if possible.

Vascular Repair

• The specific techniques of definitive vascular repair are beyond the focus of this course and manual but include the following options:
  • Lateral arteriorrhaphy or venorrhaphy
  • Patch angioplasty
  • Resection with end-to-end anastomosis
  • Resection with interposition graft (vein, PTFE/Dacron, CryoVein, Artegraft, etc.)
  • Bypass graft
  • Extra-anatomic bypass
  • Stent–graft repair