Management of Pediatric Vascular Injury

Introduction

In the United States, injuries account for approximately 10,000 childhood fatalities every year. Unintentional injury results in one in four pediatric medical visits, and the direct cost of these injuries is estimated to be over $50 billion annually.

Vascular injuries represent a small proportion of this disease burden (0.6%–1%), and the incidence of noniatrogenic pediatric vascular injury rates may be decreasing due principally to public health initiatives centered on motor vehicle safety. However, unsafe handling and storage of firearms remain an important risk factor for penetrating vascular trauma in young children, and combat operations represent an increasingly recognized cause of both blunt and penetrating pediatric vascular trauma. Iatrogenic injury represents another important cause of pediatric vascular compromise, and the incidence of these injuries has increased with widespread use of catheter-based procedures, especially in tertiary pediatric hospitals.

Although the overall incidence of pediatric vascular injury is relatively small, children with vascular injury require significantly more surgical and procedural interventions, have longer hospitalizations, and have a higher mortality than those without vascular compromise. Furthermore, despite advances in trauma care, the mortality rate of children who have sustained vascular injury has not improved over the past decade ranging from 3% to 23%.

Significant variability exists in the initial evaluation, diagnostic work-up, therapeutic approach, and follow-up of children with vascular injuries for a number of reasons ( Box 25.1 ). In an effort to minimize this variability in the future, this chapter begins with a brief overview of the epidemiology of both iatrogenic and noniatrogenic vascular trauma as well as anatomic and physiologic considerations unique to children. We examine diagnostic modalities and therapeutic approaches available to the pediatric vascular surgery team as well as outline specific injury patterns in the head/neck, torso, and upper and lower extremities. We conclude with a discussion of postinjury surveillance and future directions for the field of pediatric vascular surgery. Key points of emphasis in the diagnosis and management of pediatric vascular trauma are summarized in Table 25.1 .

Epidemiology

Approximately half of all vascular injuries in children are iatrogenic with most of these injuries occurring in neonatal and school-age children. Causes of these iatrogenic vascular injuries include diagnostic catheterization, cannulation for extracorporeal membrane oxygenation (ECMO) or cardiopulmonary bypass, umbilical artery catheter placement, arterial line placement, arterial puncture for blood gas analysis, and complications from routine venipuncture. Vascular complication rates from these procedures vary from 2% to 45% depending on patient age, the type of procedure, size of catheter, and proceduralist experience. Unfortunately, as noted above, the true demographics of iatrogenic vascular injuries remains unknown due to underreporting and lack of multi-institutional observational research.

Noniatrogenic vascular injuries are more common than iatrogenic in children age 7 and above, and of these injuries, approximately 75% result from a penetrating mechanism. Since 2010, there have been nearly 16,000 injuries and 2711 deaths from gunshot wounds in children aged between 0 and 19 in the United States. Firearms are the second leading cause of trauma-related deaths in the pediatric population, and among those who survive, 50% suffer long-term disability. Analysis of the National Trauma Data Bank revealed that firearm-associated vascular injury was the most lethal mechanism, and whereas injuries associated with motor vehicle crashes have decreased, the incidence of firearm injury in 2007–12 was unchanged compared with 2002–06.

Modern warfare commonly occurs in proximity to civilian populations leading to injuries in host-nation children. In contrast to civilian vascular injuries, combat injuries tend to result from high-velocity weapons or from explosions. These mechanisms cause significant disruption of surrounding tissue, making repair more complex. In a series of 155 pediatric patients with vascular injuries representing 3.5% of pediatric admissions, 96% were caused by a penetrating mechanism, and 66% involved extremity vessels ( Fig. 25.1 ).

Anatomic and Physiologic Considerations

Numerous anatomic factors contribute to iatrogenic vascular injuries in children. Pediatric vascular access involves cannulation of small vessels in remarkably compact anatomic spaces with relatively large catheters. Ultrasound studies have shown that as many as 12% of femoral vessels in children from birth to 9 years old are either partially or completely overlapping. Thus, landmark-based attempts at venous access in the groin can easily result in inadvertent arterial puncture. The use of inappropriately sized arterial catheters also predisposes the child to vasospasm, increasing the risk of limb ischemia.

Physiologic factors in children who undergo invasive vascular procedures often promote arterial occlusion. Compromised cardiac output, polycythemia, and low intravascular volume secondary to hemorrhage can all contribute to thrombosis. Furthermore, severe persistent vasospasm (lasting hours) and spontaneous arterial thrombosis both suggest pediatric vessels are hyperreactive as compared with the adult vasculature.

A wide array of injuries can lead to complete vascular occlusion including intimal flaps, arterial dissections, and avulsion injury. The inciting traumatic event may cause luminal obstruction and/or local vasospasm with resultant thrombosis. Limb hypoperfusion can also occur as a result of traumatic arteriovenous (AV) fistulae, pseudoaneurysm, or complete vascular transection following venous or arterial puncture. Traumatic AV fistulae can also result in high-output cardiac failure in children.

Diagnosis and Evaluation

Diagnosis of pediatric vascular injuries requires a high index of suspicion and a careful physical examination as the presentation of vascular occlusion may be more nuanced compared with adults. A thorough vascular examination in patients with potential vascular injury includes an assessment of potential sites of injury for both hard and soft signs of vascular injury, skin color, capillary refill, and a thorough assessment of both central and peripheral pulses. Before performing invasive vascular procedures, establishing a preprocedure baseline pulse examination is essential for subsequent detection of subtle blood flow compromise. In the multiply injured child, hemorrhagic shock alone may cause extremity hypoperfusion in the absence of vascular injury. With resuscitation and rewarming, vasospasm will tend to resolve, whereas a major vascular injury will not improve.

In the setting of penetrating trauma, hard signs of vascular injury include pulsatile hemorrhage, an expanding hematoma, obvious distal ischemia, or findings of a bruit or thrill on auscultation of the site of injury. In more subtle cases with a potential injury, measurement of the injury extremely index (IEI) using continuous-wave Doppler is a reliable, noninvasive means of initially assessing for pediatric arterial injury. Accurate and precise IEI relies on measurement with appropriately sized blood pressure cuffs. The cuff should easily encircle the circumference of the arm and should cover 75% of the extremity length. A continuous-wave Doppler probe is used to determine the pressure at which the arterial signal occludes with cuff inflation. The calculation is taken from the branchial artery in an uninjured extremity. If both arms are uninjured, the higher of the two occlusion pressures is used as the denominator of the ratio equation. For lower extremity injury, an appropriately sized cuff is positioned just proximal to the ankle and Doppler occlusion pressures are measured at both the dorsalis pedis and posterior tibial arteries. The highest value is used as the numerator to calculate the IEI ratio. If an injured upper extremity is being assessed, the cuff is placed distal to the injury and the occlusion pressure measured at the wrist, taking the higher value of the radial or ulnar artery occlusion pressure. An abnormally low IEI (less than 0.9 in children over 2 and less than 0.88 in children 2 and under) indicates a potential vascular injury that warrants further assessment.

In a child with clinical concern for vascular injury who does not respond appropriately to resuscitation, localizing and confirmatory studies should be pursued. In children, duplex ultrasound is extremely safe, can confirm vascular occlusion and is able to localize the site of injury as well as diagnose the presence of an AV fistula or pseudoaneurysm. Sonography can also differentiate acute occlusion and vasospasm. Limitations of ultrasound include limited utility for small vessels, and a steep learning curve for optimal image acquisition. Moreover, sedation may be necessary for complete sonographic examination in a young child.

Computed tomography angiography (CTA) is being used more often in children for the diagnosis of vascular injury and has been shown to be more reliable for truncal and great vessel trauma than for injuries of the peripheral vasculature ( Fig. 25.2 ). If the diagnosis remains unclear despite noninvasive testing, conventional angiography can be useful to identify the site of injury or to differentiate vascular injury from vasospasm. In the setting of hemodynamic compromise or if invasive and noninvasive tests are inconclusive, surgical exploration is indicated.

Therapeutic Approach

Historically, short of exsanguinating hemorrhage following major arterial disruption, pediatric vascular injury was managed with systemic anticoagulation. However, poor long-term results from this medical management approach are now more widely recognized, including early tissue loss and long-term limb length disparity. Historic concerns of a high negative exploration rate due to vasospasm and seemingly poor postoperative results in children less than 2 years old have been assuaged with improved diagnostic imaging and more experience with operative exploration across all age groups. Furthermore, mounting evidence of the negative consequences of even relatively short warm ischemia times compels early intervention to optimize long-term functional outcomes.