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Epidemiology of Vascular Trauma


Lambert’s dictum describes “what” vascular surgeons do. This has remained constant throughout the centuries. However, “why” and “how” surgeons do this has changed drastically from decade to decade. The vascular trauma subspecialty in particular has experienced changing practices with regard to fluid versus blood products resuscitation, tourniquet use, point-of-care imaging and endovascular innovations, such as REBOA and the covered stent.

The true purpose of epidemiological study should not be limited to the listing of injury patterns by mechanism of injury (MOI), anatomical location or geography. These provide interesting facts but are somewhat artificial academic exercises that have limited clinical applications. The real purpose of epidemiology is to understand how society changes and the mechanisms by which human suffering occurs. Epidemiology serves the surgeon by providing an understanding of how injury patterns arise from the patient’s and the surgeon’s broad social and political context. More importantly, it allows anticipation of how different infrastructures can serve to mitigate or exacerbate this harm. Vascular trauma is both catastrophic and complex. Studying its origins and patterns provides a more subtle representation of health-care issues, which have a far greater reach than the routines of the operating room. Furthermore, the evolution of the vascular surgeon’s armamentarium, from the cauterizing iron to the endovascular stent, has itself impacted on the landscape of vascular injuries as the range of iatrogenic injuries has grown.

Contemporary drivers of epidemiological change in vascular injury include:

  • 1.

    Military conflict.

  • 2.

    Civilian trauma and urban unrest, including accidental injury, terrorism, and gang-related civilian violence.

  • 3.

    Trauma at the extremes of age.

  • 4.

    Iatrogenic vascular injury as a result of minimally invasive or endovascular procedures.

Principles of Vascular Epidemiology

Epidemiology (from the Greek: the study of that which befalls the people ) is defined as the study of the distribution and determinants of health-related states or events in human populations, and the application of this study to the prevention and control of health problems. The global burden and impact of trauma as an agent of death and disability is increasingly well characterized ( Table 2.1 ). However, while the prevalence and incidence of individual vascular injury patterns have been well depicted in local situations, the epidemiological study of vascular trauma is a relatively underexploited field. Possible reasons for this include the heterogeneity of the circumstances in which vascular injury may be sustained, the protean direct and indirect consequences of vascular trauma to bodily systems, and the unsuitability of modern scoring methodologies to capture the specific effects of vascular injury on patient outcome. In the first edition of Rich’s Vascular Trauma , Geza de Takats summarized richness and complexity of traumatic mechanisms of injury as follows:

From time immemorial, hungry or suspicious cavemen, frustrated and jealous lovers, violent criminals, and, more recently… machinery and automobiles, have inflicted serious and often irreparable injury on the human body and soul.

Table 2.1
Summary: Deaths (000s) by Cause, in WHO Regions (a), Estimates for 2010 and 2016.
From the World Health Organization (WHO) Global Health Observatory Data Repository. Accessed May 2019. https://www.who.int/healthinfo/global_burden_disease/estimates/en/ .
Cause World (2016) World (2010)
Population (thousands) 7,461,884 6,140,789
000 % total 000 % total Change (000)
Injuries 297,394 11 290,806 10 6589
A . Unintentional injuries 215,158 8 209,494 7 5664
1 . Road injury 82,538 3 69,837 2 12,701
2 . Poisonings 6269 0 8341 0 −2073
3 . Falls 38,162 1 30,431 1 7731
4 . Fire, heat, and hot substances 10,610 0 12,876 0 −2266
5 . Drowning 20,134 1 28,715 1 −8581
6 . Exposure to mechanical forces 13,225 0 14,057 1 −832
7 . Natural disasters 361 0 670 0 −309
8 . Other unintentional injuries 43,860 2 44,567 2 −707
B . Intentional injuries 82,236 3 81,311 3 924
1 . Self-harm 37,564 1 39,194 1 −1630
2 . Interpersonal violence 31,237 1 32,174 1 −938
3 . Collective violence and legal intervention 13,436 1 9943 0 3492

Consequently, understanding the historic and contemporary epidemiology of vascular trauma is important. Box 2.1 lists the generic components of epidemiological endeavor. With respect to trauma, recognizing the prevalent populations underpins the alignment and targeting of hospital resources, as well as education of health-care providers. In essence, this informs the design of trauma and vascular-care systems. More widely, the standardized and open-access description of the incidence, mechanisms, and demography of traumatic injury empowers comparison of properly stratified outcomes from injury. In turn, these aid not only research, but also clinical governance, quality-improvement initiatives, and fair reimbursement for treating hospitals. Subsequently, these provide knowledge of socioeconomic realities and influence the design and assessment of preventative public health interventions, thus informing health and social policy.

Box 2.1
Core Purposes of Epidemiological Programs (1)

  • Identifying risk factors for disease, injury, and death

  • Describing the natural history of disease

  • Identifying individuals and populations at greatest risk for disease

  • Identifying where the public health problem is the greatest

  • Monitoring diseases and other health-related events over time

  • Evaluating the efficacy and effectiveness of prevention and treatment programs

  • Providing information that is useful in health planning and decision making for establishing health programs with appropriate priorities

  • Assisting in carrying out public health programs

If vascular and trauma clinicians are to anticipate injury patterns, to track changes, and to put into place effective programs to prevent or to mitigate the effects of vascular trauma, then the study of injury epidemiology is an essential function of practice. The aim of this chapter is to provide the context to more-detailed illustrations of specific anatomical injuries given elsewhere in the text.

Context and Categorization of Vascular Trauma

The epidemiological study of vascular injury is hampered by the protean nature of trauma and the multiple and interrelated factors that determine functional outcome. Examples include co-injury to critical soft tissue, as well as bony and neurological structures. This difficulty is made more acute by the lack of uniformity among authors as to appropriate injury descriptors, outcome metrics, and follow-up periods. Most studies in both the military and civilian domains offer descriptions of cohorts comprising specific vascular regions (extremities) or anatomical areas (e.g., calf vessels); this provides detail at the expense of proper epidemiological perspective. Rates of vascular trauma are conflicted by use of different definitions of population-at-risk, invoking different denominators, and inflating or deflating prevalence accordingly. Outcomes are defined differently and with varying degrees of accuracy. For instance, mortality rates may variously be built on definitions such as death while an inpatient, ignoring those who expire before reaching the hospital. Epidemiology is dependent on data; countries with mature trauma systems and mandatory data-collection infrastructures offer a more fruitful perspective on injury rates and causes. Similarly, while wartime populations often have higher vascular injury rates than peacetime cohorts, the presence of detailed injury data (with accurate description of the denominator populations) is directly related to whether a trauma systems approach to data collection is deployed by the medical services of the combatant parties. It is fair to say that countries without a “trauma systems” approach to injury management are usually unable to describe the effect of vascular trauma in populations-at-risk. Because most developing countries fall into such categories, it is correct to assume that the global burden of vascular trauma is unknown.

Vascular trauma may be broadly categorized according to:

  • 1.

    MOI: e.g., iatrogenic, blunt, penetrating, blast, combination injuries

  • 2.

    Anatomical site of injury: e.g., compressible versus noncompressible hemorrhage

  • 3.

    Contextual circumstances: e.g., military versus civilian

Each of these domains may be further stratified, with military injury being subdivided by patient status (combatant vs. noncombatant) and category of conflict (civil war, counter-insurgency warfare, maneuver warfare). Civilian injuries may be similarly contextualized by local circumstances (e.g., urban trauma vs. rural trauma).

1

Military Conflict

Warfare since the 2000s has lost many of the characteristics that defined previous engagements, such as World War I (WWI), World War II (WWII), Korea, and Vietnam. Current conflict is a “war among the people,” where “people in the streets and houses and fields… are the battlefield. Military engagements can take place anywhere, with civilians around, against civilians, in defense of civilians. Civilians are the targets, objectives to be won, as much as an opposing force.” As such, vascular trauma inflicted by high-energy military ballistic projectiles and purpose-built or improvised blast weaponry can affect two populations-at-risk: combatants and noncombatant (civilians).

Vascular Trauma in Combat Troops

It is important to remember that military combatants represent a specific demographic group. Compared with civilian injuries, military arterial injury occurred predominantly in males in their twenties (25 vs. 32 years and 98.7% vs. 82% males, respectively). Furthermore, the predominant mechanisms of injury to US and UK soldiers (Afghanistan) are either improvised explosive devices (48%) or gunshot wounds (29%). Contemporary data confirms that exsanguination is the major cause of death in fatally wounded soldiers. It is also estimated that 80% of arterial injuries sustained in combat affect the extremities. More than 70% of these are associated with blast injuries.

Vascular injury rates seem only to have increased as warfare has become more sophisticated: allied surgeons in WWI noted vascular trauma rates of 0.4% to 1.3% ; DeBakey characterized the vascular injury burden in WWII as affecting 0.96% of all patients; later, in the Korean and Vietnam wars, the rate of vascular injury was judged to be higher, at 2% to 3%. Coalition militaries engaged in combat operations in Afghanistan and Iraq have invested substantially in detailed trauma registries in order to capture injury data. Such databases have been used to characterize miscellaneous injury patterns so that force protection (e.g., body armor or vehicle design) and treatment protocols can be continually updated and aligned to contemporary trauma archetypes. Interestingly, present rates of wartime vascular trauma confirm a much higher prevalence than in previous campaigns, with arterial injury rates being reported by some as high as 7.1%.

A comparative study of the outcomes of major arterial injuries in military and civilian populations was undertaken by Markov et al. One-quarter of all military arterial injuries were not amenable to control by tourniquet application or compression (noncompressible arterial injuries [NCAIs]). Military arterial injuries were shown to have a lower incidence of NCAIs compared with the civilian populations (28% vs. 61%). These differences were attributed to a higher rate of blunt trauma to the torso in the civilian setting, as a result of motor vehicle collisions. Blast injuries were the predominant mechanism of injury in military settings (69%), while the civilian population was equally affected by either blunt or penetrating trauma (50% and 50%, respectively). No difference in mortality was found between matched military and civilian cohorts where compressible arterial injuries were involved (2% military vs. 4.1% civilian). However, their study suggested that NCAIs carried a lower mortality in the military setting (4.2% vs. 12.16%). This was potentially attributed to the use of body armor and implementation of combat casualty care strategy. This includes advanced military resuscitative strategies and the necessary infrastructures that allow rapid evacuation and prehospital care.

A comprehensive study summarizing recent US military experience (13,076 cases) analyzed vascular injuries from the United States Joint Theater Trauma Registry (JTTR) (2002–09). It defined battle-related injuries as those sufficiently severe to prevent return to duty into the combat theater. The specific incidence of vascular injury (“total incidence injury”) was found to be 12%, while the incidence of injuries requiring surgery (“operative incidence”) was found to be 9%. The study also identified differences in vascular injury rates between troops deployed to Iraq (12.5%) and Afghanistan (9%). Other differences included causative mechanism, with blast accounting for 74% and 67% of injuries in Iraq and Afghanistan, respectively (with an overall contribution of 73%). There was no difference in the anatomical distribution of the injuries, nor the “died of wounds” (DOW) rate (6.4%) between theaters. Wounds were principally sustained to the extremities (79%), torso (12%), and cervical regions (8%). In the torso, the most commonly injured vessels were the iliac arteries (3.8%), followed by the aorta (2.9%), the subclavian arteries (2.3%), and the inferior vena cava (IVC) (1.4%). In the neck, 109 carotid injuries accounted for 7% of injuries. It was noted that the vascular injury burden borne by the extremities was remarkably similar to that noted by DeBakey in WWII. In contrast, the higher contemporary rate of cervical and aortic injury was attributed to increased survivability and far-shortened medivac times.

Overall, the authors concluded that the rate of vascular injury in these wars was five times that previously reported from Vietnam and Korea. The early reported incidence of vascular injury was estimated at around 4.4% to 4.8%, based on data published from US military hospitals in Iraq. However, when this analysis includes nonoperated cases and vascular injury that was unrecognized on reception, the prevalence can be as high as 7%. This marked increase in vascular injury rates is striking and not entirely clear. In addition to increased wound survivability, possible reasons include:

  • 1.

    the very high rate of blast-related injury etiology in these campaigns,

  • 2.

    overestimation of the population-at-risk in earlier reports (thus deflating the denominator), or

  • 3.

    more accurate capture of “minor” nonoperated vascular wounds (adding to the numerator).

In a similar but smaller British study, Stannard et al. scrutinized the records of 1203 UK servicemen injured through enemy action between 2003 and 2008. Unlike the US JTTR, the British JTTR dataset also included patients who were killed in action (KIA)—that is, who died before reaching a medical treatment facility (an aspect of injury burden not scrutinized in US accounts). Characterization of injury was made from clinical data and from postmortem examinations conducted by the UK Coroner system. It was determined that 9.1% of this cohort sustained injuries to named vessels. Blast wounds accounted for 54% torsocervical injuries and 76% of extremity wounds, respectively. Critically, the study showed that more than half of patients who sustained an injury to a named vessel died before any surgical intervention could be undertaken. Injury to named vessels in the thorax and aorta proved almost universally fatal. Cervical vascular injuries also proved highly lethal, with 13 of 17 patients affected eventually succumbing. Two-thirds of the vascular injuries sustained involved the extremities. Almost half of these patients survived, albeit with eventual amputations in a significant proportion. The limb salvage (primary assisted patency) rate was 84%. This UK group concluded that while favorable limb-salvage rates are achievable in casualties able to withstand revascularization, torso vascular injury is not usually amenable to successful surgical intervention.

The rate of lower limb amputation following vascular injury to the extremities is important, being a major cause of disability and avoidable mortality. Lower limb arterial injuries are thought to be caused predominantly by blast injuries (70%) or gun-shot wounds (30%). The commonest affected vessels in penetrating limb injuries include the superficial femoral artery, the popliteal artery and the posterior tibial arteries, each being affected in around 20% of cases. Perkins et al. studied 579 injured extremities in US service members from the wars in Iraq and Afghanistan. Their primary amputation rates were 8.5%, with salvage attempts occurring in 91% of patients. Tissue loss and damage control were the principal reasons for primary amputations. Secondary amputations occurred in 15.5% of limbs. Early secondary amputations were associated by nonviable or infected tissue, while late ones with poor limb function. 57% of amputations were transtibial, while 30% were transfemoral. It is also important to note that 82.7% of those undertaking limb salvage were amputation free at 10 years. This highlights the significant threat that military vascular injuries pose to the lower limbs, but also the value of attempting limb revascularization within adequately prepared trauma infrastructures.

Vascular Trauma among Local National Populations

Few studies have examined the burden and impact of vascular trauma in civilians injured in time of war. The registries of military trauma systems may be biased toward data collection among their own troops, or in such cases where information is captured there is usually no data on long-term outcomes due to lack of follow-up in war-afflicted societies. In a study by Clouse et al. analyzing vascular casualties treated at a Level III a

a Level III facility is equivalent to a major trauma center (MTC).

US facility in Iraq, 30% were civilians while and 24% were local national combat forces. Extremity vascular injuries were significantly more prevalent in US forces compared with the local population (81% vs. 70%). Vascular injury to the torso was significantly less common in US forces (4% vs. 13%), but neck injuries occurred with similar prevalence (14% vs. 17%). The authors hypothesized that the lack of protective body armor might increase the nonextremity vessel injury rate in the Iraqi population. Interestingly, vascular injuries were noted to be overrepresented in the local nationals: although 40% of those admitted to the facility were of Iraqi origin, they made up to 51% of the vascular injury cohort.

Deployed military hospitals are primarily configured and resourced for the care of their own nation’s soldiers, so understanding the additional burden presented with a large local national population of injured civilians, insurgents, and military remains important. In a supplementary report from the Air Force Theater Hospital in Balad, Iraq, it was determined that the incidence of vascular trauma among 4323 locals treated at the facility was 4.4%. The authors focused on extremity injuries—which affected 70% of vascular casualties—and observed that the median length of stay from presentation to definitive wound closure was 11 days. Casualties underwent a median of three operations. Notably, the age range was 4 to 68 years and included 12 pediatric injuries. Mortality was 1.5% with significant complications in 14% but despite this a 95% limb salvage rate was recorded.

This experience matches earlier reports. Sfeir et al. described a population of 366 lower limb–wounded vascular cases, sustained by a mixed population of combatant and noncombatants during the Lebanese civil war over a 16-year period ending in 1990. Two-thirds of patients had received gunshot wounds. Patients included 118 who had popliteal arterial injuries, 252 with femoral injuries and 16 who had tibial vessel injuries. The overall mortality rate was 2.3% with no mortality in the popliteal and tibial injury group whereas there were nine deaths in the femoral injuries group. The overall amputation rate was 6% (11.7% for the popliteal injuries group). Mirroring more contemporary experience, the authors associated failure of limb salvage with physiological instability, delay in repair (of more than 6 hours from injury), and presence of long bone fracture.

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