How Common Are Civilian Blast Injuries in the National Trauma Databank, and What Are the Most Common Mechanisms and Characteristics of Associated Injuries?

Abstract

Background

Recent military conflicts have produced substantial improvements in the care of service members who experience blast injuries. As conflicts draw down, it is important to preserve and improve skills gained in combat. It is unknown whether civilian blast injuries can serve as a surrogate for military blast trauma. To guide further research, it is crucial to understand the volume, severity, and distribution of civilian blast injury in the civilian population.

Questions/purposes

(1) What proportion of US trauma admissions are a result of blast injury? (2) What are the common mechanisms, and what is the demographic breakdown of civilian patients presenting to trauma centers after blast injuries? (3) What is the severity, and what are the characteristics of injuries sustained by civilian patients after blast injuries?

Methods

We queried the American College of Surgeons National Trauma Databank (NTDB), a national aggregation of trauma registry data which captures robust mechanism of injury and wounding pattern information, for any patient admitted for trauma and an initial mechanism of injury corresponding to a predefined list of ICD-9 and ICD-10 external cause of injury codes related to blast injuries and reported as a proportion of all trauma-related admissions. Mechanisms were categorized into similar groups, and data were collected regarding demographics as well as location and intentionality of blast (that is, unintentional, the result of assault, or self-inflicted). Patient injuries were characterized by ICD-9 or ICD-10 diagnosis codes and sorted according to the body area affected and severity of injury, measured via the Injury Severity Score (ISS). The ISS is a measure of trauma severity, with scores ranging from 1 to 75 points based on injury severity, which is calculated according to injury scores in six separate body domains (head or neck, face, chest, abdomen or pelvis, extremities, external). A score of 1 represents a minor trauma to one region, while a score of 75 indicates injuries deemed nonsurvivable in one or more domains. Data were limited to trauma admissions in 2016.

Results

Patients injured by blast mechanisms represented 0.3% (2682 of 968,843) of patients in NTDB-participating trauma centers who were treated after a blast injury in the year 2016; 86% (2315 of 2682) of these patients were men, and the mean ± SD age was 38 ± 21 years. Blast injuries most commonly occurred after detonation of fireworks (29% [773 of 2682]) or explosion of gas or pressurized containers (27% [732 of 2682]). The most commonly injured area of the body was the upper extremity (33% [894 of 2682]), followed by the face (28% [747 of 2682]), lower extremity (11% [285 of 2682]), thorax (10% [280 of 2682]), and head (10% [259 of 2682]). Fifty-eight percent (1564 of 2682) of patients had at least one burn injury. A total of 2% (51 of 2682) of the injuries were fatal, with a mean ISS score of 6 ± 8; 23% (608 of 2682) of patients presented with injuries classified as severe (ISS > 8).

Conclusion

Civilian blast-associated injuries are not common, but they can be severe, and in many (though not all) respects they seem similar to those described in published case series of military blast victims. Key differences include age and gender (civilian injuries more commonly involve women and older patients than do those in military studies). The potential of civilian blast patient care as a surrogate for study and clinical experience for military surgeons in the interwar period—as recommended by the National Academies of Sciences, Engineering, and Medicine report—is supported by our preliminary results. Future interventions or training programs would likely need to rely on multisite or targeted partnerships to encounter appropriate numbers of patients with blast injuries.

Level of Evidence

Level IV, prognostic study.

Introduction

Since the initiation of Operation Enduring Freedom on October 7, 2001, the United States has been engaged in the longest continuous period of active warfare in its history. Despite the horrors of war, every conflict has seen advancements in medical knowledge that can be and have been adopted into civilian practice (Table 1) [2, 13, 15]. In the current overseas contingency operations (formerly known as the Global War on Terror), trauma care in the military health system has progressed to a level characterized by the highest rates of survival in history [8]. However, the lessons learned and clinical practice gained over time have been slow to transfer to civilians [6, 11]. The United States’ civilian trauma systems have yet to reach the goal of “zero preventable deaths” [20]. Furthermore, because casualties from the current wartime operations continue to decline, the military health system is at risk of atrophy of the institutional knowledge and skills developed during that time. In 2016, the Committee on Military Trauma at the National Academies of Sciences, Engineering, and Medicine proposed a series of interventions and federal policies aimed at standardizing trauma care for US service members and civilians to reduce preventable deaths because of trauma [5]. Tighter integration of cooperation between civilian and military trauma systems ensures that these systems may mutually benefit from the expertise and knowledge gained in combat, while also preserving these skills during the interwar periods.

Table 1.

Examples of medical advancements developed during war that have been incorporated into civilian practice

Year	War	Advancements
1803 to 1815	Napoleonic Wars	1. Lemon juice to prevent scurvy
1853 to 1856	Crimean War	1. Ambulance corps established
1861 to 1865	United States Civil War	1. Charles Tripler and Jonathan Letterman established a military ambulance service 2. Forward aid stations
1899 to 1901	Boer War	1. Use of antiseptic techniques 2. Field hospitals 3. Radiography
1914 to 1918	World War I	1. “Golden hour” concept 2. Mobile bacteriological units 3. Tropical medicine 4. Vaccines against tetanus and typhoid 5. Developments in orthopaedics, neurosurgery, and psychiatry
1939 to 1945	World War II	1. Penicillin 2. Rehabilitation 3. Intravenous fluids (saline) 4. Public health
1936 to 1939	Spanish Civil War	1. Blood storage, transportation, and transfusion
1950 to 1953	Korean War	1. Air evacuation (helicopter) 2. Mobile army surgical hospital 3. Vascular surgery
1955 to 1975	Vietnam War	1. Mobile blood banks and frozen blood product 2. Advances in on-site medicine 3. Recognition of posttraumatic stress disorder
2001 to Now	Global War on Terror	1. Tourniquet use 2. Golden hour blood carriers 3. Fibrin-impregnated dressings

It is not known whether civilian trauma centers treat enough patients with severe blast injuries to serve as a training surrogate for military combat injuries. Prior work suggests that there are marked differences between surgery performed on civilians during peacetime and surgery on military service members during wartime, and injury patterns seen in combat differ from those seen in civilian centers [17, 18]. For policymakers to effectively distribute resources and design programs aimed at maintaining blast care readiness through partnership with civilian institutions, it is important to understand the frequency of these events, as well as the severity and resemblance to military blast trauma. In addition, insights into patterns of civilian blast injuries could identify specific gaps not addressed by the current understanding of treatment of patients injured in military blasts.

We therefore asked, (1) What proportion of US trauma admissions are a result of blast injury? (2) What are the common mechanisms, and what is the demographic breakdown of civilian patients presenting to trauma centers after blast injuries? (3) What is the severity, and what are the characteristics of injuries sustained by civilian patients after blast injuries?

Patients and Methods

Study Design and Setting

This observational cross-sectional study aimed to characterize the mechanism of injury and injury patterns in all patients who received care for blast-associated injuries at participating National Trauma Databank (NTDB) Registry trauma centers in 2016. The NTDB, a multicenter registry maintained by the American College of Surgeons Committee on Trauma, is an aggregate of trauma registry data from 747 American and Canadian Trauma Centers that provides information necessary for descriptive analysis of patients’ presenting injuries and their demographics and mechanisms of injury. As we did not evaluate trends over time, we limited our study to the year 2016, the most recent edition of the database available, to provide the most current description of blast injuries at civilian trauma centers [10].

Participants

The population of interest was defined as any patient admitted with at least one valid trauma diagnosis as defined by the NTDB and an initial mechanism of injury corresponding to a predefined list of ICD-9 or ICD-10 external cause of injury codes (E-codes) with “explosion,” “explosive,” “blast,” or “bomb” in the descriptors [21].

Variables, Outcome Measures, Data Sources, and Bias

To answer our primary research question, we calculated the proportion of patients who presented after blast injury in the 2016 NTDB database.

To answer our secondary research question regarding mechanisms of blast injury, we subclassified 68 blast-related E-Codes into one of eight groups defined by research staff: boiler, explosion related to fire, explosive gas, other explosive material, fireworks, gasoline container, pressurized vessel, and bomb or weapon discharge (Appendix Table 1; Supplemental Digital Content, http://links.lww.com/CORR/A494). To provide further context regarding the mechanism of injury, we recorded the location of the blast and whether it was an occupation-related event. To provide context for the mechanism of injury, other variables recorded included alcohol and drug test results and intentionality of the injury (that is, whether the injury was unintentional, the result of assault, or self-inflicted).

To answer our tertiary research question regarding injury severity and characteristics, we obtained a list of all ICD-9 or ICD-10 diagnosis codes and procedure codes for each patient during their hospitalization. Injuries were divided into the following categories according to the Abbreviated Injury Scale (AIS) classification system, as described by the Association of Advancement for Automotive Medicine: head injury, face injury, neck injury, thorax injury, abdominal injury, spinal injury, upper extremity injury, lower extremity injury, and burn injury. The total Injury Severity Score (ISS) was calculated according to the original formula described by Baker et. al. [3] The ISS ranges from a minimum score of 1 for uninjured patients and maximum score of 75, with scores greater than 16 indicative of a “severe trauma.” We considered patient disposition as an additional indicator of initial injury severity, and captured patient emergency room disposition, intensive care unit admission and length of stay, as well as total hospital length of stay and final hospital disposition.

Ethical Approval

Ethical approval for this study was waived by the Dell Medical School institutional review board.

Results

Frequency of Civilian Blast Injuries

In 2015, 0.3% (2682 of 968,843) of patients in NTDB-participating trauma centers were treated after a blast injury. Although this represents a small proportion of the patient encounters in our cohort when compared with the most common causes of trauma, blast injuries occurred about as often as trauma resulting from “fire/flame” (0.9% [7877 of 861,888]), “bites and stings” (0.7% [5868 of 861,888]), “exposure/overexertion” (0.3% [2613 of 861,888]), and “natural/environmental causes” (0.3% [2387 of 861,888]).

Mechanism and Demography of Civilian Blast Injuries

Fireworks-related blasts represented a plurality of E-codes (29% [773 of 2682]), followed by with explosion of gas or pressurized containers (27% [732 of 2682]). Blast injuries that resulted from a bomb or weapon discharge were rare and accounted for fewer than 1% of patient presentations (6 of 2682) (Fig. 1).

Fig. 1.

Mechanism of injury categories by number of patients, based on ICD-9/ICD-10 E-codes.

Eighty-six percent (2315 of 2682) of the patients were men with a mean age of 38 ± 21 years (Table 2). Ninety-seven percent (2610 of 2682) of injuries were the result of an unintentional process, compared with 2.3% (61 of 2682) and 0.2% (6 of 2682) that occurred as a result of assault or attempt at self-harm, respectively. The location of the blast was recorded for 33% (892 of 2682) of patients and was listed as home in 66% (592 of 892) of patients. The second most commonly recorded location for blast injuries were work or industrial sites, and this applied to 18% (163 of 892) of injuries, followed by street or other public area with 15% (133 of 892). Sixteen percent (438 of 2682) of injuries were identified as occupation-related, with the most commonly involved industries being manufacturing (13% [56 of 439]), transportation (10% [46 of 439]), construction (10% [44 of 439]), and natural resources or mining (8% [37 of 439]). Patient intoxication was sparsely recorded, with recorded serum alcohol tests in 40% (1069 of 2682) of patients and tests for other illicit drugs in 23% (612 of 2682). In these subsets of tested patients, 24% (259 of 1069) of patients had positive test results for the presence of alcohol and 30% (186 of 612) had positive test results for the presence of illicit drugs.

Table 2.

Cohort demographics and mechanism of injury (n = 2682 patients)

Variables	Percentage (n)
Sex
Female	14 (367)
Male	86 (2315)
Age in years
< 18	15 (397)
18-29	24 (640)
30-39	18 (492)
39-49	14 (375)
50-59	16 (429)
60-69	9 (240)
70-79	3 (83)
≥ 80	1 (26)
Race
Native American	1 (30)
Asian	1 (19)
Black	11 (308)
Unknown	2 (62)
Other race	9 (234)
White	76 (2029)
Mechanism of injury
Boiler	2 (50)
Explosion related to fire	4 (94)
Explosive gas	16 (441)
Explosive material	22 (587)
Firework	29 (773)
Gas container	4 (120)
Pressurized container	23 (611)
Bomb or weapons	< 1 (6)

Injury Severity and Characteristics of Civilian Blast Injuries

The mean ± SD ISS score was 6 ± 8 (Fig. 2). The most commonly injured domain was the upper extremity (33% [894 of 2682]), followed by the face (28% [747 of 2682]), lower extremity (11% [285 of 2682]), thorax (10% [280 of 2682]), head (10% [259 of 2682]), abdomen (7% [182 of 2682]), spine (2% [61 of 2682]), and neck (2% [60 of 2682]). Fifty-eight percent (1564 of 2682) of patients sustained at least one burn injury (Table 3). Certain fractures and soft tissue injuries were more common (Fig. 3).

Fig. 2.

Injury Severity Scale scores for the cohort by category.

Table 3.

Injuries sustained according to Abbreviated Injury Scale (AIS) domain

AIS domain	Percent of patients (n)	Mean ± SD injuries per patient	Mean ± SD domain-specific injury severity
Head	10 (259)	2 ± 2	3 ± 1
Face	28 (747)	2 ± 2	1 ± 1
Neck	2 (60)	1 ± 1	2 ± 2
Thorax	10 (280)	1 ± 19	2 ± 2
Abdomen	7 (182)	2 ± 1	2 ± 2
Spine	2 (61)	2 ± 1	2 ± 1
Upper extremity	33 (894)	3 ± 2	2 ± 1
Lower extremity	11 (285)	2 ± 1	2 ± 1
Burn	58 (1564)	2 ± 2	2 ± 1

Percent of patients with injuries to various body regions and the average number of injuries per region per patient. Injury severity is scored on a scale from 1 to 6, with 1 representing a minor injury and 6 representing a maximum, nonsurvivable injury.

Fig. 3.

Most common (A) fractures and (B) softtissue injuries sustained by patients in the NTDB with blast injuries. Labels indicate the osteoarthritis classification of bone; data are provided as the number of patients (percentage of injury codes). Injuries responsible for more than 1% of codes are provided in bold.

Overall mortality following blast injury was 2% (51 of 2682). A total of 19% (507 of 2682) received immediate surgery from the emergency room, and 17% (461 of 2682) of patients were admitted to the intensive care unit. The mean hospital length of stay for all admitted patients was 5 ± 8 days, with 64% (1723 of 2682) of patients discharged home with or without home care (Fig. 4).

Fig. 4.

Emergency department disposition of the cohort.

Discussion

Blast injuries are common in contemporary military conflicts, and the experiences gained from care of patients with blast injuries in wartime have led to advancements and improvements in care of both service members and civilians. As conflicts have drawn down, military and civilian physicians and policymakers must identify opportunities for maintenance and advancement in care for blast-associated injuries. Since blast injuries sometimes also occur in civilian settings, it is reasonable to wonder whether those injuries are similar enough to those incurred in battle that they can serve as a potential pool of patients to study or target with new treatments or training programs. However, their frequency, characteristics, and resemblance to military blast trauma is unknown outside of large, isolated blast events such as the Boston Marathon bombings. Our study found that although civilian blast events are not among the most frequent causes of injuries treated at trauma centers, the prevalence of blast injuries is large enough to merit further investigation. Furthermore, blast-associated injuries result in substantial morbidity and often result in multiple injuries, most commonly involving the head, face, and upper extremities. Our results point to the potential for blast injury research to be conducted in civilian settings, although multicenter studies or civilian blast-specific registries may be needed. Further research into how blasts specifically affect women and/or older patients may also be better done in civilian settings, since these patient populations were more frequently represented in this series than in typical military studies on this topic.

Limitations

This study has several limitations. First, our study was retrospective and consisted of data limited to the initial presentation with limited ability to capture treatments provided or patient outcomes. However, the database we used is robust, and it was sufficiently large and diverse to characterize the parameters we were most interested in here. Second, we would have preferred to compare our cohort to military blast injuries. However, given the lack of access to comparable datasets, our analysis is limited to descriptive comparisons. Our results reveal that civilian blasts often result in serious injury with involvement of multiple body areas. Thus, we believe that even with descriptive comparisons, we can make some general conclusions regarding the similarities and differences between the two groups. Finally, although the patients were drawn from a national patient pool, the data were only from a 1-year period. Although we agree that understanding trends over time would provide value to the discussion of blast injury, we believe a snapshot of injuries in a given year is appropriate to provide some insight into our research questions.

Frequency of Civilian Blast Injuries

Of all patients captured in the NTDB, 0.3% were seen after a blast injury. According to the American College of Surgeons 2016 NTDB annual report, the most recent year available, the most common listed mechanism of injuries were “fall” (44% [380,800 of 861,888]) and “motorvehicle collision” (26% [223,866 of 861,888]). Patients with blast injuries were treated in comparable proportions to those treated as a result of injuries resulting from fire, stings, overexertion, and other environmental causes. [1]. Although blast injuries led to a small proportion of the patient encounters in our cohort, especially compared with other, more common causes of trauma, they roughly occurred as often as other mechanisms of trauma deemed impactful enough to justify focused research and education. Based on this, we believe that civilians with injuries present to NTDB trauma centers with sufficient regularity to serve as a population that can allow for research and training opportunities with military relevance, but such studies likely would need to involve multicenter collaborations.

Mechanism and Demography of Civilian Blast Injuries

In our study, fireworks and accidental explosions of various pressurized containers represented the most reported mechanisms of blast injuries (56% [1504 of 2682]). Injuries that resulted from pressurized container explosions likely can be directly compared with blast injuries in military settings, as materials used in those devices release their explosive energy over the course of microseconds. The rapid conversion of solid or liquid into a quickly expanding hot gas produces a blast wave, which can lead to primary blast injuries as a result of barotrauma, endangering gas-filled organs such as the lungs or middle ear. Fireworks and other pyrotechnics release their energy much more slowly, and thus do not produce substantial barotrauma-induced (“primary”) blast injuries nor blunt injuries resulting from the body being thrown after a blast wave (tertiary blast injuries) [19]. However, these materials can produce serious secondary injuries (such as those resulting from shrapnel) or quaternary injuries (that is, those resulting from exposure to heat, light, or in some cases, toxic substances generated after a blast) [12]. Although this may limit the generalizability of research into firework-related injuries with regard to higher-energy blasts, they may be comparable to lower energy blasts, such as those produced by improvised explosive devices (IEDs). In a case series of IED injuries sustained by 100 coalition service members in Iraq, Ramasamy et al. [16] noted significant primary blast injuries in only 3.7% of patients. The authors hypothesized the design of IEDs at that time led to a narrow blast wave with a wide area of shrapnel leading to higher rates of secondary injury. Therefore, it may be reasonable to consider civilian blast mechanisms as comparable with those in modern military combat.

Our results suggest that in 2016, most patients with blast injuries presenting to NTDB-participating centers were men (86% [2315 of 2682]). Compared with published case series of military casualties from recent conflicts, our study group included more women (14% versus ranges from 2.5% to 5% in military studies), and our population skewed older, with a mean age of 38 years in our study (compared with average ages in published cohorts of 24, 26, and 27 years) [4, 7, 14]. Additionally, 13% (349 of 2682) of patients in our cohort were older than 60 years, pointing to a population of patients who experience civilian blast injuries and who may not have an close military analogue. Thus, civilian providers can expect an older and more diverse cohort, likely requiring modified workup and treatment approaches compared with those developed from experience gained during military conflict.

Injury Severity and Characteristics of Civilian Blast Injuries

In this series, 2% of patients died as a result of their injuries, which compared favorably with overall NTDB case fatality rates of 4%. However, these injuries resulted in substantial morbidity [1]. The mean number of injuries, ISS (6 ± 7.9), and percentage of patients with an ISS score representing a serious or severe injury (23% [618 of 2682]) in our cohort are comparable with those in patients treated for blast injuries in Operation Iraqi Freedom [9]. Of 4623 patients treated for blast injuries in Operation Iraqi Freedom from 2004 to 2007, the mean ISS was 5, with an average of four injuries per episode. However, in this study, battlefield casualties who died before transfer to a Level III military treatment facility were not included, likely diminishing the extent to which battlefield injuries appeared to be severe [9].

When we compared the overall pattern of injuries in our cohort with those sustained by a cohort of 279 Marines and United States Navy personnel who were injured during the major combat phase of Operation Iraqi Freedom (March 2003 to April 2003) [14], we noted a similar proportion of upper extremity involvement (33% in both cohorts) and more frequent involvement of the face (28% versus 14%) and head (10% versus 4%) in our study. In contrast, our civilian cohort had lower involvement of the lower extremity than patients in the previous cohort (11% versus 35%). Proportions of thoracic, pelvic, spinal, and abdominal involvement were similarly low in both cohorts [22]

We found that civilian blast injuries seem comparable in overall severity and upper extremity involvement to those in military populations. In addition, they are more likely to involve the head and face, with fewer lower extremity injuries. Although there is some reason to believe published ISS scores may underestimate the extent of military blast trauma, our results suggest experience with or innovation in treating civilians with blast injuries should be at least somewhat applicable to military cohorts.

Conclusion

We found that blast injury appears to occur within the US civilian population frequently enough to justify increased research attention and to serve as a clinical surrogate for military studies in future interwar periods. Civilian blast injuries appear more likely to involve women and older patients as well, and further research into the effects of blast injuries on these groups could lead to improved treatments for more diverse cohorts. Given the relative infrequency of blast injuries, we believe that further research would be most effective if conducted through multicenter collaborations and/or with the use of blast-specific registries. Analysis of temporal and or geographic variations in blast may identify “hot spots” or trauma centers that treat a disproportionate number of patients with blast injuries and might help identify sites that would be especially appropriate as training centers. The mechanism of blast, although more likely to result from accidental interaction with fireworks or pressurized containers than military blast trauma, results in injuries with similar severity and wounding patterns. This suggests interventions targeted at improving civilian blast care could provide benefit to military patients.