Page 114 - JSOM Winter 2022

We undertook this study to better characterize the influence We collected data on patient demographics, prehospital clin-
of ARDS in combat casualties from recent combat operations ical parameters, procedures performed, aeromedical evacu-
between 2003 and 2015. We hypothesized that risk from mor- ation, and laboratory data. Specifically, patient age, gender,
tality from ARDS would be higher for an explosive mechanism weight, height, race, ICD-9 codes, ISS, and Current Procedural
of injury (MOI), increased injury severity score, early vital Terminology (CPT) codes for complications were extracted.
sign abnormalities, laboratory derangements, and increased MOI was categorized as gunshot wound, explosion, motor ve-
amounts of blood product transfusion. hicle collision, or other. Ventilator data could not be reliably
collected and was omitted. Fluid volumes of resuscitation and
Methods blood transfusion within the first 24 hours after injury was
also calculated. Any additional recorded medical complica-
Study Design and Participants tions were also collected.
Approval for this study was obtained from the US Army In-
stitute of Surgical Research and Brooke Army Medical Center Statistical Analysis
Institutional Review Board. While maintaining full compliance Univariate analysis of mortality was performed with signifi-
with the Department of Health and Human Services’ Health cance set at p ≤ .05. The χ or Fisher exact tests were used for
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Insurance Portability and Accountability Act, we conducted a categorical data. Median and interquartile range (IQR) were
retrospective study of all US Servicemembers 18 years old or reported, and Wilcoxon rank-sum tests were performed for
older serving in theaters of operation from 2003 to 2015 using continuous and nonnormally distributed variables. Significant
the DoDTR, formerly the Joint Theater Trauma Registry, by factors were then included in a multivariable logistic regres-
ICD-9 code listed as ARDS/respiratory failure. We retrieved all sion model for mortality. Statistical analysis was conducted
DoDTR ARDS patients. ARDS is classically defined according using JMP version 13.2 (SAS Institute Inc., https://www.sas.
to Berlin Criteria: having bilateral opacities, a Pao :Fio ratio com/en_us/home.html).
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(PFR) <300, imaging suggestive of noncardiogenic pulmonary
edema, acute onset within 7 days of injury, and no evidence
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of cardiac dysfunction. However, for this study, we defined Results
ARDS simply by ICD-9 coding and not by the typical Berlin Table 1 shows patient demographics. We identified 182 Ser-
Criteria, as several data points needed to make the criteria de- vicemembers with a diagnosis of ARDS. The average age was
termination were not available. Our study group’s exclusion 26.6 years old (21–31), and 96.7% of patients were male.
criteria included any patient who was not a US Servicemember, Most patients served in the US Army (n = 140, 76.9%) and
age < 18 years old, and those without an identifiable diagnosis suffered their injuries in Operation Iraqi Freedom (OIF). The
of ARDS. Informed consent was waived for this analysis due most common mechanism of injury was an explosion, ac-
to the retrospective nature. The primary outcome of this study counting for 67.6% of all injuries. Mean ISS was 29.2 and
was death at or before 30 days based on chart review. overall mortality was 32.8%.

TABLE 1 Demographic and Injury Data of the Study Cohort
Survivors NonSurvivors
Factor n = 137 n = 45 p Value
Age mean (range) 26.6 (19–43) 26.4 (19–47) .564
Male, No. (%) 134 (97.8%) 42 (93.3%) .162
Branch .721
Army, No. (%) 103 (75.2%) 37 (82.2%)
Marine, No. (%) 24 (17.5%) 6 (13.3%)
Mechanism of injury .035
Gunshot wound, No. (%) 24 (17.5%) 4 (8.89%)
Explosion, No. (%) 90 (65.7%) 33 (73.3%)
MVC, No. (%) 12 (8.76%) 4 (8.89%)
Other, No. (%) 11 (8.0%) 4 (8.89%)
Theater (OIF), No. (%) 94 (68.6%) 31 (68.9%) .972
Injury Severity Score, mean (range) 27.4 (2–75) 34.7 (1–75) .01
AIS BR1 head, mean (range) 1.45 (0, 5) 1.51 (0,6) .847
AIS BR2 face, mean (range) 0.64 (0, 2) 0.62 (0,4) .765
AIS BR3 neck, mean (range) 2.05 (0, 5) 2.36 (0,6) .355
AIS BR4 thorax, mean (range) 1.55 (0, 5) 1.27 (0,5) .333
AIS BR5 abdomen/pelvis, mean (range) 2.22 (0, 5) 1.91 (0,5) .338
AIS BR6 spine, mean (range) 1.44 (0, 5) 2.42 (0,6) <.001
ICU days, mean (range) 14 (9–26) 9 (4–27) .026
Ventilator days, mean (range) 11 (7–20) 9 (3–21) .275
Hospital days, mean (range) 31.5 (10–60) 9 (3–23) <.001
All reported in N (%), p value, or mean (range), Wilcoxon/KW test.
MVC = motor vehicle collision, OIF = Operation Iraqi Freedom, AIS = Asia Impairment Scale, ICU = intensive care unit.

112 | JSOM Volume 22, Edition 4 / Winter 2022