Page 94 - JSOM Summer 2019

Methods affiliations, similar mechanisms of injury, similar theaters of
operations and similar composite injury severity scores (ISS),
Data Acquisition but less severe scores for the thorax body region (Table 1).
We identified subjects as part of a larger descriptive study of There was a trend toward worse AIS for the face region in
ED interventions for trauma patients in Iraq and Afghanistan the cricothyrotomy group but, conversely, a trend toward less
using predefined search codes. This is a retrospective review severe scores for the abdomen. Survival to hospital discharge
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of prospectively collected data within the registry. We searched rates were similar (Table 1). When using a binary cutoff of AIS
our data set for all subjects who had a documented SGA de- 3 or greater (serious) for the head, the cricothyrotomy group
vice or cricothyrotomy performed as the sole documented had a higher rate of serious head injuries (67.5%, n = 131
airway intervention before reaching the ED at a combat sup- versus 45.5%, n = 10, p = .0393). When applying the same
port hospital (CSH) or forward surgical team (FST). We ex- binary measurement to the face, we were unable to detect a
cluded subjects if they had more than one airway intervention significant difference (4.6%, n = 9 versus 4.6%, n = 1, p =
documented. .984). When documented in the prehospital setting, median
GCS scores were similar for the two groups (median 3 [IQR
The US Army Institute of Surgical Research regulatory office 3–6], n = 95 versus median 3 [IQR 3–7.5], n = 20, p = .591).
reviewed protocol H-16-005 and determined it was exempt We also found no difference for emergency department arrival
from institutional review board oversight. We obtained only GCS (3 [3–5.5], n = 188 versus 3 [3–5.25], n = 21, p = .469).
deidentified data.
Regression Analyses
Department of Defense Trauma Registry Description On univariable analysis, the odds ratio of survival was similar
The Department of Defense Trauma Registry (DODTR), for- for SGA versus cricothyrotomy (1.20, 95% CI 0.49–2.94). We
merly known as the Joint Theater Trauma Registry (JTTR), is then performed a series of multivariable analyses controlling
the data repository for DoD trauma-related injuries. 13,14 The for confounders comparing SGA versus cricothyrotomy. When
DODTR includes documentation regarding demographics, controlling for injury scores by body region, the odds ratio
injury-producing incidents, diagnoses, treatments, and out- was not significant (OR 1.14, 0.42–3.10). When controlling
comes of injuries sustained by US/non-US military and US/ for the presence of a serious head injury (AISBR1 3 or greater,
non-US civilian personnel in wartime and peacetime from the binary), the odds ratio was not significant (OR 1.06, 0.43–
point of injury to final disposition. The DODTR comprises 2.65). No significant difference was noted when controlling
all patients admitted to a Role 3 (fixed-facility) or FST with for the mechanism of injury (OR 1.12, 0.45–2.76), patient cat-
an injury diagnosis using the International Classification of egory (OR 1.17, 0.47–2.90), or ED GCS (OR 1.64 0.62–4.30).
Disease, Ninth Edition (ICD-9) between 800 and 959.9, near-
drowning/drowning with associated injury (ICD-9 994.1) or
inhalational injury (ICD-9 987.9) and trauma occurring within Discussion
72 hours from presentation. The registry defines the prehospi- We evaluated combat casualties undergoing either cricothy-
tal setting as any location prior to reaching an FST or a CSH rotomy or SGA for advanced airway management in the pre-
to include the Role 1 (point of injury, casualty collection point, hospital setting. We found no difference in survival between
battalion aid station) and Role 2 (temporary limited-capability these two groups. This finding persisted on multiple regression
forward-positioned hospital inside combat zone without sur- analyses controlling for several factors, including injury scores
gical support). The registry categorization scheme considers a by body region.
Role 2+ (or variant with surgical support) to be the ED.
Survival among patients undergoing either intervention
Analysis (54.6% for cricothyrotomy and 59.1% for SGA) was higher
We performed all statistical analyses using Microsoft Excel than previously published data. Studies on military prehospital
(version 10, Redmond, WA) and JMP Statistical Discovery airway interventions during the recent conflicts that reported
from SAS (version 13, Cary, NC). We compared study vari- mortality outcomes found a combined survival of 38.5% (15
ables between subjects undergoing cricothyrotomy versus of 39) for cricothyrotomy and 7.1% (1 of 14) for SGA. 15–18
SGA placement using a Student t-test for continuous variables The higher survival in our study may reflect exclusion from
expressed as means with standard deviations, Wilcoxon rank the DODTR of casualties who died before arrival to an FST
sum test for ordinal variables expressed as medians and in- or fixed-facility, whereas previous studies included those killed
terquartile ranges (IQRs), and χ test for nominal variables in action. Likewise, subjects in our study may have undergone
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expressed as numbers and percentages. For binary outcomes, stabilization at a battalion aid station or higher echelon of care,
we used a logistic regression analysis to report odds ratios. while previous reports primarily analyzed casualties evacuated
directly from the point-of-injury to an FST or fixed-facility.
Additionally, our study captured more exposures by compar-
Results
ison: 194 versus 39 cricothyrotomies and 22 versus 14 SGA.
Overall Analysis Our findings suggest clinically appropriate cricothyrotomy
During the study period, there were a total of 38,769 en- and SGA may be equally efficacious prehospital advanced air-
counters in the DODTR. Our predefined ED search codes way interventions for the combat trauma population.
captured 28,222 (72.8%) of those subjects. Within this data
set, there were 194 (0.7%) subjects who underwent cricothy- Overall, we found low incidence rates for both airway inter-
rotomy versus 22 (0.1%) who underwent SGA placement as ventions: 0.7% underwent cricothyrotomy, while 0.1% had a
the sole documented means of airway intervention. Subjects SGA inserted. These rates, however, are consistent with pub-
in the cricothyrotomy group compared with the SGA group lished military data. Multiple studies on US military prehos-
had a lower median age, similar gender distribution, similar pital cricothyrotomy describe incidence rates ranging 0.25%

92 | JSOM Volume 19, Edition 2 / Summer 2019