Page 79 - JSOM Winter 2021

Development of a Swine Polytrauma Model

in the Absence of Fluid Resuscitation

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Hossam Abdou, MD ; Neerav Patel, MD ; Joseph Edwards, MD ;
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Michael J. Richmond, BS ; Noha Elansary, BS ; Jonathan Du, BS ;
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David Poliner, DO, MPH ; Jonathan J. Morrison, MB, ChB, PhD, FRCS, FACS *
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ABSTRACT
Background: In locations in which access to resuscitative therapy immediately available. There is a pressing need for resuscita-
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may be limited, treating polytraumatized patients present a chal- tive adjuncts that can be utilized in patients with NCTH or
lenge. There is a pressing need for adjuncts that can be delivered polytrauma who have delayed access to appropriate medical
in these settings. To assess these adjuncts, a model representative care. To this end, we need an appropriate model to evaluate
of this clinical scenario is necessary. We aimed to develop a hem- these potential resuscitative adjuncts. Though hemorrhage
orrhage and polytrauma model in the absence of fluid resuscita- and polytrauma models exist, they importantly involve active
tion. Materials and Methods: This study consisted of two parts: fluid resuscitation within an acute timeframe. This simulates
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pulmonary contusion dose-finding (n = 6) and polytrauma with a level of access to care that does not reflect the context we
evaluation of varying hemorrhage volumes (n = 6). We applied hope to evaluate further.
three, six, or nine nonpenetrating captive bolt-gun discharges
to the dose-finding group and obtained computed tomography In this study, the aim is to develop a reliable hemorrhage and
(CT) images. We segmented images to assess contusion volumes. polytrauma model in the absence of fluid resuscitation or other
We subjected the second group to tibial fracture, pulmonary intervention. This model will include pulmonary contusion,
contusion, and controlled hemorrhage of 20%, 30%, or 40% tibial fracture, and controlled hemorrhage. The pulmonary
and observed for 3 hours or until death. We used Kaplan-Meier contusion should be replicable and quantifiable. The ideal
analysis to assess survival. We also assessed hemodynamic and model would afford enough time for delivery of a resuscitative
metabolic parameters. Results: Contusion volumes for three, adjunct immediately after end of trauma but be lethal within a
six, and nine nonpenetrating captive bolt-gun discharges were period of 2–3 hours in the absence of any intervention.
24 ± 28, 50 ± 31, and 63 ± 77 cm , respectively (p = .679).
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Animals receiving at least six discharges suffered concomitant
parenchymal laceration, whereas one of two swine subjected to Methods
three discharges had lacerations. Mortality was 100% at 12 and Study Design and Overview
115 minutes in the 40% and 30% hemorrhage groups, respec- The experiment was conducted at the University of Maryland
tively, and 50% at 3 hours in the 20% group. Conclusion: This School of Medicine, which is accredited by the American Asso-
study characterizes a titratable hemorrhage and polytrauma ciation for Laboratory Animal Science. The Institutional Ani-
model in the absence of fluid resuscitation. This model can be mal Care and Use Committee approved the protocol prior the
useful in evaluating resuscitative adjuncts that can be delivered start of animal study. We used adult male Hanford miniature
in areas remote to healthcare access. swine weighing between 60 and 80 kg. All swine were sub-
jected to an acclimatization period of at least 48 hours under
Keywords: Polytrauma model; pulmonary contusion; controlled the care of licensed veterinary staff. We provided the animals
hemorrhage; tibial fracture; delayed medical care; prolonged free access to food and water until the night prior to surgery at
casualty care; prolonged field care which point we fasted them overnight.

We divided the study into two parts: pulmonary contusion
dose-finding and delivery of polytrauma with evaluation of
Introduction
varying hemorrhage volumes. Both parts consisted of the same
About 90% of potentially preventable combat deaths are the three phases: anesthesia and instrumentation, induction of
result of acute hemorrhage, with the majority occurring prior trauma, and observation. We recorded hemodynamic indices
to admission to a medical facility. Mechanical hemorrhage continuously throughout the experiment. The laboratory pur-
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control has improved greatly; extremity tourniquets have re- chased all equipment used to conduct the experiment. At the
duced combat casualties 85%. However, control via direct end of the protocol, we euthanized animals with potassium
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pressure is ineffective in the setting of noncompressible torso chloride (> 2mmol/kg).
hemorrhage (NCTH), which accounts for two-thirds of com-
bat hemorrhage related casualties. 1,3,4 Anesthesia and Instrumentation
We sedated swine with Telazol (tiletamine and zolazepam for
It is difficult to provide therapy to complex patients with injection; 4–5mg/kg) and xylazine (1.5–2.2mg/kg) via intra-
NCTH or polytrauma, particularly in remote regions where muscular injection. We administered general anesthesia with
access to resuscitation fluid and operative intervention are not isoflurane by facemask followed by orotracheal intubation.
*Correspondence to jonathan.morrison@som.umaryland.edu
1–8 All authors are affiliated with the R Adams Cowley Shock Trauma Center, University of Maryland Medical System, Baltimore, MD.

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