Page 34 - JSOM Spring 2021

Ringers solution were administered as needed to maintain a of the REBOA catheter) was 4.2 ± 2.2 minutes for all REBOA
MAP greater than 60mmHg. Animals were observed for an animals and did not differ between the two REBOA groups
additional 3.5 hours without further interventions. Arterial (Table 2). The two-step conversion of AAJT to REBOA in the
blood samples were taken at baseline, following hemorrhage, SAO group resulted in various acute effects, including a drop
after the initial AAJT period (T0), then 30, 60, 120, 180, and in carotid blood pressure, decrease in pectoralis NIRS, increase
240 minutes after randomized intervention. Animals were eu- in both left and right thigh NIRS, and increased EtCO during
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thanized using intravenous pentobarbital 100 mg/kg (i.e., eu- the conversion. Additionally, an increase in carotid MAP and
thanasia solution) and in accordance with the 2013 American EtCO was observed after balloon inflation (Table 2, Figure 2).
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Veterinary Medical Association Guidelines for the Euthana-
sia of Animals. Immediate laparotomy with inspection of the Posttreatment
small and large bowels for signs of compression damage was Hemodynamic values during the observation period were not
performed. different between the groups (Figure 2). All groups experienced
a modest increase in MAP of about 15mmHg in response to
Outcomes and Analysis the administration of 500mL of shed blood prior to interven-
Primary outcomes of this study were the ability to correctly tion deflation. After AAJT or REBOA deflation, all groups
place the REBOA and time of REBOA deployment. Other out- had a return of femoral arterial waveform within 5 minutes.
comes included survival, hemodynamics (e.g., blood pressure All groups also had an acute increase in EtCO 5 minutes after
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measurement, end-tidal CO [EtCO ] level, heart rate [HR]), removal, with values remaining above baseline for the remain-
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and markers of tissue damage (e.g., lactate, blood urea nitro- der of the observation period. Biochemical markers of shock
gen [BUN], creatinine, pH, potassium, myoglobin levels). and tissue injury were assessed throughout the protocol (Fig-
ure 3). No differences were observed among groups in any of
Data are presented as mean ± standard deviation for contin- the laboratory values assessed at any time point. A sharp drop
uous variables. One-way analysis of variance (ANOVA) was in blood pH and a corresponding increase in lactate levels
used for baseline comparisons, and two-way repeated mea- were observed in all groups following intervention removal.
sures ANOVA was used for continuous variables over a time Potassium, BUN, creatinine, interleukin-6, and myoglobin lev-
course. Survival was analyzed using log-rank analysis. Fisher’s els all were elevated throughout the observation period in all
exact test was used for categoric variables. Statistical analy- groups, with no differences among groups. However, creati-
sis and data management were performed using Excel 2010 nine and myoglobin levels were persistently higher in the CAO
( Microsoft) and SigmaPlot 12 (Systat Software). group following intervention removal, but these differences
did not reach statistical significance. At laparotomy, no gross
evidence of intestinal injury was observed in any animal, and
Results
no abdominal tissue damage was noted on inspection. How-
Baseline Characteristics ever, histologic testing was not performed.
A total of 17 animals weighing 82.2 ± 7.4kg were included for
analysis: CAO (n = 5), OAO (n = 6), SAO (n = 6). One animal Discussion
was removed from analysis in the CAO group because of iat-
rogenic injuries that occurred during surgical preparation. The We have demonstrated that conversion from the AAJT to
groups were similar at baseline (Table 1). Zone 3 REBOA is technically feasible in a swine model of se-
vere controlled hemorrhage and that transition between the
Hemorrhage and Intervention two devices can be accomplished with or without prior defla-
At baseline, animals had a mean MAP of 63.2 ± 5.9mmHg, an tion of the AAJT device. Initiation of REBOA prior to AAJT
HR of 94 ± 11 beats per minute (bpm), and an EtCO of 40.6 deflation mitigated BP, HR, and EtCO variability compared
2
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± 3.2mmHg, with no statistically significant difference among with advancement and inflation after AAJT deflation but was
groups (Table 1). All animals except one required temporary associated with increased difficulty in obtaining and confirm-
suspension of hemorrhage, resulting in an average loss of 35.9 ing transfemoral access to the infrarenal aorta.
± 4.2% of the estimated blood volume. Hemorrhage resulted
with a MAP of 41.8 ± 11.0mmHg, a HR of 155 ± 31bpm, and After induction of class IV shock and placement of the AAJT
an EtCO of 36.6 ± 4.5mmHg. Inflation of the AAJT resulted device, proximal aortic MAP returned to pre-hemorrhage val-
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in an absence of waveform in the femoral arteries, with a MAP ues. while the decrease in femoral artery MAP was consis-
of 26.2 ± 15.7mmHg and a pulse pressure of 2.5 ± 5.8mmHg tent with prior studies. 18,19 In each of the three groups (CAO,
after 10 minutes. Most animals required some additional in- OAO, SAO), no sustained significant hemodynamic differ-
flation to maintain the required 300mmHg inflation pressure ences were observed with respect to carotid MAP, femoral
in the air bladder. At the end of the initial 60-minute period of MAP, EtCO , and HR (Figure 2). However, SAO was found
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AAJT inflation, MAP was 67.7 ± 17.4mmHg, HR was 174 ± to yield statistically significantly different hemodynamic ef-
34bpm, and EtCO was 42.2 ± 4.3mmHg. fects within the time periods during and shortly after con-
2
version of AAJT to REBOA. These differences included a
In the REBOA groups, catheterization was attempted using ul- drop in carotid MAP, decreased pectoralis NIRS, increased
trasound guidance. All femoral arteries in the SAO group were left and right leg NIRS, and increased EtCO (Table 2). These
2
successfully cannulated and the REBOA correctly placed. One changes are consistent with hemodynamic effects seen directly
artery in the OAO group was improperly cannulated, with following cessation of aortic occlusion. The variations can be
the REBOA inserted into the femoral vein. This was noted as attributed to the temporary lapse in aortic occlusion during
a failure of REBOA insertion, and the animal was excluded SAO placement, which allows for transient reperfusion of the
from further analysis. Time to REBOA inflation (including ar- bilateral lower extremities, likely resulting in a washout of
terial access, introducer sheath placement, and advancement built-up lactate and carbon dioxide. These effects are seen in

32 | JSOM Volume 21, Edition 1 / Spring 2021