Page 72 - JSOM Summer 2019

junctional or limb tourniquets or current standard of care For the first 5 minutes after the hemicorporectomy, all exsan-
(i.e., CG). guinated blood was collected in a catchment bag, including
blood from the dismembered half of the animal. The MAP was
maintained to a goal of 60mmHg using volume infusions per
Materials and Methods
IACUC protocol. After 5 minutes, the first blood-catchment
This was an Institutional Animal Care and Use Committee bag was removed, weighed, and a 500mL pressurized bolus of
(IACUC)-approved, prospective, interventional trial using a Hextend (BioTime, https://www.biotimeinc.com) was infused.
porcine model. The animals were randomly assigned to either MAPs were recorded every minute for the first 5 minutes and
the AAJT arm or CG arm of the study. Veterinarians induced then every 5 minutes until the animal expired or the 60-minute
and maintained anesthesia at all times, according to the IA- predefined end point was reached. At 60 minutes, the second
CUC-approved protocol. After induction and orotracheal in- blood-catchment bag was removed and weighed. Dressings
tubation, peak airway pressures were obtained. Pressures were and gauze were also weighed before and after the procedure to
taken before placing the AAJT and again with the AAJT in determine additional blood loss, and this amount was added
place (but before wound creation). Neuromuscular blockade to total blood loss. Total normal saline given and time of ini-
was maintained throughout the trial using a long-acting, non- tial hemostasis were recorded. The primary outcome measure
depolarizing neuromuscular blocking agent. was survival at 60 minutes. Secondary outcomes were time
to initial hemostasis, MAP, blood loss at 5 minutes, and total
Before hemicorporectomy, the weight of the animal was re- blood loss.
corded and a carotid arterial catheter was placed to measure
mean arterial pressure (MAP). The internal jugular vein was Results
cannulated and used for medication infusion and resuscita-
tion, which included both crystalloid and Hextend, based on A total of six animals were used in the study. Given the initial
MAP. MAP was measured throughout the trial, which had an results of the study, researchers and veterinarians believed that
end point of 60 minutes. additional animal use could not be justified.

For the hemicorporectomy, a blade lever device was used to Mean pre-intervention weight was similar for the AAJT and
reliably produce a wound through the bilateral femoral heads, CG groups. Mean initial MAP was slightly higher for the
transversely across the pelvis approximately 2.2cm distal to AAJT group, indicating that this group would be somewhat
the navel. This wound resulted in a transection of the internal disadvantaged pre-intervention. Medians, means, and stan-
and external iliac arteries and veins bilaterally with complete dard deviations of important outcome variables are provided
segmentation of the animal at the abdominal/pelvic junction. in Table 1.
For the AAJT group, the AAJT was placed across the abdomen A one-sided Fisher exact test was used to test the hypothesis
of the animal with the expandable bladder located in the mid- that the proportion surviving to 60 minutes was greater in the
line at the navel, just superior to the location of the hemicor- AAJT group compared with the CG group. The 60- minute
porectomy. Before creating the wound, a researcher placed a survival was significantly better in the AAJT group (100%
fist proximal to the navel and applied pressure. After hemicor- survival) versus the CG group (none survived at 60 minutes;
porectomy, the abdominal pressure from the fist was removed death occurred at 8, 15, and 41 minutes). A Kaplan-Meier
and the AAJT was immediately inflated. After 5 minutes, the survival analysis (with a log-rank test) was performed to com-
wound was covered with two rolls of Kerlix gauze (Covid- pare the survival experience of the two groups. Statistical sig-
ien/Medtronic, https://www.medtronic.com/) and was held in nificance was achieved after six swine procedures. The AAJT
place with an elastic bandage (i.e., Israeli dressing). group had a significantly better survival experience than the
CG group (log-rank χ [1 df] = 5.052; p = .025).
2
For the CG group, a researcher placed his fist proximal to the na-
vel, as was done in the AAJT arm. After hemicorporectomy, two The mean time to hemostasis was 30 seconds for the AAJT.
rolls of CG were packed over the areas of hemorrhage, direct Only one animal achieved hemostasis in the CG group (at
pressure was initiated by two additional researchers, and then 1,980 seconds). MAP data are reported in Figure 1. The mean
the initial researcher’s fist was removed. The dressing was held in MAP at 5 minutes was higher in the AAJT arm than the CG
place by two researchers for 3 minutes. After this 3 minutes of di- arm (77mmHg versus 18mmHg, respectively). The AAJT
rect pressure, the CG was backed with two rolls of Kerlix gauze arm maintained blood pressure until the 60-minute end point
and held in place with an elastic bandage (i.e., Israeli dressing). (mean MAP, 73 mm Hg).

TABLE 1 Outcome Variables Data
Variable Median Mean SD Median Mean SD
Weight, kg 50 49.23 1.33 50.9 49.97 1.62
Initial MAP, mmHg 88 87 12.53 67 70 9.85
Initial hemostasis, seconds 29 30.67 3.79 N/A N/A N/A
a
Blood loss in 5 min, g 545 525 155.96 1,300 1,323.33 97.13
Total blood loss, g 920 918.33 2.89 2,550 2,718.33 390.72
Peak airway, pre AAJT 20 19.67 2.52 18 18.67 1.15
Peak airway, post AAJT 28 26 3.46 25 25.33 4.51
AAJT, Abdominal Aortic and Junctional Tourniquet, CG, Combat Gauze; N/A, not applicable; MAP, mean arterial pressure.
a Only one animal achieved hemostasis in the CG group (at 1,980 seconds).

70 | JSOM Volume 19, Edition 2 / Summer 2019