Page 22 - JSOM Winter 2024

In the pelvic distal compartment, IAP reached a mean of derangement or histological evidence of organ ischemia at
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36cmH O with no fluid and a mean of 41cmH O with 28 and 90 days. However, higher IAPs were required to

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500mL of intraperitoneal fluid. An AAJT-S inflation pressure adequately contact the liver, diaphragm, and paracolic gutters
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of 250mmHg has already been shown to completely occlude in human cadavers. Titratability and requirement for higher
aorta and inferior vena cava flow in zone 3, making pelvic IAPs to control hepatoportal hemorrhage have been dem-
compartment pressure change less important. The previously onstrated—38.9mmHg IAP achieved 90% survival. Foam
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described pressure response curve of rapid initial increase fol- applications to achieve an IAP of 60mmHg for 10 minutes
lowed by a leveling off was also seen in the distal pelvic com- demonstrated survival benefit with no significant alteration of
partment but slightly later. We also demonstrated significant physiological parameters with the exception of transient creat-
pressure increases both before and after adding 500mL of in- inine and lactate elevation for less than 24 hours. There was no
traperitoneal fluid. The presence of 500mL of free fluid in the clinical or histological evidence of organ ischemia, necrosis, or
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peritoneal space did not adversely change the effect of AAJT-S intra-abdominal compartment syndrome. REBOA in zone 1
application. While larger volumes of intraperitoneal bleeding is only to be performed when an operation will proceed within
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may certainly occur with NCTH, if the AAJT-S is applied at 15 minutes, while the AAJT-S could stay on for 90 minutes
the point of injury, a 500-mL volume would appear to be rea- (or longer with titratable inflation) before lasting physiologi-
sonable for this study. cal derangement occurs. 34,35
We did consider indirect manometric pressure measurements Our cadavers understandably had low BMIs. There was a
via balloon manometers inserted into the bladder and stom- statistically significant positive effect of BMI on achieved epi-
ach. However, we opted for direct measurements via intraperi- gastric pressures with (P=0.003) and without 500mL of in-
toneal balloon manometers. Direct abdominal gas insufflation traperitoneal fluid (P=0.001.) However, regardless of BMI,
pressure is equivalently reflected in intravisceral balloon ma- the mean epigastric pressure achieved was still sufficient to
nometer pressure, 30,31 and this approach may be used in future tamponade celiac trunk branches and solid organ flow. The
live animal and human research. BMI range of our sample population was 16.7 to 22.9kg/m ,
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undoubtedly slightly lower than the average in military pop-
It has been demonstrated separately that, in hypovolaemia, ulations. Adiposity and muscle mass profiles likely also differ,
increasing IAP can only lead to increases in proximal ve- with all weights in this study being under 65kg and all heights
nous pressures when right atrial pressure exceeds the IAP. 32,33 under 173cm. A broader study involving more cadavers with
A normal central venous pressure reading is between 8 and BMIs more typical of the military population and account-
12mmHg. This value is altered by volume status and/or venous ing for a range of adiposity and muscle mass would be re-
compliance. The epigastric compartment pressures we gener- quired to understand BMI’s contribution more definitively, but
ated with AAJT-S would, therefore, be sufficient to tampon- we believe that this is of lesser importance. It is also unclear
ade venous injury. We did experience some variation in the whether gender has a clinically or statistically significant effect
AAJT-S inflation pressure required to generate clinically sig- on achievable epigastric or pelvic compartment pressures due
nificant proximal epigastric compartment pressures, but this is to the small sample size, with only one male cadaver, but it
clearly a titratable effect. The titratability is demonstrated by seems unlikely.
our data points, as well as intra-abdominal insufflation with
gas, self-expanding polyurethane foam, and hyper- pressure Consideration was given toward intubating the cadavers and
intra-abdominal fluid titratably reducing hemorrhage in ventilating with a bag-valve-mask to examine the effects of
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splenic, portal, hepatic, and mesenteric injuries, as well ventilatory pressures on compartment pressures. While this
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as iliac and pelvic injuries. Further research will examine proved unachievable, the epigastric pressures achieved (54.6
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whether lower AAJT-S inflation pressure can achieve optimal and 52.25cmH O) would not be considerably affected by
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epigastric compartment pressure for temporizing arterial ver- the bag-valve-mask tidal range of pressures. Positive end-
sus venous hemorrhage and whether ventilatory pressures in- expiratory pressure in acute respiratory distress syndrome ap-
fluence this. proaching 20cmH O could conceivably see abdominal pressure
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variation, but bag-valve-mask ventilation, typically in the range
Concerns have naturally been raised about intestinal dam- of 4–6cmH O end pressure, is unlikely to have a clinically sig-
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age and necrosis after application of the AAJT-S. Previous nificant effect. Animal studies have not shown an effect, and
short-application, ethically approved human trials have shown human volunteers wearing the device over short periods can
no issues. Animal studies have identified that after a 60-minute breathe and even deliver lectures.
AAJT-S application, any minimal ischemic reperfusion injuries
in hemorrhagic swine were resolved at 2 weeks, including in We accept that the abdomen of a living patient with multiple
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all intestinal, skeletal muscle, and neural tissues. Applications wounds may prove less compliant in holding pressure, but tis-
beyond 90 minutes led to some distal necrotic changes. One sue planes do move after trauma (except in the most severe
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study looked at whether AAJT-S abdominal application for up eviscerating injuries) and seal most holes. Infrarenal occlu-
to 240 minutes resulted in hepatic impairment, but found that sion (zone 3) was previously thought to have the potential to
an application of this duration was still recoverable within an increase hemorrhage if bleeding was occurring proximally due
intensive care unit environment. The current manufacturer’s to increased hydrostatic pressures in arteries that may be pro-
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guidelines for AAJT-S recommend abdominal application for duced proximal to the occlusion. We have now demonstrated
no longer than 60 minutes. 36 that AAJT-S offsets potentially increased proximal hydrostatic
pressure by the marked intra-abdominal compartment pres-
Thermo-reversible phase-shift foam applications for 3 hours sure increase temporizing zone 1 vascular injury—in hypo-
have demonstrated significant survival benefit, with IAPs of volemia from haemorrhage, this offsetting would perhaps be
around 20mmHg and without hepatic, renal, or metabolic most marked.
20 | JSOM Volume 24, Edition 4 / Winter 2024