REBOA for the Treatment of Blast Polytrauma: Zone 3 Provides Cerebral Perfusion, Attenuates Organ Dysfunction and Reperfusion Coagulopathy Compared to Zone 1 in a Swine Model

Abstract

Background: Resuscitative endovascular balloon occlusion of the aorta (REBOA) is a lifesaving therapy for hemorrhagic shock following pelvic/lower extremity injuries in military settings. However, Zone 1 aortic occlusion (AO; above the celiac artery), while providing brain/cardiac perfusion, may induce/worsen visceral ischemia and organ dysfunction. In contrast, AO Zone 3 (below the renal arteries) provides abdominal perfusion potentially minimizing ischemia/reperfusion injury. We hypothesized that, compared with AO Zone 1, AO Zone 3 provides neuro/cardioprotection while minimizing visceral ischemia and reperfusion coagulopathy after severe traumatic hemorrhage due to pelvic/lower extremity injuries.

Methods: Fifty-kilogram male Yorkshire swine underwent a blast polytrauma injury followed by a resuscitation protocol with randomization to no AO (No AO, n = 6) or AO with REBOA at Zone 1 (AO Zone 1; n = 6) or Zone 3 (AO Zone 3; n = 4). Vital signs and intracranial pressure (ICP) were monitored for 240 minutes. Citrate native and tissue plasminogen activator challenge thrombelastography, prothrombin time, creatinine, lipase, total bilirubin, troponin, and enzyme-linked immunosorbent assays protein levels were measured at set intervals.

Results: Both AO groups had significant increases in mean arterial pressure during aortic occlusion. All three groups had significant increases in ICP, but final ICP in the No AO group (26 ± 5.8 mm Hg) was significantly elevated compared with AO Zone 1 (17 ± 5.2 mm Hg) and AO Zone 3 (16 ± 4.2 mm Hg) ( p < 0.01). The final mean troponin in the No AO group (4.10 ± 5.67 ng/mL) was significantly higher than baseline (0.03 ± 0.02 ng/mL, p < 0.05), while the two AO groups had no significant changes ( p > 0.05). AO Zone 1 was the only group associated with hyperfibrinolysis ( p < 0.05) and significantly increased prothrombin time ( p < 0.05). Only AO Zone 1 group had significantly higher markers of organ damage.

Conclusion: Compared with AO Zone 1, AO Zone 3 provided similar neuro/cardioprotection but with less organ dysfunction and coagulopathy. This study suggests that Zone 3 REBOA may be preferable over Zone 1 for treating military relevant blast polytrauma with minimal intra-abdominal and chest trauma, but further clinical investigation is warranted.

Figure 1.

Graphical representation of experiment. Following instrumentation and anesthesia swine underwent an injury series comprised of bTBI, TI (bilateral, open femur fractures), and HS. AO Zone 1, AO Zone 3, or No-AO was employed during the last 30 minutes of HS. Resuscitation was initiated following HS utilizing 500mL of 5% albumin, followed by 1 unit of fresh whole blood, 500mL of 5% albumin, and then the remainder of each swine’s volume of shed fresh whole blood. Swine were euthanized 240 minutes after the conclusion of HS.

Figure 2.

Physiology temporal trends. Panel a) Mean Systolic Blood Pressure: * indicates p<0.05 in the comparison No-AO vs AO Zone-1; + indicates p<0.05 in the comparison of No-AO vs AO Zone-3; Panel b) Mean Intracranial Pressure: * indicates p<0.05 in the comparison of No AO vs both AO Zone-1 and AO Zone-3; c) Mean Cerebral Perfusion Pressure: * indicates p<0.05 in the comparison No-AO vs AO Zone-1; + indicates p<0.05 in the comparison of No-AO vs AO Zone-3.

Figure 3.

Coagulation changes in TEG R time and LY30% throughout the experiment. Left image, Thrombelastogram (TEG) R-time (min): AO Zone-1 had a significant increase in R-time above baseline at 60min postinjury (indicted by *), and significantly higher than No-AO’s and AO Zone-3’s (indicted by ^X). Right image, tPA Challenge TEG LY30: Only AO Zone-1 showed a significant change from baseline at 30 and 60min postinjury (indicted by *). At 60min postinjury, the AO Zone-1 tPA Challenge LY30 was significantly higher than AO Zone-3’s and No-AO groups (indicted by ^X).

Figure 4.

Changes in levels of active tPA. At 30 and 60min postinjury, AO Zone-1 active tPA levels were significantly elevated above the group’s mean baseline (indicted by *).