Transition of Resuscitative Endovascular Balloon Occlusion of the Aorta from Zone 3 to Zone 1 to Treat Hemodynamic Collapse during Continued Hemorrhage
Authors: Rall Jason M , Baker Kimberly J , Sandoval Melody L , Flinn Ashley N , Causey Marlin W 
Published: August 2023

ABSTRACT

Introduction
Noncompressible torso hemorrhage (NCTH) accounts for most potentially survivable deaths on the battlefield. Treatment of NCTH is challenging, especially in far-forward environments with limited capabilities. Resuscitative endovascular balloon occlusion of the aorta (REBOA) has shown promise in the care of patients with NCTH. REBOA involves introducing a balloon catheter into the descending aorta in a specific occlusion region (zones 1, 2, or 3) and acts as a hemorrhage control adjunct with resuscitative support. The balloon is placed in zone 3 in the infrarenal aorta for high junctional or pelvic injuries and in zone 1 proximal to the diaphragm for torso hemorrhage. Zone 1 REBOA provides more resuscitative support than zone 3; however, the potential for ischemia and reperfusion injuries is greater with zone 1 than with zone 3 REBOA placement. This study aims to determine the possible benefit of transitioning the REBOA balloon from zone 3 to zone 1 to rescue a patient with ongoing venous bleeding and impending cardiovascular collapse.

Materials and Methods
Yorkshire male swine (70–90 kg, n = 6 per group) underwent injury to the femoral artery, which was allowed to bleed freely for 60 s, along with a simultaneous controlled venous hemorrhage. After 60 s, the arterial bleed was controlled with hemostatic gauze and zone 3 REBOA was inflated. Five hundred milliliters of Hextend was used for initial fluid resuscitation. The controlled venous bleed continued until a mean arterial pressure (MAP) of 30 mmHg was reached to create an impending cardiovascular collapse. The animals were then randomized into either continued zone 3 REBOA or transition from zone 3 to zone 1 REBOA. Following 30 min, a “hospital phase” was initiated, consisting of cessation of the venous hemorrhage, deflation of the REBOA balloon, and transfusion of one unit of whole blood administered along with saline and norepinephrine to maintain a MAP of 60 mmHg or higher. The animals then underwent a 2-h observation period. Survival, hemodynamics, and blood chemistries were compared between groups.

Results
No significant differences between groups were observed in hemodynamic or laboratory values at baseline, postinitial injury, or when MAP reached 30 mmHg. Survival was significantly longer in animals that transitioned into zone 1 REBOA (log-rank analysis, P = .012). The average time of survival was 14 ± 10 min for zone 3 animals vs. 65 ± 59 min for zone 1 animals (P = .064). No animals in the zone 3 group survived to the hospital phase. Zone 1–treated animals showed immediate hemodynamic improvement after transition, with maximum blood pressure reaching near baseline values compared to those in the zone 3 group.

Conclusions
In this swine model of NCTH, hemodynamics and survival were improved when the REBOA balloon was transitioned from zone 3 to zone 1 during an impending cardiovascular collapse. Furthermore, these improved outcome data support the pursuit of additional research into mitigating ischemia–reperfusion insult to the abdominal viscera while still providing excellent resuscitative support, such as intermittent or partial REBOA.