Exploration of abdominal aorta morphology for resuscitative endovascular balloon occlusion of the aorta (REBOA) placement evaluation with an analysis of zone II anatomy and aortic branch diameters

Resuscitative endovascular balloon occlusion of the aorta (REBOA) use closer to the point-of-trauma could reduce prehospital mortality by temporary controlling non-compressible truncal hemorrhage (NCTH). Reliable external anatomic landmarks or body surface reference points, such as mid-sternum for zone I, are not available for zone III balloon placement. In the absence of radiographic or ultrasound balloon position confirmation, unintentional zone II placement can therefore occur. Although evidence is limited, the concerns regarding possible zone II occlusion could hamper implementation of REBOA in prehospital settings as imaging guidance is not always available. The aim of this study was to provide an extensive overview of aortic anatomy with zone II morphology and aortic branch diameters in European patients without vascular disease history. Concurrently, multiple previously proposed REBOA insertion lengths were validated with comparison of accidental out of zone III error rates, extensiveness of unintentional zone II placements, and occlusion of the aortic branches. Contrast enhanced computed tomography scans from 242 Dutch non-trauma patients (146 females; mean age, 46 years) were analyzed. Central luminal line distances, including skin depths, were measured from the bilateral common femoral artery access points (FAAPs) to the middle and boundaries of the aortic occlusion zones and proximal and distal origins of the visceral branches. Mean intravascular distances from the FAAPs to the levels of interest and branch diameters were determined for all combined sex and age-based subgroups. Subsequently, a 40-mm long balloon introduction simulation was performed to precisely determine the extensiveness and degree of zone II branch occlusion of earlier proposed REBOA insertion lengths. The mean distance from the left and right FAAPs to mid-zone III ranged between 233 and 251 mm and 238 and 257 mm, respectively. Mean zone III length was 87 mm (females, 85.4 mm; males, 88.7 mm) with a maximum difference of 4 mm (4.7%) between the four subgroups. The right iliofemoral trajectory was 5 mm longer regardless of sex or age. Mean zone II length was 45 mm (females, 43.8 mm; males, 47.3 mm), with a maximum 6 mm difference (14.3%). The mean superior mesenteric artery and celiac trunk diameters were 11.4 and 11.2 mm in females and 12.7 and 11.9 mm in males, respectively. Up to the celiac trunk, 66% of the mean age-based elongation originated in the iliofemoral trajectory (6 of total 9 mm), regardless of insertion side. No statistically significant age-based differences were seen for the zone lengths or branch diameters. Unintentional zone II placement error rates up to 71% were observed for previously proposed fixed-distance insertion lengths, but the extensiveness of aortic branch occlusion varied. Partial iliac artery placement error rates varied between 0 and 26%. Variable distance REBOA insertion lengths would cause erroneous zone II occlusion in maximal 15% of placements and never cause blood flow obstruction to the other major visceral branches. Unintentional zone II balloon placement rates varied between the previously proposed zone III REBOA insertion lengths, but the total percentage and degree of erroneous visceral branch occlusion was acceptably low. The presumed and feared high risk of unintentional zone II occlusion in the absence of imaging guidance is not justified.