INTRODUCTION: Retrograde Endovascular Balloon Occlusion of the Aorta (REBOA) is an effective management for the transient responder, but the ischemic consequences of complete aortic occlusion currently limit its use. Multiple DoD-funded preclinical studies have clearly demonstrated that partial REBOA reduces distal ischemia to potentially extend safe occlusion times, while still providing effective temporization of noncompressible torso hemorrhage. Early versions of REBOA devices were designed to completely occlude the aorta and had little ability to provide partial occlusion. Recently, a new REBOA device (pREBOA-PRO) was designed specifically to allow for partial occlusion, with the hypothesis that this may reduce the complications of aortic occlusion and extend safe occlusion times while maintaining the benefits on cardiac and cerebrovascular circulation as well as reductions in resuscitation requirements.
MATERIALS AND METHODS: To ascertain the impact of a new purpose-built partial REBOA device on the extension of safe occlusion time, the Partial REBOA Outcomes Multicenter ProspecTive (PROMPT) trial compared available data from the pREBOA-PRO with existing data from 200 clinical uses of pREBOA-PRO and available data in the AAST AORTA Registry were reviewed to design primary endpoints and clinical evidence for a prospective multi-center trial, the PROMPT Study. Together with the endpoints identified in preclinical studies of partial REBOA, primary endpoints for the PROMPT study were identified and power analyses were conducted to determine the target patient enrollment goals.
RESULTS: Results from the clinical implementation of partial REBOA at a single trauma center were used to conduct the initial power analysis for the primary endpoint of Acute Kidney Injury (AKI) after prolonged occlusion. The rate of AKI after complete REBOA was 55% (12/20) compared to 33% (4/12) after partial REBOA (Madurska et al., 2021). With an alpha of 0.05 and power (β) of 0.8, the projected sample size for comparison on a dichotomous outcome is 85 patients for the assessment of AKI. Initial power and endpoint analyses have been confirmed and extended with the ongoing analysis of partial and complete REBOA reported in the AORTA database. These analyses confirm preclinical findings which show that compared to complete REBOA, partial REBOA is associated with extended occlusion time in zone 1 (complete: 31 min vs. partial: 45 min, P = 0.003), lower rates of AKI after zone 1 occlusion (complete: 33% vs. partial: 19%, P = 0.05) and reduced resuscitation requirements (e.g., 25% reduction in pRBC administration: complete: 18 units vs. partial: 13 units, P = 0.02).
CONCLUSIONS: The DoD-funded PROMPT study of partial REBOA will provide prospective observational clinical data on patients being treated with pREBOA-PRO. Outcomes will be stratified based on partial or complete occlusion to address whether partial REBOA has additional clinical benefits over complete REBOA, such as decreased distal ischemia, extension of safe occlusion time, improved hemodynamics during transition to and from occlusion, and reduced interoperative bleeding and blood product use. The results from this study are expected to confirm previous data demonstrating reduction of ischemic sequalae, improved transition to reperfusion, and reduced resuscitative requirements compared to complete REBOA.