LAUSR

BACKGROUND Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) is a significant advancement in the control of non-compressible truncal hemorrhage. However, its ischemic burden and reperfusion injury following balloon deflation limits its utilization. Partial restoration of aortic flow during REBOA has the potential to balance hemorrhage control and ischemia. This study validates the mechanics, physiology, and optimal partial flow rates using a prototype partial REBOA (pREBOA) device. METHODS 25 swine underwent placement of aortic flow probes and zone 1 pREBOA. Experiment 1(N=5) animals were not injured and assessed the tested the catheters ability to titrate and control flow. Experiment 2 (N=10) added 20% hemorrhage and either solid organ, or abdominal vascular injury to compare flow rate and re-bleeding from injuries. Experiment 3 (N=10) swine were similarly prepared, hemorrhaged, and underwent pREBOA at set partial flow rates for 2hr followed by complete deflation for 30min. RESULTS Balloon volume at minimum flow (mean .09 L/min) was 3.5-6.0mL. Half maximal flow was achieved with 56.5% of maximum balloon inflation. pREBOA allowed very fine titration of flow rates. Rebleeding occurred at 0.45-0.83 L/min. Distal flow of 0.7 L/min had 50% survival, 0.5 had 100% survival, and 0.3L had 50% survival with mean end lactates of 9.6, 12.6, and 13.3 respectively. There was a trend towards hyperkalemia and hypocalcemia in non-survivors. CONCLUSIONS The pREBOA device demonstrated a high level of titratability for restoration of aortic flow. An optimal partial flow of 0.5L/min was effective at hemorrhage control while limiting the burden of ischemic injury, and extending the tolerable duration of zone 1 occlusion. Aggressive calcium supplementation prior to and during partial occlusion and reperfusion may be warranted to prevent hyperkalemic arrest. LEVEL OF EVIDENCE III STUDY TYPE: Therapeutic.