Abstract 310: Retrograde Hemorrhage and Ischemic Injury after REBOA in a Porcine Model of Uncontrolled Aortic Injury

Introduction: Resuscitative Balloon Occlusion of the Aorta (REBOA) has gained popularity as a less invasive approach to temporize traumatic noncompressible hemorrhage, yet mortality remains over 70%. Although associated injuries may account for some deaths, contributions from ischemia and ongoing retrograde bleeding are also likely, with REBOA occlusion frequently in Zone 1 (descending thoracic aorta) and often greater than 20 minutes. This study examined retrograde blood loss and ischemic injury after REBOA in a porcine model of aortic injury. Methods: Six anesthetized swine with invasive hemodynamic and neurophysiologic monitoring (Muscle Evoked Potentials and Somatosensory Evoked Potentials) underwent 8 Fr femoral access and Zone 1 positioning of a REBOA balloon prior to aortic injury. The thoracic aorta was injured with a 22 Fr dilator, followed by aortography and immediate REBOA inflation proximal to the injury. Profound deterioration of the first three animals with one hour of REBOA prompted the next three animals to undergo only 30 minutes of REBOA. Blood loss was recovered with a cellsaver. Animals underwent permanent stent repair of the aortic injury and resuscitation with the intent to recover. Results: Despite proximal hemorrhage control documented angiographically, blood loss from retrograde bleeding was substantial averaging 3.7 L and 3.5 L for the 30- and 60-minute groups, respectively. After balloon inflation, mean pressure fell an average of 62 mmHg within 20 minutes (p < 0.001), while cardiac output decreased 20-40%. In the lower extremities, Neuromonitoring revealed ischemic loss of motor signals at a mean of 27 minutes. Even after resuscitation with blood, bicarbonate, saline and pressors, all six animals arrested shortly after balloon deflation, amidst falling bicarbonate (p less than 0.001), and rising lactate (p less than 0.01) relative to baseline. Conclusions: Retrograde hemorrhage is an underappreciated event during REBOA control of aortic injuries, that may contribute to spinal cord ischemia, tissue ischemia and death. This study suggests that improved outcomes for noncompressible hemorrhage will require balance of competing goals of hemorrhage control and distal perfusion.