Background 

• Hemorrhage continues to be a leading cause of preventable death on the battlefield. It can be broadly categorized as compressible or non-compressible, depending on its location. Non-compressible Torso Hemorrhage (NCTH) arises from trauma to the torso vessels, pulmonary parenchyma, solid abdominal organs, or the bony pelvis.² Because NCTH is not amenable to control by direct pressure or extremity tourniquet application, it is particularly lethal.³
• Resuscitative Aortic Occlusion (RAO) affords distal hemorrhage control while increasing cardiac afterload and thereby maintaining coronary and cerebral perfusion pressure until (or while) hemorrhage control is achieved.⁴ RAO has traditionally required a left thoracotomy or laparotomy for aortic exposure.^5-8 Resuscitative thoracotomy has a high mortality rate, due largely to the nature of the injuries and because this technique is not typically employed until after arrest.^9-11 Nonetheless, data from combat theaters indicate that there is a reasonable probability of long-term survival and recovery following RAO in appropriately selected casualties as described in the JTS Emergent Resuscitative Thoracotomy (ERT) CPG.^12-14
• REBOA is an alternative form of RAO for patients at risk of imminent cardiovascular collapse. It is performed through a common femoral artery approach without the need for thoracotomy. REBOA is best applied prior to cardiovascular collapse when the site of hemorrhage is below the diaphragm and no open thoracic intervention is otherwise indicated.¹⁵
• ERT allows management of thoracic injuries and manual cardiac compression and thus remains the procedure of choice for patients with significant thoracic or cardiac injury. However, REBOA has been used in combination with open thoracotomy and/or sternotomy as a resuscitative bridge to open surgical control of hemorrhage to treat thoracic great vessel injury.¹⁶
• ERT may improve cardiac index as well as coronary and cerebral perfusion pressure compared to closed chest compression.¹⁷ However, when closed chest compressions are combined with REBOA, cardiopulmonary resuscitation is more effective allowing for higher end-tidal carbon dioxide (EtCO2) and cardiac compression fraction compared to open cardiac massage and aortic cross clamping.¹⁸
• RAO poses a significant risk of life-threatening and limb-threatening complications. RAO is a time-critical intervention that should never be undertaken without expedient access to definitive surgical hemorrhage control and without adequate vascular access for simultaneous resuscitation with blood. ^{2–20,8-17,19-30,19,22,25}

• The major rate limiting step with REBOA is accurate and expedient common femoral artery (CFA) access. Ultrasound guided access is the preferred method for CFA access; however, in early experience, up to 50% of cases required open exposure. Smaller access sheaths are associated with improved outcomes.^31-34 As early CFA access has become more routine in select trauma centers, the need for open CFA exposure has decreased to below 10%.³⁵
• Literature for REBOA are mixed; some demonstrate a survival benefit^20-21 while others suggest REBOA may actually worsen mortality.^22-23 The advent of the wireless ER-REBOA™ and COBRA-OS®, combined with a better understanding of REBOA indications led to recent studies demonstrating the non-inferiority of REBOA. In patients that do not require cardiopulmonary resuscitation (CPR), REBOA has now shown a survival benefit.^24-27,15 In 2018, a prospective analysis documented that REBOA improved survival beyond the emergency department and to hospital discharge compared to ERT when applied prior to traumatic cardiac arrest in patients with hemorrhagic shock.¹⁵
• A primary limitation of first generation REBOA (ER-REBOA-PLUS™ and COBRA-OS®) is the short Zone 1 aortic occlusion time prior to the increasing risk of distal ischemia (See page 10 for an Illustration of the zones of the aorta). The AAST AORTA database revealed that 63% of REBOA cases exceeded 30 minutes in Zone 1 and the median occlusion time was 40 minutes.¹ Partial REBOA (pREBOA) addresses some of these limitations by allowing a small volume of blood to continuously flow past the balloon and perfuse distal tissues and organs while mitigating ongoing hemorrhage. The patient selection and indication guidelines for pREBOA are largely based on consensus guidelines from select civilian trauma centers.^36,75,77
• In a preclinical study done by Polcz et al. 2021, Targeted Regional Optimization (TRO), a partial REBOA strategy, enhanced blood flow to vital organs like the heart and brain while maintaining a minimum level of perfusion to the lower body and limbs. Furthermore, partial occlusion facilitated faster renal function recovery. Finally, a linear correlation between distal Mean Arterial Pressure (MAP) and distal aortic flow rate was observed, providing a valuable clinical metric for informed decision-making.³⁷
• Third generation pREBOA-PRO™ devices allow prolonged partial aortic occlusion in Zone 1 for at least 2 hours without increase in ischemic complications.³⁸ In animal and civilian studies, it has been shown that Zone 1 partial occlusion can increase to 4 hours with treatable distal ischemic changes.³⁹ In civilian trauma centers utilizing this technique, partial REBOA use has reduced cardiac arrest and blood product usage, and increased use of angioembolization with reduced distal ischemia.⁴⁰
• Critical hemorrhage models in swine demonstrate that pREBOA can extend aortic occlusion time to at least 2 hours with continuous controlled pulsatile distal pressure of at least 20 mmHg systolic blood pressure (SBP) without increased distal ischemic complications.³⁹ Clinical data in civilian trauma centers and early military data from the Ukraine War^41-42 demonstrate similar results. Partial REBOA with an extension of occlusion time of up to 4 hours without compromising survival or worsening ischemic injury may be feasible.

• With increasing REBOA availability and provider experience, REBOA has successfully been utilized in multiple austere military locations.^43-47 In austere resuscitations, REBOA use has facilitated blood product conservation, and been used as an adjunct during damage control surgery, creating a “bloodless” environment.^45,47-48,79
• To our knowledge pREBOA has not yet been utilized in the deployed environment. To successfully perform pREBOA in the civilian hospital setting, significant team training is required to perform it effectively. Similarly, performing REBOA in deployed or austere settings requires significant team training.