REBOA Zones and Key Anatomical Points for Balloon Occlusion

Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) is a critical technique in trauma and emergency medicine for controlling hemorrhage. By inflating a balloon within the aorta, blood flow is redirected to vital organs, buying time for definitive surgical intervention. Proper placement is essential to maximize effectiveness while minimizing complications.

Aortic Regions for Balloon Occlusion

The aorta is divided into three zones for REBOA placement, each with specific clinical indications and physiological consequences. Selecting the appropriate occlusion site balances hemorrhage control with preserving distal perfusion.

Zone 1 extends from the origin of the left subclavian artery to the celiac trunk. Occlusion here is used for life-threatening hemorrhage from torso injuries, particularly involving the abdominal cavity. Inflating the balloon in this region maintains blood flow to the heart and brain while halting distal hemorrhage. However, prolonged occlusion can lead to significant ischemic complications in abdominal organs, requiring careful monitoring and timely intervention.

Zone 2, between the celiac trunk and renal arteries, is generally avoided. This region supplies critical abdominal organs, and occlusion would compromise perfusion to the intestines, kidneys, and pancreas without a clear hemorrhage control benefit. Instead, clinicians place the balloon either above or below this zone to maximize effectiveness while minimizing ischemic risk.

Zone 3, from the renal arteries to the aortic bifurcation, is used to control hemorrhage from the pelvis or lower extremities. Occlusion here preserves blood flow to upper abdominal organs while restricting bleeding from pelvic fractures or femoral artery trauma. Compared to Zone 1, Zone 3 carries a lower risk of ischemic complications, making it preferable when feasible.

Anatomical Landmarks for Zone Identification

Accurate REBOA balloon placement relies on anatomical landmarks that delineate aortic zones. These landmarks, identified through fluoroscopy, ultrasound, or direct measurement, guide clinicians in ensuring effective hemorrhage control while minimizing complications.

The diaphragm helps distinguish Zone 1 from Zone 2. The celiac trunk, marking the lower boundary of Zone 1, typically originates at the T12 vertebra, making the T12-L1 junction a reliable radiographic reference. In clinical practice, fluoroscopy highlights the celiac axis as a branching point from the aorta, confirming balloon placement. In situations without imaging, the xiphoid process serves as a rough external estimate.

The renal arteries define the lower boundary of Zone 2 and the upper limit of Zone 3, typically emerging at the L1-L2 vertebral level. Fluoroscopy with contrast enhances localization, while patient height and vertebral landmarks provide secondary estimation when imaging is unavailable.

The aortic bifurcation, near the L4 vertebral level, marks the inferior boundary of Zone 3. This is critical for cases involving pelvic or lower extremity hemorrhage, where placement must control bleeding while preserving perfusion to the kidneys and intestines. The umbilicus serves as a rough external reference, though individual anatomical variations require imaging confirmation when possible. Intravascular pressure monitoring further ensures precise balloon positioning.

Zone 1 Classification

Zone 1, from the left subclavian artery to the celiac trunk, is the primary target for balloon occlusion in severe hemorrhagic shock from torso injuries. This segment supplies critical perfusion to the brain and heart, making its occlusion a high-stakes intervention.

Placement in this zone is indicated for major vascular injuries such as penetrating chest or upper abdominal trauma and ruptured abdominal aortic aneurysms. Rapid balloon inflation provides temporary hemostasis, allowing time for surgical intervention. However, complete thoracic aortic occlusion increases afterload, potentially straining the heart, particularly in patients with pre-existing conditions. Additionally, ischemic injury can develop in the intestines and kidneys within 30-45 minutes, necessitating strict time management.

Zone 1 occlusion causes an immediate rise in central arterial pressure, improving coronary and cerebral perfusion. However, upon balloon deflation, a reperfusion response occurs, leading to metabolic acidosis, hyperkalemia, and systemic inflammatory reactions. Advanced monitoring, including arterial blood gas analysis and continuous hemodynamic assessment, is essential to mitigate these risks.

Zone 2 Classification

Zone 2, between the celiac trunk and renal arteries, is largely avoided in REBOA due to its anatomical and physiological implications. Major branches from this region supply critical abdominal organs, and occlusion would disrupt perfusion without offering hemorrhage control benefits.

Clinicians ensure the balloon is positioned either above or below Zone 2 to avoid ischemic injury to perfusion-sensitive organs. The intestines, for example, are vulnerable to hypoxia, with even brief ischemia causing mucosal barrier breakdown and bacterial translocation, increasing sepsis risk. Similarly, the kidneys, which receive about 20% of cardiac output, are highly susceptible to ischemia-reperfusion injury, potentially leading to acute kidney failure.

Zone 3 Classification

Zone 3, from the renal arteries to the aortic bifurcation, is a primary target for REBOA in hemorrhage from the pelvis or lower extremities. This placement preserves perfusion to upper abdominal organs while effectively controlling bleeding from pelvic fractures or femoral vascular injuries.

Compared to Zone 1, occlusion in Zone 3 results in less pronounced increases in afterload, reducing cardiac strain. Since the intestines and kidneys remain perfused, the risk of ischemia-reperfusion injury is significantly lower. However, prolonged balloon inflation can still cause lower extremity ischemia, necessitating careful monitoring and early transition to surgical management. Clinicians must also watch for thrombus formation at the occlusion site, which could compromise distal circulation upon balloon deflation.

Measurement Techniques

Accurate REBOA balloon placement relies on imaging, external anatomical landmarks, and catheter-based measurements. These methods ensure optimal positioning within the intended aortic zone, maximizing hemorrhage control while minimizing ischemic risks.

Fluoroscopy is the gold standard for confirming balloon location, providing real-time visualization of the catheter relative to aortic landmarks. Contrast injections enhance clarity, identifying the celiac trunk, renal arteries, and aortic bifurcation. In settings without fluoroscopy, ultrasound offers a viable alternative, particularly in pre-hospital or austere environments. Transabdominal ultrasound approximates aortic anatomy, while intravascular ultrasound (IVUS) provides high-resolution imaging of the catheter’s position.

When imaging is unavailable, external landmarks serve as practical guides. The xiphoid process approximates the upper boundary of Zone 1, while the umbilicus aligns closely with the aortic bifurcation, marking the lower boundary of Zone 3. Additionally, catheter-based measurements, using the femoral artery access site as a reference, help determine insertion lengths based on patient height and standardized tables. Combining these methods with continuous hemodynamic monitoring improves procedural accuracy and outcomes.