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There are three meninges covering the brain: the dura mater, the arachnoid mater, and the pia mater.
The dura mater is the thickest and strongest membrane, and is firmly attached to the inner surface of the cranial bone, especially along the sutures. It contains the meningeal arteries.
The arachnoid mater is a thin membrane under the dura mater. Its inner surface has numerous thin trabeculae extending downward, into the subarachnoid space.
The pia mater is a thin membrane that covers the surface of the brain, entering the grooves and fissures.
Due to the tight adhesion of the dura mater to the inner skull, significant force is required to separate them. In contrast, separation of the dura from the subarachnoid mater can occur with relatively little force.
The middle meningeal artery arises from the external carotid artery. It enters the foramen spinosum and branches into the anterior, middle, and posterior branches with various patterns. It is a common source of bleeding in acute epidural hematomas (EDHs).
The bridging veins connect the cortical superficial veins to the sagittal sinus in the dura. They are a common source of bleeding in acute subdural hematomas (SDHs).
Severe bleeding in complex pelvic fractures usually originates from branches of the internal iliac artery, presacral venous plexus, fractured bones, and soft tissues. Major iliac vascular injuries are encountered in about 10% of patients with severe pelvic fracture.
The abdominal aorta bifurcates into the two common iliac arteries at the L4-L5 level. The iliac veins are located posterior and to the right of the common iliac arteries. The ureter crosses over the bifurcation of the common iliac artery as it branches into the external and internal iliac arteries.
The internal iliac artery is about 4 cm long. At the level of the greater sciatic foramen, it divides into the anterior and posterior trunks. It supplies numerous splanchnic and muscular branches and terminates as the internal pudendal artery, which is a potential source of hemorrhage in anterior ring disruptions. Hemorrhage following pelvic fracture can occur from any branch.
The most commonly injured internal iliac artery branches (in decreasing order of frequency) are the superior gluteal, internal pudendal, and obturator arteries.
The superior gluteal artery is the largest branch of the internal iliac artery. It exits the pelvis through the greater sciatic foramen above the piriformis muscle. It provides blood supply to gluteus medius and minimus muscles.
The internal pudendal artery passes through the greater sciatic foramen, courses around the sciatic spine, and enters the perineum through the lesser sciatic foramen.
The obturator artery courses along the lateral pelvic wall and exits the pelvis through the obturator canal. In 30% of cases, the obturator artery is perfused from both internal and external iliac arteries, making angioembolization more complicated.
Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) is a compliant, endovascular balloon designed to occlude the thoracic or lower abdominal aorta in hemorrhagic shock, for temporary control of bleeding in the abdomen or pelvis.
The REBOA catheter is placed through a sheath in the right or left common femoral artery, accessed using anatomic landmarks, ultrasound guidance, or with open surgical technique. The balloon is then inflated in the thoracic or abdominal aorta, effectively acting as a minimally invasive aortic cross-clamp.
The procedure for placing a REBOA takes only a few minutes.
REBOA is ideally suited for hypotensive patients with abdominal or pelvic bleeding and can be placed in the emergency room, intensive care unit, or the operating theater.
REBOA balloon placement can be guided and confirmed using external landmarks, X-ray, fluoroscopy, or ultrasound. Balloon inflation volumes are titrated based on invasive blood pressure monitoring, haptic feedback, and imaging.
REBOA is contraindicated in patients with intrathoracic, neck, or facial bleeding, in cases with high suspicion for blunt thoracic aortic injury, and in patients in cardiac arrest.
Aortic occlusion is a temporary, resuscitative measure and should be considered a transition to definitive care. After inflation, the patient should be immediately transported to the operating room or the interventional suite for definitive management of their traumatic injuries.
REBOA balloon inflation results in distal ischemia and as such, occlusion times should be minimized.