Bleed back control assembly

This invention relates generally to a bleed back control assembly for controlling blood loss during vascular diagnostic or interventional procedures, such as insertion and removal of catheters from the blood vessels of a patient. A bleed back control assembly for controlling blood loss during catheterization procedures includes a side arm body having a proximal end engaging and retaining a cap assembly and a seal assembly. The seal assembly includes a single elastomeric bleed back seal. The bleed back seal has an aperture and is normally closed. The bleed back seal self-sizes to devices introduced through the aperture. The cap assembly includes a funnel cap having a dilator. Depressing the funnel cap causes the dilator to open the aperture in the bleed back seal. A spring, wound around the dilator, biases the funnel cap to its original position. The side arm body includes a secondary branch having a lumen, and a finger rest on the exterior of the secondary branch.