An apparatus for preventing stroke by occluding blood flow through a right carotid artery and a left carotid artery of a patient is provided. The apparatus has a first occluding catheter that carries a first occluding balloon that has an inflated configuration that occludes either the right carotid artery or the left carotid artery. The apparatus also includes a second occluding catheter that carries a second occluding balloon that has an inflated configuration that occludes the other one of the right carotid artery or the left carotid artery that is not occluded by the first occluding balloon. An insertion device may also be present to allow for insertion of the first and second occluding catheters.