One of the challenges in first aid treatment for stroke is “is it ischemic or hemorrhagic?”. The symptoms are similar, but the treatments almost the reverse of each other. Do you want to increase clotting to stop the bleeding, or decrease clotting to keep an existing brain clot small?

Sometimes (for example if it would take hours to bring the patient to a MRI/CT machine) an educated guess as to the answer is the optimal strategy.