Final answer:
In the event of a severe adverse reaction to alteplase therapy, the nurse should have antidotes available to counteract the effects of the medication and control any bleeding.
Step-by-step explanation:
In the event of a severe adverse reaction to alteplase therapy for pulmonary embolism, the nurse should have antidotes available. Antidotes are drugs that can counteract or neutralize the effects of certain medications. In the case of alteplase, an antidote called aminocaproic acid or tranexamic acid can be used to stop any excessive bleeding that may occur as a result of the therapy. These antidotes work by inhibiting the breakdown of clots, helping to control any bleeding.