Final answer:
The nurse's first action should be to notify the health care provider. Documenting the findings and continuing to monitor the drainage are important, but not as the first step. Outlining the drainage on the bandage is not a priority.
Step-by-step explanation:
The nurse's first action should be to notify the health care provider. After a brain tumour removal, drainage on the dressing could indicate a potential complication or infection. It is crucial to inform the health care provider so that they can assess the situation and provide appropriate treatment if necessary.
Documenting the findings and continuing to monitor for an increase in drainage are important actions, but they should be done after notifying the health care provider. Outlining the drainage on the bandage is not a priority and does not address the potential complication.