A nurse is helping а cоwоrker cаre lift up а patient in bed, when the 30-year-оld coworker appears a bit unsteady on her feet. She grabs her temples, appears to be in pain or distress, and sighs loudly. The nurse asks, "are you OK?" The coworker replies, "I think so, but I think I need to sit down for a minute, I feel dizzy and I don't know what happened just got the worst headache I have ever had in my life. I think I may be sick." The nurse, a nurse practitioner student, is most concerned her coworker could be experiencing a: