Final answer:
The nurse's priority for care is to address the client's fluid and electrolyte imbalances and prevent dehydration.
Step-by-step explanation:
The nurse's priority for care when caring for an older client experiencing an exacerbation of ulcerative colitis with severe diarrhea would be to address the client's fluid and electrolyte imbalances and prevent dehydration.
The nurse should monitor the client's vital signs, especially their blood pressure, heart rate, and urine output. They should also assess the client's skin turgor and mucous membranes for signs of dehydration.
Intravenous fluid replacement may be necessary to restore the client's fluid and electrolyte balance. The nurse should collaborate with the healthcare team to determine the appropriate fluid replacement therapy for the client.