A 76-year-old woman has 4 days history of low-grade fever, diarrhea, and generalized aches. She has been taking ibuprofen for pain for the past 48 hours. Her BP 100/50, HR 100/min, temp 37.8, her serum creatinine has doubted since her last visit 2 months ago. Urine analysis is normal. What is the best intervention for this patient?