the nurse is caring for a client who had a resection of an abdominal aortic aneurysm yesterday. the client has an intravenous (iv) infusion at a rate of 150 ml/hour, unchanged for the last 10 hours. the client's urine output for the last 3 hours has been 90, 50, and 28 ml (28 ml is most recent). the client's blood urea nitrogen level is 35 mg/dl (12.6 mmol/l), and the serum creatinine level is 1.8 mg/dl (159 mcmol/l), measured this morning. which nursing action is the priority?