Final answer:
The nurse should first initiate IV fluids to stabilize the client's vital signs and then obtain a urine sample to investigate possible causes of delirium, such as a UTI (option C and A respectively).
Step-by-step explanation:
The nurse should prioritize interventions for this client who is experiencing delirium post knee arthroplasty. The client's hypotension (90/48 mm Hg) and tachycardia (HR 115/min), coupled with the recent surgical procedure and symptoms of delirium, suggest that the first action should be C) Initiate IV fluids as prescribed by the provider to address possible dehydration and stabilize vital signs. This is a priority because it directly addresses the physiological instability that may be contributing to the delirium.
Following the initiation of IV fluids, the nurse should focus on A) Obtain a urine sample as ordered by the provider for urinalysis and culture and sensitivity, to investigate possible causes of delirium such as a urinary tract infection (UTI), which is a common and treatable cause of acute confusion in elderly patients.
Additional interventions such as administering acetaminophen or weighing the client are important but are of lower priority compared to physiological stabilization and investigation of the underlying cause of the delirium. Once the immediate safety concerns are addressed and a possible infection is being investigated, other prescriptions can be administered as needed and further care planning can be done.
Hence, the answer is option C and A respectively.