A nurse is caring for a patient who has been diagnosed with severe diarrhea and has exhibited signs of dehydration. The patient presents with hypotension, tachycardia, and dry mucous membranes. Laboratory results reveal a sodium level of 120 mEq/L and a potassium level of 5.8 mEq/L. Given these findings, which of the following nursing interventions should the nurse prioritize to manage the patient's condition?