Critical Nursing Intervention for Hypernatremia and Hypokalemia

A 60-year-old patient is admitted to the emergency department with confusion, dry mucous membranes, and a heart rate of 120 beats per minute. Laboratory results indicate a sodium level of 152 mEq/L and a potassium level of 3.0 mEq/L. The physician diagnoses the patient with hypernatremia and hypokalemia. The nurse is responsible for planning care for this patient. Which of the following nursing interventions is the most critical to address first?