A client has a triple lumen subclavian central venous catheter (CVC) with D51/2NS infusing through one lumen (port) at 75 mL per hour. The nurse has an order to transfuse one unit of packed red blood cells (PRBCs). The nurse's safest action is to:

A. "The diaphragmatic nerve overdrives the rapid rhythm:" The phrenic (diaphragmatic) nerve controls the diaphragm for breathing and plays no role in cardiac rhythm regulation. It is unrelated to the autonomic control of heart rate or supraventricular tachycardia (SVT) management.

B. "Vagal stimulation decreases peripheral vascular resistance:" Vagal stimulation primarily affects the heart by decreasing the rate and conduction through the AV node. Its effect on vascular resistance is minimal, making this explanation inaccurate in the context of SVT treatment.

C. "The vagus nerve increases the heart rate, overdriving the rhythm:" The vagus nerve has a parasympathetic effect, slowing down the heart rate, not increasing it. Overdrive pacing is a different concept and not related to vagal maneuvers like carotid massage.

D. "The vagus nerve slows the heart rate": The carotid sinuses in the neck contain baroreceptors that are sensitive to pressure. Massaging these sinuses stimulates the vagus nerve to release acetylcholine, which in turn slows conduction through the AV node and may terminate episodes of SVT. This response demonstrates an accurate understanding of the purpose of the procedure.

A. contact the prescriber to decrease the rate of the D51/2NS during the blood transfusion: There's no need to alter the rate of maintenance fluids unless there's a fluid volume concern. Additionally, decreasing the rate would not address the need for a dedicated blood transfusion line if another lumen is available.

B. stop the D51/2NS, check the client's vitals & notify the prescriber: Stopping necessary fluids without cause may compromise fluid balance. Unless there's a compatibility issue or no other lumen, stopping the infusion is not the safest or most efficient action.

C. Fluids cannot be given through a CVC: Central venous catheters are routinely used for administering fluids, medications, and blood products, especially in critical care settings.

D. Insert a 22 gauge peripheral IV to administer the transfusion: While blood can be given through a peripheral IV, using an existing central venous catheter is safer and more efficient, especially when multiple lumens are available. Inserting a new IV unnecessarily increases infection and complication risks.

E. transfuse the unit of packed red blood cells through a separate lumen of the CVC: This is the safest and most appropriate action. Triple-lumen CVCs allow for simultaneous infusions through separate channels without mixing. Blood should be transfused through a dedicated lumen to avoid incompatibility or dilution by other fluids.