One reason normal saline is used to prime and recirculate the extracorporeal circuit prior to treatment is to remove

• A. Blood
• B. Infectious agents
• C. Heat transfer
• D. Air

Answer: (D)

Priming the extracorporeal circuit with normal saline is done to purge all air from the tubing before treatment. Air in the circuit can form bubbles that travel to the patient, causing air embolism, obstructing blood flow, and compromising the treatment. Normal saline is used because it is sterile, compatible with blood, and displaces air effectively so the lines are free of bubbles when the blood pump starts. The goal isn’t to remove blood or infectious agents with the saline itself—aseptic technique handles sterility—nor is it about transferring heat. The key point is eliminating air from the circuit to keep the patient safe during circulation.