What is typically used to rinse and prime the tubing of the extracorporeal circuit?

Normal saline is typically used to rinse and prime the tubing of the extracorporeal circuit in dialysis. The prime solution must be isotonic and compatible with the blood to prevent hemolysis or other complications. Normal saline serves this purpose well as it is a sterile solution of sodium chloride in water, mimicking the body's plasma osmolarity. This ensures that as the tubing is filled, it maintains a balance that does not adversely affect the patient’s metabolism or hematological status.

Using any of the other options can lead to various issues. For instance, water lacks the necessary electrolytes, which can lead to hemolysis when it comes into contact with blood cells. Dialysate, while crucial for the dialysis process, is designed to facilitate the diffusion of toxins and excess electrolytes and is not sterile; it is not suitable for priming purposes. Heparin is an anticoagulant used to prevent clotting within the circuit, but it should not be used for priming since it alters blood coagulation without providing the necessary sterile rinsing necessary to set up the circuit effectively.