Final answer:
Increased recirculation in an internal access like an AV fistula or graft used for hemodialysis may be due to factors such as blood pressure within the vein, blood flow within the vein, return of blood to the heart, or a combination of these.
Step-by-step explanation:
Increased recirculation in an internal access, such as an arteriovenous (AV) fistula or graft often used in hemodialysis, may be due to various factors including a. blood pressure within the vein, b. blood flow within the vein, c. return of blood to the heart, and d. all of the above. An increase in the internal resistance of an access can lead to these issues. This resistance is somewhat analogous to the internal resistance in a battery, which can lead to decreased terminal voltage and potential overheating. Similarly, in vascular access, increased resistance can result in inadequate dialysis due to poor blood flow and high venous pressures, which may necessitate medical intervention.