You must apply a tourniquet before cannulating which type of access?

Applying a tourniquet before cannulating a fistula is essential because it helps to engorge the veins, making them more prominent and easier to access. A fistula is created by connecting an artery to a vein, typically in the forearm, and is used for hemodialysis. When a tourniquet is applied above the fistula site, it increases venous pressure and distends the vein, facilitating the insertion of the needle and improving the success rate of the cannulation process.

In contrast, central venous catheters, peritoneal dialysis catheters, and port-a-caths involve different access techniques and do not require a tourniquet in the same way that a fistula does. For central venous access, the clinician typically uses anatomical landmarks and ultrasound guidance to locate the vein without the need for engorgement. Similarly, peritoneal dialysis catheters and port-a-caths are designed for different types of access that are less reliant on visibility through engorgement. Therefore, the use of a tourniquet specifically applies to fistula cannulation to optimize the procedure.