Which sequence correctly describes venipuncture for cannulation?

• A. Puncture skin, apply tourniquet, bevel down, advance cannula.
• B. Bevel up, apply traction to the vein, insert at a 20- to 30-degree angle, advance until blood flash back, advance another 2 mm, hold needle still, advance cannula, remove tourniquet, remove needle, attach saline lock.
• C. Advance cannula before obtaining blood flash back.
• D. Always insert at a 90-degree angle for rapid access.

Answer: (B)

The essential idea is to gain and confirm venous entry before advancing the cannula, using a bevel-up needle, a shallow entry angle, and stabilization of the vein.

Begin with the vein stabilized and prepared: apply a tourniquet to dilate the vein and gently pull the skin or vein to prevent rolling. Insert the needle with the bevel facing up at about a 20–30 degree angle toward the vein. You’ll know you’ve entered the vein when blood flashes back into the hub. At that moment, advance the cannula a small amount (about 2 mm) while keeping the needle steady, then slide the cannula into the vein, remove the needle, release the tourniquet, and attach the saline lock or start the flow.

Choosing a 90-degree angle or advancing the cannula before you see flashback aren’t appropriate, as they increase tissue trauma and risk missing the vein. Bevel-down and other deviations from bevel-up are not standard practice for this procedure.