Which technique is least likely to be effective in avoiding hematoma formation?

Probing multiple times is least likely to be effective in avoiding hematoma formation because it may cause additional trauma to the blood vessel and surrounding tissue. Each time the needle punctures the skin and enters a vein, there is a risk of damaging the vessel walls and surrounding capillaries, which can lead to bleeding and the formation of a hematoma.

In contrast, applying pressure to the puncture site after the needle is removed helps to constrict the blood vessels and stop any potential bleeding promptly, thereby reducing the risk of hematoma formation. Keeping the needle in place can maintain the integrity of the vein and prevent further injury that might occur with repetitive punctures. Using the correct needle size ensures that the vessel is optimally accessed without causing undue trauma, which also minimizes the risk of hematoma.