Formation of hematomas of varying size is an inherent risk associated with venipunctures. They are not only "unsightly;" they become especially problematic in patients that require multiple diagnostic or therapeutic venipunctures. What procedure do you use to minimize venipuncture-induced hematomas?
Following collection of blood from the veins in the antecubital region of my right or left arm, I have yet to encounter a nurse in a physician's office, or a medical technologist in a hospital, who hasn't asked me to apply firm digital pressure over the site of venipuncture with the objective of minimizing hemorrhage into the surrounding tissue. In my experience, if I comply with the directions given by the nurse or technologist and completely occlude blood flow through the vein, loss of blood is minimized as long as the vein is completely occluded (Figure 1). However, when I remove the digital pressure, bleeding from the site often recurs, resulting in varying degrees of perivascular hemorrhage. What is the probable explanation of this sequence of events?
Figure 1 Loss of blood is minimized as long as the vein is completely occluded.
In healthy individuals, lack of perfusion caused by applying firm digital pressure to the site of venipuncture prevents blood platelets and other clotting factors from occluding the hole in the vein's wall caused by the hypodermic needle. The same phenomenon can occur in animals.
Figure 2: Maintaining gentle digital pressure over the venipuncture site can facilitate clotting.
It can be minimized in humans or animals by applying sufficient digital pressure over the venipuncture site to occlude the hole in the wall of the vein, but not so much pressure that the lumen of the vein is occluded (Figure 2). Maintaining gentle digital pressure over the venipuncture site for approximately three minutes is usually sufficient to allow blood platelets and other clotting factors to interrupt extravasation of blood through the needle tract in the wall of the vein.