An initial attempt to draw blood does not always succeed. There are a number of different procedural errors that can cause venipuncture failure. An effective phlebotomist should be aware of these types of errors and know how to correct any that may occur. This knowledge is extremely helpful in determining if blood can be obtained the first time or if a procedure must be repeated. Whenever a procedure fails the first time, an experienced an effective phlebotomist should calmly evaluate the situation for the following potential problems:
The way the tube is positioned can affect blood collection. Check that the tube is properly seated and that the needle in the tube holder has penetrated the tube stopper. Ensure that the needle sleeve is properly placed and not pushing the tube off the needle.
The tube may loose vacuum if the needle bevel is not completely inserted under the skin or if the bevel backs out of the skin. This problem can often be identified by a short hissing sound that can be heard. Also, blood may spurt into the tube before the blood flow stops. There are several other causes for a tube to loose its vacuum that include, damage to the tube during shipping and handling, if the tube is dropped, or if the tube is pushed too far onto the needle prior to venipuncture.
A common cause of failure to collect blood has to do with improper needle position. There are visual cues that an experienced phlebotomist can easily identify to determine if a needle is incorrectly positioned in a vein. If it is difficult to determine the needle position visually, it may be necessary to use your finger to relocate the vein.
The vacuum draw of a tube can sometimes create too much pressure for a vein. The pressure can cause the vein to collapse temporarily. When this happens blood will cease to flow through that vein. A collapsed vein can also occur if a tourniquet is tied too tightly or too close to the venipuncture site. The rapid removal of blood from a vein can cause it to collapse if the blood is not replaced fast enough.