The vacuum system consists of a double-pointed needle, a plastic holder or adapter, and a series of vacuum tubes with rubber stoppers of various colors. The colors indicate the type of additive present. Another kind of holder is available, which allows resheathing of the needle with the holder after venipuncture. Blood collection using the evacuated tube collection system will produce the best blood samples for analysis by the laboratory. The blood goes directly from the patient into the appropriate test tube.
Blood Collection Needle
The vacuum collection needle is pointed at both ends, with one end shorter than the other. The long end of the needle is used for insertion into the vein; the shorter end is used to pierce the rubber stopper of the vacuum tube and usually is covered by a rubber sheath. The sheath makes it possible to draw several tubes of blood by preventing leakage of blood as tubes are changed; this is called a multi-draw or multi-sample needle. If the short end is not covered with a rubber sheath, it is a single sample needle and only one tube of blood can be collected.
There are several sizes of needles available; the size depends on the length and gauge of the needle that goes into the vein. Blood collection needle lengths range from 1 to 1 ½ inches. One inch needles are used for routine venipuncture, 1 ½ inch needles are used for patients with very deep veins. The gauge of a needle is a number that indicates the diameter of its lumen; the lumen, also called the bore, is the circular hollow space inside the needle. The higher the gauge, the smaller the lumen.