The evacuated tube system is the most used method for drawing blood. It comes with a needle, a tube holder, and a vacutainer tube. One end of the needle is screwed unto the tube holder. The other end of the needle is inserted into the vein and the vacutainer tube is placed into the holder to perform the blood draw.
The evacuated tube system or ETS is easy to setup and use but it can be difficult to maneuver depending on the location of the vein and the position of the arm or phlebotomist.
The ETS is used to draw blood from good veins in the antecubital fossa. A 21, 22, or 23 needle gauge can be used depending on the size of the vein found there.
The median cubital vein is probably the number one vein used when using the evacuated tube system. It’s usually visible or just below the skin and asking for you to stick it.
In general, the ETS is used for all good veins, above the skin surface or below the surface. When the veins are deep or are difficult, you would use a syringe and sometimes a butterfly instead.
Here are some advantages and disadvantages of the evacuated tube system:
Advantages of the Evacuated Tube System
Amount of blood collected is accurate. The vacutainer tube fills up to a certain level indicated on the tube. For PT/INR or PTT tests, that level is important as the amount of blood collected must reach that level. However, for CBCs for example, if using a 4 ml tube, filling the tube to the maximum level may not be necessary. Probably 1 ml of blood would be sufficient. The type of test or tests being done would indicate how much blood to draw.
Speed of blood collection is safe. The tube vial is designed to draw blood at a control speed that protects the cells from bursting, reducing the risk of hemolysis.
Pre-filled with the accurate amount of additive. There are different kinds of additive. One kind prevents blood from clotting and the other, speeds up the blood clotting process. The ratio of blood to anticoagulant must be maintained for good test results.
Can draw multiple samples. Probably the number one advantage of the ETS is that you can take multiple samples while the needle is positioned in the vein. If you have to fill 4 tubes, you can fill all 4 from one stick. You don’t have to stick the person a second time.
Uses a closed system. The evacuated tube system provides a closed system that reduces the risk of spilled blood thus protecting the phlebotomist from accidental exposure to blood drawn pathogens.
Faster way of collecting blood. The ETS is quick at blood collection. While the speed at which the vacuum tube fills is controlled, the vial fills up fast. If you are using a 21 needle gauge, the process is quick. If you are using a 23 needle gauge, fill up slows down.
Easy to setup. The ETS is easy to assemble and once the vein is good, using it is relatively simple. If the vein poses some kind of difficulty, though, it tends to be more difficult to use.
Decreases the possibility of needlesticks.
Allows blood to pass directly from the vein to the evacuated tube.
Disadvantages of the Evacuated Tube System
Can be difficult to use. The evacuated tube system is fairly easy to use when veins a plump and good. However, It becomes difficult when you are faced with difficult veins or patients. It is cumbersome in that instance and controlling the device well is on the downside.
No flash back to let you know the needle is in the vein. Unlike the syringe method or butterfly, the ETS doesn’t give you any signs that the needle is in the vein. The only way of knowing is by placing the tube into the holder and seeing if blood flows into the tube. If there is no blood, you may have to adjust the needle a little so see if blood comes. Otherwise, you will have to remove the needle and redo the venipuncture using another vein. That leads to another disadvantage.
If the tube is attached and no blood flows into the tube, it may have to be discarded.
Not well suited for difficult veins/patients.
The chances of trauma (hematoma) may be greater. The ETS is a bit cumbersome and so controlling the needle can be more difficult at times, and therefore there is the possibility of bruising the patient while positioning the needle in the vein.
Not suitable for newborn or pediatric patients. A syringe or butterfly is used for pediatric patients.
May not collect sufficient amount of blood if tube was used or opened previously. An opened tube releases the vacuum inside the tube, making the amount of blood collected much less.
Some tubes lose their vacuum or at least some. Some brands of tubes lose their vacuum with time. I have noticed that the blue top tubes for PT/INR or PTT, lose some of its vacuum over time, while not expired.
When do you not use the Evacuated Tube System?
The evacuated tube system is for good veins in the antecubital fossa area. Most people have good veins and so most times the ETS will be used by a phlebotomist. But there are moments when you won’t be able to find a good vein in the antecubital fossa area. That’s when you begin to think of using another method of venipuncture, either the syringe or the butterfly.
The syringe or butterfly gives you more control when attempting to draw blood from difficult veins or patients. There are different sizes of syringes which can come in handy and the butterfly system can be let to recline on the person’s arm while you draw blood.
For hand veins, you would use a butterfly or a syringe. The syringe can be a bit difficult when used for the back of the hand, though. The butterfly is easier to use.
The ETS system is not used on newborn or pediatric patients. These patients’ veins are small and using the ETS system can cause their vein to collapse.
The evacuated tube system is not suitable for the elderly, as well. They elderly usually has fragile and rolling veins. Using a syringe or butterfly is recommended.
What about the clinical setting? Patients at the hospital, including critical care patients and those on other wards, normally pose difficulty when getting their blood drawn for a variety of reasons. Therefore, it will be that, on many occasions you will use a syringe or butterfly when doing venipuncture.
Definitely, you will come across patients who have good veins. In those instances you can use the evacuated tube system for blood draw.
Other methods of blood draw: go read about the syringe method here.
Related Question
Why the Evacuated Tube System is the preferred method over syringe and needle? The vacutainer system is easy to set up, simple to use and quick at blood collection, wasting no time when there are multiple samples to be drawn. It also produces a higher quality of specimen since the vacuum filled tube controls the speed at which blood is drawn.