Sometimes, blood will stop flowing when taking a blood sample for testing. When that happens don’t panic. There are several reasons why blood may stop. The most obvious reason, however, is simple:
Blood may stop flowing if a vein collapses or the needle is pulled out of the vein when switching tubes or the person moves. Other factors that may lead to a stop include dehydration, thick blood or clotting possibilities.
The first thing to do when blood stops is to observe the area to determine what has caused the stop. There may be visible signs that will tell you.
Try drawing blood again to see if it will flow. If that is unsuccessful, stop the procedure and redraw using a different site and vein.
What Causes Blood To Stop Flowing?
If there is anything a phlebotomist hates is when blood stops flowing. That usually means you have to redraw blood. Below are several factors that can lead or influence blood to stop flowing. These include:
Collapsed Veins
This happens a lot of the time with the elderly. The elderly veins are fragile and can collapse easily if there is too much tourniquet pressure or the pull of the vacuum in the tube is too great. Also, a vein can collapse if the pull from a syringe is too quick.
Dehydration
Veins do well when the body is hydrated. Lack of water in the body can lead to thick blood which can lead to slow blood flow which then can lead to clotting possibilities.
Fear of Needles and Stress
We all know what fear can do to our bodies and how stress can make us feel. Fear of needles can hinder blood flow as the sympathetic innervation is affected. Stress can affect veins by suppressing the parasympathetic innervation of the body.
This may diminish blood flow near the skin which may result in less blood flowing into the needle.
Removal of Needle from the Lumen
If the needle is removed from the vein or the bevel is against the vein wall blood will stop flowing. That can happen when switching tubes or if a person jerks or moves their arm.
Chemotherapy
Some chemotherapy drugs can cause the patient’s vein to harden. Drawing blood from such veins can be difficult. In some instances, blood flow is slow and stops.
What To Do If Blood Stops Flowing?
If blood stops flowing try these steps below to troubleshoot the problem:
- If the vein has collapsed assess the situation and if blood is not flowing stop the venipuncture. Redo the process using a different site and vein.
If blood stops flowing into the tube or syringe try these steps:
- Adjust the position of the needle by moving it forward in case it is not in the lumen or backward incase it has penetrated too far.
- Adjust the angle of the needle. The bevel may be against the vein wall.
- Check the tourniquet and see if it’s too tight. If so, loosen slightly.
- Check the tube and try another. It may be that the tube doesn’t have any vacuum.
- Check the venipuncture site and see if the needle has missed the vein or the vein has rolled away.
- Have the person drink water if they are dehydrated. Let them relax and after a few moments try doing the blood draw again.
Why Do My Veins Collapse When I Have A Blood Test?
A vein collapses when the sides of the vein caves in toward each other sealing off the vein so blood can’t flow.
This mostly happens with the elderly. With age the veins become less sturdy and more fragile. A lot of care is needed when drawing blood from veins like that. They can easily collapse and another vein would have to be chosen for a second venipuncture.
The vacuum in the tube can cause that when using the vacutainer method. Try using a smaller tube if a bigger tube collapses the vein.
Also, too much force (pull) from the plunger can cause the vein to collapse when using the syringe.
What Does A Slow Blood Draw Mean?
It could mean that a person is dehydrated. It could also mean that the needle is not in the center of the vein or lumen. Either of these reasons can lead to a slow blood draw.
Sometimes, when I can’t find a vein or blood keeps stopping I will ask the person if they have been drinking fluids and if not I will ask them to do so. That is because hydration makes for a good vein and a successful venipuncture.
Blood will also flow slowly or not at all if the needle is barely in the vein or too much inside. In that case, the bevel may be against the vein wall resulting in less blood flowing into the needle.
What Are the Reasons For a Failed Venipuncture?
There are several factors that can cause a failed venipuncture. Some of these are brought about by the patient. Some are because of the phlebotomist’s technique. They include:
- Improper needle position. Check the angle of the needle and adjust accordingly to correct.
- Dehydration. Have the person drink fluids if they are dehydrated.
- Moving of the arm. Jerking or moving the arm will cause the needle to move out of its position.
- Wrong gauge of needle. The size of needle must suit the vein. Bigger size for big veins, smaller size for small veins.
- Hardened veins can result in a failed attempt.
In conclusion, the most obvious reason why blood stops flowing during a venipuncture is due to either the vein collapsing or the needle moving out of its position. Other factors that could lead to a stop include dehydration, slow blood flow, clotting possibilities and hardened veins.